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lexer.coffee

#

The CoffeeScript Lexer. Uses a series of token-matching regexes to attempt matches against the beginning of the source code. When a match is found, a token is produced, we consume the match, and start again. Tokens are in the form:

[tag, value, line_number]

Which is a format that can be fed directly into Jison.

 
             		           
                               
                            
                 #               
               
Set up the Lexer for both Node.js and the browser, depending on where we are.
             		                            
if process?
  Rewriter: require('./rewriter').Rewriter
else
  this.exports: this
  Rewriter: this.Rewriter
             		           
                               
                            
                 #               
               
The Lexer Class
             		                            
             		           
                               
                            
                 #               
               
The Lexer class reads a stream of CoffeeScript and divvys it up into tagged
tokens. Some potential ambiguity in the grammar has been avoided by
pushing some extra smarts into the Lexer.
             		                            
exports.Lexer: class Lexer
             		           
                               
                            
                 #               
               
tokenize is the Lexer's main method. Scan by attempting to match tokens
one at a time, using a regular expression anchored at the start of the
remaining code, or a custom recursive token-matching method
(for interpolations). When the next token has been recorded, we move forward
within the code past the token, and begin again.



Each tokenizing method is responsible for incrementing @i by the number of
characters it has consumed. @i can be thought of as our finger on the page
of source.



Before returning the token stream, run it through the Rewriter
unless explicitly asked not to.
             		                            
  tokenize: (code, options) ->
    o        : options or {}
    @code    : code         # The remainder of the source code.
    @i       : 0            # Current character position we're parsing.
    @line    : o.line or 0  # The current line.
    @indent  : 0            # The current indentation level.
    @indents : []           # The stack of all current indentation levels.
    @tokens  : []           # Stream of parsed tokens in the form ['TYPE', value, line]
    while @i < @code.length
      @chunk: @code.slice(@i)
      @extract_next_token()
    @close_indentation()
    return @tokens if o.rewrite is off
    (new Rewriter()).rewrite @tokens
             		           
                               
                            
                 #               
               
At every position, run through this list of attempted matches,
short-circuiting if any of them succeed. Their order determines precedence:
@literal_token is the fallback catch-all.
             		                            
  extract_next_token: ->
    return if @identifier_token()
    return if @number_token()
    return if @heredoc_token()
    return if @regex_token()
    return if @comment_token()
    return if @line_token()
    return if @whitespace_token()
    return if @js_token()
    return if @string_token()
    return    @literal_token()
             		           
                               
                            
                 #               
               
Tokenizers
             		                            
             		           
                               
                            
                 #               
               
Matches identifying literals: variables, keywords, method names, etc.
Check to ensure that JavaScript reserved words aren't being used as
identifiers. Because CoffeeScript reserves a handful of keywords that are
allowed in JavaScript, we're careful not to tag them as keywords when
referenced as property names here, so you can still do jQuery.is() even
though is means === otherwise.
             		                            
  identifier_token: ->
    return false unless id: @match IDENTIFIER, 1
    @name_access_type()
    tag: 'IDENTIFIER'
    tag: id.toUpperCase() if include(KEYWORDS, id) and
      not (include(ACCESSORS, @tag(0)) and not @prev().spaced)
    @identifier_error id  if include RESERVED, id
    tag: 'LEADING_WHEN'   if tag is 'WHEN' and include BEFORE_WHEN, @tag()
    @token(tag, id)
    @i += id.length
    true
             		           
                               
                            
                 #               
               
Matches numbers, including decimals, hex, and exponential notation.
             		                            
  number_token: ->
    return false unless number: @match NUMBER, 1
    @token 'NUMBER', number
    @i += number.length
    true
             		           
                               
                            
                 #               
               
Matches strings, including multi-line strings. Ensures that quotation marks
are balanced within the string's contents, and within nested interpolations.
             		                            
  string_token: ->
    return false unless starts(@chunk, '"') or starts(@chunk, "'")
    string: @balanced_token ['"', '"'], ['${', '}']
    string: @balanced_token ["'", "'"] unless string
    return false unless string
    @interpolate_string string.replace STRING_NEWLINES, " \\\n"
    @line += count string, "\n"
    @i += string.length
    true
             		           
                               
                            
