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: Which is a format that can be fed directly into Jison. | {Rewriter} = require './rewriter' |
| Import the helpers we need. | {count, starts, compact, last} = require './helpers' |
The Lexer Class | |
| The Lexer class reads a stream of CoffeeScript and divvies 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 returning the number of characters it has consumed. Before returning the token stream, run it through the Rewriter unless explicitly asked not to. | tokenize: (code, opts = {}) ->
code = "\n#{code}" if WHITESPACE.test code
code = code.replace(/\r/g, '').replace TRAILING_SPACES, ''
@code = code # The remainder of the source code.
@line = opts.line or 0 # The current line.
@indent = 0 # The current indentation level.
@indebt = 0 # The over-indentation at the current level.
@outdebt = 0 # The under-outdentation at the current level.
@indents = [] # The stack of all current indentation levels.
@tokens = [] # Stream of parsed tokens in the form `['TYPE', value, line]`. |
| At every position, run through this list of attempted matches,
short-circuiting if any of them succeed. Their order determines precedence:
| i = 0
while @chunk = code.slice i
i += @identifierToken() or
@commentToken() or
@whitespaceToken() or
@lineToken() or
@heredocToken() or
@stringToken() or
@numberToken() or
@regexToken() or
@jsToken() or
@literalToken()
@closeIndentation()
return @tokens if opts.rewrite is off
(new Rewriter).rewrite @tokens |
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 | identifierToken: ->
return 0 unless match = IDENTIFIER.exec @chunk
[input, id, colon] = match
if id is 'own' and @tag() is 'FOR'
@token 'OWN', id
return id.length
forcedIdentifier = colon or
(prev = last @tokens) and (prev[0] in ['.', '?.', '::'] or
not prev.spaced and prev[0] is '@')
tag = 'IDENTIFIER'
if id in JS_KEYWORDS or
not forcedIdentifier and id in COFFEE_KEYWORDS
tag = id.toUpperCase()
if tag is 'WHEN' and @tag() in LINE_BREAK
tag = 'LEADING_WHEN'
else if tag is 'FOR'
@seenFor = yes
else if tag is 'UNLESS'
tag = 'IF'
else if tag in UNARY
tag = 'UNARY'
else if tag in RELATION
if tag isnt 'INSTANCEOF' and @seenFor
tag = 'FOR' + tag
@seenFor = no
else
tag = 'RELATION'
if @value() is '!'
@tokens.pop()
id = '!' + id
if id in JS_FORBIDDEN
if forcedIdentifier
tag = 'IDENTIFIER'
id = new String id
id.reserved = yes
else if id in RESERVED
@identifierError id
unless forcedIdentifier
id = COFFEE_ALIAS_MAP[id] if id in COFFEE_ALIASES
tag = switch id
when '!' then 'UNARY'
when '==', '!=' then 'COMPARE'
when '&&', '||' then 'LOGIC'
when 'true', 'false', 'null', 'undefined' then 'BOOL'
when 'break', 'continue', 'debugger' then 'STATEMENT'
else tag
@token tag, id
@token ':', ':' if colon
input.length |
| Matches numbers, including decimals, hex, and exponential notation. Be careful not to interfere with ranges-in-progress. | numberToken: ->
return 0 unless match = NUMBER.exec @chunk
number = match[0]
@token 'NUMBER', number
number.length |
| Matches strings, including multi-line strings. Ensures that quotation marks are balanced within the string's contents, and within nested interpolations. | stringToken: ->
switch @chunk.charAt 0
when "'"
return 0 unless match = SIMPLESTR.exec @chunk
@token 'STRING', (string = match[0]).replace MULTILINER, '\\\n'
when '"'
return 0 unless string = @balancedString @chunk, '"'
if 0 < string.indexOf '#{', 1
@interpolateString string.slice 1, -1
else
@token 'STRING', @escapeLines string
else
return 0
@line += count string, '\n'
string.length |
