fix(gazelle): generate a single py_test for coarse_grained setups (#1538)

With a recent change to generate a single test target per python file
we introduced a regression for projects using
`# gazelle:python_generation_mode project` configuration directive
if there are multiple files with the same filenames but under different
directories within the source tree. This PR fixes the behaviour so that
we just generate a single target containing all test files as there is
no sure way to denormalize the paths so that they never clash.

Fixes #1442.

Author: aignas

CHANGELOG.md

@@ -75,6 +75,9 @@ Breaking changes:
 * (py_wheel) Produce deterministic wheel files and make `RECORD` file entries
   follow the order of files written to the `.whl` archive.
 
+* (gazelle) Generate a single `py_test` target when `gazelle:python_generation_mode project`
+  is used.
+
 ### Added
 
 * (bzlmod) Added `.whl` patching support via `patches` and `patch_strip`

gazelle/python/generate.go

@@ -371,7 +371,7 @@ func (py *Python) GenerateRules(args language.GenerateArgs) language.GenerateRes
 			addModuleDependencies(deps).
 			generateImportsAttribute()
 	}
-	if hasPyTestEntryPointFile || hasPyTestEntryPointTarget {
+	if hasPyTestEntryPointFile || hasPyTestEntryPointTarget || cfg.CoarseGrainedGeneration() {
 		if hasPyTestEntryPointFile {
 			// Only add the pyTestEntrypointFilename to the pyTestFilenames if
 			// the file exists on disk.

gazelle/python/testdata/monorepo/coarse_grained/BUILD.out

@@ -1,4 +1,4 @@
-load("@rules_python//python:defs.bzl", "py_library")
+load("@rules_python//python:defs.bzl", "py_library", "py_test")
 
 # gazelle:python_extension enabled
 # gazelle:python_root
@@ -18,3 +18,12 @@ py_library(
     visibility = ["//:__subpackages__"],
     deps = ["@root_pip_deps//rootboto3"],
 )
+
+py_test(
+    name = "coarse_grained_test",
+    srcs = [
+        "bar/bar_test.py",
+        "foo/bar/bar_test.py",
+    ],
+    main = "__test__.py",
+)