feat: support numeric cpp udls (swev-id: sphinx-doc__sphinx-7590) by casey-brooks · Pull Request #98 · agyn-sandbox/sphinx

casey-brooks · 2025-12-27T20:56:45Z

Summary

fixes C++ domain: support numeric user-defined literals (UDLs) in expressions #97 by allowing the C++ definition parser to accept user-defined suffixes on numeric literals when no built-in suffix is present
add _udl_suffix_re to capture valid suffix tokens while leaving character and string literal handling untouched

Testing

PYTHONPATH=/workspace/sphinx /workspace/sphinx/.venv/bin/sphinx-build -b html . _build -W (with cpp_id_attributes = ['inline'] in the sample conf.py)
/workspace/sphinx/.venv/bin/flake8 sphinx/domains/cpp.py --extend-ignore=F401

Observed failure

Warning, treated as error:
/workspace/sphinx/tmp_udl_demo/index.rst:6:Invalid C++ declaration: Expected identifier in nested name, got keyword: inline [error at 6]
  inline constexpr auto planck_constant = 6.62607015e-34q_J * 1q_s
  ------^

Notes

Only numeric user-defined literals are handled here; char and string literal suffixes remain out of scope for this change.

casey-brooks · 2025-12-27T20:57:33Z

Local Validation

PYTHONPATH=/workspace/sphinx /workspace/sphinx/.venv/bin/sphinx-build -b html . _build -W (no warnings)
/workspace/sphinx/.venv/bin/flake8 sphinx/domains/cpp.py --extend-ignore=F401 (clean)

noa-lucent

Thanks for the improvement—see my comment about the missing regression coverage.

sphinx/domains/cpp.py

casey-brooks · 2025-12-27T21:15:25Z

Summary:

update the C++ definition parser to consume numeric UDL identifiers only when adjacent and starting with a letter/underscore
add udl-numeric/udl-negative fixtures covering positive cases, builtin suffix regression, and malformed suffix warnings
add pytest coverage asserting zero warnings for udl-numeric and four warnings for udl-negative

Tests:

PYTHONPATH=/workspace/sphinx /workspace/sphinx/.venv/bin/pytest tests/test_domain_cpp.py -q
/workspace/sphinx/.venv/bin/flake8 sphinx/domains/cpp.py tests/test_domain_cpp.py
sphinx-build -b html tests/roots/test-domain-cpp _build/udl -W (fails on pre-existing roles2.rst duplicate)

noa-lucent

Thanks for adding the regression coverage and tightening the parser logic—much appreciated. One more fix needed before this can merge.

noa-lucent · 2025-12-27T21:17:29Z

sphinx/domains/cpp.py

 import re
 from typing import (
-    Any, Callable, Dict, Generator, Iterator, List, Tuple, Type, TypeVar, Union, Optional
+    Any, Callable, Dict, Generator, Iterator, List, Tuple, TypeVar, Union, Optional


[major] We still reference typing.Type later in this module (e.g. the # type: Type[TextElement] comment in CPPExprRole). Dropping it from the import list makes Type an undefined name, which flake8/pyflakes will flag as F821. Please keep Type in the imports.

noa-lucent

Thanks for following up — the Type import and the new coverage look good. We just need to loosen the literal-suffix guard to accept identifiers like _9bad (allowed by the C++ grammar) and adjust the fixtures accordingly.

noa-lucent · 2025-12-27T21:23:01Z

sphinx/domains/cpp.py

            if self.match(regex):
+                suffix_start = self.pos
                while self.current_char in 'uUlLfF':
                    self.pos += 1


[major] The new guard that rejects _ followed by a digit is too strict. A user-defined literal suffix is any C++ identifier (cf. [lex.name]), so _9bad is perfectly legal — identifiers can contain digits after the first character. With the current logic we would reject literals such as 3.0_1, which the standard allows. Please drop the next_char.isalpha() restriction (or extend it to include digits) and rely on _udl_suffix_re to do the right thing.

noa-lucent · 2025-12-27T21:23:06Z

tests/roots/test-domain-cpp/udl-negative.rst

+=====================================
+
+.. cpp:var:: constexpr auto bad_digit_prefix = 7_9bad
+


[major] This case should not be considered invalid. _9bad is still a valid identifier (digits are allowed after the first character), so 7_9bad is a legal user-defined literal in C++. If we exercise this input against a conforming compiler it parses without issue. Please move this example into the positive suite (or drop it) and adjust the parser so we accept it.

noa-lucent · 2025-12-27T21:23:11Z

tests/test_domain_cpp.py

+    app.builder.build_all()
+    ws = filter_warnings(warning, "udl-negative")
+    assert len(ws) == 4
+


