Treat loaded snapshot files as test dependencies

This enables the watcher to rerun the correct test when a snapshot file
is modified.

lib/process-adapter.js

@@ -94,7 +94,7 @@ exports.installDependencyTracking = (dependencies, testPath) => {
 
 		require.extensions[ext] = (module, filename) => {
 			if (filename !== testPath) {
-				dependencies.push(filename);
+				dependencies.add(filename);
 			}
 
 			wrappedHandler(module, filename);

lib/runner.js

@@ -188,6 +188,7 @@ class Runner extends EventEmitter {
 			const dir = path.join(path.dirname(this.file), '__snapshots__');
 			const relFile = path.relative(this.projectDir, this.file);
 			this.snapshots = snapshotManager.load(dir, name, relFile, this.updateSnapshots);
+			this.emit('dependency', this.snapshots.snapPath);
 		}
 
 		return this.snapshots.compare(options);

lib/snapshot-manager.js

@@ -286,6 +286,7 @@ class Manager {
 		this.relFile = options.relFile;
 		this.reportFile = options.reportFile;
 		this.snapFile = options.snapFile;
+		this.snapPath = options.snapPath;
 		this.snapshotsByHash = options.snapshotsByHash;
 
 		this.hasChanges = false;
@@ -336,7 +337,7 @@ class Manager {
 			return null;
 		}
 
-		const snapPath = path.join(this.dir, this.snapFile);
+		const snapPath = this.snapPath;
 		const buffer = encodeSnapshots(this.snapshotsByHash);
 
 		const reportPath = path.join(this.dir, this.reportFile);
@@ -356,12 +357,12 @@ class Manager {
 function load(dir, name, relFile, updating) {
 	const reportFile = `${name}.md`;
 	const snapFile = `${name}.snap`;
+	const snapPath = path.join(dir, snapFile);
 
 	let appendOnly = !updating;
 	let snapshotsByHash;
 
 	if (!updating) {
-		const snapPath = path.join(dir, snapFile);
 		const buffer = tryRead(snapPath);
 		if (buffer) {
 			snapshotsByHash = decodeSnapshots(buffer, snapPath);
@@ -376,6 +377,7 @@ function load(dir, name, relFile, updating) {
 		relFile,
 		reportFile,
 		snapFile,
+		snapPath,
 		snapshotsByHash: snapshotsByHash || new Map()
 	});
 }

lib/test-worker.js

@@ -39,7 +39,7 @@ adapter.installPrecompilerHook();
 
 const testPath = opts.file;
 
-const dependencies = [];
+const dependencies = new Set();
 adapter.installDependencyTracking(dependencies, testPath);
 
 const touchedFiles = new Set();
@@ -48,6 +48,9 @@ const touchedFiles = new Set();
 let runner = null;
 exports.setRunner = newRunner => {
 	runner = newRunner;
+	runner.on('dependency', file => {
+		dependencies.add(file);
+	});
 	runner.on('touched', files => {
 		for (const file of files) {
 			touchedFiles.add(file);
@@ -132,7 +135,10 @@ process.on('ava-teardown', () => {
 	// set of dependencies is included no matter how the process exits, unless
 	// it flat out crashes. Also include any files that AVA touched during the
 	// test run. This allows the watcher to ignore modifications to those files.
-	adapter.send('teardown', {dependencies, touchedFiles: Array.from(touchedFiles)});
+	adapter.send('teardown', {
+		dependencies: Array.from(dependencies),
+		touchedFiles: Array.from(touchedFiles)
+	});
 });
 
 process.on('ava-exit', () => {

test/cli.js

@@ -333,6 +333,34 @@ test('watcher does not rerun test files when they write snapshot files', t => {
 	});
 });
 
+test('watcher reruns test files when snapshot dependencies change', t => {
+	let killed = false;
+
+	const child = execCli(['--verbose', '--watch', '--update-snapshots', 'test.js'], {dirname: 'fixture/snapshots'}, err => {
+		t.ok(killed);
+		t.ifError(err);
+		t.end();
+	});
+
+	let buffer = '';
+	let passedFirst = false;
+	child.stderr.on('data', str => {
+		buffer += str;
+		if (/2 tests passed/.test(buffer)) {
+			buffer = '';
+			if (passedFirst) {
+				child.kill();
+				killed = true;
+			} else {
+				passedFirst = true;
+				setTimeout(() => {
+					touch.sync(path.join(__dirname, 'fixture/snapshots/__snapshots__/test.js.snap'));
+				}, 500);
+			}
+		}
+	});
+});
+
 test('`"tap": true` config is ignored when --watch is given', t => {
 	let killed = false;