📦Only enable line tracing when w/Cython tracing

This patch modifies the build backend to dynamically enable Cython
line tracing only when explicitly requested via the
`with-cython-tracing=true` config setting. Previously, having
`linetrace = "True"` in `pyproject.toml` was making our PyPI-published
wheels slower.

Now, line tracing is opt-in:
- Regular builds: `pip install .`
  (no line tracing)
- Tracing builds:
  `pip install . --config-setting=with-cython-tracing=true`

  (enables line tracing)

When tracing is requested, the build backend automatically adds the
`linetrace=True` and `profile=True` Cython directives and sets the
appropriate C compiler flags.

Resolves ansible#767

Author: webknjaz

packaging/pep517_backend/_backend.py

@@ -256,7 +256,10 @@ def _prebuild_c_extensions(
     with build_dir_ctx:
         config = _get_local_cython_config()
 
-        cythonize_args = _make_cythonize_cli_args_from_config(config)
+        cythonize_args = _make_cythonize_cli_args_from_config(
+            config,
+            cython_line_tracing_requested,
+        )
         with _patched_cython_env(config['env'], cython_line_tracing_requested):
             _cythonize_cli_cmd(cythonize_args)
         with patched_distutils_cmd_install():

packaging/pep517_backend/_cython_configuration.py

@@ -129,12 +129,32 @@ def get_local_cythonize_config() -> dict:
     return config_mapping['tool']['local']['cythonize']
 
 
-def make_cythonize_cli_args_from_config(config: dict) -> 'list[str]':
+def _configure_cython_line_tracing(
+    config_kwargs: dict[str, str | dict[str, str]],
+    cython_line_tracing_requested: bool,
+) -> None:
+    """Configure Cython line tracing directives if requested."""
+    # If line tracing is requested, add it to the directives
+    if cython_line_tracing_requested:
+        directives = config_kwargs.setdefault('directive', {})
+        assert isinstance(directives, dict)  # Type narrowing for mypy
+        directives['linetrace'] = 'True'
+        directives['profile'] = 'True'
+
+
+def make_cythonize_cli_args_from_config(
+    config: dict,
+    cython_line_tracing_requested: bool = False,
+) -> 'list[str]':
     """Compose ``cythonize`` CLI args from config."""
     py_ver_arg = f'-{_python_version_tuple.major!s}'  # noqa: WPS305
 
     cli_flags = get_enabled_cli_flags_from_config(config['flags'])
-    cli_kwargs = get_cli_kwargs_from_config(config['kwargs'])
+    config_kwargs = config['kwargs']
+
+    _configure_cython_line_tracing(config_kwargs, cython_line_tracing_requested)
+
+    cli_kwargs = get_cli_kwargs_from_config(config_kwargs)
 
     return cli_flags + [py_ver_arg] + cli_kwargs + ['--'] + config['src']
 

packaging/pep517_backend/_transformers.py

@@ -4,6 +4,7 @@
 
 from itertools import chain
 from re import sub as _substitute_with_regexp
+from typing import Union
 
 
 def _emit_opt_pairs(opt_pair):
@@ -20,7 +21,9 @@ def _emit_opt_pairs(opt_pair):
     )
 
 
-def get_cli_kwargs_from_config(kwargs_map):
+def get_cli_kwargs_from_config(  # noqa: WPS234
+    kwargs_map: dict[str, Union[str, dict[str, str]]],
+) -> list[str]:
     """Make a list of options with values from config."""
     return list(chain.from_iterable(map(_emit_opt_pairs, kwargs_map.items())))
 

pyproject.toml

@@ -114,8 +114,6 @@ parallel = 1
 # Ref: https://github.com/cython/cython/blob/d6e6de9/Cython/Compiler/Options.py#L170-L242
 embedsignature = "True"
 emit_code_comments = "True"
-linetrace = "True"
-profile = "True"
 
 [tool.local.cythonize.kwargs.compile-time-env]
 # This section can contain compile time env vars