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allendowney
GitHub Repository: allendowney/cpython
 Path: blob/main/Doc/tools/extensions/peg_highlight.py
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from pygments.lexer import RegexLexer, bygroups, include

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from pygments.token import Comment, Keyword, Name, Operator, Punctuation, Text

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from sphinx.highlighting import lexers

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class PEGLexer(RegexLexer):

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    """Pygments Lexer for PEG grammar (.gram) files

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    This lexer strips the following elements from the grammar:

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        - Meta-tags

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        - Variable assignments

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        - Actions

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        - Lookaheads

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        - Rule types

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        - Rule options

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        - Rules named `invalid_*` or `incorrect_*`

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    """

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    name = "PEG"

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    aliases = ["peg"]

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    filenames = ["*.gram"]

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    _name = r"([^\W\d]\w*)"

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    _text_ws = r"(\s*)"

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    tokens = {

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        "ws": [(r"\n", Text), (r"\s+", Text), (r"#.*$", Comment.Singleline),],

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        "lookaheads": [

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            # Forced tokens

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            (r"(&&)(?=\w+\s?)", bygroups(None)),

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            (r"(&&)(?='.+'\s?)", bygroups(None)),

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            (r'(&&)(?=".+"\s?)', bygroups(None)),

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            (r"(&&)(?=\(.+\)\s?)", bygroups(None)),

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            (r"(?<=\|\s)(&\w+\s?)", bygroups(None)),

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            (r"(?<=\|\s)(&'.+'\s?)", bygroups(None)),

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            (r'(?<=\|\s)(&".+"\s?)', bygroups(None)),

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            (r"(?<=\|\s)(&\(.+\)\s?)", bygroups(None)),

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        ],

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        "metas": [

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            (r"(@\w+ '''(.|\n)+?''')", bygroups(None)),

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            (r"^(@.*)$", bygroups(None)),

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        ],

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        "actions": [

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            (r"{(.|\n)+?}", bygroups(None)),

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        ],

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        "strings": [

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            (r"'\w+?'", Keyword),

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            (r'"\w+?"', Keyword),

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            (r"'\W+?'", Text),

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            (r'"\W+?"', Text),

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        ],

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        "variables": [

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            (_name + _text_ws + "(=)", bygroups(None, None, None),),

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            (_name + _text_ws + r"(\[[\w\d_\*]+?\])" + _text_ws + "(=)", bygroups(None, None, None, None, None),),

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        ],

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        "invalids": [

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            (r"^(\s+\|\s+.*invalid_\w+.*\n)", bygroups(None)),

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            (r"^(\s+\|\s+.*incorrect_\w+.*\n)", bygroups(None)),

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            (r"^(#.*invalid syntax.*(?:.|\n)*)", bygroups(None),),

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        ],

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        "root": [

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            include("invalids"),

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            include("ws"),

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            include("lookaheads"),

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            include("metas"),

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            include("actions"),

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            include("strings"),

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            include("variables"),

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            (r"\b(?!(NULL|EXTRA))([A-Z_]+)\b\s*(?!\()", Text,),

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            (

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                r"^\s*" + _name + r"\s*" + r"(\[.*\])?" + r"\s*" + r"(\(.+\))?" + r"\s*(:)",

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                bygroups(Name.Function, None, None, Punctuation),

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            ),

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            (_name, Name.Function),

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            (r"[\||\.|\+|\*|\?]", Operator),

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            (r"{|}|\(|\)|\[|\]", Punctuation),

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            (r".", Text),

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        ],

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    }

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def setup(app):

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    lexers["peg"] = PEGLexer()

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    return {"version": "1.0", "parallel_read_safe": True}

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