Add tests when realpath supresses the casing error

src/testRunner/tsconfig.json

@@ -151,6 +151,7 @@
         "unittests/tsc/cancellationToken.ts",
         "unittests/tsc/composite.ts",
         "unittests/tsc/declarationEmit.ts",
+        "unittests/tsc/forceConsistentCasingInFileNames.ts",
         "unittests/tsc/incremental.ts",
         "unittests/tsc/listFilesOnly.ts",
         "unittests/tsc/projectReferences.ts",

src/testRunner/unittests/tsc/forceConsistentCasingInFileNames.ts

@@ -0,0 +1,18 @@
+namespace ts {
+    describe("unittests:: tsc:: forceConsistentCasingInFileNames::", () => {
+        verifyTsc({
+            scenario: "forceConsistentCasingInFileNames",
+            subScenario: "with relative and non relative file resolutions",
+            commandLineArgs: ["/src/project/src/struct.d.ts", "--forceConsistentCasingInFileNames", "--explainFiles"],
+            fs: () => loadProjectFromFiles({
+                "/src/project/src/struct.d.ts": Utils.dedent`
+                    import * as xs1 from "fp-ts/lib/Struct";
+                    import * as xs2 from "fp-ts/lib/struct";
+                    import * as xs3 from "./Struct";
+                    import * as xs4 from "./struct";
+                `,
+                "/src/project/node_modules/fp-ts/lib/struct.d.ts": `export function foo(): void`,
+            }),
+        });
+    });
+}

tests/baselines/reference/tsc/forceConsistentCasingInFileNames/with-relative-and-non-relative-file-resolutions.js

@@ -0,0 +1,59 @@
+Input::
+//// [/lib/lib.d.ts]
+/// <reference no-default-lib="true"/>
+interface Boolean {}
+interface Function {}
+interface CallableFunction {}
+interface NewableFunction {}
+interface IArguments {}
+interface Number { toExponential: any; }
+interface Object {}
+interface RegExp {}
+interface String { charAt: any; }
+interface Array<T> { length: number; [n: number]: T; }
+interface ReadonlyArray<T> {}
+declare const console: { log(msg: any): void; };
+
+//// [/src/project/node_modules/fp-ts/lib/struct.d.ts]
+export function foo(): void
+
+//// [/src/project/src/struct.d.ts]
+import * as xs1 from "fp-ts/lib/Struct";
+import * as xs2 from "fp-ts/lib/struct";
+import * as xs3 from "./Struct";
+import * as xs4 from "./struct";
+
+
+
+
+Output::
+/lib/tsc /src/project/src/struct.d.ts --forceConsistentCasingInFileNames --explainFiles
+src/project/src/struct.d.ts:3:22 - error TS1149: File name '/src/project/src/Struct.d.ts' differs from already included file name '/src/project/src/struct.d.ts' only in casing.
+  The file is in the program because:
+    Root file specified for compilation
+    Imported via "./Struct" from file '/src/project/src/struct.d.ts'
+    Imported via "./struct" from file '/src/project/src/struct.d.ts'
+
+3 import * as xs3 from "./Struct";
+                       ~~~~~~~~~~
+
+  src/project/src/struct.d.ts:4:22
+    4 import * as xs4 from "./struct";
+                           ~~~~~~~~~~
+    File is included via import here.
+
+lib/lib.d.ts
+  Default library for target 'es3'
+src/project/node_modules/fp-ts/lib/struct.d.ts
+  Imported via "fp-ts/lib/Struct" from file 'src/project/src/struct.d.ts'
+  Imported via "fp-ts/lib/struct" from file 'src/project/src/struct.d.ts'
+src/project/src/struct.d.ts
+  Root file specified for compilation
+  Imported via "./Struct" from file 'src/project/src/struct.d.ts'
+  Imported via "./struct" from file 'src/project/src/struct.d.ts'
+
+Found 1 error in src/project/src/struct.d.ts:3
+
+exitCode:: ExitStatus.DiagnosticsPresent_OutputsGenerated
+
+