                 #               
               
Matches heredocs, adjusting indentation to the correct level, as heredocs
preserve whitespace, but ignore indentation to the left.
             		                            
  heredoc_token: ->
    return false unless match = @chunk.match(HEREDOC)
    doc: @sanitize_heredoc match[2] or match[4]
    @token 'STRING', "\"$doc\""
    @line += count match[1], "\n"
    @i += match[1].length
    true
             		           
                               
                            
                 #               
               
Matches JavaScript interpolated directly into the source via backticks.
             		                            
  js_token: ->
    return false unless starts @chunk, '`'
    return false unless script: @balanced_token ['`', '`']
    @token 'JS', script.replace(JS_CLEANER, '')
    @i += script.length
    true
             		           
                               
                            
                 #               
               
Matches regular expression literals. Lexing regular expressions is difficult
to distinguish from division, so we borrow some basic heuristics from
JavaScript and Ruby.
             		                            
  regex_token: ->
    return false unless regex: @match REGEX, 1
    return false if include NOT_REGEX, @tag()
    @token 'REGEX', regex
    @i += regex.length
    true
             		           
                               
                            
                 #               
               
Matches a token in which which the passed delimiter pairs must be correctly
balanced (ie. strings, JS literals).
             		                            
  balanced_token: (delimited...) ->
    @balanced_string @chunk, delimited...
             		           
                               
                            
                 #               
               
Matches and conumes comments. We pass through comments into JavaScript,
so they're treated as real tokens, like any other part of the language.
             		                            
  comment_token: ->
    return false unless comment: @match COMMENT, 1
    @line += (comment.match(MULTILINER) or []).length
    lines: comment.replace(COMMENT_CLEANER, '').split(MULTILINER)
    @token 'COMMENT', compact lines
    @token 'TERMINATOR', "\n"
    @i += comment.length
    true
             		           
                               
                            
                 #               
               
Matches newlines, indents, and outdents, and determines which is which.
If we can detect that the current line is continued onto the the next line,
then the newline is suppressed:



elements
  .each( ... )
  .map( ... )




Keeps track of the level of indentation, because a single outdent token
can close multiple indents, so we need to know how far in we happen to be.
             		                            
  line_token: ->
    return false unless indent: @match MULTI_DENT, 1
    @line += indent.match(MULTILINER).length
    @i    += indent.length
    prev: @prev(2)
    size: indent.match(LAST_DENTS).reverse()[0].match(LAST_DENT)[1].length
    next_character: @chunk.match(MULTI_DENT)[4]
    no_newlines: next_character is '.' or (@value() and @value().match(NO_NEWLINE) and
      prev and (prev[0] isnt '.') and not @value().match(CODE))
    if size is @indent
      return @suppress_newlines() if no_newlines
      return @newline_token(indent)
    else if size > @indent
      return @suppress_newlines() if no_newlines
      diff: size - @indent
      @token 'INDENT', diff
      @indents.push diff
    else
      @outdent_token @indent - size, no_newlines
    @indent: size
    true
             		           
                               
                            
                 #               
               
Record an outdent token or multiple tokens, if we happen to be moving back
inwards past several recorded indents.
             		                            
  outdent_token: (move_out, no_newlines) ->
    while move_out > 0 and @indents.length
      last_indent: @indents.pop()
      @token 'OUTDENT', last_indent
      move_out -= last_indent
    @token 'TERMINATOR', "\n" unless @tag() is 'TERMINATOR' or no_newlines
    true
             		           
                               
                            
                 #               
               
Matches and consumes non-meaningful whitespace. Tag the previous token
as being "spaced", because there are some cases where it makes a difference.
             		                            
  whitespace_token: ->
    return false unless space: @match WHITESPACE, 1
    prev: @prev()
    prev.spaced: true if prev
    @i += space.length
    true
             		           
                               
                            
                 #               
               
Generate a newline token. Consecutive newlines get merged together.
             		                            
  newline_token: (newlines) ->
    @token 'TERMINATOR', "\n" unless @tag() is 'TERMINATOR'
    true
             		           
                               
                            
                 #               
               
Use a \ at a line-ending to suppress the newline.
The slash is removed here once its job is done.
             		                            
  suppress_newlines: ->
    @tokens.pop() if @value() is "\\"
    true
             		           
                               
                            
