📦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

@@ -261,6 +261,7 @@ def _prebuild_c_extensions(
 
         cythonize_args = _make_cythonize_cli_args_from_config(
             config,
+            cython_line_tracing_requested=cython_line_tracing_requested,
         )
         with _patched_cython_env(
             config['env'],

packaging/pep517_backend/_cython_configuration.py

@@ -144,14 +144,37 @@ def get_local_cythonize_config() -> Config:
     return config_mapping['tool']['local']['cythonize']  # type: ignore[no-any-return]
 
 
+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)  # noqa: S101  # typing
+        directives['linetrace'] = 'True'
+        directives['profile'] = 'True'
+
+
 def make_cythonize_cli_args_from_config(
     config: Config,
+    *,
+    cython_line_tracing_requested: bool = False,
 ) -> list[str]:
     """Compose ``cythonize`` CLI args from config."""
     py_ver_arg = f'-{_python_version_tuple.major!s}'
 
     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=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

@@ -25,7 +25,7 @@ def _emit_opt_pairs(
         yield '='.join(map(str, (flag_opt, *pair)))
 
 
-def get_cli_kwargs_from_config(
+def get_cli_kwargs_from_config(  # noqa: WPS234
     kwargs_map: dict[str, str | dict[str, str]],
 ) -> list[str]:
     """Make a list of options with values from config."""

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