Add --no-diff option (fixes #2514)

bin/_mocha

@@ -90,6 +90,7 @@ program
   .option('--preserve-symlinks', 'Instructs the module loader to preserve symbolic links when resolving and caching modules')
   .option('--icu-data-dir', 'include ICU data')
   .option('--inline-diffs', 'display actual/expected differences inline within each string')
+  .option('--no-diff', 'do not show a diff on failure')
   .option('--inspect', 'activate devtools in chrome')
   .option('--inspect-brk', 'activate devtools in chrome and break on the first line')
   .option('--interfaces', 'display available interfaces')
@@ -250,6 +251,12 @@ if (program.inlineDiffs) {
   mocha.useInlineDiffs(true);
 }
 
+// --no-diff
+
+if (process.argv.indexOf('--no-diff') !== -1) {
+  mocha.hideDiff(true);
+}
+
 // --slow <ms>
 
 if (program.slow) {

lib/mocha.js

@@ -389,6 +389,20 @@ Mocha.prototype.useInlineDiffs = function (inlineDiffs) {
   return this;
 };
 
+/**
+ * Do not show diffs at all.
+ *
+ * @param {Boolean} hideDiff
+ * @return {Mocha}
+ * @api public
+ * @param {boolean} hideDiff
+ * @return {Mocha}
+ */
+Mocha.prototype.hideDiff = function (hideDiff) {
+  this.options.hideDiff = hideDiff !== undefined && hideDiff;
+  return this;
+};
+
 /**
  * Set the timeout in milliseconds.
  *
@@ -545,6 +559,7 @@ Mocha.prototype.run = function (fn) {
     exports.reporters.Base.useColors = options.useColors;
   }
   exports.reporters.Base.inlineDiffs = options.useInlineDiffs;
+  exports.reporters.Base.hideDiff = options.hideDiff;
 
   function done (failures) {
     if (reporter.done) {

lib/reporters/base.js

@@ -208,7 +208,10 @@ exports.list = function (failures) {
     if (err.uncaught) {
       msg = 'Uncaught ' + msg;
     }
+
     // explicitly show diff
+    if (exports.hideDiff !== true && err.showDiff !== false && sameType(actual, expected) && expected !== undefined) {
+      escape = false;
     if (showDiff(err)) {
       stringifyDiffObjs(err);
       fmt = color('error title', '  %s) %s:\n%s') + color('error stack', '\n%s\n');

test/integration/fixtures/no-diff.fixture.js

@@ -0,0 +1,8 @@
+'use strict';
+var assert = require('assert');
+
+describe('Example test', function () {
+  it('should fail', function () {
+    assert.deepEqual([1, 2, 3], ['foo', 'bar', 'baz']);
+  });
+});

test/integration/no-diff.spec.js

@@ -0,0 +1,14 @@
+'use strict';
+
+var helpers = require('./helpers');
+var run = helpers.runMocha;
+
+describe('no-diff', function () {
+  it('should be honoured', function (done) {
+    run('no-diff.fixture.js', ['--no-diff'], function (err, res) {
+      res.output.should.not.match(/\+ expected/);
+      res.output.should.not.match(/- actual/);
+      done(err);
+    });
+  });
+});

test/reporters/base.spec.js

@@ -96,6 +96,21 @@ describe('Base reporter', function () {
       expect(errOut).to.not.match(/- actual/);
       expect(errOut).to.not.match(/\+ expected/);
     });
+
+    it('should not show diffs when hideDiff is set', function () {
+      var err = new Assert({ actual: 'foo', expected: 'bar' });
+      var errOut;
+
+      var test = makeTest(err);
+
+      Base.hideDiff = true;
+      Base.list([test]);
+      Base.hideDiff = false; // Revert to original value
+
+      errOut = stdout.join('\n');
+      errOut.should.not.match(/\- actual/);
+      errOut.should.not.match(/\+ expected/);
+    });
   });
 
   describe('Getting two strings', function () {