Merge pull request #7350 from atom/ns-assertions

Add assertion mechanism

src/atom.coffee

@@ -198,28 +198,31 @@ class Atom extends Model
   initialize: ->
     sourceMapCache = {}
 
-    window.onerror = =>
-      @lastUncaughtError = Array::slice.call(arguments)
-      [message, url, line, column, originalError] = @lastUncaughtError
+    window.onerror = (message, url, line, column, error) =>
+      @lastUncaughtError = error
 
-      convertedLine = convertLine(url, line, column, sourceMapCache)
-      {line, column} = convertedLine if convertedLine?
-      originalError.stack = convertStackTrace(originalError.stack, sourceMapCache) if originalError
-
-      eventObject = {message, url, line, column, originalError}
+      # TODO: These should be deprecated for 2.0 once we transition the
+      # exception-reporting package to the new API.
+      error ?= {}
+      error.message ?= message
+      error.url = url
+      error.line = line
+      error.column = column
+      error.originalError = error
 
       openDevTools = true
-      eventObject.preventDefault = -> openDevTools = false
+      error.preventDefault = -> openDevTools = false
 
-      @emitter.emit 'will-throw-error', eventObject
+      # TODO: Deprecate onWillThrowError once we transition the notifications
+      # package to use onDidThrowError instead.
+      @emitter.emit 'will-throw-error', error
+      @emit 'uncaught-error', arguments... if includeDeprecatedAPIs
+      @emitter.emit 'did-throw-error', error
 
       if openDevTools
         @openDevTools()
         @executeJavaScriptInDevTools('DevToolsAPI.showConsole()')
 
-      @emit 'uncaught-error', arguments... if includeDeprecatedAPIs
-      @emitter.emit 'did-throw-error', {message, url, line, column, originalError}
-
     @disposables?.dispose()
     @disposables = new CompositeDisposable
 
@@ -321,18 +324,16 @@ class Atom extends Model
 
   # Extended: Invoke the given callback whenever there is an unhandled error.
   #
-  # * `callback` {Function} to be called whenever there is an unhandled error
-  #   * `event` {Object}
-  #     * `originalError` {Object} the original error object
-  #     * `message` {String} the original error object
-  #     * `url` {String} Url to the file where the error originated.
-  #     * `line` {Number}
-  #     * `column` {Number}
+  # * `callback` {Function} to be called whenever there is an unhandled error.
+  #   * `error` The unhandled {Error} object.
   #
   # Returns a {Disposable} on which `.dispose()` can be called to unsubscribe.
   onDidThrowError: (callback) ->
     @emitter.on 'did-throw-error', callback
 
+  onDidFailAssertion: (callback) ->
+    @emitter.on 'did-fail-assertion', callback
+
   ###
   Section: Atom Details
   ###
@@ -715,6 +716,22 @@ class Atom extends Model
   Section: Private
   ###
 
+  assert: (condition, message, metadata) ->
+    return true if condition
+
+    error = new Error("Assertion failed: " + message)
+    Error.captureStackTrace(error, @assert)
+
+    if metadata?
+      if typeof metadata is 'function'
+        error.metadata = metadata()
+      else
+        error.metadata = metadata
+
+    @emitter.emit 'did-fail-assertion', error
+
+    false
+
   deserializeProject: ->
     Project = require './project'
 

src/tokenized-buffer.coffee

@@ -292,7 +292,17 @@ class TokenizedBuffer extends Model
   # Returns a {Boolean} indicating whether the given buffer row starts
   # a a foldable row range due to the code's indentation patterns.
   isFoldableCodeAtRow: (row) ->
-    return false if @buffer.isRowBlank(row) or @tokenizedLineForRow(row).isComment()
+    # Investigating an exception that's occurring here due to the line being
+    # undefined. This should paper over the problem but we want to figure out
+    # what is happening:
+    tokenizedLine = @tokenizedLineForRow(row)
+    atom.assert tokenizedLine?, "TokenizedLine is defined", =>
+      metadata:
+        row: row
+        rowCount: @tokenizedLines.length
+    return false unless tokenizedLine?
+
+    return false if @buffer.isRowBlank(row) or tokenizedLine.isComment()
     nextRow = @buffer.nextNonBlankRow(row)
     return false unless nextRow?