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114 lines
3.1 KiB
Python
Executable file
114 lines
3.1 KiB
Python
Executable file
#!/usr/bin/env python3.8
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""" Convert a grammar into a dot-file suitable for use with GraphViz
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For example:
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Generate the GraphViz file:
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# scripts/grammar_grapher.py data/python.gram > python.gv
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Then generate the graph...
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# twopi python.gv -Tpng > python_twopi.png
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or
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# dot python.gv -Tpng > python_dot.png
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NOTE: The _dot_ and _twopi_ tools seem to produce the most useful results.
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The _circo_ tool is the worst of the bunch. Don't even bother.
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"""
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import argparse
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import sys
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from typing import Any, List
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sys.path.insert(0, ".")
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from pegen.build import build_parser
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from pegen.grammar import (
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Alt,
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Cut,
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Grammar,
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Group,
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Leaf,
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Lookahead,
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Rule,
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NameLeaf,
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NamedItem,
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Opt,
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Repeat,
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Rhs,
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)
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argparser = argparse.ArgumentParser(prog="graph_grammar", description="Graph a grammar tree",)
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argparser.add_argument(
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"-s",
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"--start",
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choices=["exec", "eval", "single"],
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default="exec",
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help="Choose the grammar's start rule (exec, eval or single)",
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)
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argparser.add_argument("grammar_file", help="The grammar file to graph")
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def references_for_item(item: Any) -> List[Any]:
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if isinstance(item, Alt):
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return [_ref for _item in item.items for _ref in references_for_item(_item)]
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elif isinstance(item, Cut):
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return []
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elif isinstance(item, Group):
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return references_for_item(item.rhs)
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elif isinstance(item, Lookahead):
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return references_for_item(item.node)
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elif isinstance(item, NamedItem):
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return references_for_item(item.item)
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# NOTE NameLeaf must be before Leaf
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elif isinstance(item, NameLeaf):
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if item.value == "ENDMARKER":
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return []
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return [item.value]
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elif isinstance(item, Leaf):
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return []
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elif isinstance(item, Opt):
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return references_for_item(item.node)
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elif isinstance(item, Repeat):
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return references_for_item(item.node)
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elif isinstance(item, Rhs):
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return [_ref for alt in item.alts for _ref in references_for_item(alt)]
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elif isinstance(item, Rule):
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return references_for_item(item.rhs)
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else:
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raise RuntimeError(f"Unknown item: {type(item)}")
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def main() -> None:
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args = argparser.parse_args()
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try:
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grammar, parser, tokenizer = build_parser(args.grammar_file)
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except Exception as err:
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print("ERROR: Failed to parse grammar file", file=sys.stderr)
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sys.exit(1)
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references = {}
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for name, rule in grammar.rules.items():
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references[name] = set(references_for_item(rule))
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# Flatten the start node if has only a single reference
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root_node = {"exec": "file", "eval": "eval", "single": "interactive"}[args.start]
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print("digraph g1 {")
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print('\toverlap="scale";') # Force twopi to scale the graph to avoid overlaps
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print(f'\troot="{root_node}";')
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print(f"\t{root_node} [color=green, shape=circle];")
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for name, refs in references.items():
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for ref in refs:
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print(f"\t{name} -> {ref};")
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print("}")
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if __name__ == "__main__":
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main()
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