There are two copies of the grammar -- the one used by Python itself as
Grammar/Grammar, and the one used by lib2to3 which has necessarily diverged at
Lib/lib2to3/Grammar.txt because it needs to support older syntax an we want it
to be reasonable stable to avoid requiring fixer rewrites.
This brings suport for syntax like `if x:= foo():` to match what the live
Python grammar does.
This should've been added at the time of the walrus operator itself, but lib2to3 being
independent is often overlooked. So we do consider this a bugfix rather than enhancement.
* Now uses pickle protocol 4
* Doesn't wrap the grammar's `__dict__` in ordered dictionaries anymore as
dictionaries in Python 3.6+ are ordered by default
This still produces deterministic pickles (that hash the same with MD5).
Tested with different PYTHONHASHSEED values.
This is more complicated than it should be because we need to preserve the
useful mtime-based regeneration feature that lib2to3.pgen2.driver.load_grammar
has. We only look for the pickled grammar file with pkgutil.get_data and only if
the source file does not exist.
Nikita Sobolev
Tim Hatch
Srinivas Thatiparthy (శ్రీనివాస్ తాటిపర్తి)
Łukasz Langa
Benjamin Peterson
Victor Stinner
Gregory P. Smith ext:(%20%5BGoogle%20Inc.%5D)
Terry Jan Reedy
Giampaolo Rodola'
Martin v. Löwis