                 #               
               
We treat all other single characters as a token. Eg.: ( ) , . !
Multi-character operators are also literal tokens, so that Jison can assign
the proper order of operations. There are some symbols that we tag specially
here. ; and newlines are both treated as a TERMINATOR, we distinguish
parentheses that indicate a method call from regular parentheses, and so on.
             		                            
  literal_token: ->
    match: @chunk.match(OPERATOR)
    value: match and match[1]
    @tag_parameters() if value and value.match(CODE)
    value ||= @chunk.substr(0, 1)
    not_spaced: not @prev() or not @prev().spaced
    tag: value
    if value.match(ASSIGNMENT)
      tag: 'ASSIGN'
      @assignment_error() if include JS_FORBIDDEN, @value
    else if value is ';'
      tag: 'TERMINATOR'
    else if value is '[' and @tag() is '?' and not_spaced
      tag: 'SOAKED_INDEX_START'
      @soaked_index: true
      @tokens.pop()
    else if value is ']' and @soaked_index
      tag: 'SOAKED_INDEX_END'
      @soaked_index: false
    else if include(CALLABLE, @tag()) and not_spaced
      tag: 'CALL_START'  if value is '('
      tag: 'INDEX_START' if value is '['
    @token tag, value
    @i += value.length
    true
             		           
                               
                            
                 #               
               
Token Manipulators
             		                            
             		           
                               
                            
                 #               
               
As we consume a new IDENTIFIER, look at the previous token to determine
if it's a special kind of accessor.
             		                            
  name_access_type: ->
    @tag(1, 'PROTOTYPE_ACCESS') if @value() is '::'
    if @value() is '.' and not (@value(2) is '.')
      if @tag(2) is '?'
        @tag(1, 'SOAK_ACCESS')
        @tokens.splice(-2, 1)
      else
        @tag 1, 'PROPERTY_ACCESS'
             		           
                               
                            
                 #               
               
Sanitize a heredoc by escaping internal double quotes and erasing all
external indentation on the left-hand side.
             		                            
  sanitize_heredoc: (doc) ->
    indent: (doc.match(HEREDOC_INDENT) or ['']).sort()[0]
    doc.replace(new RegExp("^" +indent, 'gm'), '')
       .replace(MULTILINER, "\\n")
       .replace(/"/g, '\\"')
             		           
                               
                            
                 #               
               
A source of ambiguity in our grammar used to be parameter lists in function
definitions versus argument lists in function calls. Walk backwards, tagging
parameters specially in order to make things easier for the parser.
             		                            
  tag_parameters: ->
    return if @tag() isnt ')'
    i: 0
    while true
      i += 1
      tok: @prev(i)
      return if not tok
      switch tok[0]
        when 'IDENTIFIER' then tok[0]: 'PARAM'
        when ')'          then tok[0]: 'PARAM_END'
        when '('          then return tok[0]: 'PARAM_START'
    true
             		           
                               
                            
                 #               
               
Close up all remaining open blocks at the end of the file.
             		                            
  close_indentation: ->
    @outdent_token(@indent)
             		           
                               
                            
                 #               
               
The error for when you try to use a forbidden word in JavaScript as
an identifier.
             		                            
  identifier_error: (word) ->
    throw new Error "SyntaxError: Reserved word \"$word\" on line ${@line + 1}"
             		           
                               
                            
                 #               
               
The error for when you try to assign to a reserved word in JavaScript,
like "function" or "default".
             		                            
  assignment_error: ->
    throw new Error "SyntaxError: Reserved word \"${@value()}\" on line ${@line + 1} can't be assigned"
             		           
                               
                            
                 #               
               
Matches a balanced group such as a single or double-quoted string. Pass in
a series of delimiters, all of which must be nested correctly within the
contents of the string. This method allows us to have strings within
interpolations within strings etc...
             		                            
  balanced_string: (str, delimited...) ->
    levels: []
    i: 0
    while i < str.length
      for pair in delimited
        [open, close]: pair
        if levels.length and starts str, '\\', i
          i += 1
          break
        else if levels.length and starts(str, close, i) and levels[levels.length - 1] is pair
          levels.pop()
          i += close.length - 1
          i += 1 unless levels.length
          break
        else if starts str, open, i
          levels.push(pair)
          i += open.length - 1
          break
      break unless levels.length
      i += 1
    throw new Error "SyntaxError: Unterminated ${levels.pop()[0]} starting on line ${@line + 1}" if levels.length
    return false if i is 0
    return str.substring(0, i)
             		           
                               
                            
                 #               
               
Expand variables and expressions inside double-quoted strings using
ECMA Harmony's interpolation syntax
for substitution of bare variables as well as arbitrary expressions.



