ci: add DD_CYTHONIZE option to setup.py (#15255)

## Description

This new option will allow us to skip cythonizing .pyx files during
source distribution building (wasted step that pollutes source tree with
extra `.c`/`.cpp` files which we won't use for source distributions).

## Testing

<!-- Describe your testing strategy or note what tests are included -->

## Risks

<!-- Note any risks associated with this change, or "None" if no risks
-->

## Additional Notes

<!-- Any other information that would be helpful for reviewers -->

Author: brettlangdon

.github/workflows/build_deploy.yml

@@ -93,7 +93,8 @@ jobs:
       - name: Build sdist
         run: |
           pip install "setuptools_scm[toml]>=4" "cython" "cmake>=3.24.2,<3.28" "setuptools-rust"
-          python setup.py sdist
+          # Disable cython extensions to avoid compiling .pyx files
+          DD_CYTHONIZE=0 python setup.py sdist
       - uses: actions/upload-artifact@ea165f8d65b6e75b540449e92b4886f43607fa02 # v4.6.2
         with:
           name: source-dist

docs/build_system.rst

@@ -183,6 +183,13 @@ These environment variables modify aspects of the build process.
     version_added:
         v3.3.0:
 
+  DD_CYTHONIZE:
+    type: Boolean
+    default: True
+    description: |
+      If enabled, then Cython extensions are included in the build. Disabling will exclude them.
+      This is mostly useful for source distribution builds so we can skip calling ``cythonize`` on source files.
+
   DD_FAST_BUILD:
     type: Boolean
     default: False

setup.py

@@ -1157,33 +1157,10 @@ def get_exts_for(name):
 else:
     ext_modules = []
 
-interpose_sccache()
-setup(
-    name="ddtrace",
-    packages=find_packages(exclude=["tests*", "benchmarks*", "scripts*"]),
-    package_data={
-        "ddtrace": ["py.typed"],
-        "ddtrace.appsec": ["rules.json"],
-        "ddtrace.appsec._ddwaf": ["libddwaf/*/lib/libddwaf.*"],
-        "ddtrace.appsec._iast._taint_tracking": ["CMakeLists.txt"],
-        "ddtrace.internal.datadog.profiling": (
-            ["libdd_wrapper*.*"]
-            + (["ddtrace/internal/datadog/profiling/test/*"] if BUILD_PROFILING_NATIVE_TESTS else [])
-        ),
-    },
-    zip_safe=False,
-    # enum34 is an enum backport for earlier versions of python
-    # funcsigs backport required for vendored debtcollector
-    cmdclass={
-        "build_ext": CustomBuildExt,
-        "build_py": LibraryDownloader,
-        "build_rust": CustomBuildRust,
-        "clean": CleanLibraries,
-        "ext_hashes": ExtensionHashes,
-    },
-    setup_requires=["setuptools_scm[toml]>=4", "cython", "cmake>=3.24.2,<3.28", "setuptools-rust"],
-    ext_modules=ext_modules
-    + cythonize(
+
+cython_exts = []
+if os.getenv("DD_CYTHONIZE", "1").lower() in ("1", "yes", "on", "true"):
+    cython_exts = cythonize(
         [
             Cython.Distutils.Extension(
                 "ddtrace.internal._rand",
@@ -1244,6 +1221,32 @@ def get_exts_for(name):
         compiler_directives={"language_level": "3"},
         cache=True,
     )
-    + get_exts_for("psutil"),
+
+interpose_sccache()
+setup(
+    name="ddtrace",
+    packages=find_packages(exclude=["tests*", "benchmarks*", "scripts*"]),
+    package_data={
+        "ddtrace": ["py.typed"],
+        "ddtrace.appsec": ["rules.json"],
+        "ddtrace.appsec._ddwaf": ["libddwaf/*/lib/libddwaf.*"],
+        "ddtrace.appsec._iast._taint_tracking": ["CMakeLists.txt"],
+        "ddtrace.internal.datadog.profiling": (
+            ["libdd_wrapper*.*"]
+            + (["ddtrace/internal/datadog/profiling/test/*"] if BUILD_PROFILING_NATIVE_TESTS else [])
+        ),
+    },
+    zip_safe=False,
+    # enum34 is an enum backport for earlier versions of python
+    # funcsigs backport required for vendored debtcollector
+    cmdclass={
+        "build_ext": CustomBuildExt,
+        "build_py": LibraryDownloader,
+        "build_rust": CustomBuildRust,
+        "clean": CleanLibraries,
+        "ext_hashes": ExtensionHashes,
+    },
+    setup_requires=["setuptools_scm[toml]>=4", "cython", "cmake>=3.24.2,<3.28", "setuptools-rust"],
+    ext_modules=ext_modules + cython_exts + get_exts_for("psutil"),
     distclass=PatchedDistribution,
 )