| Matches heredocs, adjusting indentation to the correct level, as heredocs preserve whitespace, but ignore indentation to the left. | heredocToken: ->
return 0 unless match = HEREDOC.exec @chunk
heredoc = match[0]
quote = heredoc.charAt 0
doc = @sanitizeHeredoc match[2], quote: quote, indent: null
if quote is '"' and 0 <= doc.indexOf '#{'
@interpolateString doc, heredoc: yes
else
@token 'STRING', @makeString doc, quote, yes
@line += count heredoc, '\n'
heredoc.length |
| Matches and consumes comments. | commentToken: ->
return 0 unless match = @chunk.match COMMENT
[comment, here] = match
if here
@token 'HERECOMMENT', @sanitizeHeredoc here,
herecomment: true, indent: Array(@indent + 1).join(' ')
@token 'TERMINATOR', '\n'
@line += count comment, '\n'
comment.length |
| Matches JavaScript interpolated directly into the source via backticks. | jsToken: ->
return 0 unless @chunk.charAt(0) is '`' and match = JSTOKEN.exec @chunk
@token 'JS', (script = match[0]).slice 1, -1
script.length |
| Matches regular expression literals. Lexing regular expressions is difficult to distinguish from division, so we borrow some basic heuristics from JavaScript and Ruby. | regexToken: ->
return 0 if @chunk.charAt(0) isnt '/'
return @heregexToken match if match = HEREGEX.exec @chunk
prev = last @tokens
return 0 if prev and (prev[0] in (if prev.spaced then NOT_REGEX else NOT_SPACED_REGEX))
return 0 unless match = REGEX.exec @chunk
[regex] = match
@token 'REGEX', if regex is '//' then '/(?:)/' else regex
regex.length |
| Matches multiline extended regular expressions. | heregexToken: (match) ->
[heregex, body, flags] = match
if 0 > body.indexOf '#{'
re = body.replace(HEREGEX_OMIT, '').replace(/\//g, '\\/')
@token 'REGEX', "/#{ re or '(?:)' }/#{flags}"
return heregex.length
@token 'IDENTIFIER', 'RegExp'
@tokens.push ['CALL_START', '(']
tokens = []
for [tag, value] in @interpolateString(body, regex: yes)
if tag is 'TOKENS'
tokens.push value...
else
continue unless value = value.replace HEREGEX_OMIT, ''
value = value.replace /\\/g, '\\\\'
tokens.push ['STRING', @makeString(value, '"', yes)]
tokens.push ['+', '+']
tokens.pop()
@tokens.push ['STRING', '""'], ['+', '+'] unless tokens[0]?[0] is 'STRING'
@tokens.push tokens...
@tokens.push [',', ','], ['STRING', '"' + flags + '"'] if flags
@token ')', ')'
heregex.length |
| 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: 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. | lineToken: ->
return 0 unless match = MULTI_DENT.exec @chunk
indent = match[0]
@line += count indent, '\n'
prev = last @tokens, 1
size = indent.length - 1 - indent.lastIndexOf '\n'
noNewlines = @unfinished()
if size - @indebt is @indent
if noNewlines then @suppressNewlines() else @newlineToken()
return indent.length
if size > @indent
if noNewlines
@indebt = size - @indent
@suppressNewlines()
return indent.length
diff = size - @indent + @outdebt
@token 'INDENT', diff
@indents.push diff
@outdebt = @indebt = 0
else
@indebt = 0
@outdentToken @indent - size, noNewlines
@indent = size
indent.length |
| Record an outdent token or multiple tokens, if we happen to be moving back inwards past several recorded indents. | outdentToken: (moveOut, noNewlines, close) ->
while moveOut > 0
len = @indents.length - 1
if @indents[len] is undefined
moveOut = 0
else if @indents[len] is @outdebt
moveOut -= @outdebt
@outdebt = 0
else if @indents[len] < @outdebt
@outdebt -= @indents[len]
moveOut -= @indents[len]
else
dent = @indents.pop() - @outdebt
moveOut -= dent
@outdebt = 0
@token 'OUTDENT', dent
@outdebt -= moveOut if dent
