RecursionError

[Martmists-GH]

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I'm writing a custom language, and a friend recommended to use this library. Grammar:

grammar = Grammar(r"""
    program    = stmt*
    class      = "class" params? compound
    while      = "while" cond compound
    function   = "function" params f_compound
    cond       = ("(" value (comp value)* ")") / (value (comp value)*)
    assign     = var "=" value
    if         = "if" cond compound else?
    else       = "else" compound
    try        = "try" compound except?
    except     = "except" compound
    params     = "(" comma_args? ")"
    f_stmt     = stmt / return
    stmt       = (assign / if / while / function / class)
    f_compound = "{" f_stmt* "}"
    compound   = "{" stmt* "}"
    return     = "return" stmt?
    array      = "[" comma_args? "]"
    comma_args = value ("," value)*
    value      = string / integer / float / var / array / binop / call / comp
    float      = integer "." integer
    attr       = var "." varname
    string     = ('"' ~'[^"]*' '"') / ("'" ~"[^']*" "'")
    binop      = value op value
    op         = ~"[\+\-\/\*]"
    comp       = "==" / "!=" / ">=" / "<=" / ">" / "<"
    call       = var params
    var        = varname / attr
    varname    = ~"[A-Z_][A-Z0-9_]*"i
    integer    = ~"[0-9]+"
    _          = ~r'\s'*
    """)

when using print(grammar.parse("x = 1 + 1")), I get the following error:

Traceback (most recent call last):
  File "test_lexer.py", line 36, in <module>
    res = grammar.parse("x=1+1")
  File "/usr/lib/python3.6/site-packages/parsimonious/grammar.py", line 115, in parse
    return self.default_rule.parse(text, pos=pos)
  File "/usr/lib/python3.6/site-packages/parsimonious/expressions.py", line 120, in parse
    node = self.match(text, pos=pos)
  File "/usr/lib/python3.6/site-packages/parsimonious/expressions.py", line 135, in match
    node = self.match_core(text, pos, {}, error)
  File "/usr/lib/python3.6/site-packages/parsimonious/expressions.py", line 178, in match_core
    error)
  File "/usr/lib/python3.6/site-packages/parsimonious/expressions.py", line 458, in _uncached_match
    node = self.members[0].match_core(text, new_pos, cache, error)
  File "/usr/lib/python3.6/site-packages/parsimonious/expressions.py", line 178, in match_core
    error)
  File "/usr/lib/python3.6/site-packages/parsimonious/expressions.py", line 356, in _uncached_match
    node = m.match_core(text, pos, cache, error)
  File "/usr/lib/python3.6/site-packages/parsimonious/expressions.py", line 178, in match_core
    error)
  File "/usr/lib/python3.6/site-packages/parsimonious/expressions.py", line 333, in _uncached_match
    node = m.match_core(text, new_pos, cache, error)
  File "/usr/lib/python3.6/site-packages/parsimonious/expressions.py", line 178, in match_core
    error)
  File "/usr/lib/python3.6/site-packages/parsimonious/expressions.py", line 356, in _uncached_match
    node = m.match_core(text, pos, cache, error)
  File "/usr/lib/python3.6/site-packages/parsimonious/expressions.py", line 178, in match_core
    error)

and this repeated until it says RecursionError: maximum recursion depth exceeded

Is it my grammar at fault, or is there something else I'm doing wrong?

[oxy]

Right now, all I can find wrong is

value = string / integer / float / var / array / binop / call / comp
binop = value op value

They seem to be self-referential, and might be the source of the recursion.

I'm not sure how to fix the grammar, but am quite sure that it's not an issue with the parser.

[mvaled]

I tried to reproduce your bug with a simpler version of the grammar:

>>> g = Grammar(r'''
...    expr = value EOF
...    value = integer / binop
...    integer = ~"[0-9]+"
...    binop   = value spaces op spaces value
...    op = ~"[\+\-]"
...    EOF = ~"$"
...    spaces = ~"\s*"
... ''')

But when trying to parse '1 + 1', the problem is that parsimonious stops after matching the 'integer':

>>> g.parse('1 + 1')
....
ParseError: Rule 'EOF' didn't match at ' + 1' (line 1, column 2).

Only after switching the order of binop and integer in the value rule, I get the RecursionError.