Improved lexer error messages

Cakefile

@@ -91,7 +91,7 @@ task 'build:ultraviolet', 'build and install the Ultraviolet syntax highlighter'
 
 task 'build:browser', 'rebuild the merged script for inclusion in the browser', ->
   code = ''
-  for name in ['helpers', 'rewriter', 'lexer', 'parser', 'scope', 'nodes', 'coffee-script', 'browser']
+  for name in ['helpers', 'error', 'rewriter', 'lexer', 'parser', 'scope', 'nodes', 'coffee-script', 'browser']
     code += """
       require['./#{name}'] = new function() {
         var exports = this;

lib/coffee-script/command.js

@@ -1,6 +1,6 @@
 // Generated by CoffeeScript 1.5.0
 (function() {
-  var BANNER, CoffeeScript, EventEmitter, SWITCHES, coffee_exts, compileJoin, compileOptions, compilePath, compileScript, compileStdio, exec, exists, forkNode, fs, helpers, hidden, joinTimeout, lint, notSources, optionParser, optparse, opts, outputPath, parseOptions, path, printLine, printTokens, printWarn, removeSource, sourceCode, sources, spawn, timeLog, unwatchDir, usage, version, wait, watch, watchDir, watchers, writeJs, _ref,
+  var BANNER, CoffeeScript, CompilerError, EventEmitter, SWITCHES, coffee_exts, compileJoin, compileOptions, compilePath, compileScript, compileStdio, exec, exists, forkNode, fs, helpers, hidden, joinTimeout, lint, notSources, optionParser, optparse, opts, outputPath, parseOptions, path, printLine, printTokens, printWarn, removeSource, sourceCode, sources, spawn, timeLog, unwatchDir, usage, version, wait, watch, watchDir, watchers, writeJs, _ref,
     __indexOf = [].indexOf || function(item) { for (var i = 0, l = this.length; i < l; i++) { if (i in this && this[i] === item) return i; } return -1; };
 
   fs = require('fs');
@@ -13,6 +13,8 @@
 
   CoffeeScript = require('./coffee-script');
 
+  CompilerError = require('./error').CompilerError;
+
   _ref = require('child_process'), spawn = _ref.spawn, exec = _ref.exec;
 
   EventEmitter = require('events').EventEmitter;
@@ -159,7 +161,7 @@
   };
 
   compileScript = function(file, input, base) {
-    var o, options, t, task;
+    var message, o, options, t, task;
     o = opts;
     options = compileOptions(file);
     try {
@@ -194,11 +196,15 @@
       if (CoffeeScript.listeners('failure').length) {
         return;
       }
+      message = err instanceof CompilerError ? err.prettyMessage(file || '[stdin]', input) : err.stack || ("ERROR: " + err);
       if (o.watch) {
-        return printLine(err.message + '\x07');
+        if (o.watch) {
+          return printLine(message + '\x07');
+        }
+      } else {
+        printWarn(message);
+        return process.exit(1);
       }
-      printWarn(err instanceof Error && err.stack || ("ERROR: " + err));
-      return process.exit(1);
     }
   };
 

lib/coffee-script/error.js

@@ -0,0 +1,44 @@
+// Generated by CoffeeScript 1.5.0
+(function() {
+  var CompilerError, repeat,
+    __hasProp = {}.hasOwnProperty,
+    __extends = function(child, parent) { for (var key in parent) { if (__hasProp.call(parent, key)) child[key] = parent[key]; } function ctor() { this.constructor = child; } ctor.prototype = parent.prototype; child.prototype = new ctor(); child.__super__ = parent.prototype; return child; };
+
+  repeat = require('./helpers').repeat;
+
+  exports.CompilerError = CompilerError = (function(_super) {
+
+    __extends(CompilerError, _super);
+
+    CompilerError.prototype.name = 'CompilerError';
+
+    function CompilerError(message, startLine, startColumn, endLine, endColumn) {
+      this.message = message;
+      this.startLine = startLine;
+      this.startColumn = startColumn;
+      this.endLine = endLine != null ? endLine : this.startLine;
+      this.endColumn = endColumn != null ? endColumn : this.startColumn;
+      if (typeof Error.captureStackTrace === "function") {
+        Error.captureStackTrace(this, CompilerError);
+      }
+    }
+
+    CompilerError.prototype.prettyMessage = function(fileName, code) {
+      var errorLength, errorLine, marker, message;
+      message = "" + fileName + ":" + this.startLine + ":" + this.startColumn + ": " + this.message;
+      if (this.startLine === this.endLine) {
+        errorLine = code.split('\n')[this.startLine - 1];
+        errorLength = this.endColumn - this.startColumn + 1;
+        marker = (repeat(' ', this.startColumn - 1)) + (repeat('^', errorLength));
+        message += "\n" + errorLine + "\n" + marker;
+      } else {
+        void 0;
+      }
+      return message;
+    };
+
+    return CompilerError;
+
+  })(Error);
+
+}).call(this);

lib/coffee-script/helpers.js

@@ -12,6 +12,10 @@
     return literal === string.substr(string.length - len - (back || 0), len);
   };
 
