Remove unused exports & dead code (using Knip) (microsoft#56817)

Co-authored-by: Jake Bailey <5341706+jakebailey@users.noreply.github.com>

Author: webpro

.github/workflows/ci.yml

@@ -83,6 +83,20 @@ jobs:
       - name: Linter
         run: npm run lint
 
+  knip:
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@b4ffde65f46336ab88eb53be808477a3936bae11 # v4.1.1
+      - uses: actions/setup-node@60edb5dd545a775178f52524783378180af0d1f8 # v4.0.2
+        with:
+          node-version: '*'
+          check-latest: true
+      - run: npm ci
+
+      - name: Unused exports
+        run: npm run knip
+
   format:
     runs-on: ubuntu-latest
 

Herebyfile.mjs

@@ -565,6 +565,13 @@ export const checkFormat = task({
     run: () => exec(process.execPath, ["node_modules/dprint/bin.js", "check"], { ignoreStdout: true }),
 });
 
+export const knip = task({
+    name: "knip",
+    description: "Runs knip.",
+    dependencies: [generateDiagnostics],
+    run: () => exec(process.execPath, ["node_modules/knip/bin/knip.js", "--tags=+internal,-knipignore", "--exclude=duplicates,enumMembers", ...(cmdLineOptions.fix ? ["--fix"] : [])]),
+});
+
 const { main: cancellationToken, watch: watchCancellationToken } = entrypointBuildTask({
     name: "cancellation-token",
     project: "src/cancellationToken",

knip.jsonc

@@ -0,0 +1,38 @@
+{
+    "$schema": "https://unpkg.com/knip@5/schema.json",
+    "includeEntryExports": true,
+    "entry": [
+        "Herebyfile.mjs",
+        "src/cancellationToken/cancellationToken.ts",
+        "src/testRunner/_namespaces/Harness.ts",
+        "src/tsc/tsc.ts",
+        "src/tsserver/server.ts",
+        "src/typescript/typescript.ts",
+        "src/typingsInstaller/nodeTypingsInstaller.ts",
+        "src/watchGuard/watchGuard.ts",
+
+        "src/testRunner/tests.ts",
+        "src/testRunner/_namespaces/Harness.ts",
+
+        // The rest of the entry files, mostly to track used dependencies:
+        ".eslint-plugin-local.cjs",
+        ".gulp.js",
+        "scripts/eslint/{rules,tests}/*.cjs",
+        "scripts/*.{cjs,mjs}"
+    ],
+    "project": [
+        "src/**",
+        "scripts/**",
+        "!src/lib/**/*.d.ts"
+    ],
+    "ignore": [
+        "scripts/failed-tests.d.cts"
+    ],
+    "ignoreDependencies": ["c8", "eslint-formatter-autolinkable-stylish", "mocha-fivemat-progress-reporter"],
+    "ignoreExportsUsedInFile": {
+        "enum": true,
+        "interface": true,
+        "type": true
+    },
+    "mocha": false
+}