From b6727ea582d1c457228dc37fad1fab070736cd8d Mon Sep 17 00:00:00 2001
From: Andy Hanson <anhans@microsoft.com>
Date: Thu, 3 Nov 2016 06:09:47 -0700
Subject: [PATCH] Only resolve symlinks in `node_modules`

---
 src/compiler/moduleNameResolver.ts            |  5 +-
 src/harness/harness.ts                        | 50 +++++++++++--------
 .../importWithTrailingSlash.trace.json        |  4 --
 .../moduleResolutionWithExtensions.trace.json |  3 --
 ...tionWithExtensions_notSupported.trace.json |  3 --
 ...ionWithExtensions_notSupported2.trace.json |  1 -
 ...ionWithExtensions_notSupported3.trace.json |  1 -
 ...solutionWithExtensions_preferTs.trace.json |  1 -
 .../reference/moduleResolutionWithSymlinks.js | 50 +++++++++++++++++--
 .../moduleResolutionWithSymlinks.symbols      | 23 ++++++++-
 .../moduleResolutionWithSymlinks.trace.json   |  2 -
 .../moduleResolutionWithSymlinks.types        | 21 ++++++++
 ...ResolutionWithSymlinks_notInNodeModules.js | 32 ++++++++++++
 ...utionWithSymlinks_notInNodeModules.symbols | 12 +++++
 ...onWithSymlinks_notInNodeModules.trace.json | 12 +++++
 ...olutionWithSymlinks_notInNodeModules.types | 13 +++++
 ...moduleResolutionWithSymlinks_withOutDir.js | 40 +++++++++++++++
 ...eResolutionWithSymlinks_withOutDir.symbols | 38 ++++++++++++++
 ...solutionWithSymlinks_withOutDir.trace.json | 30 +++++++++++
 ...uleResolutionWithSymlinks_withOutDir.types | 40 +++++++++++++++
 ...pingBasedModuleResolution3_node.trace.json |  2 -
 ...pingBasedModuleResolution4_node.trace.json |  2 -
 ...pingBasedModuleResolution5_node.trace.json |  3 --
 ...pingBasedModuleResolution6_node.trace.json |  2 -
 ...pingBasedModuleResolution7_node.trace.json |  4 --
 .../typeReferenceDirectives10.trace.json      |  1 -
 .../typeReferenceDirectives11.trace.json      |  1 -
 .../typeReferenceDirectives12.trace.json      |  3 --
 .../typeReferenceDirectives13.trace.json      |  1 -
 .../typeReferenceDirectives5.trace.json       |  1 -
 .../typeReferenceDirectives8.trace.json       |  1 -
 .../typeReferenceDirectives9.trace.json       |  3 --
 .../compiler/moduleResolutionWithSymlinks.ts  | 25 +++++++++-
 ...ResolutionWithSymlinks_notInNodeModules.ts | 40 +++++++++++++++
 ...moduleResolutionWithSymlinks_withOutDir.ts | 22 ++++++++
 35 files changed, 423 insertions(+), 69 deletions(-)
 create mode 100644 tests/baselines/reference/moduleResolutionWithSymlinks_notInNodeModules.js
 create mode 100644 tests/baselines/reference/moduleResolutionWithSymlinks_notInNodeModules.symbols
 create mode 100644 tests/baselines/reference/moduleResolutionWithSymlinks_notInNodeModules.trace.json
 create mode 100644 tests/baselines/reference/moduleResolutionWithSymlinks_notInNodeModules.types
 create mode 100644 tests/baselines/reference/moduleResolutionWithSymlinks_withOutDir.js
 create mode 100644 tests/baselines/reference/moduleResolutionWithSymlinks_withOutDir.symbols
 create mode 100644 tests/baselines/reference/moduleResolutionWithSymlinks_withOutDir.trace.json
 create mode 100644 tests/baselines/reference/moduleResolutionWithSymlinks_withOutDir.types
 create mode 100644 tests/cases/compiler/moduleResolutionWithSymlinks_notInNodeModules.ts
 create mode 100644 tests/cases/compiler/moduleResolutionWithSymlinks_withOutDir.ts

diff --git a/src/compiler/moduleNameResolver.ts b/src/compiler/moduleNameResolver.ts
index 86e0157d847..6c9ce00b3b8 100644
--- a/src/compiler/moduleNameResolver.ts
+++ b/src/compiler/moduleNameResolver.ts
@@ -548,7 +548,7 @@ namespace ts {
         const result = tryResolve(Extensions.TypeScript) || tryResolve(Extensions.JavaScript);
         if (result) {
             const { resolved, isExternalLibraryImport } = result;
-            return createResolvedModuleWithFailedLookupLocations(resolved && resolvedWithRealpath(resolved, host, traceEnabled), isExternalLibraryImport, failedLookupLocations);
+            return createResolvedModuleWithFailedLookupLocations(resolved, isExternalLibraryImport, failedLookupLocations);
         }
         return { resolvedModule: undefined, failedLookupLocations };
 
@@ -563,7 +563,8 @@ namespace ts {
                     trace(host, Diagnostics.Loading_module_0_from_node_modules_folder, moduleName);
                 }
                 const resolved = loadModuleFromNodeModules(extensions, moduleName, containingDirectory, failedLookupLocations, state, /*checkOneLevel*/ false);
-                return resolved && { resolved, isExternalLibraryImport: true };
+                // For node_modules lookups, get the real path so that multiple accesses to an `npm link`-ed module do not create duplicate files.
+                return resolved && { resolved: resolvedWithRealpath(resolved, host, traceEnabled), isExternalLibraryImport: true };
             }
             else {
                 const candidate = normalizePath(combinePaths(containingDirectory, moduleName));
diff --git a/src/harness/harness.ts b/src/harness/harness.ts
index 57ee46299b5..b5dd39b1542 100644
--- a/src/harness/harness.ts
+++ b/src/harness/harness.ts
@@ -958,28 +958,38 @@ namespace Harness {
             // Local get canonical file name function, that depends on passed in parameter for useCaseSensitiveFileNames
             const getCanonicalFileName = ts.createGetCanonicalFileName(useCaseSensitiveFileNames);
 
-            const realPathMap: ts.FileMap<string> = ts.createFileMap<string>();
-            const fileMap: ts.FileMap<() => ts.SourceFile> = ts.createFileMap<() => ts.SourceFile>();
+            /** Maps a symlink name to a realpath. Used only for exposing `realpath`. */
+            const realPathMap = ts.createFileMap<string>();
+            /**
+             * Maps a file name to a source file.
+             * This will have a different SourceFile for every symlink pointing to that file;
+             * if the program resolves realpaths then symlink entries will be ignored.
+             */
+            const fileMap = ts.createFileMap<ts.SourceFile>();
             for (const file of inputFiles) {
                 if (file.content !== undefined) {
                     const fileName = ts.normalizePath(file.unitName);
                     const path = ts.toPath(file.unitName, currentDirectory, getCanonicalFileName);
                     if (file.fileOptions && file.fileOptions["symlink"]) {
-                        const link = file.fileOptions["symlink"];
-                        const linkPath = ts.toPath(link, currentDirectory, getCanonicalFileName);
-                        realPathMap.set(linkPath, fileName);
-                        fileMap.set(path, (): ts.SourceFile => { throw new Error("Symlinks should always be resolved to a realpath first"); });
+                        const links = file.fileOptions["symlink"].split(",");
+                        for (const link of links) {
+                            const linkPath = ts.toPath(link, currentDirectory, getCanonicalFileName);
+                            realPathMap.set(linkPath, fileName);
+                            // Create a different SourceFile for every symlink.
+                            const sourceFile = createSourceFileAndAssertInvariants(linkPath, file.content, scriptTarget);
+                            fileMap.set(linkPath, sourceFile);
+                        }
                     }
                     const sourceFile = createSourceFileAndAssertInvariants(fileName, file.content, scriptTarget);
-                    fileMap.set(path, () => sourceFile);
+                    fileMap.set(path, sourceFile);
                 }
             }
 
             function getSourceFile(fileName: string) {
                 fileName = ts.normalizePath(fileName);
-                const path = ts.toPath(fileName, currentDirectory, getCanonicalFileName);
-                if (fileMap.contains(path)) {
-                    return fileMap.get(path)();
+                const fromFileMap = fileMap.get(toPath(fileName));
+                if (fromFileMap) {
+                    return fromFileMap;
                 }
                 else if (fileName === fourslashFileName) {
                     const tsFn = "tests/cases/fourslash/" + fourslashFileName;
@@ -998,6 +1008,9 @@ namespace Harness {
                     newLineKind === ts.NewLineKind.LineFeed ? lineFeed :
                         Harness.IO.newLine();
 
