fix: force patched subprocesses to write data to the original directory. #2025

Author: nedbat

CHANGES.rst

@@ -23,9 +23,15 @@ upgrading your version of coverage.py.
 Unreleased
 ----------
 
-- Fix: ``patch = subprocess`` didn't fully account for subprocesses spawning
-  yet more subprocesses simultaneously, and some coveage could be missed.  This
-  is now fixed, closing `issue 2024`_.
+- Fixes for ``patch = subprocess``:
+
+  - It didn't fully account for subprocesses spawning yet more subprocesses
+    simultaneously, and some coverage could be missed.  This is now fixed,
+    closing `issue 2024`_.
+
+  - If subprocesses were created in other directories, their data files were
+    stranded there and not combined into the totals, as described in `issue
+    2025`_.  This is now fixed.
 
 - Fix: really close all SQLite databases, even in-memory ones. Closes `issue
   2017`_.
@@ -37,6 +43,7 @@ Unreleased
 .. _issue 2017: https://github.com/nedbat/coveragepy/issues/2017
 .. _pull 2018: https://github.com/nedbat/coveragepy/pull/2018
 .. _issue 2024: https://github.com/nedbat/coveragepy/issues/2024
+.. _issue 2025: https://github.com/nedbat/coveragepy/issues/2025
 
 
 .. start-releases

coverage/control.py

@@ -1448,7 +1448,10 @@ def process_startup() -> Coverage | None:
         # started coverage.py in this process.  Nothing to do.
         return None
 
-    cov = Coverage(config_file=cps)
+    cov = Coverage(
+        config_file=cps,
+        data_file=os.getenv("COVERAGE_PROCESS_DATAFILE") or DEFAULT_DATAFILE,
+    )
     process_startup.coverage = cov      # type: ignore[attr-defined]
     cov._warn_no_data = False
     cov._warn_unimported_source = False

coverage/patch.py

@@ -83,6 +83,7 @@ def coverage_execv_patch(*args: Any, **kwargs: Any) -> Any:
                 atexit.register(pth_file.unlink, missing_ok=True)
             assert config.config_file is not None
             os.environ["COVERAGE_PROCESS_START"] = config.config_file
+            os.environ["COVERAGE_PROCESS_DATAFILE"] = os.path.abspath(config.data_file)
 
         else:
             raise ConfigError(f"Unknown patch {patch!r}")

tests/test_process.py

@@ -1325,9 +1325,8 @@ def test_removing_directory_with_error(self) -> None:
 class ProcessStartupTest(CoverageTest):
     """Test that we can measure coverage in subprocesses."""
 
-    def setUp(self) -> None:
-        super().setUp()
-
+    def make_main_and_sub(self) -> None:
+        """Create main.py and sub.py."""
         # Main will run sub.py
         self.make_file("main.py", """\
             import os, os.path, sys
@@ -1342,6 +1341,7 @@ def setUp(self) -> None:
             """)
 
     def test_patch_subprocess(self) -> None:
+        self.make_main_and_sub()
         self.make_file(".coveragerc", """\
             [run]
             patch = subprocess
@@ -1358,6 +1358,7 @@ def test_subprocess_with_pth_files(self, _create_pth_file: None) -> None:
         # An existing data file should not be read when a subprocess gets
         # measured automatically.  Create the data file here with bogus data in
         # it.
+        self.make_main_and_sub()
         data = coverage.CoverageData(".mycovdata")
         data.add_lines({os.path.abspath('sub.py'): range(100)})
         data.write()
@@ -1380,6 +1381,7 @@ def test_subprocess_with_pth_files(self, _create_pth_file: None) -> None:
 
     def test_subprocess_with_pth_files_and_parallel(self, _create_pth_file: None) -> None:
         # https://github.com/nedbat/coveragepy/issues/492
+        self.make_main_and_sub()
         self.make_file("coverage.ini", """\
             [run]
             parallel = true
@@ -1407,6 +1409,37 @@ def test_subprocess_with_pth_files_and_parallel(self, _create_pth_file: None) ->
         )
         assert len(data_files) == 1, msg
 
+    def test_subprocess_in_directories(self) -> None:
+        # Bug 2025: patch=subprocess didn't find data files from subdirectory
+        # subprocesses.
+        self.make_file("main.py", """\
+            import subprocess
+            import sys
+            print(subprocess.check_output(
+                [sys.executable, "subproc.py"],
+                cwd="subdir",
+                encoding="utf-8",
+            ))
+            """)
+        self.make_file("subdir/subproc.py", """\
+            with open("readme.txt", encoding="utf-8") as f:
+                print(f.read(), end="")
+            """)
+        self.make_file(".coveragerc", """\
+            [run]
+            patch = subprocess
+            data_file = .covdata
+            """)
+        self.make_file("subdir/readme.txt", "hello")
+        out = self.run_command("coverage run main.py")
+        assert out == "hello\n"
+        self.run_command("coverage combine")
+        data = coverage.CoverageData(".covdata")
+        data.read()
+        print(line_counts(data))
+        assert line_counts(data)["main.py"] == 6
+        assert line_counts(data)["subproc.py"] == 2
+
 
 @pytest.mark.skipif(env.WINDOWS, reason="patch=execv isn't supported on Windows")
 @pytest.mark.xdist_group(name="needs_pth")