@token 'TERMINATOR', '\n' unless @tag() is 'TERMINATOR' or noNewlines
this |
| Matches and consumes non-meaningful whitespace. Tag the previous token as being "spaced", because there are some cases where it makes a difference. | whitespaceToken: ->
return 0 unless (match = WHITESPACE.exec @chunk) or
(nline = @chunk.charAt(0) is '\n')
prev = last @tokens
prev[if match then 'spaced' else 'newLine'] = true if prev
if match then match[0].length else 0 |
| Generate a newline token. Consecutive newlines get merged together. | newlineToken: ->
@token 'TERMINATOR', '\n' unless @tag() is 'TERMINATOR'
this |
| Use a | suppressNewlines: ->
@tokens.pop() if @value() is '\\'
this |
| We treat all other single characters as a token. E.g.: | literalToken: ->
if match = OPERATOR.exec @chunk
[value] = match
@tagParameters() if CODE.test value
else
value = @chunk.charAt 0
tag = value
prev = last @tokens
if value is '=' and prev
@assignmentError() if not prev[1].reserved and prev[1] in JS_FORBIDDEN
if prev[1] in ['||', '&&']
prev[0] = 'COMPOUND_ASSIGN'
prev[1] += '='
return value.length
if value is ';' then tag = 'TERMINATOR'
else if value in MATH then tag = 'MATH'
else if value in COMPARE then tag = 'COMPARE'
else if value in COMPOUND_ASSIGN then tag = 'COMPOUND_ASSIGN'
else if value in UNARY then tag = 'UNARY'
else if value in SHIFT then tag = 'SHIFT'
else if value in LOGIC or value is '?' and prev?.spaced then tag = 'LOGIC'
else if prev and not prev.spaced
if value is '(' and prev[0] in CALLABLE
prev[0] = 'FUNC_EXIST' if prev[0] is '?'
tag = 'CALL_START'
else if value is '[' and prev[0] in INDEXABLE
tag = 'INDEX_START'
switch prev[0]
when '?' then prev[0] = 'INDEX_SOAK'
when '::' then prev[0] = 'INDEX_PROTO'
@token tag, value
value.length |
Token Manipulators | |
| Sanitize a heredoc or herecomment by erasing all external indentation on the left-hand side. | sanitizeHeredoc: (doc, options) ->
{indent, herecomment} = options
if herecomment
if HEREDOC_ILLEGAL.test doc
throw new Error "block comment cannot contain \"*/\", starting on line #{@line + 1}"
return doc if doc.indexOf('\n') <= 0
else
while match = HEREDOC_INDENT.exec doc
attempt = match[1]
indent = attempt if indent is null or 0 < attempt.length < indent.length
doc = doc.replace /// \n #{indent} ///g, '\n' if indent
doc = doc.replace /^\n/, '' unless herecomment
doc |
| 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. | tagParameters: ->
return this if @tag() isnt ')'
stack = []
{tokens} = this
i = tokens.length
tokens[--i][0] = 'PARAM_END'
while tok = tokens[--i]
switch tok[0]
when ')'
stack.push tok
when '(', 'CALL_START'
if stack.length then stack.pop()
else if tok[0] is '('
tok[0] = 'PARAM_START'
return this
this |
| Close up all remaining open blocks at the end of the file. | closeIndentation: ->
@outdentToken @indent |
| The error for when you try to use a forbidden word in JavaScript as an identifier. | identifierError: (word) ->
throw 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". | assignmentError: ->
throw 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, ad infinitum. | balancedString: (str, end) ->
stack = [end]
for i in [1...str.length]
switch letter = str.charAt i
when '\\'
i++
continue
when end
stack.pop()
unless stack.length
return str.slice 0, i + 1
end = stack[stack.length - 1]
continue
if end is '}' and letter in ['"', "'"]
stack.push end = letter
else if end is '}' and letter is '{'
stack.push end = '}'
else if end is '"' and prev is '#' and letter is '{'
stack.push end = '}'
prev = letter
throw new Error "missing #{ stack.pop() }, starting on line #{ @line + 1 }" |