+            function toPath(fileName: string): ts.Path {
+                return ts.toPath(fileName, currentDirectory, getCanonicalFileName);
+            }
 
             return {
                 getCurrentDirectory: () => currentDirectory,
@@ -1007,24 +1020,19 @@ namespace Harness {
                 getCanonicalFileName,
                 useCaseSensitiveFileNames: () => useCaseSensitiveFileNames,
                 getNewLine: () => newLine,
-                fileExists: fileName => {
-                    const path = ts.toPath(fileName, currentDirectory, getCanonicalFileName);
-                    return fileMap.contains(path) || (realPathMap && realPathMap.contains(path));
+                fileExists: fileName => fileMap.contains(toPath(fileName)),
+                readFile: (fileName: string): string => fileMap.get(toPath(fileName)).getText(),
+                realpath: (fileName: string): ts.Path => {
+                    const path = toPath(fileName);
+                    return (realPathMap.get(path) as ts.Path) || path;
                 },
-                readFile: (fileName: string): string => {
-                    return fileMap.get(ts.toPath(fileName, currentDirectory, getCanonicalFileName))().getText();
-                },
-                realpath: realPathMap && ((f: string) => {
-                    const path = ts.toPath(f, currentDirectory, getCanonicalFileName);
-                    return realPathMap.get(path) || path;
-                }),
                 directoryExists: dir => {
                     let path = ts.toPath(dir, currentDirectory, getCanonicalFileName);
                     // Strip trailing /, which may exist if the path is a drive root
                     if (path[path.length - 1] === "/") {
                         path = <ts.Path>path.substr(0, path.length - 1);
                     }
-                    return mapHasFileInDirectory(path, fileMap) || mapHasFileInDirectory(path, realPathMap);
+                    return mapHasFileInDirectory(path, fileMap);
                 },
                 getDirectories: d => {
                     const path = ts.toPath(d, currentDirectory, getCanonicalFileName);
diff --git a/tests/baselines/reference/importWithTrailingSlash.trace.json b/tests/baselines/reference/importWithTrailingSlash.trace.json
index 3c99d4eb6a0..56de914f395 100644
--- a/tests/baselines/reference/importWithTrailingSlash.trace.json
+++ b/tests/baselines/reference/importWithTrailingSlash.trace.json
@@ -3,26 +3,22 @@
     "Explicitly specified module resolution kind: 'NodeJs'.",
     "Loading module as file / folder, candidate module location '/a'.",
     "File '/a.ts' exist - use it as a name resolution result.",
-    "Resolving real path for '/a.ts', result '/a.ts'",
     "======== Module name '.' was successfully resolved to '/a.ts'. ========",
     "======== Resolving module './' from '/a/test.ts'. ========",
     "Explicitly specified module resolution kind: 'NodeJs'.",
     "Loading module as file / folder, candidate module location '/a/'.",
     "File '/a/package.json' does not exist.",
     "File '/a/index.ts' exist - use it as a name resolution result.",
-    "Resolving real path for '/a/index.ts', result '/a/index.ts'",
     "======== Module name './' was successfully resolved to '/a/index.ts'. ========",
     "======== Resolving module '..' from '/a/b/test.ts'. ========",
     "Explicitly specified module resolution kind: 'NodeJs'.",
     "Loading module as file / folder, candidate module location '/a'.",
     "File '/a.ts' exist - use it as a name resolution result.",
-    "Resolving real path for '/a.ts', result '/a.ts'",
     "======== Module name '..' was successfully resolved to '/a.ts'. ========",
     "======== Resolving module '../' from '/a/b/test.ts'. ========",
     "Explicitly specified module resolution kind: 'NodeJs'.",
     "Loading module as file / folder, candidate module location '/a/'.",
     "File '/a/package.json' does not exist.",
     "File '/a/index.ts' exist - use it as a name resolution result.",
-    "Resolving real path for '/a/index.ts', result '/a/index.ts'",
     "======== Module name '../' was successfully resolved to '/a/index.ts'. ========"
 ]
\ No newline at end of file
diff --git a/tests/baselines/reference/moduleResolutionWithExtensions.trace.json b/tests/baselines/reference/moduleResolutionWithExtensions.trace.json
index 5060006ac56..6860c61bb17 100644
--- a/tests/baselines/reference/moduleResolutionWithExtensions.trace.json
+++ b/tests/baselines/reference/moduleResolutionWithExtensions.trace.json
@@ -3,7 +3,6 @@
     "Module resolution kind is not specified, using 'NodeJs'.",
     "Loading module as file / folder, candidate module location '/src/a'.",
     "File '/src/a.ts' exist - use it as a name resolution result.",
-    "Resolving real path for '/src/a.ts', result '/src/a.ts'",
     "======== Module name './a' was successfully resolved to '/src/a.ts'. ========",
     "======== Resolving module './a.js' from '/src/d.ts'. ========",
     "Module resolution kind is not specified, using 'NodeJs'.",
@@ -13,7 +12,6 @@
     "File '/src/a.js.d.ts' does not exist.",
     "File name '/src/a.js' has a '.js' extension - stripping it",
     "File '/src/a.ts' exist - use it as a name resolution result.",
-    "Resolving real path for '/src/a.ts', result '/src/a.ts'",
     "======== Module name './a.js' was successfully resolved to '/src/a.ts'. ========",
     "======== Resolving module './jquery.js' from '/src/jquery_user_1.ts'. ========",
     "Module resolution kind is not specified, using 'NodeJs'.",
@@ -25,6 +23,5 @@
     "File '/src/jquery.ts' does not exist.",
     "File '/src/jquery.tsx' does not exist.",
     "File '/src/jquery.d.ts' exist - use it as a name resolution result.",
-    "Resolving real path for '/src/jquery.d.ts', result '/src/jquery.d.ts'",
     "======== Module name './jquery.js' was successfully resolved to '/src/jquery.d.ts'. ========"
 ]
\ No newline at end of file
diff --git a/tests/baselines/reference/moduleResolutionWithExtensions_notSupported.trace.json b/tests/baselines/reference/moduleResolutionWithExtensions_notSupported.trace.json
index 0073abaca3a..f2b0214602c 100644
--- a/tests/baselines/reference/moduleResolutionWithExtensions_notSupported.trace.json
+++ b/tests/baselines/reference/moduleResolutionWithExtensions_notSupported.trace.json
@@ -4,7 +4,6 @@
     "Loading module as file / folder, candidate module location '/tsx'.",
     "File '/tsx.ts' does not exist.",
     "File '/tsx.tsx' exist - use it as a name resolution result.",
-    "Resolving real path for '/tsx.tsx', result '/tsx.tsx'",
     "======== Module name './tsx' was successfully resolved to '/tsx.tsx'. ========",
     "======== Resolving module './jsx' from '/a.ts'. ========",
     "Module resolution kind is not specified, using 'NodeJs'.",
@@ -19,7 +18,6 @@
     "Loading module as file / folder, candidate module location '/jsx'.",
     "File '/jsx.js' does not exist.",
     "File '/jsx.jsx' exist - use it as a name resolution result.",
-    "Resolving real path for '/jsx.jsx', result '/jsx.jsx'",
     "======== Module name './jsx' was successfully resolved to '/jsx.jsx'. ========",
     "======== Resolving module './js' from '/a.ts'. ========",
     "Module resolution kind is not specified, using 'NodeJs'.",
@@ -33,6 +31,5 @@
     "File '/js/index.d.ts' does not exist.",
     "Loading module as file / folder, candidate module location '/js'.",
     "File '/js.js' exist - use it as a name resolution result.",
-    "Resolving real path for '/js.js', result '/js.js'",
     "======== Module name './js' was successfully resolved to '/js.js'. ========"
 ]
\ No newline at end of file
diff --git a/tests/baselines/reference/moduleResolutionWithExtensions_notSupported2.trace.json b/tests/baselines/reference/moduleResolutionWithExtensions_notSupported2.trace.json
index c366843ce86..89bd061301e 100644
--- a/tests/baselines/reference/moduleResolutionWithExtensions_notSupported2.trace.json
+++ b/tests/baselines/reference/moduleResolutionWithExtensions_notSupported2.trace.json
@@ -12,6 +12,5 @@
     "Loading module as file / folder, candidate module location '/jsx'.",
     "File '/jsx.js' does not exist.",
     "File '/jsx.jsx' exist - use it as a name resolution result.",
-    "Resolving real path for '/jsx.jsx', result '/jsx.jsx'",
     "======== Module name './jsx' was successfully resolved to '/jsx.jsx'. ========"
 ]
\ No newline at end of file
diff --git a/tests/baselines/reference/moduleResolutionWithExtensions_notSupported3.trace.json b/tests/baselines/reference/moduleResolutionWithExtensions_notSupported3.trace.json
index c366843ce86..89bd061301e 100644
--- a/tests/baselines/reference/moduleResolutionWithExtensions_notSupported3.trace.json
+++ b/tests/baselines/reference/moduleResolutionWithExtensions_notSupported3.trace.json
@@ -12,6 +12,5 @@
     "Loading module as file / folder, candidate module location '/jsx'.",
     "File '/jsx.js' does not exist.",
     "File '/jsx.jsx' exist - use it as a name resolution result.",
-    "Resolving real path for '/jsx.jsx', result '/jsx.jsx'",
     "======== Module name './jsx' was successfully resolved to '/jsx.jsx'. ========"
 ]
\ No newline at end of file
diff --git a/tests/baselines/reference/moduleResolutionWithExtensions_preferTs.trace.json b/tests/baselines/reference/moduleResolutionWithExtensions_preferTs.trace.json
index 292472c710c..f6612b84cc3 100644
--- a/tests/baselines/reference/moduleResolutionWithExtensions_preferTs.trace.json
+++ b/tests/baselines/reference/moduleResolutionWithExtensions_preferTs.trace.json
@@ -7,6 +7,5 @@
     "File '/b.d.ts' does not exist.",
     "File '/b/package.json' does not exist.",
     "File '/b/index.ts' exist - use it as a name resolution result.",
-    "Resolving real path for '/b/index.ts', result '/b/index.ts'",
     "======== Module name './b' was successfully resolved to '/b/index.ts'. ========"
 ]
\ No newline at end of file
diff --git a/tests/baselines/reference/moduleResolutionWithSymlinks.js b/tests/baselines/reference/moduleResolutionWithSymlinks.js
index fa6fea5520b..fbf97fa3ba0 100644
--- a/tests/baselines/reference/moduleResolutionWithSymlinks.js
+++ b/tests/baselines/reference/moduleResolutionWithSymlinks.js
@@ -1,6 +1,8 @@
 //// [tests/cases/compiler/moduleResolutionWithSymlinks.ts] ////
 
