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 mochajs#3363 Fixes mochajs#2576

bin/options.js

@@ -5,6 +5,7 @@
  */
 
 const fs = require('fs');
+const path = require('path');
 
 /**
  * Export `getOptions`.
@@ -24,10 +25,12 @@ function getOptions() {
     return;
   }
 
-  const optsPath =
-    process.argv.indexOf('--opts') === -1
-      ? 'test/mocha.opts'
-      : process.argv[process.argv.indexOf('--opts') + 1];
+  const optsIndex = process.argv.indexOf('--opts');
+  const optsPathSpecified = optsIndex !== -1;
+  const defaultOptsPath = path.join('test', 'mocha.opts');
+  const optsPath = optsPathSpecified
+    ? process.argv[optsIndex + 1]
+    : defaultOptsPath;
 
   try {
     const opts = fs
@@ -38,12 +41,19 @@ function getOptions() {
       .filter(Boolean)
       .map(value => value.replace(/%20/g, ' '));
 
-    process.argv = process.argv
-      .slice(0, 2)
-      .concat(opts.concat(process.argv.slice(2)));
-  } catch (ignore) {
-    // NOTE: should console.error() and throw the error
+    if (opts.length > 0) {
+      process.argv = process.argv
+        .slice(0, 2)
+        .concat(opts.concat(process.argv.slice(2)));
+    }
+  } 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

@@ -127,7 +127,7 @@ function invokeMocha(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

@@ -440,6 +440,42 @@ 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.