Added custom error objects including code

docs/index.md

@@ -73,6 +73,7 @@ Mocha is a feature-rich JavaScript test framework running on [Node.js](https://n
 - [Configuring Mocha (Node.js)](#configuring-mocha-nodejs)
 - [`mocha.opts`](#mochaopts)
 - [The `test/` Directory](#the-test-directory)
+- [Error Codes](#error-codes)
 - [Editor Plugins](#editor-plugins)
 - [Examples](#examples)
 - [Testing Mocha](#testing-mocha)
@@ -1658,6 +1659,20 @@ $ mocha "./spec/**/*.js"
 
 *Note*: Double quotes around the glob are recommended for portability.
 
+## Error Codes
+
+List of codes associated with Errors thrown inside Mocha. Following NodeJS practices.
+
+| Code        | Meaning |
+| ------------- | ------------- |
+| ERR_MOCHA_INVALID_ARG_TYPE | argument of the wrong type was passed to Mocha's API |
+| ERR_MOCHA_INVALID_ARG_VALUE | invalid or unsupported value was passed for a given argument |
+| ERR_MOCHA_INVALID_INTERFACE | interface specified in options not found |
+| ERR_MOCHA_INVALID_REPORTER | reporter specified in options not found |
+| ERR_MOCHA_NO_FILES_MATCH_PATTERN | file/s of test could not be found |
+| ERR_MOCHA_NOT_SUPPORTED | type of output specified was not supported |
+| ERR_MOCHA_UNDEFINED_ERROR | an error was thrown but no details were specified |
+
 ## Editor Plugins
 
 The following editor-related packages are available:

lib/cli/run-helpers.js

@@ -143,10 +143,8 @@ exports.handleFiles = ({
     try {
       newFiles = utils.lookupFiles(arg, extension, recursive);
     } catch (err) {
-      if (err.message.indexOf('cannot resolve path') === 0) {
-        console.error(
-          `Warning: Could not find any test files matching pattern: ${arg}`
-        );
+      if (err.code === 'ERR_MOCHA_NO_FILES_MATCH_PATTERN') {
+        console.warn('Warning: %s: %O', err.message, err.pattern);
         return;
       }
 

lib/cli/run.js

@@ -9,6 +9,8 @@
 
 const Mocha = require('../mocha');
 const ansi = require('ansi-colors');
+var errors = require('../errors');
+var createInvalidArgumentValueError = errors.createInvalidArgumentValueError;
 
 const {
   list,
@@ -190,7 +192,12 @@ exports.builder = yargs =>
             const pair = opt.split('=');
 
             if (pair.length > 2 || !pair.length) {
-              throw new Error(`invalid reporter option '${opt}'`);
+              throw createInvalidArgumentValueError(
+                `invalid reporter option '${opt}'`,
+                '--reporter-option',
+                opt,
+                'expected "key=value" format'
+              );
             }
 
             acc[pair[0]] = pair.length === 2 ? pair[1] : true;