 //// [index.ts]
+// When symlinked files are in node_modules, they are resolved with realpath;
+// so a linked file does not create a duplicate SourceFile of the real one.
 
 export class MyClass { private x: number; }
 
@@ -15,9 +17,31 @@ import { MyClass2 } from "./library-b";
 let x: MyClass;
 let y: MyClass2;
 x = y;
-y = x;
+y = x;
+
+/*
+# To reproduce in a real project:
+
+mkdir src; cd src
+mkdir library-a
+echo 'export class MyClass { private x: number; }' > library-a/index.ts
+
+mkdir library-b; cd library-b
+echo 'import {MyClass} from "library-a"; export { MyClass as MyClass2 }' > index.ts
+mkdir node_modules; cd node_modules
+
+ln -s ../../library-a library-a # Linux
+# Windows: open command prompt as administrator and run: mklink /D library-a ..\..\library-a
+
+cd ../.. # back to src
+echo 'import { MyClass } from "./library-a"; import { MyClass2 } from "./library-b"; let x: MyClass; let y: MyClass2; x = y; y = x;' > app.ts
+tsc app.ts # Should write to library-a/index.js, library-b/index.js, and app.js
+*/
 
-//// [index.js]
+
+//// [/src/library-a/index.js]
+// When symlinked files are in node_modules, they are resolved with realpath;
+// so a linked file does not create a duplicate SourceFile of the real one.
 "use strict";
 var MyClass = (function () {
     function MyClass() {
@@ -25,13 +49,31 @@ var MyClass = (function () {
     return MyClass;
 }());
 exports.MyClass = MyClass;
-//// [index.js]
+//// [/src/library-b/index.js]
 "use strict";
 var library_a_1 = require("library-a");
 exports.MyClass2 = library_a_1.MyClass;
-//// [app.js]
+//// [/src/app.js]
 "use strict";
 var x;
 var y;
 x = y;
 y = x;
+/*
+# To reproduce in a real project:
+
+mkdir src; cd src
+mkdir library-a
+echo 'export class MyClass { private x: number; }' > library-a/index.ts
+
+mkdir library-b; cd library-b
+echo 'import {MyClass} from "library-a"; export { MyClass as MyClass2 }' > index.ts
+mkdir node_modules; cd node_modules
+
+ln -s ../../library-a library-a # Linux
+# Windows: open command prompt as administrator and run: mklink /D library-a ..\..\library-a
+
+cd ../.. # back to src
+echo 'import { MyClass } from "./library-a"; import { MyClass2 } from "./library-b"; let x: MyClass; let y: MyClass2; x = y; y = x;' > app.ts
+tsc app.ts # Should write to library-a/index.js, library-b/index.js, and app.js
+*/
diff --git a/tests/baselines/reference/moduleResolutionWithSymlinks.symbols b/tests/baselines/reference/moduleResolutionWithSymlinks.symbols
index 9e9e3ee8a67..ede12be3555 100644
--- a/tests/baselines/reference/moduleResolutionWithSymlinks.symbols
+++ b/tests/baselines/reference/moduleResolutionWithSymlinks.symbols
@@ -21,11 +21,32 @@ y = x;
 >y : Symbol(y, Decl(app.ts, 4, 3))
 >x : Symbol(x, Decl(app.ts, 3, 3))
 
+/*
+# To reproduce in a real project:
+
+mkdir src; cd src
+mkdir library-a
+echo 'export class MyClass { private x: number; }' > library-a/index.ts
+
+mkdir library-b; cd library-b
+echo 'import {MyClass} from "library-a"; export { MyClass as MyClass2 }' > index.ts
+mkdir node_modules; cd node_modules
+
+ln -s ../../library-a library-a # Linux
+# Windows: open command prompt as administrator and run: mklink /D library-a ..\..\library-a
+
+cd ../.. # back to src
+echo 'import { MyClass } from "./library-a"; import { MyClass2 } from "./library-b"; let x: MyClass; let y: MyClass2; x = y; y = x;' > app.ts
+tsc app.ts # Should write to library-a/index.js, library-b/index.js, and app.js
+*/
+
 === /src/library-a/index.ts ===
+// When symlinked files are in node_modules, they are resolved with realpath;
+// so a linked file does not create a duplicate SourceFile of the real one.
 
