[test-dist-not-imported-from-src] Add a regression test for TypeScrip…

…t autocompletions from dist.

This is a workaround to prevent a regression for microsoft/TypeScript#47184
If microsoft/TypeScript#35395 (Exclude specific files from auto import suggestions) is implemented, we should just use that instead.

.github/workflows/build.yml

@@ -37,4 +37,5 @@ jobs:
       - run: make build-site-experiments
       - run: make test-dist-experiments
       - run: make test-dist-esm-parcel
+      - run: make test-dist-not-imported-from-src
       - run: make clean

package.json

@@ -61,6 +61,7 @@
     "test-dist-esm-parcel": "node ./script/test/dist/esm/parcel/main.js",
     "test-dist-esm-perf": "node script/test/dist/esm/perf/*.mjs",
     "test-dist-experiments": "node ./script/test/dist/experiments/main.js",
+    "test-dist-not-imported-from-src": "node ./script/test/dist/not-imported-from-src/main.js",
     "test-import-restrictions": "node ./script/test/import-restrictions/main.js",
     "test-jest": "npx jest --collectCoverage",
     "test-tsc": "npm run build-types && npx tsc --project ./tsconfig.json",

script/test/dist/not-imported-from-src/main.js

@@ -0,0 +1,48 @@
+import { exit, stderr } from "process";
+import { execPromise } from "../../../lib/execPromise.js";
+
+// Test that the `dist` dir is not imported from the source (which causes unwanted autocompletion in VSCode).
+// In theory we could test this together with import restrictions, but `npx tsc --explainFiles` lets us test directly against the completions.
+
+await execPromise("make build"); // TODO: check for full expected build without compiling from scratch.
+
+let output;
+try {
+  output = await execPromise("npx tsc --explainFiles -p ./tsconfig.json");
+} catch (e) {
+  stderr.write(
+    "`npx tsc --explainFiles` failed. Please run `make test-tsc` to debug.",
+  );
+  exit(1);
+}
+const files = {};
+let currentFile = null;
+for (const line of output.split("\n")) {
+  if (currentFile === null || !line.startsWith("  ")) {
+    currentFile = {
+      path: line,
+      from: [],
+    };
+    files[line] = currentFile;
+  } else {
+    if (!line.includes("from file 'dist")) {
+      // This theoretically has false positics, but it's good enough for us in practice.
+      currentFile.anyNotImportedFromDist = true;
+    }
+    currentFile.from.push(line);
+  }
+}
+
+for (const file of Object.values(files)) {
+  if (file.path.startsWith(".")) {
+    stderr.write(stderr, "Did not expect relative path:\n");
+    stderr.write(stderr, file);
+    exit(1);
+  }
+  if (file.path.startsWith("dist/") && file.anyNotImportedFromDist) {
+    stderr.write("Imports from the `dist` dir are not allowed:\n");
+    stderr.write(file.path + "\n");
+    stderr.write(file.from.join("\n"));
+    exit(1);
+  }
+}