fix(gazelle): __init__.py in per-file targets

gazelle/python/__main__.py

@@ -16,10 +16,11 @@
 # STDIN receives parse requests, one per line. It outputs the parsed modules and
 # comments from all the files from each request.
 
-import parse
-import std_modules
 import sys
 
+import python.parse as parse
+import python.std_modules as std_modules
+
 if __name__ == "__main__":
     if len(sys.argv) < 2:
         sys.exit("Please provide subcommand, either print or std_modules")

gazelle/python/generate.go

@@ -19,6 +19,7 @@ import (
 	"io/fs"
 	"log"
 	"os"
+	pathpkg "path"
 	"path/filepath"
 	"strings"
 
@@ -252,18 +253,31 @@ func (py *Python) GenerateRules(args language.GenerateArgs) language.GenerateRes
 		result.Imports = append(result.Imports, pyLibrary.PrivateAttr(config.GazelleImportsKey))
 	}
 	if cfg.PerFileGeneration() {
+		hasInit, nonEmptyInit := hasLibraryEntrypointFile(args.Dir)
 		pyLibraryFilenames.Each(func(index int, filename interface{}) {
+			var pyLibraryTargetName string
 			if filename == pyLibraryEntrypointFilename {
-				stat, err := os.Stat(filepath.Join(args.Dir, filename.(string)))
-				if err != nil {
-					log.Fatalf("ERROR: %v\n", err)
+				if !nonEmptyInit {
+					return // ignore empty __init__.py.
 				}
-				if stat.Size() == 0 {
-					return // ignore empty __init__.py
+				if args.File.Pkg == "" {
+					// As per Python spec, an __init__.py file does not make sense without
+					// a package name, but someone can technically configure the Bazel
+					// workspace as the Python package (i.e. parent of the Bazel workspace
+					// is part of PYTHONPATH), in which case this should be the workspace
+					// name, but there is no mechanism to obtain that here. So let's just
+					// call it "__init__".
+					pyLibraryTargetName = "__init__"
+				} else {
+					pyLibraryTargetName = pathpkg.Base(args.File.Pkg)
 				}
+			} else {
+				pyLibraryTargetName = strings.TrimSuffix(filepath.Base(filename.(string)), ".py")
 			}
 			srcs := treeset.NewWith(godsutils.StringComparator, filename)
-			pyLibraryTargetName := strings.TrimSuffix(filepath.Base(filename.(string)), ".py")
+			if hasInit && nonEmptyInit {
+				srcs.Add(pyLibraryEntrypointFilename)
+			}
 			appendPyLibrary(srcs, pyLibraryTargetName)
 		})
 	} else if !pyLibraryFilenames.Empty() {
@@ -463,6 +477,19 @@ func hasEntrypointFile(dir string) bool {
 	return false
 }
 
+// hasLibraryEntrypointFile returns if the given directory has the library
+// entrypoint file, and if it is non-empty.
+func hasLibraryEntrypointFile(dir string) (bool, bool) {
+	stat, err := os.Stat(filepath.Join(dir, pyLibraryEntrypointFilename))
+	if os.IsNotExist(err) {
+		return false, false
+	}
+	if err != nil {
+		log.Fatalf("ERROR: %v\n", err)
+	}
+	return true, stat.Size() != 0
+}
+
 // isEntrypointFile returns whether the given path is an entrypoint file. The
 // given path can be absolute or relative.
 func isEntrypointFile(path string) bool {

gazelle/python/resolve.go

@@ -61,11 +61,17 @@ func (py *Resolver) Imports(c *config.Config, r *rule.Rule, f *rule.File) []reso
 	provides := make([]resolve.ImportSpec, 0, len(srcs)+1)
 	for _, src := range srcs {
 		ext := filepath.Ext(src)
-		if ext == ".py" {
-			pythonProjectRoot := cfg.PythonProjectRoot()
-			provide := importSpecFromSrc(pythonProjectRoot, f.Pkg, src)
-			provides = append(provides, provide)
+		if ext != ".py" {
+			continue
 		}
+		if cfg.PerFileGeneration() && len(srcs) > 1 && src == pyLibraryEntrypointFilename {
+			// Do not provide import spec from __init__.py when it is being included as
+			// part of another module.
+			continue
+		}
+		pythonProjectRoot := cfg.PythonProjectRoot()
+		provide := importSpecFromSrc(pythonProjectRoot, f.Pkg, src)
+		provides = append(provides, provide)
 	}
 	if len(provides) == 0 {
 		return nil

gazelle/python/testdata/per_file_non_empty_init/BUILD.out

@@ -11,6 +11,9 @@ py_library(
 
 py_library(
     name = "foo",
-    srcs = ["foo.py"],
+    srcs = [
+        "__init__.py",
+        "foo.py",
+    ],
     visibility = ["//:__subpackages__"],
 )

gazelle/python/testdata/per_file_subdirs/BUILD.out

@@ -6,5 +6,5 @@ py_library(
     name = "foo",
     srcs = ["foo.py"],
     visibility = ["//:__subpackages__"],
-    deps = ["//bar:__init__"],
+    deps = ["//bar"],
 )

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

@@ -1,14 +1,17 @@
 load("@rules_python//python:defs.bzl", "py_library", "py_test")
 
 py_library(
-    name = "__init__",
+    name = "bar",
     srcs = ["__init__.py"],
     visibility = ["//:__subpackages__"],
 )
 
 py_library(
     name = "foo",
-    srcs = ["foo.py"],
+    srcs = [
+        "__init__.py",
+        "foo.py",
+    ],
     visibility = ["//:__subpackages__"],
 )