| Expand variables and expressions inside double-quoted strings using Ruby-like notation for substitution of arbitrary expressions. If it encounters an interpolation, this method will recursively create a new Lexer, tokenize the interpolated contents, and merge them into the token stream. | interpolateString: (str, options = {}) ->
{heredoc, regex} = options
tokens = []
pi = 0
i = -1
while letter = str.charAt i += 1
if letter is '\\'
i += 1
continue
unless letter is '#' and str.charAt(i+1) is '{' and
(expr = @balancedString str.slice(i + 1), '}')
continue
tokens.push ['NEOSTRING', str.slice(pi, i)] if pi < i
inner = expr.slice(1, -1)
if inner.length
nested = new Lexer().tokenize inner, line: @line, rewrite: off
nested.pop()
nested.shift() if nested[0]?[0] is 'TERMINATOR'
if len = nested.length
if len > 1
nested.unshift ['(', '(']
nested.push [')', ')']
tokens.push ['TOKENS', nested]
i += expr.length
pi = i + 1
tokens.push ['NEOSTRING', str.slice pi] if i > pi < str.length
return tokens if regex
return @token 'STRING', '""' unless tokens.length
tokens.unshift ['', ''] unless tokens[0][0] is 'NEOSTRING'
@token '(', '(' if interpolated = tokens.length > 1
for [tag, value], i in tokens
@token '+', '+' if i
if tag is 'TOKENS'
@tokens.push value...
else
@token 'STRING', @makeString value, '"', heredoc
@token ')', ')' if interpolated
tokens |
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) ->
(tok = last @tokens, index) and if tag then tok[0] = tag else tok[0] |
| Peek at a value in the current token stream. | value: (index, val) ->
(tok = last @tokens, index) and if val then tok[1] = val else tok[1] |
| Are we in the midst of an unfinished expression? | unfinished: ->
LINE_CONTINUER.test(@chunk) or
(prev = last @tokens, 1) and prev[0] isnt '.' and
(value = @value()) and not value.reserved and
NO_NEWLINE.test(value) and not CODE.test(value) and not ASSIGNED.test(@chunk) |
| Converts newlines for string literals. | escapeLines: (str, heredoc) ->
str.replace MULTILINER, if heredoc then '\\n' else '' |
| Constructs a string token by escaping quotes and newlines. | makeString: (body, quote, heredoc) ->
return quote + quote unless body
body = body.replace /\\([\s\S])/g, (match, contents) ->
if contents in ['\n', quote] then contents else match
body = body.replace /// #{quote} ///g, '\\$&'
quote + @escapeLines(body, heredoc) + quote |
Constants | |
| Keywords that CoffeeScript shares in common with JavaScript. | JS_KEYWORDS = [
'true', 'false', 'null', 'this'
'new', 'delete', 'typeof', 'in', 'instanceof'
'return', 'throw', 'break', 'continue', 'debugger'
'if', 'else', 'switch', 'for', 'while', 'do', 'try', 'catch', 'finally'
'class', 'extends', 'super'
] |
| CoffeeScript-only keywords. | COFFEE_KEYWORDS = ['undefined', 'then', 'unless', 'until', 'loop', 'of', 'by', 'when']
COFFEE_ALIAS_MAP =
and : '&&'
or : '||'
is : '=='
isnt : '!='
not : '!'
yes : 'true'
no : 'false'
on : 'true'
off : 'false'
COFFEE_ALIASES = (key for key of COFFEE_ALIAS_MAP)
COFFEE_KEYWORDS = COFFEE_KEYWORDS.concat COFFEE_ALIASES |
| 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', 'function', 'var', 'void', 'with'
'const', 'let', 'enum', 'export', 'import', 'native'
'__hasProp', '__extends', '__slice', '__bind', '__indexOf'
] |
| 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
exports.RESERVED = RESERVED.concat(JS_KEYWORDS).concat(COFFEE_KEYWORDS) |
| Token matching regexes. | IDENTIFIER = /// ^
( [$A-Za-z_\x7f-\uffff][$\w\x7f-\uffff]* )
( [^\n\S]* : (?!:) )? # Is this a property name?