 export class MyClass { private x: number; }
 >MyClass : Symbol(MyClass, Decl(index.ts, 0, 0))
->x : Symbol(MyClass.x, Decl(index.ts, 1, 22))
+>x : Symbol(MyClass.x, Decl(index.ts, 3, 22))
 
 === /src/library-b/index.ts ===
 import {MyClass} from "library-a";
diff --git a/tests/baselines/reference/moduleResolutionWithSymlinks.trace.json b/tests/baselines/reference/moduleResolutionWithSymlinks.trace.json
index 7f1c2890180..bd23ccdb366 100644
--- a/tests/baselines/reference/moduleResolutionWithSymlinks.trace.json
+++ b/tests/baselines/reference/moduleResolutionWithSymlinks.trace.json
@@ -7,7 +7,6 @@
     "File '/src/library-a.d.ts' does not exist.",
     "File '/src/library-a/package.json' does not exist.",
     "File '/src/library-a/index.ts' exist - use it as a name resolution result.",
-    "Resolving real path for '/src/library-a/index.ts', result '/src/library-a/index.ts'",
     "======== Module name './library-a' was successfully resolved to '/src/library-a/index.ts'. ========",
     "======== Resolving module './library-b' from '/src/app.ts'. ========",
     "Module resolution kind is not specified, using 'NodeJs'.",
@@ -17,7 +16,6 @@
     "File '/src/library-b.d.ts' does not exist.",
     "File '/src/library-b/package.json' does not exist.",
     "File '/src/library-b/index.ts' exist - use it as a name resolution result.",
-    "Resolving real path for '/src/library-b/index.ts', result '/src/library-b/index.ts'",
     "======== Module name './library-b' was successfully resolved to '/src/library-b/index.ts'. ========",
     "======== Resolving module 'library-a' from '/src/library-b/index.ts'. ========",
     "Module resolution kind is not specified, using 'NodeJs'.",
diff --git a/tests/baselines/reference/moduleResolutionWithSymlinks.types b/tests/baselines/reference/moduleResolutionWithSymlinks.types
index 3c0ccd168dd..04781dcac0f 100644
--- a/tests/baselines/reference/moduleResolutionWithSymlinks.types
+++ b/tests/baselines/reference/moduleResolutionWithSymlinks.types
@@ -23,7 +23,28 @@ y = x;
 >y : MyClass
 >x : MyClass
 
+/*
+# To reproduce in a real project:
+
+mkdir src; cd src
+mkdir library-a
+echo 'export class MyClass { private x: number; }' > library-a/index.ts
+
+mkdir library-b; cd library-b
+echo 'import {MyClass} from "library-a"; export { MyClass as MyClass2 }' > index.ts
+mkdir node_modules; cd node_modules
+
+ln -s ../../library-a library-a # Linux
+# Windows: open command prompt as administrator and run: mklink /D library-a ..\..\library-a
+
+cd ../.. # back to src
+echo 'import { MyClass } from "./library-a"; import { MyClass2 } from "./library-b"; let x: MyClass; let y: MyClass2; x = y; y = x;' > app.ts
+tsc app.ts # Should write to library-a/index.js, library-b/index.js, and app.js
+*/
+
 === /src/library-a/index.ts ===
+// When symlinked files are in node_modules, they are resolved with realpath;
+// so a linked file does not create a duplicate SourceFile of the real one.
 