"Hello $name."
"Hello ${name.capitalize()}."




If it encounters an interpolation, this method will recursively create a
new Lexer, tokenize the interpolated contents, and merge them into the
token stream.
             		                            
  interpolate_string: (str) ->
    if str.length < 3 or not starts str, '"'
      @token 'STRING', str
    else
      lexer:    new Lexer()
      tokens:   []
      quote:    str.substring(0, 1)
      [i, pi]:  [1, 1]
      while i < str.length - 1
        if starts str, '\\', i
          i += 1
        else if match: str.substring(i).match INTERPOLATION
          [group, interp]: match
          interp: "this.${ interp.substring(1) }" if starts interp, '@'
          tokens.push ['STRING', "$quote${ str.substring(pi, i) }$quote"] if pi < i
          tokens.push ['IDENTIFIER', interp]
          i += group.length - 1
          pi: i + 1
        else if (expr: @balanced_string str.substring(i), ['${', '}'])
          tokens.push ['STRING', "$quote${ str.substring(pi, i) }$quote"] if pi < i
          inner: expr.substring(2, expr.length - 1)
          if inner.length
            nested: lexer.tokenize "($inner)", {rewrite: no, line: @line}
            nested.pop()
            tokens.push ['TOKENS', nested]
          else
            tokens.push ['STRING', "$quote$quote"]
          i += expr.length - 1
          pi: i + 1
        i += 1
      tokens.push ['STRING', "$quote${ str.substring(pi, i) }$quote"] if pi < i and pi < str.length - 1
      for each, i in tokens
        if each[0] is 'TOKENS'
          @tokens: @tokens.concat each[1]
        else
          @token each[0], each[1]
        @token '+', '+' if i < tokens.length - 1
             		           
                               
                            
                 #               
               
Helpers
             		                            
             		           
                               
                            
                 #               
               
Add a token to the results, taking note of the line number.
             		                            
  token: (tag, value) ->
    @tokens.push([tag, value, @line])
             		           
                               
                            
                 #               
               
Peek at a tag in the current token stream.
             		                            
  tag: (index, tag) ->
    return unless tok: @prev(index)
    return tok[0]: tag if tag?
    tok[0]
             		           
                               
                            
                 #               
               
Peek at a value in the current token stream.
             		                            
  value: (index, val) ->
    return unless tok: @prev(index)
    return tok[1]: val if val?
    tok[1]
             		           
                               
                            
                 #               
               
Peek at a previous token, entire.
             		                            
  prev: (index) ->
    @tokens[@tokens.length - (index or 1)]
             		           
                               
                            
                 #               
               
Attempt to match a string against the current chunk, returning the indexed
match if successful, and false otherwise.
             		                            
  match: (regex, index) ->
    return false unless m: @chunk.match(regex)
    if m then m[index] else false
             		           
                               
                            
                 #               
               
Constants
             		                            
             		           
                               
                            
                 #               
               
Keywords that CoffeeScript shares in common with JavaScript.
             		                            
JS_KEYWORDS: [
  "if", "else",
  "true", "false",
  "new", "return",
  "try", "catch", "finally", "throw",
  "break", "continue",
  "for", "in", "while",
  "delete", "instanceof", "typeof",
  "switch", "super", "extends", "class"
]
             		           
                               
                            
                 #               
               
CoffeeScript-only keywords, which we're more relaxed about allowing. They can't
be used standalone, but you can reference them as an attached property.
             		                            
COFFEE_KEYWORDS: [
  "then", "unless",
  "yes", "no", "on", "off",
  "and", "or", "is", "isnt", "not",
  "of", "by", "where", "when"
]
             		           
                               
                            
                 #               
               
The combined list of keywords is the superset that gets passed verbatim to
the parser.
             		                            
KEYWORDS: JS_KEYWORDS.concat COFFEE_KEYWORDS
             		           
                               
                            
                 #               
               
The list of keywords that are reserved by JavaScript, but not used, or are
used by CoffeeScript internally. We throw an error when these are encountered,
to avoid having a JavaScript error at runtime.
             		                            