///
NUMBER = ///
^ 0x[\da-f]+ | # hex
^ (?: \d+(\.\d+)? | \.\d+ ) (?:e[+-]?\d+)? # decimal
///i
HEREDOC = /// ^ ("""|''') ([\s\S]*?) (?:\n[^\n\S]*)? \1 ///
OPERATOR = /// ^ (
?: [-=]> # function
| [-+*/%<>&|^!?=]= # compound assign / compare
| >>>=? # zero-fill right shift
| ([-+:])\1 # doubles
| ([&|<>])\2=? # logic / shift
| \?\. # soak access
| \.{2,3} # range or splat
) ///
WHITESPACE = /^[^\n\S]+/
COMMENT = /^###([^#][\s\S]*?)(?:###[^\n\S]*|(?:###)?$)|^(?:\s*#(?!##[^#]).*)+/
CODE = /^[-=]>/
MULTI_DENT = /^(?:\n[^\n\S]*)+/
SIMPLESTR = /^'[^\\']*(?:\\.[^\\']*)*'/
JSTOKEN = /^`[^\\`]*(?:\\.[^\\`]*)*`/ |
| Regex-matching-regexes. | REGEX = /// ^
/ (?! [\s=] ) # disallow leading whitespace or equals signs
[^ [ / \n \\ ]* # every other thing
(?:
(?: \\[\s\S] # anything escaped
| \[ # character class
[^ \] \n \\ ]*
(?: \\[\s\S] [^ \] \n \\ ]* )*
]
) [^ [ / \n \\ ]*
)*
/ [imgy]{0,4} (?!\w)
///
HEREGEX = /// ^ /{3} ([\s\S]+?) /{3} ([imgy]{0,4}) (?!\w) ///
HEREGEX_OMIT = /\s+(?:#.*)?/g |
| Token cleaning regexes. | MULTILINER = /\n/g
HEREDOC_INDENT = /\n+([^\n\S]*)/g
HEREDOC_ILLEGAL = /\*\//
ASSIGNED = /^\s*@?([$A-Za-z_][$\w\x7f-\uffff]*|['"].*['"])[^\n\S]*?[:=][^:=>]/
LINE_CONTINUER = /// ^ \s* (?: , | \??\.(?![.\d]) | :: ) ///
TRAILING_SPACES = /\s+$/
NO_NEWLINE = /// ^ (?: # non-capturing group
[-+*&|/%=<>!.\\][<>=&|]* | # symbol operators
and | or | is(?:nt)? | n(?:ot|ew) | # word operators
delete | typeof | instanceof
) $ /// |
| Compound assignment tokens. | COMPOUND_ASSIGN = [
'-=', '+=', '/=', '*=', '%=', '||=', '&&=', '?=', '<<=', '>>=', '>>>=', '&=', '^=', '|='
] |
| Unary tokens. | UNARY = ['!', '~', 'NEW', 'TYPEOF', 'DELETE', 'DO'] |
| Logical tokens. | LOGIC = ['&&', '||', '&', '|', '^'] |
| Bit-shifting tokens. | SHIFT = ['<<', '>>', '>>>'] |
| Comparison tokens. | COMPARE = ['==', '!=', '<', '>', '<=', '>='] |
| Mathematical tokens. | MATH = ['*', '/', '%'] |
| Relational tokens that are negatable with | RELATION = ['IN', 'OF', 'INSTANCEOF'] |
| Boolean tokens. | BOOL = ['TRUE', 'FALSE', 'NULL', 'UNDEFINED'] |
| 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', 'BOOL', '++', '--', ']'] |
| If the previous token is not spaced, there are more preceding tokens that force a division parse: | NOT_SPACED_REGEX = NOT_REGEX.concat ')', '}', 'THIS', 'IDENTIFIER', 'STRING' |
| 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', 'STRING', 'REGEX', ')', ']', '}', '?', '::', '@', 'THIS', 'SUPER']
INDEXABLE = CALLABLE.concat 'NUMBER', 'BOOL' |
| Tokens that, when immediately preceding a | LINE_BREAK = ['INDENT', 'OUTDENT', 'TERMINATOR']
|