 export class MyClass { private x: number; }
 >MyClass : MyClass
diff --git a/tests/baselines/reference/moduleResolutionWithSymlinks_notInNodeModules.js b/tests/baselines/reference/moduleResolutionWithSymlinks_notInNodeModules.js
new file mode 100644
index 00000000000..a927a496a96
--- /dev/null
+++ b/tests/baselines/reference/moduleResolutionWithSymlinks_notInNodeModules.js
@@ -0,0 +1,32 @@
+//// [tests/cases/compiler/moduleResolutionWithSymlinks_notInNodeModules.ts] ////
+
+//// [abc.ts]
+// When symlinked files are not in node_modules, realpath is not used.
+// A symlink file acts like the real thing. So, 2 symlinks act like 2 different files.
+// See GH#10364. 
+
+export const x = 0;
+
+//// [app.ts]
+import { x } from "./shared/abc";
+import { x as x2 } from "./shared2/abc";
+x + x2;
+
+
+//// [/src/bin/shared/abc.js]
+// When symlinked files are not in node_modules, realpath is not used.
+// A symlink file acts like the real thing. So, 2 symlinks act like 2 different files.
+// See GH#10364. 
+"use strict";
+exports.x = 0;
+//// [/src/bin/shared2/abc.js]
+// When symlinked files are not in node_modules, realpath is not used.
+// A symlink file acts like the real thing. So, 2 symlinks act like 2 different files.
+// See GH#10364. 
+"use strict";
+exports.x = 0;
+//// [/src/bin/app.js]
+"use strict";
+var abc_1 = require("./shared/abc");
+var abc_2 = require("./shared2/abc");
+abc_1.x + abc_2.x;
diff --git a/tests/baselines/reference/moduleResolutionWithSymlinks_notInNodeModules.symbols b/tests/baselines/reference/moduleResolutionWithSymlinks_notInNodeModules.symbols
new file mode 100644
index 00000000000..b496e1b76ac
--- /dev/null
+++ b/tests/baselines/reference/moduleResolutionWithSymlinks_notInNodeModules.symbols
@@ -0,0 +1,12 @@
+=== /src/app.ts ===
+import { x } from "./shared/abc";
+>x : Symbol(x, Decl(app.ts, 0, 8))
+
+import { x as x2 } from "./shared2/abc";
+>x : Symbol(x2, Decl(app.ts, 1, 8))
+>x2 : Symbol(x2, Decl(app.ts, 1, 8))
+
+x + x2;
+>x : Symbol(x, Decl(app.ts, 0, 8))
+>x2 : Symbol(x2, Decl(app.ts, 1, 8))
+
diff --git a/tests/baselines/reference/moduleResolutionWithSymlinks_notInNodeModules.trace.json b/tests/baselines/reference/moduleResolutionWithSymlinks_notInNodeModules.trace.json
new file mode 100644
index 00000000000..c2f0c04d07f
--- /dev/null
+++ b/tests/baselines/reference/moduleResolutionWithSymlinks_notInNodeModules.trace.json
@@ -0,0 +1,12 @@
+[
+    "======== Resolving module './shared/abc' from '/src/app.ts'. ========",
+    "Module resolution kind is not specified, using 'NodeJs'.",
+    "Loading module as file / folder, candidate module location '/src/shared/abc'.",
+    "File '/src/shared/abc.ts' exist - use it as a name resolution result.",
+    "======== Module name './shared/abc' was successfully resolved to '/src/shared/abc.ts'. ========",
+    "======== Resolving module './shared2/abc' from '/src/app.ts'. ========",
+    "Module resolution kind is not specified, using 'NodeJs'.",
+    "Loading module as file / folder, candidate module location '/src/shared2/abc'.",
+    "File '/src/shared2/abc.ts' exist - use it as a name resolution result.",
+    "======== Module name './shared2/abc' was successfully resolved to '/src/shared2/abc.ts'. ========"
+]
\ No newline at end of file
diff --git a/tests/baselines/reference/moduleResolutionWithSymlinks_notInNodeModules.types b/tests/baselines/reference/moduleResolutionWithSymlinks_notInNodeModules.types
new file mode 100644
index 00000000000..0d7fe290334
--- /dev/null
+++ b/tests/baselines/reference/moduleResolutionWithSymlinks_notInNodeModules.types
@@ -0,0 +1,13 @@
+=== /src/app.ts ===
+import { x } from "./shared/abc";
+>x : 0
+
+import { x as x2 } from "./shared2/abc";
+>x : 0
+>x2 : 0
+
+x + x2;
+>x + x2 : number
+>x : 0
+>x2 : 0
+
diff --git a/tests/baselines/reference/moduleResolutionWithSymlinks_withOutDir.js b/tests/baselines/reference/moduleResolutionWithSymlinks_withOutDir.js
new file mode 100644
index 00000000000..312bcf4c174
--- /dev/null
+++ b/tests/baselines/reference/moduleResolutionWithSymlinks_withOutDir.js
@@ -0,0 +1,40 @@
+//// [tests/cases/compiler/moduleResolutionWithSymlinks_withOutDir.ts] ////
+
+//// [index.ts]
+// Same as moduleResolutionWithSymlinks.ts, but with outDir
+
+export class MyClass { private x: number; }
+
+//// [index.ts]
+import {MyClass} from "library-a";
+export { MyClass as MyClass2 }
+
+//// [app.ts]
+import { MyClass } from "./library-a";
+import { MyClass2 } from "./library-b";
+
+let x: MyClass;
+let y: MyClass2;
+x = y;
+y = x;
+
+
+//// [/src/bin/library-a/index.js]
+// Same as moduleResolutionWithSymlinks.ts, but with outDir
+"use strict";
+var MyClass = (function () {
+    function MyClass() {
+    }
+    return MyClass;
+}());
+exports.MyClass = MyClass;
+//// [/src/bin/library-b/index.js]
+"use strict";
+var library_a_1 = require("library-a");
+exports.MyClass2 = library_a_1.MyClass;
+//// [/src/bin/app.js]
+"use strict";
+var x;
+var y;
+x = y;
+y = x;
diff --git a/tests/baselines/reference/moduleResolutionWithSymlinks_withOutDir.symbols b/tests/baselines/reference/moduleResolutionWithSymlinks_withOutDir.symbols
new file mode 100644
index 00000000000..3e7598815de
--- /dev/null
+++ b/tests/baselines/reference/moduleResolutionWithSymlinks_withOutDir.symbols
@@ -0,0 +1,38 @@
+=== /src/app.ts ===
+import { MyClass } from "./library-a";
+>MyClass : Symbol(MyClass, Decl(app.ts, 0, 8))
+
+import { MyClass2 } from "./library-b";
+>MyClass2 : Symbol(MyClass2, Decl(app.ts, 1, 8))
+
+let x: MyClass;
+>x : Symbol(x, Decl(app.ts, 3, 3))
+>MyClass : Symbol(MyClass, Decl(app.ts, 0, 8))
+
+let y: MyClass2;
+>y : Symbol(y, Decl(app.ts, 4, 3))
+>MyClass2 : Symbol(MyClass2, Decl(app.ts, 1, 8))
+
+x = y;
+>x : Symbol(x, Decl(app.ts, 3, 3))
+>y : Symbol(y, Decl(app.ts, 4, 3))
+
+y = x;
+>y : Symbol(y, Decl(app.ts, 4, 3))
+>x : Symbol(x, Decl(app.ts, 3, 3))
+
+=== /src/library-a/index.ts ===
+// Same as moduleResolutionWithSymlinks.ts, but with outDir
+
+export class MyClass { private x: number; }
+>MyClass : Symbol(MyClass, Decl(index.ts, 0, 0))
+>x : Symbol(MyClass.x, Decl(index.ts, 2, 22))
+
+=== /src/library-b/index.ts ===
+import {MyClass} from "library-a";
+>MyClass : Symbol(MyClass, Decl(index.ts, 0, 8))
+
+export { MyClass as MyClass2 }
+>MyClass : Symbol(MyClass2, Decl(index.ts, 1, 8))
+>MyClass2 : Symbol(MyClass2, Decl(index.ts, 1, 8))
+
diff --git a/tests/baselines/reference/moduleResolutionWithSymlinks_withOutDir.trace.json b/tests/baselines/reference/moduleResolutionWithSymlinks_withOutDir.trace.json
new file mode 100644
index 00000000000..bd23ccdb366
--- /dev/null
+++ b/tests/baselines/reference/moduleResolutionWithSymlinks_withOutDir.trace.json
@@ -0,0 +1,30 @@
+[
+    "======== Resolving module './library-a' from '/src/app.ts'. ========",
+    "Module resolution kind is not specified, using 'NodeJs'.",
+    "Loading module as file / folder, candidate module location '/src/library-a'.",
+    "File '/src/library-a.ts' does not exist.",
+    "File '/src/library-a.tsx' does not exist.",
+    "File '/src/library-a.d.ts' does not exist.",
+    "File '/src/library-a/package.json' does not exist.",
+    "File '/src/library-a/index.ts' exist - use it as a name resolution result.",
+    "======== Module name './library-a' was successfully resolved to '/src/library-a/index.ts'. ========",
+    "======== Resolving module './library-b' from '/src/app.ts'. ========",
+    "Module resolution kind is not specified, using 'NodeJs'.",
+    "Loading module as file / folder, candidate module location '/src/library-b'.",
+    "File '/src/library-b.ts' does not exist.",
+    "File '/src/library-b.tsx' does not exist.",
+    "File '/src/library-b.d.ts' does not exist.",
+    "File '/src/library-b/package.json' does not exist.",
+    "File '/src/library-b/index.ts' exist - use it as a name resolution result.",
+    "======== Module name './library-b' was successfully resolved to '/src/library-b/index.ts'. ========",
+    "======== Resolving module 'library-a' from '/src/library-b/index.ts'. ========",
+    "Module resolution kind is not specified, using 'NodeJs'.",
+    "Loading module 'library-a' from 'node_modules' folder.",
+    "File '/src/library-b/node_modules/library-a.ts' does not exist.",
+    "File '/src/library-b/node_modules/library-a.tsx' does not exist.",
+    "File '/src/library-b/node_modules/library-a.d.ts' does not exist.",
+    "File '/src/library-b/node_modules/library-a/package.json' does not exist.",
+    "File '/src/library-b/node_modules/library-a/index.ts' exist - use it as a name resolution result.",
+    "Resolving real path for '/src/library-b/node_modules/library-a/index.ts', result '/src/library-a/index.ts'",
+    "======== Module name 'library-a' was successfully resolved to '/src/library-a/index.ts'. ========"
+]
\ No newline at end of file
diff --git a/tests/baselines/reference/moduleResolutionWithSymlinks_withOutDir.types b/tests/baselines/reference/moduleResolutionWithSymlinks_withOutDir.types
new file mode 100644
index 00000000000..35fa2167920
--- /dev/null
+++ b/tests/baselines/reference/moduleResolutionWithSymlinks_withOutDir.types
@@ -0,0 +1,40 @@
+=== /src/app.ts ===
+import { MyClass } from "./library-a";
+>MyClass : typeof MyClass
+
+import { MyClass2 } from "./library-b";
+>MyClass2 : typeof MyClass
+
+let x: MyClass;
+>x : MyClass
+>MyClass : MyClass
+
+let y: MyClass2;
+>y : MyClass
+>MyClass2 : MyClass
+
+x = y;
+>x = y : MyClass
+>x : MyClass
+>y : MyClass
+
