feat(gazelle): Add ancestor conftest.py files (bazel-contrib#3498)

Re-introduces the gazelle behavior of adding conftest targets to tests
so that
they inherit parent directory configs.

Fixes bazel-contrib#3497

Author: thejcannon

CHANGELOG.md

@@ -66,6 +66,8 @@ END_UNRELEASED_TEMPLATE
 ### Fixed
 * (tests) No more coverage warnings are being printed if there are no sources.
   ([#2762](https://github.com/bazel-contrib/rules_python/issues/2762))
+* (gazelle) Ancestor `conftest.py` files are added in addition to sibling `conftest.py`.
+  ([#3497](https://github.com/bazel-contrib/rules_python/issues/3497))
 
 {#v0-0-0-added}
 ### Added

gazelle/python/generate.go

@@ -66,6 +66,24 @@ func matchesAnyGlob(s string, globs []string) bool {
 	return false
 }
 
+// findConftestPaths returns package paths containing conftest.py, from currentPkg
+// up through ancestors, stopping at module root.
+func findConftestPaths(repoRoot, currentPkg, pythonProjectRoot string) []string {
+	var result []string
+	for pkg := currentPkg; ; pkg = filepath.Dir(pkg) {
+		if pkg == "." {
+			pkg = ""
+		}
+		if _, err := os.Stat(filepath.Join(repoRoot, pkg, conftestFilename)); err == nil {
+			result = append(result, pkg)
+		}
+		if pkg == "" {
+			break
+		}
+	}
+	return result
+}
+
 // GenerateRules extracts build metadata from source files in a directory.
 // GenerateRules is called in each directory where an update is requested
 // in depth-first post-order.
@@ -481,14 +499,17 @@ func (py *Python) GenerateRules(args language.GenerateArgs) language.GenerateRes
 	}
 
 	for _, pyTestTarget := range pyTestTargets {
-		if conftest != nil {
-			conftestModule := Module{Name: importSpecFromSrc(pythonProjectRoot, args.Rel, conftestFilename).Imp}
-			if pyTestTarget.annotations.includePytestConftest == nil {
-				// unset; default behavior
-				pyTestTarget.addModuleDependency(conftestModule)
-			} else if *pyTestTarget.annotations.includePytestConftest {
-				// set; add if true, do not add if false
-				pyTestTarget.addModuleDependency(conftestModule)
+		shouldAddConftest := pyTestTarget.annotations.includePytestConftest == nil ||
+		*pyTestTarget.annotations.includePytestConftest
+
+		if shouldAddConftest {
+			for _, conftestPkg := range findConftestPaths(args.Config.RepoRoot, args.Rel, pythonProjectRoot) {
+				pyTestTarget.addModuleDependency(
+					Module{
+						Name: importSpecFromSrc(pythonProjectRoot, conftestPkg, conftestFilename).Imp, 
+						Filepath: filepath.Join(conftestPkg, conftestFilename),
+					},
+				)
 			}
 		}
 		pyTest := pyTestTarget.build()

gazelle/python/testdata/simple_test_with_conftest/bar/BUILD.out

@@ -23,5 +23,6 @@ py_test(
     deps = [
         ":bar",
         ":conftest",
+        "//:conftest",
     ],
 )

gazelle/python/testdata/simple_test_with_conftest_sibling_imports_disabled/bar/BUILD.out

@@ -22,6 +22,7 @@ py_test(
     main = "__test__.py",
     deps = [
         ":conftest",
+        "//:conftest",
         "//:simple_test_with_conftest_sibling_imports_disabled",
     ],
 )