fix: use getsitepackages for writing .pth files. #2006

Author: nedbat

CHANGES.rst

@@ -23,7 +23,10 @@ upgrading your version of coverage.py.
 Unreleased
 ----------
 
-Nothing yet.
+- Fix: changed where .pth files are written for ``patch = subprocess``, closing
+  `issue 2006`_.
+
+.. _issue 2006: https://github.com/nedbat/coveragepy/issues/2006
 
 
 .. start-releases

coverage/files.py

@@ -11,12 +11,12 @@
 import os.path
 import posixpath
 import re
+import site
 import sys
-import sysconfig
 
 from pathlib import Path
 from typing import Callable
-from collections.abc import Iterable, Iterator
+from collections.abc import Iterable
 
 from coverage import env
 from coverage.exceptions import ConfigError
@@ -220,8 +220,8 @@ def prep_patterns(patterns: Iterable[str]) -> list[str]:
 
 def create_pth_file() -> Path | None:
     """Create .pth file for measuring subprocesses."""
-    for pth_dir in _possible_pth_dirs():  # pragma: part covered
-        pth_file = pth_dir / "subcover.pth"
+    for pth_dir in site.getsitepackages():  # pragma: part covered
+        pth_file = Path(pth_dir) / "subcover.pth"
         try:
             pth_file.write_text("import coverage; coverage.process_startup()\n", encoding="utf-8")
         except OSError:  # pragma: cant happen
@@ -231,20 +231,6 @@ def create_pth_file() -> Path | None:
     return None  # pragma: cant happen
 
 
-def _possible_pth_dirs() -> Iterator[Path]:
-    """Produce a sequence of directories for trying to write .pth files."""
-    # First look through sys.path, and if we find a .pth file, then it's a good
-    # place to put ours.
-    for pth_dir in map(Path, sys.path):  # pragma: part covered
-        pth_files = list(pth_dir.glob("*.pth"))
-        if pth_files:
-            yield pth_dir
-
-    # If we're still looking, then try the Python library directory.
-    # https://github.com/nedbat/coveragepy/issues/339
-    yield Path(sysconfig.get_path("purelib"))  # pragma: cant happen
-
-
 class TreeMatcher:
     """A matcher for files in a tree.