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Make is_valid_syntax parts lazy loaded #14

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112 changes: 32 additions & 80 deletions src/rfc3987_syntax/syntax_helpers.py
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Original file line number Diff line number Diff line change
@@ -1,3 +1,8 @@
__all__ = [
"is_valid_syntax",
]
Comment on lines +1 to +3

Copilot AI Apr 30, 2026

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There are behavior changes here around lazy module attributes (grammar, syntax_parser, is_valid_syntax_*) and around what gets exported at package import time. Existing tests only exercise is_valid_syntax via import rfc3987_syntax as h, so regressions like missing re-exports (parse, RFC3987_SYNTAX_TERMS, is_valid_syntax_iri, etc.) or __getattr__ behavior won't be caught. Add tests that assert these public attributes are available and callable after importing rfc3987_syntax.

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Comment on lines +1 to +3

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Defining __all__ as only ['is_valid_syntax'] changes what from .syntax_helpers import * exports. Since src/rfc3987_syntax/__init__.py uses a star import, this will stop re-exporting parse, RFC3987_SYNTAX_TERMS, and the documented is_valid_syntax_* helpers (breaking the public API/README examples). Consider removing the star import from __init__.py and explicitly re-exporting symbols (possibly via package-level __getattr__), or otherwise ensuring the previous public surface remains available without eagerly constructing all validators on import.

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import functools
from typing import Any
from lark import Lark, ParseTree, exceptions

from pathlib import Path
Expand All @@ -12,7 +17,7 @@
"absolute_iri",
"scheme",
"irelative_ref",
"irelative_part"
"irelative_part",
"ihier_part",
"iauthority",
"iuserinfo",
Expand Down Expand Up @@ -45,13 +50,24 @@
"pct_encoded",
]

grammar: str = load_grammar(RFC3987_SYNTAX_GRAMMAR_PATH)

syntax_parser = Lark(grammar, start=["iri", "iri_reference", "absolute_iri"], parser=RFC3987_SYNTAX_PARSER_TYPE)
@functools.lru_cache(maxsize=None)
def get_grammar():
return load_grammar(RFC3987_SYNTAX_GRAMMAR_PATH)


@functools.lru_cache(maxsize=None)
def get_syntax_parser():
syntax_parser = Lark(
get_grammar(),
start=["iri", "iri_reference", "absolute_iri"],
parser=RFC3987_SYNTAX_PARSER_TYPE,
)
return syntax_parser


def parse(term: str, value: str) -> ParseTree:
return syntax_parser.parse(value, start=term)
return get_syntax_parser().parse(value, start=term)


def is_valid_syntax(term: str, value: str):
Expand All @@ -62,8 +78,9 @@ def is_valid_syntax(term: str, value: str):
return False


@functools.lru_cache(maxsize=None)
def make_syntax_validator(rule_name):
parser = Lark(grammar, start=rule_name, parser=RFC3987_SYNTAX_PARSER_TYPE)
parser = Lark(get_grammar(), start=rule_name, parser=RFC3987_SYNTAX_PARSER_TYPE)

def syntax_validator(text):
try:
Expand All @@ -75,78 +92,13 @@ def syntax_validator(text):
return syntax_validator


is_valid_syntax_iri = make_syntax_validator("iri")

is_valid_syntax_iri_reference = make_syntax_validator("iri_reference")

is_valid_syntax_absolute_iri = make_syntax_validator("absolute_iri")

is_valid_syntax_irelative_ref = make_syntax_validator("irelative_ref")

is_valid_syntax_irelative_part = make_syntax_validator("irelative_part")

is_valid_syntax_ihier_part = make_syntax_validator("ihier_part")

is_valid_syntax_iauthority = make_syntax_validator("iauthority")

is_valid_syntax_iuserinfo = make_syntax_validator("iuserinfo")

is_valid_syntax_ihost = make_syntax_validator("ihost")

is_valid_syntax_ireg_name = make_syntax_validator("ireg_name")

is_valid_syntax_ipath = make_syntax_validator("ipath")

is_valid_syntax_ipath_abempty = make_syntax_validator("ipath_abempty")

is_valid_syntax_ipath_absolute = make_syntax_validator("ipath_absolute")

is_valid_syntax_ipath_noscheme = make_syntax_validator("ipath_noscheme")

is_valid_syntax_ipath_rootless = make_syntax_validator("ipath_rootless")

is_valid_syntax_ipath_empty = make_syntax_validator("ipath_empty")

is_valid_syntax_isegment = make_syntax_validator("isegment")

is_valid_syntax_isegment_nz = make_syntax_validator("isegment_nz")

is_valid_syntax_isegment_nz_nc = make_syntax_validator("isegment_nz_nc")

is_valid_syntax_ipchar = make_syntax_validator("ipchar")

is_valid_syntax_iquery = make_syntax_validator("iquery")

is_valid_syntax_ifragment = make_syntax_validator("ifragment")

is_valid_syntax_iunreserved = make_syntax_validator("iunreserved")

is_valid_syntax_ucschar = make_syntax_validator("ucschar")

is_valid_syntax_iprivate = make_syntax_validator("iprivate")

is_valid_syntax_sub_delims = make_syntax_validator("sub_delims")

is_valid_syntax_ip_literal = make_syntax_validator("ip_literal")

is_valid_syntax_ipvfuture = make_syntax_validator("ipvfuture")

is_valid_syntax_ipv6address = make_syntax_validator("ipv6address")

is_valid_syntax_h16 = make_syntax_validator("h16")

is_valid_syntax_ls32 = make_syntax_validator("ls32")

is_valid_syntax_ipv4address = make_syntax_validator("ipv4address")

is_valid_syntax_dec_octet = make_syntax_validator("dec_octet")

is_valid_syntax_unreserved = make_syntax_validator("unreserved")

is_valid_syntax_alpha = make_syntax_validator("alpha")

is_valid_syntax_digit = make_syntax_validator("digit")

is_valid_syntax_hexdig = make_syntax_validator("hexdig")

is_valid_syntax_port = make_syntax_validator("port")
def __getattr__(name: str) -> Any:
if name == "grammar":
return get_grammar()
if name == "syntax_parser":
return get_syntax_parser()
if name.startswith("is_valid_syntax_"):
term = name.removeprefix("is_valid_syntax_")
return make_syntax_validator(term)

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__getattr__ currently treats any is_valid_syntax_* attribute as valid and passes the suffix straight into make_syntax_validator(). Combined with @lru_cache(maxsize=None) this allows unbounded creation/caching of parsers for arbitrary attribute names (and can also surface confusing Lark configuration errors for typos). Consider checking term against RFC3987_SYNTAX_TERMS and raising AttributeError for unknown terms.

Suggested change
return make_syntax_validator(term)
if term in RFC3987_SYNTAX_TERMS:
return make_syntax_validator(term)

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msg = f"Attribute {name} not found"
raise AttributeError(msg, name=name)

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raise AttributeError(msg, name=name) is not a valid way to construct AttributeError (it doesn't accept keyword arguments). This will raise a TypeError when an unknown attribute is accessed. Raise AttributeError(msg) (or AttributeError(msg, name) positionally if you want .name set) instead.

Suggested change
raise AttributeError(msg, name=name)
raise AttributeError(msg)

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