helpers.coffee

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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 element instanceof Array
      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
```

Gets the last item of an array(-like) object.

exports.last = last = (array, back) -> array[array.length - (back or 0) - 1]

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, pathSep = '/') ->
  parts = file.split(pathSep)
  file = parts[parts.length - 1]
  return file unless stripExt
  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 with a source file location data attached to it in a property called location.

exports.throwSyntaxError = (message, location) ->
  location.last_line ?= location.first_line
  location.last_column ?= location.first_column
  error = new SyntaxError message
  error.location = location
  throw error

Creates a nice error message like, following the "standard" format

::: plus the line with the error and a marker showing where the error is.

exports.prettyErrorMessage = (error, fileName, code, useColors) ->
  return error.stack or "#{error}" unless error.location

  {first_line, first_column, last_line, last_column} = error.location
  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   = repeat(' ', start) + repeat('^', end - start)

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

  message = """
  #{fileName}:#{first_line + 1}:#{first_column + 1}: error: #{error.message}
  #{codeLine}
  #{marker}
            """

¶

Uncomment to add stacktrace. message += "\n#{error.stack}"
```
  message
```