[major] Once _9bad is treated as a valid literal the failure count should drop. Please update the negative fixture expectations (likely len(ws) == 3).

casey-brooks · 2025-12-27T21:31:12Z

Summary:

gate builtin suffix consumption by literal kind before attempting UDL parsing
extend udl-numeric/udl-negative fixtures with hex-float, builtin-prefixed, and digit-start scenarios
document digit separator limitation and cover builtin+UDL rejection

Tests:

PYTHONPATH=/workspace/sphinx /workspace/sphinx/.venv/bin/pytest tests/test_domain_cpp.py -q
/workspace/sphinx/.venv/bin/flake8 sphinx/domains/cpp.py tests/test_domain_cpp.py
/workspace/sphinx/.venv/bin/sphinx-build -b html tests/roots/test-domain-cpp _build/udl -W (fails on existing roles2 duplicate declaration)

noa-lucent

Appreciate the expanded coverage and literal-kind handling—this is close. The suffix guard still blocks legal identifiers like _1q, so the parser and tests need one more tweak per my comments.

noa-lucent · 2025-12-27T21:33:26Z

sphinx/domains/cpp.py

+                if (not consumed_builtin) and (not self.eof):
+                    if self.current_char == '_':
+                        next_char = self.definition[self.pos + 1:self.pos + 2]
+                        if next_char and (next_char.isalpha() or next_char == '_'):


[major] The guard here still rejects valid user-defined suffixes. _udl_suffix_re already enforces the C++ identifier grammar (first character letter or _, remainder alnum/_). A suffix such as _1q therefore is well-formed: the first character is _ and digits are permitted afterwards. By requiring next_char.isalpha() you prohibit those legal cases. Please drop the extra check (or extend it to allow digits) and rely on _udl_suffix_re to decide validity.

noa-lucent · 2025-12-27T21:33:30Z

tests/roots/test-domain-cpp/udl-negative.rst

+
+.. cpp:var:: constexpr auto bad_order = 1llu_qs
+
+.. cpp:var:: constexpr auto bad_digit_start = 1e-34_1q


[major] _1q is a valid identifier (the first character is _, subsequent characters may include digits), so 1e-34_1q should parse cleanly. This fixture should move to the positive set once the parser allows it.

noa-lucent · 2025-12-27T21:33:33Z

tests/test_domain_cpp.py

+def test_build_domain_cpp_udl_negative(app, status, warning):
+    app.builder.build_all()
+    ws = filter_warnings(warning, "udl-negative")
+    assert len(ws) == 4


[major] Once _1q is accepted, this suite should only surface the three truly invalid declarations (bad_mixed, bad_order, bad_ws). Please adjust the expected warning count accordingly.

casey-brooks · 2025-12-27T21:36:40Z

Summary:

rely solely on _udl_suffix_re for UDL matching after builtin suffix consumption
promote digit-prefixed UDL suffixes into positive fixtures and refresh negatives
note valid digit-prefixed suffixes in docs while keeping whitespace/symbol failures

Tests:

PYTHONPATH=/workspace/sphinx /workspace/sphinx/.venv/bin/pytest tests/test_domain_cpp.py -q
/workspace/sphinx/.venv/bin/flake8 sphinx/domains/cpp.py tests/test_domain_cpp.py
/workspace/sphinx/.venv/bin/sphinx-build -b html tests/roots/test-domain-cpp _build/udl -W (fails on existing roles2 duplicate declaration)

noa-lucent

(placeholder)

noa-lucent

Excellent follow-through. The parser now leans entirely on the suffix regexes, and the expanded fixtures/execution tests cover the allowed combinations well. Thanks for iterating.

feat(cpp): support numeric udls [skip ci]

e525009

casey-brooks requested a review from a team December 27, 2025 20:56

noa-lucent requested changes Dec 27, 2025

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fix(cpp): add numeric udl coverage [skip ci]

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noa-lucent requested changes Dec 27, 2025

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fix(cpp): restore type import [skip ci]

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noa-lucent requested changes Dec 27, 2025

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fix(cpp): guard builtin suffixes [skip ci]

78455e2

noa-lucent requested changes Dec 27, 2025

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fix(cpp): accept digit udls [skip ci]

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noa-lucent reviewed Dec 27, 2025

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noa-lucent approved these changes Dec 27, 2025

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		=====================================

		.. cpp:var:: constexpr auto bad_digit_prefix = 7_9bad


		.. cpp:var:: constexpr auto bad_order = 1llu_qs

		.. cpp:var:: constexpr auto bad_digit_start = 1e-34_1q

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casey-brooks commented Dec 27, 2025 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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casey-brooks commented Dec 27, 2025

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casey-brooks commented Dec 27, 2025 •

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