"""JsLex: a lexer for Javascript"""
# Originally from https://bitbucket.org/ned/jslex
import re
class Tok:
"""
A specification for a token class.
"""
num = 0
def __init__(self, name, regex, next=None):
self.id = Tok.num
Tok.num += 1
self.name = name
self.regex = regex
self.next = next
def literals(choices, prefix="", suffix=""):
"""
Create a regex from a space-separated list of literal `choices`.
If provided, `prefix` and `suffix` will be attached to each choice
individually.
"""
return "|".join(prefix + re.escape(c) + suffix for c in choices.split())
class Lexer:
"""
A generic multi-state regex-based lexer.
"""
def __init__(self, states, first):
self.regexes = {}
self.toks = {}
for state, rules in states.items():
parts = []
for tok in rules:
groupid = "t%d" % tok.id
self.toks[groupid] = tok
parts.append("(?P<%s>%s)" % (groupid, tok.regex))
self.regexes[state] = re.compile("|".join(parts), re.MULTILINE | re.VERBOSE)
self.state = first
def lex(self, text):
"""
Lexically analyze `text`.
Yield pairs (`name`, `tokentext`).
"""
end = len(text)
state = self.state
regexes = self.regexes
toks = self.toks
start = 0
while start < end:
for match in regexes[state].finditer(text, start):
name = match.lastgroup
tok = toks[name]
toktext = match.group(name)
start += len(toktext)
yield (tok.name, toktext)
if tok.next:
state = tok.next
break
self.state = state
class JsLexer(Lexer):
"""
A Javascript lexer
>>> lexer = JsLexer()
>>> list(lexer.lex("a = 1"))
[('id', 'a'), ('ws', ' '), ('punct', '='), ('ws', ' '), ('dnum', '1')]
This doesn't properly handle non-ASCII characters in the Javascript source.
"""
# Because these tokens are matched as alternatives in a regex, longer
# possibilities must appear in the list before shorter ones, for example,
# '>>' before '>'.
#
# Note that we don't have to detect malformed Javascript, only properly
# lex correct Javascript, so much of this is simplified.
# Details of Javascript lexical structure are taken from
# http://www.ecma-international.org/publications/files/ECMA-ST/ECMA-262.pdf
# A useful explanation of automatic semicolon insertion is at
# http://inimino.org/~inimino/blog/javascript_semicolons
both_before = [
Tok("comment", r"/\*(.|\n)*?\*/"),
Tok("linecomment", r"//.*?$"),
Tok("ws", r"\s+"),
Tok("keyword", literals("""
break case catch class const continue debugger
default delete do else enum export extends
finally for function if import in instanceof
new return super switch this throw try typeof
var void while with
""", suffix=r"\b"), next='reg'),
Tok("reserved", literals("null true false", suffix=r"\b"), next='div'),
Tok("id", r"""
([a-zA-Z_$ ]|\\u[0-9a-fA-Z]{4}) # first char
([a-zA-Z_$0-9]|\\u[0-9a-fA-F]{4})* # rest chars
""", next='div'),
Tok("hnum", r"0[xX][0-9a-fA-F]+", next='div'),
Tok("onum", r"0[0-7]+"),
Tok("dnum", r"""
( (0|[1-9][0-9]*) # DecimalIntegerLiteral
\. # dot
[0-9]* # DecimalDigits-opt
([eE][-+]?[0-9]+)? # ExponentPart-opt
|
\. # dot
[0-9]+ # DecimalDigits
([eE][-+]?[0-9]+)? # ExponentPart-opt
|
(0|[1-9][0-9]*) # DecimalIntegerLiteral
([eE][-+]?[0-9]+)? # ExponentPart-opt
)
""", next='div'),
Tok("punct", literals("""
>>>= === !== >>> <<= >>= <= >= == != << >> &&
|| += -= *= %= &= |= ^=
"""), next="reg"),
Tok("punct", literals("++ -- ) ]"), next='div'),
Tok("punct", literals("{ } ( [ . ; , < > + - * % & | ^ ! ~ ? : ="), next='reg'),
Tok("string", r'"([^"\\]|(\\(.|\n)))*?"', next='div'),
Tok("string", r"'([^'\\]|(\\(.|\n)))*?'", next='div'),
]
both_after = [
Tok("other", r"."),
]
states = {
# slash will mean division
'div': both_before + [
Tok("punct", literals("/= /"), next='reg'),
] + both_after,
# slash will mean regex
'reg': both_before + [
Tok("regex",
r"""
/ # opening slash
# First character is..
( [^*\\/[] # anything but * \ / or [
| \\. # or an escape sequence
| \[ # or a class, which has
( [^\]\\] # anything but \ or ]
| \\. # or an escape sequence
)* # many times
\]
)
# Following characters are same, except for excluding a star
( [^\\/[] # anything but \ / or [
| \\. # or an escape sequence
| \[ # or a class, which has
( [^\]\\] # anything but \ or ]
| \\. # or an escape sequence
)* # many times
\]
)* # many times
/ # closing slash
[a-zA-Z0-9]* # trailing flags
""", next='div'),
] + both_after,
}
def __init__(self):
super().__init__(self.states, 'reg')
def prepare_js_for_gettext(js):
"""
Convert the Javascript source `js` into something resembling C for
xgettext.
What actually happens is that all the regex literals are replaced with
"REGEX".
"""
def escape_quotes(m):
"""Used in a regex to properly escape double quotes."""
s = m.group(0)
if s == '"':
return r'\"'
else:
return s
lexer = JsLexer()
c = []
for name, tok in lexer.lex(js):
if name == 'regex':
# C doesn't grok regexes, and they aren't needed for gettext,
# so just output a string instead.
tok = '"REGEX"'
elif name == 'string':
# C doesn't have single-quoted strings, so make all strings
# double-quoted.
if tok.startswith("'"):
guts = re.sub(r"\\.|.", escape_quotes, tok[1:-1])
tok = '"' + guts + '"'
elif name == 'id':
# C can't deal with Unicode escapes in identifiers. We don't
# need them for gettext anyway, so replace them with something
# innocuous
tok = tok.replace("\\", "U")
c.append(tok)
return ''.join(c)