+y = x;
+>y = x : MyClass
+>y : MyClass
+>x : MyClass
+
+=== /src/library-a/index.ts ===
+// Same as moduleResolutionWithSymlinks.ts, but with outDir
+
+export class MyClass { private x: number; }
+>MyClass : MyClass
+>x : number
+
+=== /src/library-b/index.ts ===
+import {MyClass} from "library-a";
+>MyClass : typeof MyClass
+
+export { MyClass as MyClass2 }
+>MyClass : typeof MyClass
+>MyClass2 : typeof MyClass
+
diff --git a/tests/baselines/reference/pathMappingBasedModuleResolution3_node.trace.json b/tests/baselines/reference/pathMappingBasedModuleResolution3_node.trace.json
index ab7210d7d02..12a32edede2 100644
--- a/tests/baselines/reference/pathMappingBasedModuleResolution3_node.trace.json
+++ b/tests/baselines/reference/pathMappingBasedModuleResolution3_node.trace.json
@@ -5,13 +5,11 @@
     "Resolving module name 'folder2/file2' relative to base url 'c:/root' - 'c:/root/folder2/file2'.",
     "Loading module as file / folder, candidate module location 'c:/root/folder2/file2'.",
     "File 'c:/root/folder2/file2.ts' exist - use it as a name resolution result.",
-    "Resolving real path for 'c:/root/folder2/file2.ts', result 'c:/root/folder2/file2.ts'",
     "======== Module name 'folder2/file2' was successfully resolved to 'c:/root/folder2/file2.ts'. ========",
     "======== Resolving module './file3' from 'c:/root/folder2/file2.ts'. ========",
     "Explicitly specified module resolution kind: 'NodeJs'.",
     "Loading module as file / folder, candidate module location 'c:/root/folder2/file3'.",
     "File 'c:/root/folder2/file3.ts' exist - use it as a name resolution result.",
-    "Resolving real path for 'c:/root/folder2/file3.ts', result 'c:/root/folder2/file3.ts'",
     "======== Module name './file3' was successfully resolved to 'c:/root/folder2/file3.ts'. ========",
     "======== Resolving module 'file4' from 'c:/root/folder2/file2.ts'. ========",
     "Explicitly specified module resolution kind: 'NodeJs'.",
diff --git a/tests/baselines/reference/pathMappingBasedModuleResolution4_node.trace.json b/tests/baselines/reference/pathMappingBasedModuleResolution4_node.trace.json
index ab7210d7d02..12a32edede2 100644
--- a/tests/baselines/reference/pathMappingBasedModuleResolution4_node.trace.json
+++ b/tests/baselines/reference/pathMappingBasedModuleResolution4_node.trace.json
@@ -5,13 +5,11 @@
     "Resolving module name 'folder2/file2' relative to base url 'c:/root' - 'c:/root/folder2/file2'.",
     "Loading module as file / folder, candidate module location 'c:/root/folder2/file2'.",
     "File 'c:/root/folder2/file2.ts' exist - use it as a name resolution result.",
-    "Resolving real path for 'c:/root/folder2/file2.ts', result 'c:/root/folder2/file2.ts'",
     "======== Module name 'folder2/file2' was successfully resolved to 'c:/root/folder2/file2.ts'. ========",
     "======== Resolving module './file3' from 'c:/root/folder2/file2.ts'. ========",
     "Explicitly specified module resolution kind: 'NodeJs'.",
     "Loading module as file / folder, candidate module location 'c:/root/folder2/file3'.",
     "File 'c:/root/folder2/file3.ts' exist - use it as a name resolution result.",
-    "Resolving real path for 'c:/root/folder2/file3.ts', result 'c:/root/folder2/file3.ts'",
     "======== Module name './file3' was successfully resolved to 'c:/root/folder2/file3.ts'. ========",
     "======== Resolving module 'file4' from 'c:/root/folder2/file2.ts'. ========",
     "Explicitly specified module resolution kind: 'NodeJs'.",
diff --git a/tests/baselines/reference/pathMappingBasedModuleResolution5_node.trace.json b/tests/baselines/reference/pathMappingBasedModuleResolution5_node.trace.json
index 2efeefa24e5..f883b2afe36 100644
--- a/tests/baselines/reference/pathMappingBasedModuleResolution5_node.trace.json
+++ b/tests/baselines/reference/pathMappingBasedModuleResolution5_node.trace.json
@@ -7,7 +7,6 @@
     "Trying substitution '*', candidate module location: 'folder2/file1'.",
     "Loading module as file / folder, candidate module location 'c:/root/folder2/file1'.",
     "File 'c:/root/folder2/file1.ts' exist - use it as a name resolution result.",
-    "Resolving real path for 'c:/root/folder2/file1.ts', result 'c:/root/folder2/file1.ts'",
     "======== Module name 'folder2/file1' was successfully resolved to 'c:/root/folder2/file1.ts'. ========",
     "======== Resolving module 'folder3/file2' from 'c:/root/folder1/file1.ts'. ========",
     "Module resolution kind is not specified, using 'NodeJs'.",
@@ -26,7 +25,6 @@
     "Trying substitution 'generated/*', candidate module location: 'generated/folder3/file2'.",
     "Loading module as file / folder, candidate module location 'c:/root/generated/folder3/file2'.",
     "File 'c:/root/generated/folder3/file2.ts' exist - use it as a name resolution result.",
-    "Resolving real path for 'c:/root/generated/folder3/file2.ts', result 'c:/root/generated/folder3/file2.ts'",
     "======== Module name 'folder3/file2' was successfully resolved to 'c:/root/generated/folder3/file2.ts'. ========",
     "======== Resolving module 'components/file3' from 'c:/root/folder1/file1.ts'. ========",
     "Module resolution kind is not specified, using 'NodeJs'.",
@@ -42,7 +40,6 @@
     "File 'c:/root/shared/components/file3/index.ts' does not exist.",
     "File 'c:/root/shared/components/file3/index.tsx' does not exist.",
     "File 'c:/root/shared/components/file3/index.d.ts' exist - use it as a name resolution result.",
-    "Resolving real path for 'c:/root/shared/components/file3/index.d.ts', result 'c:/root/shared/components/file3/index.d.ts'",
     "======== Module name 'components/file3' was successfully resolved to 'c:/root/shared/components/file3/index.d.ts'. ========",
     "======== Resolving module 'file4' from 'c:/root/folder1/file1.ts'. ========",
     "Module resolution kind is not specified, using 'NodeJs'.",
diff --git a/tests/baselines/reference/pathMappingBasedModuleResolution6_node.trace.json b/tests/baselines/reference/pathMappingBasedModuleResolution6_node.trace.json
index 28e51a11915..7c5e76a2847 100644
--- a/tests/baselines/reference/pathMappingBasedModuleResolution6_node.trace.json
+++ b/tests/baselines/reference/pathMappingBasedModuleResolution6_node.trace.json
@@ -18,7 +18,6 @@
     "Loading 'project/file3' from the root dir 'c:/root/generated/src', candidate location 'c:/root/generated/src/project/file3'",
     "Loading module as file / folder, candidate module location 'c:/root/generated/src/project/file3'.",
     "File 'c:/root/generated/src/project/file3.ts' exist - use it as a name resolution result.",
-    "Resolving real path for 'c:/root/generated/src/project/file3.ts', result 'c:/root/generated/src/project/file3.ts'",
     "======== Module name './project/file3' was successfully resolved to 'c:/root/generated/src/project/file3.ts'. ========",
     "======== Resolving module '../file2' from 'c:/root/generated/src/project/file3.ts'. ========",
     "Module resolution kind is not specified, using 'NodeJs'.",
@@ -45,6 +44,5 @@
     "File 'c:/root/src/file2/index.ts' does not exist.",
     "File 'c:/root/src/file2/index.tsx' does not exist.",
     "File 'c:/root/src/file2/index.d.ts' exist - use it as a name resolution result.",
-    "Resolving real path for 'c:/root/src/file2/index.d.ts', result 'c:/root/src/file2/index.d.ts'",
     "======== Module name '../file2' was successfully resolved to 'c:/root/src/file2/index.d.ts'. ========"
 ]
\ No newline at end of file
diff --git a/tests/baselines/reference/pathMappingBasedModuleResolution7_node.trace.json b/tests/baselines/reference/pathMappingBasedModuleResolution7_node.trace.json
index 48633c85e3b..24139361b0b 100644
--- a/tests/baselines/reference/pathMappingBasedModuleResolution7_node.trace.json
+++ b/tests/baselines/reference/pathMappingBasedModuleResolution7_node.trace.json
@@ -18,7 +18,6 @@
     "Loading 'project/file2' from the root dir 'c:/root/generated/src', candidate location 'c:/root/generated/src/project/file2'",
     "Loading module as file / folder, candidate module location 'c:/root/generated/src/project/file2'.",
     "File 'c:/root/generated/src/project/file2.ts' exist - use it as a name resolution result.",
-    "Resolving real path for 'c:/root/generated/src/project/file2.ts', result 'c:/root/generated/src/project/file2.ts'",
     "======== Module name './project/file2' was successfully resolved to 'c:/root/generated/src/project/file2.ts'. ========",
     "======== Resolving module 'module3' from 'c:/root/src/file1.ts'. ========",
     "Module resolution kind is not specified, using 'NodeJs'.",
@@ -100,7 +99,6 @@
     "File 'c:/shared/module1/index.ts' does not exist.",
     "File 'c:/shared/module1/index.tsx' does not exist.",
     "File 'c:/shared/module1/index.d.ts' exist - use it as a name resolution result.",
-    "Resolving real path for 'c:/shared/module1/index.d.ts', result 'c:/shared/module1/index.d.ts'",
     "======== Module name 'module1' was successfully resolved to 'c:/shared/module1/index.d.ts'. ========",
     "======== Resolving module 'templates/module2' from 'c:/root/generated/src/project/file2.ts'. ========",
     "Module resolution kind is not specified, using 'NodeJs'.",
@@ -110,7 +108,6 @@
     "Trying substitution 'generated/src/templates/*', candidate module location: 'generated/src/templates/module2'.",
     "Loading module as file / folder, candidate module location 'c:/root/generated/src/templates/module2'.",
