From b596c6148f33970bed91d84cafa569cb9dfefab3 Mon Sep 17 00:00:00 2001
From: Nathan Shively-Sanders <293473+sandersn@users.noreply.github.com>
Date: Fri, 30 Jul 2021 09:11:54 -0700
Subject: [PATCH] Scribbles, nothing works yet

---
 src/compiler/emitter.ts                                 | 9 +++++++++
 src/testRunner/unittests/tsbuild/declarationEmit.ts     | 7 +++++++
 src/testRunner/unittests/tsbuild/emitDeclarationOnly.ts | 2 ++
 src/testRunner/unittests/tsbuild/outFile.ts             | 3 +++
 4 files changed, 21 insertions(+)

diff --git a/src/compiler/emitter.ts b/src/compiler/emitter.ts
index 5667e792b46..b83877b5ec6 100644
--- a/src/compiler/emitter.ts
+++ b/src/compiler/emitter.ts
@@ -438,6 +438,8 @@ namespace ts {
             if (bundleBuildInfo) bundleBuildInfo.js = printer.bundleFileInfo;
         }
 
+        const horrible: Record<string, readonly SourceFile[]> = {}
+
         function emitDeclarationFileOrBundle(
             sourceFileOrBundle: SourceFile | Bundle | undefined,
             declarationFilePath: string | undefined,
@@ -449,6 +451,13 @@ namespace ts {
                 return;
             }
             const sourceFiles = isSourceFile(sourceFileOrBundle) ? [sourceFileOrBundle] : sourceFileOrBundle.sourceFiles;
+            const key = sourceFiles.map(f => f.fileName).join("|")
+            console.log(key)
+            horrible[key] = sourceFiles
+            // Let's do this WRONG
+            // 1. cache with key=filesForEmit, value=[emit, diagnostics]
+            // 2. include custom transformers in the key, plus "other api things" (??)
+            // Afterward, need to measure performance to see which projects this helps/how much. Ask Andrew about this.
             const filesForEmit = forceDtsEmit ? sourceFiles : filter(sourceFiles, isSourceFileNotJson);
             // Setup and perform the transformation to retrieve declarations from the input files
             const inputListOrBundle = outFile(compilerOptions) ? [factory.createBundle(filesForEmit, !isSourceFile(sourceFileOrBundle) ? sourceFileOrBundle.prepends : undefined)] : filesForEmit;
diff --git a/src/testRunner/unittests/tsbuild/declarationEmit.ts b/src/testRunner/unittests/tsbuild/declarationEmit.ts
index 122912e026d..fb61e8932b4 100644
--- a/src/testRunner/unittests/tsbuild/declarationEmit.ts
+++ b/src/testRunner/unittests/tsbuild/declarationEmit.ts
@@ -114,5 +114,12 @@ export function fn4() {
             }),
             commandLineArgs: ["--b", "/src/packages/pkg2/tsconfig.json", "--verbose"]
         });
+        verifyTsc({
+            scenario: "doubleEmit",
+            subScenario: "cache declaration emit from build",
+            fs: () => loadProjectFromFiles({
+            }),
+            commandLineArgs: ["--b", "/src/packages/pkg2/tsconfig.json", "--verbose"]
+        });
     });
 }
diff --git a/src/testRunner/unittests/tsbuild/emitDeclarationOnly.ts b/src/testRunner/unittests/tsbuild/emitDeclarationOnly.ts
index c673cd11bcd..31327105483 100644
--- a/src/testRunner/unittests/tsbuild/emitDeclarationOnly.ts
+++ b/src/testRunner/unittests/tsbuild/emitDeclarationOnly.ts
@@ -8,6 +8,8 @@ namespace ts {
             projFs = undefined!;
         });
 
+        // This is pretty close but the example only has one project. Still it's worth debugging it to see.
+        // (for initial debugging, it's STILl probably easier to attach to ~/dmp/buildbasic/test though)
         function verifyEmitDeclarationOnly(disableMap?: true) {
             verifyTscSerializedIncrementalEdits({
                 subScenario: `only dts output in circular import project with emitDeclarationOnly${disableMap ? "" : " and declarationMap"}`,
diff --git a/src/testRunner/unittests/tsbuild/outFile.ts b/src/testRunner/unittests/tsbuild/outFile.ts
index 4ebcd2e7001..ee756b1ca23 100644
--- a/src/testRunner/unittests/tsbuild/outFile.ts
+++ b/src/testRunner/unittests/tsbuild/outFile.ts
@@ -201,6 +201,9 @@ namespace ts {
             modifyFs: fs => replaceText(fs, sources[Project.third][Source.config], `"composite": true,`, ""),
         });
 
+        it("only generates declaration emit once on subsequent edits and recompiles", () => {
+        })
+
         it("rebuilds completely when version in tsbuildinfo doesnt match ts version", () => {
             const { fs, tick } = getFsWithTime(outFileFs);
             const host = fakes.SolutionBuilderHost.create(fs);