+  exports.repeat = function(string, n) {
+    return (Array(n + 1)).join(string);
+  };
+
   exports.compact = function(array) {
     var item, _i, _len, _results;
     _results = [];

lib/coffee-script/lexer.js

@@ -1,12 +1,14 @@
 // Generated by CoffeeScript 1.5.0
 (function() {
-  var BOM, BOOL, CALLABLE, CODE, COFFEE_ALIASES, COFFEE_ALIAS_MAP, COFFEE_KEYWORDS, COMMENT, COMPARE, COMPOUND_ASSIGN, HEREDOC, HEREDOC_ILLEGAL, HEREDOC_INDENT, HEREGEX, HEREGEX_OMIT, IDENTIFIER, INDEXABLE, INVERSES, JSTOKEN, JS_FORBIDDEN, JS_KEYWORDS, LINE_BREAK, LINE_CONTINUER, LITERATE, LOGIC, Lexer, MATH, MULTILINER, MULTI_DENT, NOT_REGEX, NOT_SPACED_REGEX, NUMBER, OPERATOR, REGEX, RELATION, RESERVED, Rewriter, SHIFT, SIMPLESTR, STRICT_PROSCRIBED, TRAILING_SPACES, UNARY, WHITESPACE, compact, count, key, last, locationDataToString, starts, _ref, _ref1,
+  var BOM, BOOL, CALLABLE, CODE, COFFEE_ALIASES, COFFEE_ALIAS_MAP, COFFEE_KEYWORDS, COMMENT, COMPARE, COMPOUND_ASSIGN, CompilerError, HEREDOC, HEREDOC_ILLEGAL, HEREDOC_INDENT, HEREGEX, HEREGEX_OMIT, IDENTIFIER, INDEXABLE, INVERSES, JSTOKEN, JS_FORBIDDEN, JS_KEYWORDS, LINE_BREAK, LINE_CONTINUER, LITERATE, LOGIC, Lexer, MATH, MULTILINER, MULTI_DENT, NOT_REGEX, NOT_SPACED_REGEX, NUMBER, OPERATOR, REGEX, RELATION, RESERVED, Rewriter, SHIFT, SIMPLESTR, STRICT_PROSCRIBED, TRAILING_SPACES, UNARY, WHITESPACE, compact, count, key, last, locationDataToString, starts, _ref, _ref1,
     __indexOf = [].indexOf || function(item) { for (var i = 0, l = this.length; i < l; i++) { if (i in this && this[i] === item) return i; } return -1; };
 
   _ref = require('./rewriter'), Rewriter = _ref.Rewriter, INVERSES = _ref.INVERSES;
 
   _ref1 = require('./helpers'), count = _ref1.count, starts = _ref1.starts, compact = _ref1.compact, last = _ref1.last, locationDataToString = _ref1.locationDataToString;
 
+  CompilerError = require('./error').CompilerError;
+
   exports.Lexer = Lexer = (function() {
 
     function Lexer() {}
@@ -786,7 +788,7 @@
     };
 
     Lexer.prototype.error = function(message) {
-      throw SyntaxError("" + message + " on line " + (this.chunkLine + 1));
+      throw new CompilerError(message, this.chunkLine + 1, this.chunkColumn + 1);
     };
 
     return Lexer;

src/command.coffee

@@ -5,15 +5,16 @@
 # interactive REPL.
 
 # External dependencies.
-fs             = require 'fs'
-path           = require 'path'
-helpers        = require './helpers'
-optparse       = require './optparse'
-CoffeeScript   = require './coffee-script'
-{spawn, exec}  = require 'child_process'
-{EventEmitter} = require 'events'
+fs              = require 'fs'
+path            = require 'path'
+helpers         = require './helpers'
+optparse        = require './optparse'
+CoffeeScript    = require './coffee-script'
+{CompilerError} = require './error'
+{spawn, exec}   = require 'child_process'
+{EventEmitter}  = require 'events'
 
-exists         = fs.exists or path.exists
+exists          = fs.exists or path.exists
 
