fix(cli): Throw error if unable to parse Mocha options file

Code now throws an error for any problems (except nonexistent default "test/mocha.opts"). Includes
tests.

Fixes #3363 Fixes #2576

bin/options.js

@@ -5,6 +5,7 @@
  */
 
 const fs = require('fs');
+const path = require('path');
 
 /**
  * Export `getOptions`.
@@ -13,13 +14,22 @@ const fs = require('fs');
 module.exports = getOptions;
 
 /**
- * Default pathname for run-control file.
+ * Default test directory.
  *
  * @constant
  * @type {string}
  * @default
  */
-const defaultPathname = 'test/mocha.opts';
+const DEFAULT_TEST_DIRECTORY = 'test';
+
+/**
+ * Default filename of run-control file.
+ *
+ * @constant
+ * @type {string}
+ * @default
+ */
+const DEFAULT_OPTS_FILENAME = 'mocha.opts';
 
 /**
  * Reads contents of the run-control file.
@@ -69,20 +79,32 @@ function getOptions() {
     return;
   }
 
-  const optsPath =
-    process.argv.indexOf('--opts') === -1
-      ? defaultPathname
-      : process.argv[process.argv.indexOf('--opts') + 1];
+  const optsIndex = process.argv.indexOf('--opts');
+  const optsPathSpecified = optsIndex !== -1;
+  const defaultOptsPath = path.join(
+    DEFAULT_TEST_DIRECTORY,
+    DEFAULT_OPTS_FILENAME
+  );
+  const optsPath = optsPathSpecified
+    ? process.argv[optsIndex + 1]
+    : defaultOptsPath;
 
   try {
     const opts = parseOptions(readOptionsFile(optsPath));
 
+    if (opts.length > 0) {
     process.argv = process.argv
       .slice(0, 2)
       .concat(opts.concat(process.argv.slice(2)));
-  } catch (ignore) {
-    // NOTE: should console.error() and throw the error
+    }
+  } catch (err) {
+    // Default options file may not exist - rethrow anything else
+    if (optsPathSpecified || err.code !== 'ENOENT') {
+      console.error(`failed to load Mocha options file: ${optsPath}`);
+      throw err;
+    }
+  } finally {
+    // Despite its name, signifies loading was attempted and should not be again
+    process.env.LOADED_MOCHA_OPTS = '1';
   }
-
-  process.env.LOADED_MOCHA_OPTS = true;
 }

test/integration/fixtures/options/opts.fixture.js

@@ -0,0 +1,5 @@
+'use strict';
+
+describe('opts', function () {
+  it('should display this spec', function () {});
+});

test/integration/helpers.js

@@ -150,7 +150,7 @@ function _spawnMochaWithListeners(args, fn, cwd) {
 }
 
 function resolveFixturePath(fixture) {
-  return path.join('./test/integration/fixtures', fixture);
+  return path.join('test', 'integration', 'fixtures', fixture);
 }
 
 function getSummary(res) {

test/integration/options.spec.js

@@ -558,6 +558,42 @@ describe('options', function() {
     });
   });
 
+  describe('--opts', function() {
+    var testFile = path.join('options', 'opts.fixture.js');
+
+    it('works despite nonexistent default options file', function(done) {
+      args = [];
+      run(testFile, args, function(err, res) {
+        if (err) {
+          return done(err);
+        }
+        expect(res, 'to have passed').and('to have passed test count', 1);
+        return done();
+      });
+    });
+
+    it('should throw an error due to nonexistent options file', function(done) {
+      args = ['--opts', 'nosuchoptionsfile', testFile];
+      directInvoke(
+        args,
+        function(err, res) {
+          if (err) {
+            return done(err);
+          }
+          expect(
+            res.output,
+            'to contain',
+            'failed to load Mocha options file',
+            'ENOENT:'
+          );
+          expect(res.code, 'to be', 1); // failed
+          return done();
+        },
+        path.join(__dirname, 'fixtures')
+      );
+    });
+  });
+
   describe('--exclude', function() {
     /*
      * Runs mocha in {path} with the given args.