lib/errors.js

@@ -0,0 +1,139 @@
+'use strict';
+/**
+ * @module Errors
+ */
+/**
+ * Factory functions to create throwable error objects
+ */
+
+/**
+ * Creates an error object used when no files to be tested could be found using specified pattern.
+ *
+ * @public
+ * @param {string} message - Error message to be displayed.
+ * @param {string} pattern - User-specified argument value.
+ * @returns {Error} instance detailing the error condition
+ */
+function createNoFilesMatchPatternError(message, pattern) {
+  var err = new Error(message);
+  err.code = 'ERR_MOCHA_NO_FILES_MATCH_PATTERN';
+  err.pattern = pattern;
+  return err;
+}
+
+/**
+ * Creates an error object used when the reporter specified in the options was not found.
+ *
+ * @public
+ * @param {string} message - Error message to be displayed.
+ * @param {string} reporter - User-specified reporter value.
+ * @returns {Error} instance detailing the error condition
+ */
+function createInvalidReporterError(message, reporter) {
+  var err = new TypeError(message);
+  err.code = 'ERR_MOCHA_INVALID_REPORTER';
+  err.reporter = reporter;
+  return err;
+}
+
+/**
+ * Creates an error object used when the interface specified in the options was not found.
+ *
+ * @public
+ * @param {string} message - Error message to be displayed.
+ * @param {string} ui - User-specified interface value.
+ * @returns {Error} instance detailing the error condition
+ */
+function createInvalidInterfaceError(message, ui) {
+  var err = new Error(message);
+  err.code = 'ERR_MOCHA_INVALID_INTERFACE';
+  err.interface = ui;
+  return err;
+}
+
+/**
+ * Creates an error object used when the type of output specified was not supported.
+ *
+ * @public
+ * @param {string} message - Error message to be displayed.
+ * @returns {Error} instance detailing the error condition
+ */
+function createNotSupportedError(message) {
+  var err = new Error(message);
+  err.code = 'ERR_MOCHA_NOT_SUPPORTED';
+  return err;
+}
+
+/**
+ * Creates an error object used when an argument is missing.
+ *
+ * @public
+ * @param {string} message - Error message to be displayed.
+ * @param {string} argument - Argument name.
+ * @param {string} expected - Expected argument datatype.
+ * @returns {Error} instance detailing the error condition
+ */
+function createMissingArgumentError(message, argument, expected) {
+  return createInvalidArgumentTypeError(message, argument, expected);
+}
+
+/**
+ * Creates an error object used when an argument did not use the supported type
+ *
+ * @public
+ * @param {string} message - Error message to be displayed.
+ * @param {string} argument - Argument name.
+ * @param {string} expected - Expected argument datatype.
+ * @returns {Error} instance detailing the error condition
+ */
+function createInvalidArgumentTypeError(message, argument, expected) {
+  var err = new TypeError(message);
+  err.code = 'ERR_MOCHA_INVALID_ARG_TYPE';
+  err.argument = argument;
+  err.expected = expected;
+  err.actual = typeof argument;
+  return err;
+}
+
+/**
+ * Creates an error object used when an argument did not use the supported value
+ *
+ * @public
+ * @param {string} message - Error message to be displayed.
+ * @param {string} argument - Argument name.
+ * @param {string} value - Argument value.
+ * @param {string} reason - Why value is invalid.
+ * @returns {Error} instance detailing the error condition
+ */
+function createInvalidArgumentValueError(message, argument, value, reason) {
+  var err = new TypeError(message);
+  err.code = 'ERR_MOCHA_INVALID_ARG_VALUE';
+  err.argument = argument;
+  err.value = value;
+  err.reason = typeof reason !== 'undefined' ? reason : 'is invalid';
+  return err;
+}
+
+/**
+ * Creates an error object used when an error was thrown but no details were specified.
+ *
+ * @public
+ * @param {string} message - Error message to be displayed.
+ * @returns {Error} instance detailing the error condition
+ */
+function createUndefinedError(message) {
+  var err = new Error(message);
+  err.code = 'ERR_MOCHA_UNDEFINED_ERROR';
+  return err;
+}
+
+module.exports = {
+  createInvalidArgumentTypeError: createInvalidArgumentTypeError,
+  createInvalidArgumentValueError: createInvalidArgumentValueError,
+  createInvalidInterfaceError: createInvalidInterfaceError,
+  createInvalidReporterError: createInvalidReporterError,
+  createMissingArgumentError: createMissingArgumentError,
+  createNoFilesMatchPatternError: createNoFilesMatchPatternError,
+  createNotSupportedError: createNotSupportedError,
+  createUndefinedError: createUndefinedError
+};

lib/interfaces/common.js

@@ -2,6 +2,8 @@
 
 var Suite = require('../suite');
 var utils = require('../utils');
+var errors = require('../errors');
+var createMissingArgumentError = errors.createMissingArgumentError;
 
 /**
  * Functions common to more than one interface.
@@ -147,11 +149,13 @@ module.exports = function(suites, context, mocha) {
           }
           suites.shift();
         } else if (typeof opts.fn === 'undefined' && !suite.pending) {
-          throw new Error(
+          throw createMissingArgumentError(
             'Suite "' +
               suite.fullTitle() +
               '" was defined but no callback was supplied. ' +
-              'Supply a callback or explicitly skip the suite.'
+              'Supply a callback or explicitly skip the suite.',
+            'callback',
+            'function'
           );
         } else if (!opts.fn && suite.pending) {
           suites.shift();

lib/mocha.js

@@ -12,6 +12,9 @@ var builtinReporters = require('./reporters');
 var utils = require('./utils');
 var mocharc = require('./mocharc.json');
 var assign = require('object.assign').getPolyfill();
+var errors = require('./errors');
+var createInvalidReporterError = errors.createInvalidReporterError;
+var createInvalidInterfaceError = errors.createInvalidInterfaceError;
 
 exports = module.exports = Mocha;
 
