feat(gazelle) Remove entry point file requirements when generating rules (bazel-contrib#2998)

Remove entry point file requirements when generating rules. Enable
python rule generation as long as there are .py source files under the
directory so all new packages will have python rules generated in the
package.

The extension used to require entrypoints for generation but:
- entry point for tests (i.e., `__test__.py` ) is no longer required
after bazel-contrib#999 and
bazel-contrib#2044
- entry point for binaries (i.e., `__main__.py` ) is no longer required
after bazel-contrib#1584

The entry point for libraries (`__init__.py` ) shouldn't be required
either, especially for Python 3.3 and after when namespace packages are
supported.

---------

Co-authored-by: yushan <yushan@uber.com>
Co-authored-by: Douglas Thor <dougthor42@users.noreply.github.com>

Author: 3 people

CHANGELOG.md

@@ -58,6 +58,8 @@ END_UNRELEASED_TEMPLATE
   to the package path. This is enabled via the
   `# gazelle:experimental_allow_relative_imports` true directive ({gh-issue}`2203`).
 * (gazelle) Types for exposed members of `python.ParserOutput` are now all public.
+* (gazelle) Removed the requirement for `__init__.py`, `__main__.py`, or `__test__.py` files to be
+  present in a directory to generate a `BUILD.bazel` file.
 
 {#v0-0-0-fixed}
 ### Fixed

gazelle/python/generate.go

@@ -85,8 +85,6 @@ func (py *Python) GenerateRules(args language.GenerateArgs) language.GenerateRes
 			if parent != nil && parent.CoarseGrainedGeneration() {
 				return language.GenerateResult{}
 			}
-		} else if !hasEntrypointFile(args.Dir) {
-			return language.GenerateResult{}
 		}
 	}
 
@@ -172,9 +170,6 @@ func (py *Python) GenerateRules(args language.GenerateArgs) language.GenerateRes
 					//   2. The directory has a BUILD or BUILD.bazel files. Then
 					//       it doesn't matter at all what it has since it's a
 					//       separate Bazel package.
-					//   3. (only for package generation) The directory has an
-					//       __init__.py, __main__.py or __test__.py, meaning a
-					//       BUILD file will be generated.
 					if cfg.PerFileGeneration() {
 						return fs.SkipDir
 					}
@@ -184,7 +179,7 @@ func (py *Python) GenerateRules(args language.GenerateArgs) language.GenerateRes
 						return nil
 					}
 
-					if !cfg.CoarseGrainedGeneration() && hasEntrypointFile(path) {
+					if !cfg.CoarseGrainedGeneration() {
 						return fs.SkipDir
 					}
 

gazelle/python/testdata/subdir_sources/BUILD.in

@@ -0,0 +1 @@
+# gazelle:python_generation_mode project

gazelle/python/testdata/subdir_sources/BUILD.out

@@ -1,5 +1,8 @@
+
 load("@rules_python//python:defs.bzl", "py_binary")
 
+# gazelle:python_generation_mode project
+
 py_binary(
     name = "subdir_sources_bin",
     srcs = ["__main__.py"],