handle exceptions when initially running files

Catch exceptions when initially running files. Don't run any tests, just report
the exception.

Move test teardown into a callback for the run promise so it can be used when
--match is used but there are no matches, and when exceptions occur while
initially running files.

Teardown causes the test promise to reject, which leads to an attempt to run
the tests. Add a guard to prevent this.

Fixes #622.

Author: novemberborn

api.js

@@ -192,8 +192,7 @@ Api.prototype.run = function (files) {
 			self.fileCount = files.length;
 			self.base = path.relative('.', commonPathPrefix(files)) + path.sep;
 
-			var tests = files.map(self._runFile);
-
+			var tests = new Array(self.fileCount);
 			return new Promise(function (resolve) {
 				function run() {
 					if (self.options.match.length > 0 && !self.hasExclusive) {
@@ -202,10 +201,6 @@ Api.prototype.run = function (files) {
 							file: undefined
 						});
 
-						tests.forEach(function (test) {
-							// No tests will be run so tear down the child processes.
-							test.send('teardown');
-						});
 						resolve([]);
 						return;
 					}
@@ -237,20 +232,42 @@ Api.prototype.run = function (files) {
 
 				// receive test count from all files and then run the tests
 				var unreportedFiles = self.fileCount;
-				tests.forEach(function (test) {
+				var bailed = false;
+				files.every(function (file, index) {
 					var tried = false;
 					function tryRun() {
-						if (!tried) {
+						if (!tried && !bailed) {
 							unreportedFiles--;
 							if (unreportedFiles === 0) {
 								run();
 							}
 						}
 					}
 
-					test.on('stats', tryRun);
-					test.catch(tryRun);
+					try {
+						var test = tests[index] = self._runFile(file);
+						test.on('stats', tryRun);
+						test.catch(tryRun);
+						return true;
+					} catch (err) {
+						bailed = true;
+						self._handleExceptions({
+							exception: err,
+							file: file
+						});
+						resolve([]);
+						return false;
+					}
 				});
+			}).then(function (results) {
+				if (results.length === 0) {
+					// No tests ran, make sure to tear down the child processes.
+					tests.forEach(function (test) {
+						test.send('teardown');
+					});
+				}
+
+				return results;
 			});
 		})
 		.then(function (results) {

test/api.js

@@ -730,3 +730,19 @@ test('using --match with no matching tests causes an AvaError to be emitted', fu
 
 	return api.run([path.join(__dirname, 'fixture/match-no-match.js')]);
 });
+
+test('errors thrown when running files are emitted', function (t) {
+	t.plan(2);
+
+	var api = new Api();
+
+	api.on('error', function (err) {
+		t.is(err.name, 'SyntaxError');
+		t.match(err.message, /Unexpected token/);
+	});
+
+	return api.run([
+		path.join(__dirname, 'fixture/es2015.js'),
+		path.join(__dirname, 'fixture/syntax-error.js')
+	]);
+});

test/fixture/syntax-error.js

@@ -0,0 +1,5 @@
+import test from 'ava';
+
+test.(t => {
+	t.pass();
+});