@@ -220,12 +223,16 @@ Mocha.prototype.reporter = function(reporter, reporterOptions) {
       try {
         _reporter = require(reporter);
       } catch (err) {
-        if (err.message.indexOf('Cannot find module') !== -1) {
+        if (
+          err.code !== 'MODULE_NOT_FOUND' ||
+          err.message.includes('Cannot find module')
+        ) {
           // Try to load reporters from a path (absolute or relative)
           try {
             _reporter = require(path.resolve(process.cwd(), reporter));
           } catch (_err) {
-            err.message.indexOf('Cannot find module') !== -1
+            _err.code !== 'MODULE_NOT_FOUND' ||
+            _err.message.includes('Cannot find module')
               ? console.warn('"' + reporter + '" reporter not found')
               : console.warn(
                   '"' +
@@ -249,7 +256,10 @@ Mocha.prototype.reporter = function(reporter, reporterOptions) {
       );
     }
     if (!_reporter) {
-      throw new Error('invalid reporter "' + reporter + '"');
+      throw createInvalidReporterError(
+        'invalid reporter "' + reporter + '"',
+        reporter
+      );
     }
     this._reporter = _reporter;
   }
@@ -275,7 +285,10 @@ Mocha.prototype.ui = function(name) {
     try {
       this._ui = require(name);
     } catch (err) {
-      throw new Error('invalid interface "' + name + '"');
+      throw createInvalidInterfaceError(
+        'invalid interface "' + name + '"',
+        name
+      );
     }
   }
   this._ui = this._ui(this.suite);

lib/reporters/xunit.js

@@ -13,7 +13,8 @@ var fs = require('fs');
 var escape = utils.escape;
 var mkdirp = require('mkdirp');
 var path = require('path');
-
+var errors = require('../errors');
+var createNotSupportedError = errors.createNotSupportedError;
 /**
  * Save timer references to avoid Sinon interfering (see GH-237).
  */
@@ -50,7 +51,7 @@ function XUnit(runner, options) {
   if (options && options.reporterOptions) {
     if (options.reporterOptions.output) {
       if (!fs.createWriteStream) {
-        throw new Error('file output not supported in browser');
+        throw createNotSupportedError('file output not supported in browser');
       }
 
       mkdirp.sync(path.dirname(options.reporterOptions.output));

lib/suite.js

@@ -12,6 +12,8 @@ var utils = require('./utils');
 var inherits = utils.inherits;
 var debug = require('debug')('mocha:suite');
 var milliseconds = require('ms');
+var errors = require('./errors');
+var createInvalidArgumentTypeError = errors.createInvalidArgumentTypeError;
 
 /**
  * Expose `Suite`.
@@ -49,10 +51,12 @@ exports.create = function(parent, title) {
  */
 function Suite(title, parentContext) {
   if (!utils.isString(title)) {
-    throw new Error(
-      'Suite `title` should be a "string" but "' +
+    throw createInvalidArgumentTypeError(
+      'Suite argument "title" must be a string. Received type "' +
         typeof title +
-        '" was given instead.'
+        '"',
+      'title',
+      'string'
     );
   }
   this.title = title;

lib/test.js

@@ -1,6 +1,8 @@
 'use strict';
 var Runnable = require('./runnable');
 var utils = require('./utils');
+var errors = require('./errors');
+var createInvalidArgumentTypeError = errors.createInvalidArgumentTypeError;
 var isString = utils.isString;
 
 module.exports = Test;
@@ -15,10 +17,12 @@ module.exports = Test;
  */
 function Test(title, fn) {
   if (!isString(title)) {
-    throw new Error(
-      'Test `title` should be a "string" but "' +
+    throw createInvalidArgumentTypeError(
+      'Test argument "title" should be a string. Received type "' +
         typeof title +
-        '" was given instead.'
+        '"',
+      'title',
+      'string'
     );
   }
   Runnable.call(this, title, fn);

lib/utils.js

@@ -14,6 +14,10 @@ var glob = require('glob');
 var path = require('path');
 var join = path.join;
 var he = require('he');
+var errors = require('./errors');
+var createNoFilesMatchPatternError = errors.createNoFilesMatchPatternError;
+var createMissingArgumentError = errors.createMissingArgumentError;
+var createUndefinedError = errors.createUndefinedError;
 
 /**
  * Ignored directories.
@@ -515,7 +519,10 @@ exports.lookupFiles = function lookupFiles(filepath, extensions, recursive) {
     } else {
       files = glob.sync(filepath);
       if (!files.length) {
-        throw new Error("cannot resolve path (or pattern) '" + filepath + "'");
+        throw createNoFilesMatchPatternError(
+          'cannot find any files matching pattern "' + filepath + '"',
+          filepath
+        );
       }
       return files;
     }
@@ -546,8 +553,10 @@ exports.lookupFiles = function lookupFiles(filepath, extensions, recursive) {
       return;
     }
     if (!extensions) {
-      throw new Error(
-        'extensions parameter required when filepath is a directory'
+      throw createMissingArgumentError(
+        'Argument "extensions" required when argument "filepath" is a directory',
+        'extensions',
+        'array'
       );
     }
     var re = new RegExp('\\.(?:' + extensions.join('|') + ')$');
@@ -567,7 +576,7 @@ exports.lookupFiles = function lookupFiles(filepath, extensions, recursive) {
  */
 
 exports.undefinedError = function() {
-  return new Error(
+  return createUndefinedError(
     'Caught undefined error, did you throw without specifying what?'
   );
 };