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- # helpers.coffee

- ¶

  This file contains the common helper functions that we’d like to share among the Lexer, Rewriter, and the Nodes. Merge objects, flatten arrays, count characters, that sort of thing.

- ¶

  Peek at the beginning of a given string to see if it matches a sequence.

      exports.starts = (string, literal, start) ->
        literal is string.substr start, literal.length

- ¶

  Peek at the end of a given string to see if it matches a sequence.

      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 = repeat = (str, n) ->

- ¶

  Use clever algorithm to have O(log(n)) string concatenation operations.

        res = ''
        while n > 0
          res += str if n & 1
          n >>>= 1
          str += str
        res

- ¶

  Trim out all falsy values from an array.

      exports.compact = (array) ->
        item for item in array when item

- ¶

  Count the number of occurrences of a string in a string.

      exports.count = (string, substr) ->
        num = pos = 0
        return 1/0 unless substr.length
        num++ while pos = 1 + string.indexOf substr, pos
        num

- ¶

  Merge objects, returning a fresh copy with attributes from both sides. Used every time `Base#compile` is called, to allow properties in the options hash to propagate down the tree without polluting other branches.

      exports.merge = (options, overrides) ->
        extend (extend {}, options), overrides

- ¶

  Extend a source object with the properties of another object (shallow copy).

      extend = exports.extend = (object, properties) ->
        for key, val of properties
          object[key] = val
        object

- ¶

  Return a flattened version of an array. Handy for getting a list of `children` from the nodes.

      exports.flatten = flatten = (array) ->
        flattened = []
        for element in array
          if '[object Array]' is Object::toString.call element
            flattened = flattened.concat flatten element
          else
            flattened.push element
        flattened

- ¶

  Delete a key from an object, returning the value. Useful when a node is looking for a particular method in an options hash.

      exports.del = (obj, key) ->
        val =  obj[key]
        delete obj[key]
        val

- ¶

  Typical Array::some

      exports.some = Array::some ? (fn) ->
        return true for e in this when fn e
        false

- ¶

  Simple function for inverting Literate CoffeeScript code by putting the documentation in comments, producing a string of CoffeeScript code that can be compiled “normally”.

      exports.invertLiterate = (code) ->
        maybe_code = true
        lines = for line in code.split('\n')
          if maybe_code and /^([ ]{4}|[ ]{0,3}\t)/.test line
            line
          else if maybe_code = /^\s*$/.test line
            line
          else
            '# ' + line
        lines.join '\n'

- ¶

  Merge two jison-style location data objects together. If `last` is not provided, this will simply return `first`.

      buildLocationData = (first, last) ->
        if not last
          first
        else
          first_line: first.first_line
          first_column: first.first_column
          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.

      exports.addLocationDataFn = (first, last) ->
        (obj) ->
          if ((typeof obj) is 'object') and (!!obj['updateLocationDataIfMissing'])
            obj.updateLocationDataIfMissing buildLocationData(first, last)

          return obj

- ¶

  Convert jison location data to a string. `obj` can be a token, or a locationData.

      exports.locationDataToString = (obj) ->
        if ("2" of obj) and ("first_line" of obj[2]) then locationData = obj[2]
        else if "first_line" of obj then locationData = obj

        if locationData
          "#{locationData.first_line + 1}:#{locationData.first_column + 1}-" +
          "#{locationData.last_line + 1}:#{locationData.last_column + 1}"
        else
          "No location data"

- ¶

  A `.coffee.md` compatible version of `basename`, that returns the file sans-extension.

      exports.baseFileName = (file, stripExt = no, useWinPathSep = no) ->
        pathSep = if useWinPathSep then /\\|\// else /\//
        parts = file.split(pathSep)
        file = parts[parts.length - 1]
        return file unless stripExt and file.indexOf('.') >= 0
        parts = file.split('.')
        parts.pop()
        parts.pop() if parts[parts.length - 1] is 'coffee' and parts.length > 1
        parts.join('.')

- ¶

  Determine if a filename represents a CoffeeScript file.

      exports.isCoffee = (file) -> /\.((lit)?coffee|coffee\.md)$/.test file

- ¶

  Determine if a filename represents a Literate CoffeeScript file.

      exports.isLiterate = (file) -> /\.(litcoffee|coffee\.md)$/.test file

- ¶

  Throws a SyntaxError from a given location. The error’s `toString` will return an error message following the “standard” format ::: plus the line with the error and a marker showing where the error is.

      exports.throwSyntaxError = (message, location) ->
        error = new SyntaxError message
        error.location = location
        error.toString = syntaxErrorToString

- ¶

  Instead of showing the compiler’s stacktrace, show our custom error message (this is useful when the error bubbles up in Node.js applications that compile CoffeeScript for example).

        error.stack = error.toString()

        throw error

- ¶

  Update a compiler SyntaxError with source code information if it didn’t have it already.

      exports.updateSyntaxError = (error, code, filename) ->

- ¶

  Avoid screwing up the `stack` property of other errors (i.e. possible bugs).

        if error.toString is syntaxErrorToString
          error.code or= code
          error.filename or= filename
          error.stack = error.toString()
        error

      syntaxErrorToString = ->
        return Error::toString.call @ unless @code and @location

        {first_line, first_column, last_line, last_column} = @location
        last_line ?= first_line
        last_column ?= first_column

        filename = @filename or '[stdin]'
        codeLine = @code.split('\n')[first_line]
        start    = first_column

- ¶

  Show only the first line on multi-line errors.

        end      = if first_line is last_line then last_column + 1 else codeLine.length
        marker   = codeLine[...start].replace(/[^\s]/g, ' ') + repeat('^', end - start)

- ¶

  Check to see if we’re running on a color-enabled TTY.

        if process?
          colorsEnabled = process.stdout?.isTTY and not process.env?.NODE_DISABLE_COLORS

        if @colorful ? colorsEnabled
          colorize = (str) -> "\x1B[1;31m#{str}\x1B[0m"
          codeLine = codeLine[...start] + colorize(codeLine[start...end]) + codeLine[end..]
          marker   = colorize marker

        """
          #{filename}:#{first_line + 1}:#{first_column + 1}: error: #{@message}
          #{codeLine}
          #{marker}
        """

      exports.nameWhitespaceCharacter = (string) ->
        switch string
          when ' ' then 'space'
          when '\n' then 'newline'
          when '\r' then 'carriage return'
          when '\t' then 'tab'
          else string