RESERVED: [
  "case", "default", "do", "function", "var", "void", "with"
  "const", "let", "debugger", "enum", "export", "import", "native",
  "__extends", "__hasProp"
]
             		           
                               
                            
                 #               
               
The superset of both JavaScript keywords and reserved words, none of which may
be used as identifiers or properties.
             		                            
JS_FORBIDDEN: JS_KEYWORDS.concat RESERVED
             		           
                               
                            
                 #               
               
Token matching regexes.
             		                            
IDENTIFIER    : /^([a-zA-Z$_](\w|\$)*)/
NUMBER        : /^(\b((0(x|X)[0-9a-fA-F]+)|([0-9]+(\.[0-9]+)?(e[+\-]?[0-9]+)?)))\b/i
HEREDOC       : /^("{6}|'{6}|"{3}\n?([\s\S]*?)\n?([ \t]*)"{3}|'{3}\n?([\s\S]*?)\n?([ \t]*)'{3})/
INTERPOLATION : /^\$([a-zA-Z_@]\w*(\.\w+)*)/
OPERATOR      : /^([+\*&|\/\-%=<>:!?]+)/
WHITESPACE    : /^([ \t]+)/
COMMENT       : /^(((\n?[ \t]*)?#[^\n]*)+)/
CODE          : /^((-|=)>)/
REGEX         : /^(\/(\S.*?)?([^\\]|\\\\)\/[imgy]{0,4})/
MULTI_DENT    : /^((\n([ \t]*))+)(\.)?/
LAST_DENTS    : /\n([ \t]*)/g
LAST_DENT     : /\n([ \t]*)/
ASSIGNMENT    : /^(:|=)$/
             		           
                               
                            
                 #               
               
Token cleaning regexes.
             		                            
JS_CLEANER      : /(^`|`$)/g
MULTILINER      : /\n/g
STRING_NEWLINES : /\n[ \t]*/g
COMMENT_CLEANER : /(^[ \t]*#|\n[ \t]*$)/mg
NO_NEWLINE      : /^([+\*&|\/\-%=<>:!.\\][<>=&|]*|and|or|is|isnt|not|delete|typeof|instanceof)$/
HEREDOC_INDENT  : /^[ \t]+/mg
             		           
                               
                            
                 #               
               
Tokens which a regular expression will never immediately follow, but which
a division operator might.



See: http://www.mozilla.org/js/language/js20-2002-04/rationale/syntax.html#regular-expressions



Our list is shorter, due to sans-parentheses method calls.
             		                            
NOT_REGEX: [
  'NUMBER', 'REGEX', '++', '--', 'FALSE', 'NULL', 'TRUE'
]
             		           
                               
                            
                 #               
               
Tokens which could legitimately be invoked or indexed. A opening
parentheses or bracket following these tokens will be recorded as the start
of a function invocation or indexing operation.
             		                            
CALLABLE: ['IDENTIFIER', 'SUPER', ')', ']', '}', 'STRING', '@']
             		           
                               
                            
                 #               
               
Tokens that indicate an access -- keywords immediately following will be
treated as identifiers.
             		                            
ACCESSORS: ['PROPERTY_ACCESS', 'PROTOTYPE_ACCESS', 'SOAK_ACCESS', '@']
             		           
                               
                            
                 #               
               
Tokens that, when immediately preceding a WHEN, indicate that the WHEN
occurs at the start of a line. We disambiguate these from trailing whens to
avoid an ambiguity in the grammar.
             		                            
BEFORE_WHEN: ['INDENT', 'OUTDENT', 'TERMINATOR']
             		           
                               
                            
                 #               
               
Utility Functions
             		                            
             		           
                               
                            
                 #               
               
Does a list include a value?
             		                            
include: (list, value) ->
  list.indexOf(value) >= 0
             		           
                               
                            
                 #               
               
Peek at the beginning of a given string to see if it matches a sequence.
             		                            
starts: (string, literal, start) ->
  string.substring(start, (start or 0) + literal.length) is literal
             		           
                               
                            
                 #               
               
Trim out all falsy values from an array.
             		                            
compact: (array) -> item for item in array when item
             		           
                               
                            
                 #               
               
Count the number of occurences of a character in a string.
             		                            
count: (string, letter) ->
  num: 0
  pos: string.indexOf(letter)
  while pos isnt -1
    num += 1
    pos: string.indexOf(letter, pos + 1)
  num