 # Allow CoffeeScript to emit Node.js events.
 helpers.extend CoffeeScript, new EventEmitter
@@ -138,9 +139,17 @@ compileScript = (file, input, base) ->
   catch err
     CoffeeScript.emit 'failure', err, task
     return if CoffeeScript.listeners('failure').length
-    return printLine err.message + '\x07' if o.watch
-    printWarn err instanceof Error and err.stack or "ERROR: #{err}"
-    process.exit 1
+
+    message = if err instanceof CompilerError
+      err.prettyMessage file or '[stdin]', input
+    else
+      err.stack or "ERROR: #{err}"
+
+    if o.watch
+      printLine message + '\x07' if o.watch
+    else
+      printWarn message
+      process.exit 1
 
 # Attach the appropriate listeners to compile scripts incoming over **stdin**,
 # and write them back to **stdout**.

src/error.coffee

@@ -0,0 +1,27 @@
+{repeat} = require './helpers'
+
+# A common error class used throughout the compiler to indicate compilation
+# errors at a given location in the source code.
+exports.CompilerError = class CompilerError extends Error
+  name: 'CompilerError'
+
+  constructor: (@message, @startLine, @startColumn,
+                @endLine = @startLine, @endColumn = @startColumn) ->
+    # Add a stack trace in V8.
+    Error.captureStackTrace? @, CompilerError
+
+  # Creates a nice error message like, following the "standard" format
+  # <filename>:<line>:<col>: <message> plus the line with the error and a marker
+  # showing where the error is.
+  # TODO: tests
+  prettyMessage: (fileName, code) ->
+    message = "#{fileName}:#{@startLine}:#{@startColumn}: #{@message}"
+    if @startLine is @endLine
+      errorLine = code.split('\n')[@startLine - 1]
+      errorLength = @endColumn - @startColumn + 1
+      marker = (repeat ' ', @startColumn - 1) + (repeat '^', errorLength)
+      message += "\n#{errorLine}\n#{marker}"
+    else
+      # TODO: How do we show multi-line errors?
+      undefined
+    message

src/helpers.coffee

@@ -11,6 +11,10 @@ exports.ends = (string, literal, back) ->
   len = literal.length
   literal is string.substr string.length - len - (back or 0), len
 
+# Repeat a string `n` times.
+exports.repeat = (string, n) ->
+  (Array n + 1).join string
+
 # Trim out all falsy values from an array.
 exports.compact = (array) ->
   item for item in array when item
@@ -71,8 +75,9 @@ buildLocationData = (first, last) ->
     last_line: last.last_line
     last_column: last.last_column
 
-# This returns a function which takes an object as a parameter, and if that object is an AST node,
-# updates that object's locationData.  The object is returned either way.
+# This returns a function which takes an object as a parameter, and if that
+# object is an AST node, updates that object's locationData.
+# The object is returned either way.
 exports.addLocationDataFn = (first, last) ->
     (obj) ->
       if ((typeof obj) is 'object') and (!!obj['updateLocationDataIfMissing'])
@@ -91,5 +96,3 @@ exports.locationDataToString = (obj) ->
       "#{locationData.last_line + 1}:#{locationData.last_column + 1}"
     else
       "No location data"
-
-

src/lexer.coffee

@@ -13,6 +13,7 @@
 
 # Import the helpers we need.
 {count, starts, compact, last, locationDataToString} = require './helpers'
+{CompilerError} = require './error'
 
 # The Lexer Class
 # ---------------
@@ -41,7 +42,7 @@ exports.Lexer = class Lexer
     @outdebt  = 0              # The under-outdentation at the current level.
     @indents  = []             # The stack of all current indentation levels.
     @ends     = []             # The stack for pairing up tokens.
-    @tokens   = []             # Stream of parsed tokens in the form `['TYPE', value, line]`.
+    @tokens   = []             # Stream of parsed tokens in the form `['TYPE', value, location data]`.
 
     @chunkLine =
         opts.line or 0         # The start line for the current @chunk.
@@ -693,11 +694,11 @@ exports.Lexer = class Lexer
     body = body.replace /// #{quote} ///g, '\\$&'
     quote + @escapeLines(body, heredoc) + quote
 
-  # Throws a syntax error on the current `@line`.
+  # Throws a compiler error on the current position.
   error: (message) ->
     # TODO: Are there some cases we could improve the error line number by
     # passing the offset in the chunk where the error happened?
-    throw SyntaxError "#{message} on line #{ @chunkLine + 1 }"
+    throw new CompilerError message, @chunkLine + 1, @chunkColumn + 1
 
 # Constants
 # ---------

test/formatting.coffee

@@ -143,4 +143,4 @@ test "#1299: Disallow token misnesting", ->
     '''
     ok no
   catch e
-    eq 'unmatched ] on line 2', e.message
+    eq 'unmatched ]', e.message