Commit Graph

3 Commits

Author SHA1 Message Date
Pablo Galindo 71876fa438
Refactor Parser/pgen and add documentation and explanations (GH-15373)
* Refactor Parser/pgen and add documentation and explanations

To improve the readability and maintainability of the parser
generator perform the following transformations:

    * Separate the metagrammar parser in its own class to simplify
      the parser generator logic.

    * Create separate classes for DFAs and NFAs and move methods that
      act exclusively on them from the parser generator to these
      classes.

    * Add docstrings and comment documenting the process to go from
      the grammar file into NFAs and then DFAs. Detail some of the
      algorithms and give some background explanations of some concepts
      that will helps readers not familiar with the parser generation
      process.

    * Select more descriptive names for some variables and variables.

    * PEP8 formatting and quote-style homogenization.

The output of the parser generator remains the same (Include/graminit.h
and Python/graminit.c remain untouched by running the new parser generator).
2019-08-22 02:38:39 +01:00
Pablo Galindo 8bc401a55c
Clean implementation of Parser/pgen and fix some style issues (GH-12156) 2019-03-04 07:26:13 +00:00
Pablo Galindo 1f24a719e7
bpo-35808: Retire pgen and use pgen2 to generate the parser (GH-11814)
Pgen is the oldest piece of technology in the CPython repository, building it requires various #if[n]def PGEN hacks in other parts of the code and it also depends more and more on CPython internals. This commit removes the old pgen C code and replaces it for a new version implemented in pure Python. This is a modified and adapted version of lib2to3/pgen2 that can generate grammar files compatibles with the current parser.

This commit also eliminates all the #ifdef and code branches related to pgen, simplifying the code and making it more maintainable. The regen-grammar step now uses $(PYTHON_FOR_REGEN) that can be any version of the interpreter, so the new pgen code maintains compatibility with older versions of the interpreter (this also allows regenerating the grammar with the current CI solution that uses Python3.5). The new pgen Python module also makes use of the Grammar/Tokens file that holds the token specification, so is always kept in sync and avoids having to maintain duplicate token definitions.
2019-03-01 15:34:44 -08:00