Different behavior for single and double quotes

[jakevdp]

I came across a bug that was rooted in what seems to be a curious feature of Parsley: changing from single to double quotes leads to a parsing error:

import sys
print(sys.version_info)
# sys.version_info(major=3, minor=5, micro=1, releaselevel='final', serial=0)

import parsley
print(parsley.__version__)
#1.3

grammar = parsley.makeGrammar("""
add = <digit+>:left sp "+" sp add:right -> ('add', left, right)
      | <digit+>:child                  -> child

sp = ' '*
""", {})

grammar('4 + 3').add()
# ('add', '4', '3')

But if we change sp = ' '* to sp = " "* and keep everything else constant, we get an error:

grammar = parsley.makeGrammar("""
add = <digit+>:left sp "+" sp add:right -> ('add', left, right)
      | <digit+>:child                  -> child

sp = " "*
""", {})

grammar('4 + 3').add()

---------------------------------------------------------------------------
ParseError                                Traceback (most recent call last)
<ipython-input-20-5d4b7ce9eeba> in <module>()
      6 """, {})
      7 
----> 8 grammar('4 + 3').add()

/Users/jakevdp/anaconda/envs/python3.5/lib/python3.5/site-packages/parsley.py in invokeRule(*args, **kwargs)
     96                     err = ParseError(err.input, err.position + 1,
     97                                      [["message", "expected EOF"]], err.trail)
---> 98             raise err
     99         return invokeRule
    100 

ParseError: 
4 + 3
^
Parse error at line 2, column 0: expected EOF. trail: []

Is the semantic difference between " " and ' ' intended? I couldn't find any discussion of this in the documentation. Thank you!

[kurtbrose]

I ran into this same issue recently.