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[parser] Error recovery tests

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Based on the blog post "Resilient LL Parsing Tutorial" by Alex Kladov, at
https://matklad.github.io/2023/05/21/resilient-ll-parsing-tutorial.html

Because I was trying to be "simple" in my grammar definition I found
a bug in the grammar class, whoops! :)
This commit is contained in:
John Doty 2024-09-22 08:46:54 -07:00
parent 071cd29d8f
commit bb52ab8da5
2 changed files with 24 additions and 10 deletions
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22
parser/parser.py
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@ -706,7 +706,12 @@ class TableBuilder(object):
assert self.goto_row[symbol] is None # ?
self.goto_row[symbol] = index
def _action_precedence(self, symbol: int, action: Action, config: Configuration):
def _action_precedence(
self,
symbol: int,
action: Action,
config: Configuration,
) -> tuple[Assoc, int]:
if isinstance(action, Shift):
return self.precedence[symbol]
else:
@ -2761,7 +2766,7 @@ class TriviaMode(enum.Enum):
# Finally, the base class for grammars
###############################################################################
PrecedenceList = list[typing.Tuple[Assoc, list[Rule]]]
PrecedenceList = list[typing.Tuple[Assoc, list[Rule | str]]]
class Grammar:
@ -2799,7 +2804,7 @@ class Grammar:
def __init__(
self,
start: str | None = None,
start: str | NonTerminal | None = None,
precedence: PrecedenceList | None = None,
generator: type[GenerateLR0] | None = None,
trivia: list[str | Terminal] | None = None,
@ -2812,6 +2817,8 @@ class Grammar:
"The default start rule must either be specified in the constructor or as an "
"attribute in the class."
)
if isinstance(start, NonTerminal):
start = start.name
if precedence is None:
precedence = getattr(self, "precedence", [])
@ -2856,8 +2863,10 @@ class Grammar:
if resolved is None:
raise ValueError(f"The trivia '{t}' is not a terminal name")
resolved_trivia.append(resolved)
else:
elif isinstance(t, Terminal):
resolved_trivia.append(t)
else:
raise ValueError(f"{t} must be either a terminal name or literally a terminal")
# Fix up the precedence table.
precedence_table = {}
@ -2871,9 +2880,8 @@ class Grammar:
elif isinstance(symbol, NonTerminal):
key = symbol.name
elif isinstance(symbol, str):
key = terminals.get(symbol)
if key is None:
key = nonterminals.get(symbol)
if symbol in terminals or symbol in nonterminals:
key = symbol
if key is None:
raise ValueError(