     "File 'c:/root/generated/src/templates/module2.ts' exist - use it as a name resolution result.",
-    "Resolving real path for 'c:/root/generated/src/templates/module2.ts', result 'c:/root/generated/src/templates/module2.ts'",
     "======== Module name 'templates/module2' was successfully resolved to 'c:/root/generated/src/templates/module2.ts'. ========",
     "======== Resolving module '../file3' from 'c:/root/generated/src/project/file2.ts'. ========",
     "Module resolution kind is not specified, using 'NodeJs'.",
@@ -137,6 +134,5 @@
     "File 'c:/root/src/file3/index.ts' does not exist.",
     "File 'c:/root/src/file3/index.tsx' does not exist.",
     "File 'c:/root/src/file3/index.d.ts' exist - use it as a name resolution result.",
-    "Resolving real path for 'c:/root/src/file3/index.d.ts', result 'c:/root/src/file3/index.d.ts'",
     "======== Module name '../file3' was successfully resolved to 'c:/root/src/file3/index.d.ts'. ========"
 ]
\ No newline at end of file
diff --git a/tests/baselines/reference/typeReferenceDirectives10.trace.json b/tests/baselines/reference/typeReferenceDirectives10.trace.json
index 61341afdab3..2dfd1fe0939 100644
--- a/tests/baselines/reference/typeReferenceDirectives10.trace.json
+++ b/tests/baselines/reference/typeReferenceDirectives10.trace.json
@@ -10,7 +10,6 @@
     "File '/ref.ts' does not exist.",
     "File '/ref.tsx' does not exist.",
     "File '/ref.d.ts' exist - use it as a name resolution result.",
-    "Resolving real path for '/ref.d.ts', result '/ref.d.ts'",
     "======== Module name './ref' was successfully resolved to '/ref.d.ts'. ========",
     "======== Resolving type reference directive 'lib', containing file '/__inferred type names__.ts', root directory '/types'. ========",
     "Resolving with primary search path '/types'",
diff --git a/tests/baselines/reference/typeReferenceDirectives11.trace.json b/tests/baselines/reference/typeReferenceDirectives11.trace.json
index 37fa7900a7c..862c941079a 100644
--- a/tests/baselines/reference/typeReferenceDirectives11.trace.json
+++ b/tests/baselines/reference/typeReferenceDirectives11.trace.json
@@ -3,7 +3,6 @@
     "Module resolution kind is not specified, using 'NodeJs'.",
     "Loading module as file / folder, candidate module location '/mod1'.",
     "File '/mod1.ts' exist - use it as a name resolution result.",
-    "Resolving real path for '/mod1.ts', result '/mod1.ts'",
     "======== Module name './mod1' was successfully resolved to '/mod1.ts'. ========",
     "======== Resolving type reference directive 'lib', containing file '/__inferred type names__.ts', root directory '/types'. ========",
     "Resolving with primary search path '/types'",
diff --git a/tests/baselines/reference/typeReferenceDirectives12.trace.json b/tests/baselines/reference/typeReferenceDirectives12.trace.json
index 1024b0cdef3..627ad13588a 100644
--- a/tests/baselines/reference/typeReferenceDirectives12.trace.json
+++ b/tests/baselines/reference/typeReferenceDirectives12.trace.json
@@ -3,13 +3,11 @@
     "Module resolution kind is not specified, using 'NodeJs'.",
     "Loading module as file / folder, candidate module location '/main'.",
     "File '/main.ts' exist - use it as a name resolution result.",
-    "Resolving real path for '/main.ts', result '/main.ts'",
     "======== Module name './main' was successfully resolved to '/main.ts'. ========",
     "======== Resolving module './mod1' from '/mod2.ts'. ========",
     "Module resolution kind is not specified, using 'NodeJs'.",
     "Loading module as file / folder, candidate module location '/mod1'.",
     "File '/mod1.ts' exist - use it as a name resolution result.",
-    "Resolving real path for '/mod1.ts', result '/mod1.ts'",
     "======== Module name './mod1' was successfully resolved to '/mod1.ts'. ========",
     "======== Resolving type reference directive 'lib', containing file '/mod1.ts', root directory '/types'. ========",
     "Resolving with primary search path '/types'",
@@ -20,7 +18,6 @@
     "Module resolution kind is not specified, using 'NodeJs'.",
     "Loading module as file / folder, candidate module location '/main'.",
     "File '/main.ts' exist - use it as a name resolution result.",
-    "Resolving real path for '/main.ts', result '/main.ts'",
     "======== Module name './main' was successfully resolved to '/main.ts'. ========",
     "======== Resolving type reference directive 'lib', containing file '/__inferred type names__.ts', root directory '/types'. ========",
     "Resolving with primary search path '/types'",
diff --git a/tests/baselines/reference/typeReferenceDirectives13.trace.json b/tests/baselines/reference/typeReferenceDirectives13.trace.json
index 61341afdab3..2dfd1fe0939 100644
--- a/tests/baselines/reference/typeReferenceDirectives13.trace.json
+++ b/tests/baselines/reference/typeReferenceDirectives13.trace.json
@@ -10,7 +10,6 @@
     "File '/ref.ts' does not exist.",
     "File '/ref.tsx' does not exist.",
     "File '/ref.d.ts' exist - use it as a name resolution result.",
-    "Resolving real path for '/ref.d.ts', result '/ref.d.ts'",
     "======== Module name './ref' was successfully resolved to '/ref.d.ts'. ========",
     "======== Resolving type reference directive 'lib', containing file '/__inferred type names__.ts', root directory '/types'. ========",
     "Resolving with primary search path '/types'",
diff --git a/tests/baselines/reference/typeReferenceDirectives5.trace.json b/tests/baselines/reference/typeReferenceDirectives5.trace.json
index 61341afdab3..2dfd1fe0939 100644
--- a/tests/baselines/reference/typeReferenceDirectives5.trace.json
+++ b/tests/baselines/reference/typeReferenceDirectives5.trace.json
@@ -10,7 +10,6 @@
     "File '/ref.ts' does not exist.",
     "File '/ref.tsx' does not exist.",
     "File '/ref.d.ts' exist - use it as a name resolution result.",
-    "Resolving real path for '/ref.d.ts', result '/ref.d.ts'",
     "======== Module name './ref' was successfully resolved to '/ref.d.ts'. ========",
     "======== Resolving type reference directive 'lib', containing file '/__inferred type names__.ts', root directory '/types'. ========",
     "Resolving with primary search path '/types'",
diff --git a/tests/baselines/reference/typeReferenceDirectives8.trace.json b/tests/baselines/reference/typeReferenceDirectives8.trace.json
index 37fa7900a7c..862c941079a 100644
--- a/tests/baselines/reference/typeReferenceDirectives8.trace.json
+++ b/tests/baselines/reference/typeReferenceDirectives8.trace.json
@@ -3,7 +3,6 @@
     "Module resolution kind is not specified, using 'NodeJs'.",
     "Loading module as file / folder, candidate module location '/mod1'.",
     "File '/mod1.ts' exist - use it as a name resolution result.",
-    "Resolving real path for '/mod1.ts', result '/mod1.ts'",
     "======== Module name './mod1' was successfully resolved to '/mod1.ts'. ========",
     "======== Resolving type reference directive 'lib', containing file '/__inferred type names__.ts', root directory '/types'. ========",
     "Resolving with primary search path '/types'",
diff --git a/tests/baselines/reference/typeReferenceDirectives9.trace.json b/tests/baselines/reference/typeReferenceDirectives9.trace.json
index 1024b0cdef3..627ad13588a 100644
--- a/tests/baselines/reference/typeReferenceDirectives9.trace.json
+++ b/tests/baselines/reference/typeReferenceDirectives9.trace.json
@@ -3,13 +3,11 @@
     "Module resolution kind is not specified, using 'NodeJs'.",
     "Loading module as file / folder, candidate module location '/main'.",
     "File '/main.ts' exist - use it as a name resolution result.",
-    "Resolving real path for '/main.ts', result '/main.ts'",
     "======== Module name './main' was successfully resolved to '/main.ts'. ========",
     "======== Resolving module './mod1' from '/mod2.ts'. ========",
     "Module resolution kind is not specified, using 'NodeJs'.",
     "Loading module as file / folder, candidate module location '/mod1'.",
     "File '/mod1.ts' exist - use it as a name resolution result.",
-    "Resolving real path for '/mod1.ts', result '/mod1.ts'",
     "======== Module name './mod1' was successfully resolved to '/mod1.ts'. ========",
     "======== Resolving type reference directive 'lib', containing file '/mod1.ts', root directory '/types'. ========",
     "Resolving with primary search path '/types'",
@@ -20,7 +18,6 @@
     "Module resolution kind is not specified, using 'NodeJs'.",
     "Loading module as file / folder, candidate module location '/main'.",
     "File '/main.ts' exist - use it as a name resolution result.",
-    "Resolving real path for '/main.ts', result '/main.ts'",
     "======== Module name './main' was successfully resolved to '/main.ts'. ========",
     "======== Resolving type reference directive 'lib', containing file '/__inferred type names__.ts', root directory '/types'. ========",
     "Resolving with primary search path '/types'",
diff --git a/tests/cases/compiler/moduleResolutionWithSymlinks.ts b/tests/cases/compiler/moduleResolutionWithSymlinks.ts
index 4819b68ffc6..069f11f85da 100644
--- a/tests/cases/compiler/moduleResolutionWithSymlinks.ts
+++ b/tests/cases/compiler/moduleResolutionWithSymlinks.ts
@@ -1,6 +1,8 @@
-// @module: commonjs
+// When symlinked files are in node_modules, they are resolved with realpath;
+// so a linked file does not create a duplicate SourceFile of the real one.
 // @noImplicitReferences: true
 // @traceResolution: true
+// @fullEmitPaths: true
 
