Make .only sticky in watch mode

api.js

@@ -106,6 +106,8 @@ Api.prototype._handleTeardown = function (data) {
 };
 
 Api.prototype._handleStats = function (stats) {
+	this.emit('stats', stats);
+
 	if (this.hasExclusive && !stats.hasExclusive) {
 		return;
 	}
@@ -165,10 +167,15 @@ Api.prototype._prefixTitle = function (file) {
 	return prefix;
 };
 
-Api.prototype.run = function (files) {
+Api.prototype.run = function (files, options) {
 	var self = this;
 
 	this._reset();
+
+	if (options && options.runOnlyExclusive) {
+		this.hasExclusive = true;
+	}
+
 	return handlePaths(files, this.excludePatterns)
 		.map(function (file) {
 			return path.resolve(file);

lib/watcher.js

@@ -39,14 +39,29 @@ function Watcher(logger, api, files, sources) {
 	this.isTest = makeTestMatcher(files, api.excludePatterns);
 	this.run = function (specificFiles) {
 		logger.reset();
-		this.busy = api.run(specificFiles || files).then(function () {
+
+		var runOnlyExclusive = false;
+		if (specificFiles) {
+			var exclusiveFiles = specificFiles.filter(function (file) {
+				return this.filesWithExclusiveTests.indexOf(file) !== -1;
+			}, this);
+
+			runOnlyExclusive = exclusiveFiles.length !== this.filesWithExclusiveTests.length;
+		}
+
+		this.busy = api.run(specificFiles || files, {
+			runOnlyExclusive: runOnlyExclusive
+		}).then(function () {
 			logger.finish();
 		}, rethrowAsync);
 	};
 
 	this.testDependencies = [];
 	this.trackTestDependencies(api, sources);
 
+	this.filesWithExclusiveTests = [];
+	this.trackExclusivity(api);
+
 	this.dirtyStates = {};
 	this.watchFiles(files, sources);
 	this.rerunAll();
@@ -85,12 +100,6 @@ Watcher.prototype.trackTestDependencies = function (api, sources) {
 	});
 };
 
-Watcher.prototype.removeUnlinkedTestDependencies = function (unlinkedTests) {
-	unlinkedTests.forEach(function (testFile) {
-		this.updateTestDependencies(testFile, []);
-	}, this);
-};
-
 Watcher.prototype.updateTestDependencies = function (file, sources) {
 	if (sources.length === 0) {
 		this.testDependencies = this.testDependencies.filter(function (dep) {
@@ -113,6 +122,30 @@ Watcher.prototype.updateTestDependencies = function (file, sources) {
 	}
 };
 
+Watcher.prototype.trackExclusivity = function (api) {
+	var self = this;
+	api.on('stats', function (stats) {
+		self.updateExclusivity(stats.file, stats.hasExclusive);
+	});
+};
+
+Watcher.prototype.updateExclusivity = function (file, hasExclusiveTests) {
+	var index = this.filesWithExclusiveTests.indexOf(file);
+
+	if (hasExclusiveTests && index === -1) {
+		this.filesWithExclusiveTests.push(file);
+	} else if (!hasExclusiveTests && index !== -1) {
+		this.filesWithExclusiveTests.splice(index, 1);
+	}
+};
+
+Watcher.prototype.cleanUnlinkedTests = function (unlinkedTests) {
+	unlinkedTests.forEach(function (testFile) {
+		this.updateTestDependencies(testFile, []);
+		this.updateExclusivity(testFile, false);
+	}, this);
+};
+
 Watcher.prototype.observeStdin = function (stdin) {
 	var self = this;
 
@@ -153,7 +186,7 @@ Watcher.prototype.runAfterChanges = function () {
 	});
 	var unlinkedTests = diff(dirtyTests, addedOrChangedTests);
 
-	this.removeUnlinkedTestDependencies(unlinkedTests);
+	this.cleanUnlinkedTests(unlinkedTests);
 	// No need to rerun tests if the only change is that tests were deleted.
 	if (unlinkedTests.length === dirtyPaths.length) {
 		return;

test/api.js

@@ -621,6 +621,21 @@ test('test file with exclusive tests causes non-exclusive tests in other files t
 		});
 });
 
+test('test files can be forced to run in exclusive mode', function (t) {
+	t.plan(4);
+
+	var api = new Api();
+	return api.run(
+		[path.join(__dirname, 'fixture/es2015.js')],
+		{runOnlyExclusive: true}
+	).then(function () {
+		t.ok(api.hasExclusive);
+		t.is(api.testCount, 0);
+		t.is(api.passCount, 0);
+		t.is(api.failCount, 0);
+	});
+});
+
 test('resets state before running', function (t) {
 	t.plan(2);
 
@@ -666,6 +681,26 @@ test('emits dependencies for test files', function (t) {
 	result.catch(function () {});
 });
 
+test('emits stats for test files', function (t) {
+	t.plan(2);
+
+	var api = new Api();
+	api.on('stats', function (stats) {
+		if (stats.file === path.normalize('test/fixture/exclusive.js')) {
+			t.is(stats.hasExclusive, true);
+		} else if (stats.file === path.normalize('test/fixture/generators.js')) {
+			t.is(stats.hasExclusive, false);
+		} else {
+			t.ok(false);
+		}
+	});
+
+	return api.run([
+		'test/fixture/exclusive.js',
+		'test/fixture/generators.js'
+	]);
+});
+
 test('verify test count', function (t) {
 	t.plan(8);