Allow pgen to produce a DOT format dump of the grammar (GH-18005)
Originally suggested by Anthony Shaw.
diff --git a/Parser/pgen/__main__.py b/Parser/pgen/__main__.py
index bb96e75..d3780a7 100644
--- a/Parser/pgen/__main__.py
+++ b/Parser/pgen/__main__.py
@@ -21,9 +21,19 @@
)
parser.add_argument("--verbose", "-v", action="count")
+ parser.add_argument(
+ "--graph",
+ type=argparse.FileType("w"),
+ action="store",
+ metavar="GRAPH_OUTPUT_FILE",
+ help="Dumps a DOT representation of the generated automata in a file",
+ )
+
args = parser.parse_args()
- p = ParserGenerator(args.grammar, args.tokens, verbose=args.verbose)
+ p = ParserGenerator(
+ args.grammar, args.tokens, verbose=args.verbose, graph_file=args.graph
+ )
grammar = p.make_grammar()
grammar.produce_graminit_h(args.graminit_h.write)
grammar.produce_graminit_c(args.graminit_c.write)
diff --git a/Parser/pgen/automata.py b/Parser/pgen/automata.py
index 545a737..d04ca7c 100644
--- a/Parser/pgen/automata.py
+++ b/Parser/pgen/automata.py
@@ -48,6 +48,26 @@
else:
writer(" %s -> %d" % (label, j))
+ def dump_graph(self, writer):
+ """Dump a DOT representation of the NFA"""
+ writer('digraph %s_nfa {\n' % self.name)
+ todo = [self.start]
+ for i, state in enumerate(todo):
+ writer(' %d [label="State %d %s"];\n' % (i, i, state is self.end and "(final)" or ""))
+ for arc in state.arcs:
+ label = arc.label
+ next = arc.target
+ if next in todo:
+ j = todo.index(next)
+ else:
+ j = len(todo)
+ todo.append(next)
+ if label is None:
+ writer(" %d -> %d [style=dotted label=ε];\n" % (i, j))
+ else:
+ writer(" %d -> %d [label=%s];\n" % (i, j, label.replace("'", '"')))
+ writer('}\n')
+
class NFAArc:
"""An arc representing a transition between two NFA states.
@@ -301,6 +321,15 @@
for label, next in sorted(state.arcs.items()):
writer(" %s -> %d" % (label, self.states.index(next)))
+ def dump_graph(self, writer):
+ """Dump a DOT representation of the DFA"""
+ writer('digraph %s_dfa {\n' % self.name)
+ for i, state in enumerate(self.states):
+ writer(' %d [label="State %d %s"];\n' % (i, i, state.is_final and "(final)" or ""))
+ for label, next in sorted(state.arcs.items()):
+ writer(" %d -> %d [label=%s];\n" % (i, self.states.index(next), label.replace("'", '"')))
+ writer('}\n')
+
class DFAState(object):
"""A state of a DFA
diff --git a/Parser/pgen/pgen.py b/Parser/pgen/pgen.py
index 2f444eb..03032d4 100644
--- a/Parser/pgen/pgen.py
+++ b/Parser/pgen/pgen.py
@@ -130,7 +130,7 @@
class ParserGenerator(object):
- def __init__(self, grammar_file, token_file, verbose=False):
+ def __init__(self, grammar_file, token_file, verbose=False, graph_file=None):
with open(grammar_file) as f:
self.grammar = f.read()
with open(token_file) as tok_file:
@@ -141,6 +141,7 @@
self.opmap["<>"] = "NOTEQUAL"
self.verbose = verbose
self.filename = grammar_file
+ self.graph_file = graph_file
self.dfas, self.startsymbol = self.create_dfas()
self.first = {} # map from symbol name to set of tokens
self.calculate_first_sets()
@@ -152,11 +153,15 @@
if self.verbose:
print("Dump of NFA for", nfa.name)
nfa.dump()
+ if self.graph_file is not None:
+ nfa.dump_graph(self.graph_file.write)
dfa = DFA.from_nfa(nfa)
if self.verbose:
print("Dump of DFA for", dfa.name)
dfa.dump()
dfa.simplify()
+ if self.graph_file is not None:
+ dfa.dump_graph(self.graph_file.write)
rule_to_dfas[dfa.name] = dfa
if start_nonterminal is None: