fix: restore a working test-watch

Pointing test-watch straight at vitest was wrong: vitest runs the compiled
output, so a .ts edit produces nothing for it to react to. The watch loop
needs tsc re-emitting alongside it, which is what the old
dev/tsc-to-mocha-watch.js was doing.

dev/tsc-to-vitest-watch.js runs both, and is smaller than its predecessor
because vitest reruns itself once the .js changes - it doesn't need to be
driven the way mocha did. It passes --watch explicitly, since vitest only
infers watch mode from a TTY and would otherwise run once and exit, taking
tsc down with it.

Also un-ignores dev/*.js, which .gitignore's blanket *.js rule would
otherwise have kept out of the repo.

Author: edusperoni

.gitignore

@@ -88,5 +88,7 @@ lib/common/test-reports.xml
 !lib/common/scripts/**
 config/test-deps-versions-generated.json
 !scripts/*.js
+!dev/*.js
+
 # build output
 /dist

dev/tsc-to-vitest-watch.js

@@ -0,0 +1,37 @@
+// Run "tsc" in watch mode alongside vitest. Vitest runs the compiled output,
+// so on its own it never notices a .ts edit - tsc has to re-emit first, and
+// vitest picks the change up from there.
+
+const { spawn } = require("child_process");
+
+// shell: true so the node_modules/.bin shims resolve on Windows as well
+const spawnOptions = { stdio: "inherit", shell: true };
+
+const children = [
+	// --preserveWatchOutput keeps tsc from clearing the screen and wiping the
+	// test results out from under you on every recompile
+	spawn("tsc", ["--watch", "--preserveWatchOutput"], spawnOptions),
+	// --watch explicitly: vitest only infers watch mode when stdout is a TTY,
+	// and would otherwise run once and exit, taking tsc down with it
+	spawn("vitest", ["--watch"], spawnOptions),
+];
+
+let shuttingDown = false;
+
+function shutdown() {
+	if (shuttingDown) {
+		return;
+	}
+	shuttingDown = true;
+	for (const child of children) {
+		child.kill("SIGINT");
+	}
+}
+
+process.on("SIGINT", shutdown);
+process.on("SIGTERM", shutdown);
+
+for (const child of children) {
+	// if either side dies, don't leave the other running in the background
+	child.on("exit", shutdown);
+}

package.json

@@ -26,7 +26,7 @@
     "prepack": "node scripts/guard-root-pack.js",
     "docs-jekyll": "node scripts/build-docs.js",
     "tsc": "tsc",
-    "test-watch": "vitest",
+    "test-watch": "node ./dev/tsc-to-vitest-watch.js",
     "changelog": "conventional-changelog -p angular -i CHANGELOG.md -s",
     "prettier": "prettier --write ./lib/**/*{.ts,.d.ts} ./test/**/*{.ts,.d.ts}",
     "build.release": "npm run clean.build && tsc -p tsconfig.release.json && node scripts/generate-test-deps.js && node scripts/copy-assets.js --release && node scripts/set-ga-id.js live --dir dist && node scripts/set-ga-id.js verify --dir dist",