 // @filename: /src/library-a/index.ts
 // @symlink: /src/library-b/node_modules/library-a/index.ts
@@ -17,4 +19,23 @@ import { MyClass2 } from "./library-b";
 let x: MyClass;
 let y: MyClass2;
 x = y;
-y = x;
\ No newline at end of file
+y = x;
+
+/*
+# To reproduce in a real project:
+
+mkdir src; cd src
+mkdir library-a
+echo 'export class MyClass { private x: number; }' > library-a/index.ts
+
+mkdir library-b; cd library-b
+echo 'import {MyClass} from "library-a"; export { MyClass as MyClass2 }' > index.ts
+mkdir node_modules; cd node_modules
+
+ln -s ../../library-a library-a # Linux
+# Windows: open command prompt as administrator and run: mklink /D library-a ..\..\library-a
+
+cd ../.. # back to src
+echo 'import { MyClass } from "./library-a"; import { MyClass2 } from "./library-b"; let x: MyClass; let y: MyClass2; x = y; y = x;' > app.ts
+tsc app.ts # Should write to library-a/index.js, library-b/index.js, and app.js
+*/
diff --git a/tests/cases/compiler/moduleResolutionWithSymlinks_notInNodeModules.ts b/tests/cases/compiler/moduleResolutionWithSymlinks_notInNodeModules.ts
new file mode 100644
index 00000000000..f861813942f
--- /dev/null
+++ b/tests/cases/compiler/moduleResolutionWithSymlinks_notInNodeModules.ts
@@ -0,0 +1,40 @@
+// When symlinked files are not in node_modules, realpath is not used.
+// A symlink file acts like the real thing. So, 2 symlinks act like 2 different files.
+// See GH#10364. 
+// @noImplicitReferences: true
+// @traceResolution: true
+// @fullEmitPaths: true
+
+// @filename: /shared/abc.ts
+// @symlink: /src/shared/abc.ts,/src/shared2/abc.ts
+export const x = 0;
+
+// @filename: /src/app.ts
+import { x } from "./shared/abc";
+import { x as x2 } from "./shared2/abc";
+x + x2;
+
+// @filename: /src/tsconfig.json
+{
+    "compilerOptions": {
+        "outDir": "bin"
+    }
+}
+
+/*
+# To reproduce in a real project:
+
+mkdir shared
+echo 'export const x = 0;' > shared/abc.ts
+
+mkdir src; cd src
+echo 'import { x } from "./shared/abc"; import { x as x2 } from "./shared2/abc"; x + x2;' > app.ts
+
+ln -s ../shared ./shared; ln -s ../shared ./shared2 # Linux
+# Windows: Open command prompt as administrator and run: `mklink /D shared ..\shared; mklink /D shared2 ..\shared`
+
+echo '{ "compilerOptions": { "outDir": "bin" } }' > tsconfig.json
+node ../../../../TypeScript/built/local/tsc.js
+
+# Should create `bin/app.js`, `bin/shared/abc.js`, and `bin/shared2/abc.js`
+*/
diff --git a/tests/cases/compiler/moduleResolutionWithSymlinks_withOutDir.ts b/tests/cases/compiler/moduleResolutionWithSymlinks_withOutDir.ts
new file mode 100644
index 00000000000..c17e9091de4
--- /dev/null
+++ b/tests/cases/compiler/moduleResolutionWithSymlinks_withOutDir.ts
@@ -0,0 +1,22 @@
+// Same as moduleResolutionWithSymlinks.ts, but with outDir
+// @noImplicitReferences: true
+// @traceResolution: true
+// @fullEmitPaths: true
+// @outDir: /src/bin
+
+// @filename: /src/library-a/index.ts
+// @symlink: /src/library-b/node_modules/library-a/index.ts
+export class MyClass { private x: number; }
+
+// @filename: /src/library-b/index.ts
+import {MyClass} from "library-a";
+export { MyClass as MyClass2 }
+
+// @filename: /src/app.ts
+import { MyClass } from "./library-a";
+import { MyClass2 } from "./library-b";
+
+let x: MyClass;
+let y: MyClass2;
+x = y;
+y = x;