Add imports property to py_library rules

This is to avoid having it hardcoded in a fork of the
py_library rule.

Most import attributes should just be set to ".", but
our previous solution always hardcoded it to ".." instead,
for ndkstubgen. ndkstubgen uses pkg_path: "ndkstubgen",
i.e., it set pkg_path to the name of the folder that
contained the Android.bp file. In this specific scenario,
imports = ".." works. Recreate that behavior here as well,
because we don't handle pkg_path properly yet.

Fixes: 233081071
Test: build/bazel/ci/bp2build.sh
Change-Id: Ib5e6a8edf428c74d4b5947f0ec53a2151001367a

python/library.go

@@ -17,6 +17,9 @@ package python
 // This file contains the module types for building Python library.
 
 import (
+	"path/filepath"
+	"strings"
+
 	"android/soong/android"
 	"android/soong/bazel"
 
@@ -43,6 +46,7 @@ func PythonLibraryHostFactory() android.Module {
 type bazelPythonLibraryAttributes struct {
 	Srcs         bazel.LabelListAttribute
 	Deps         bazel.LabelListAttribute
+	Imports      bazel.StringListAttribute
 	Srcs_version *string
 }
 
@@ -64,16 +68,44 @@ func pythonLibBp2Build(ctx android.TopDownMutatorContext, m *Module) {
 		// do nothing, since python_version defaults to PY2ANDPY3
 	}
 
+	// Bazel normally requires `import path.from.top.of.tree` statements in
+	// python code, but with soong you can directly import modules from libraries.
+	// Add "imports" attributes to the bazel library so it matches soong's behavior.
+	imports := "."
+	if m.properties.Pkg_path != nil {
+		// TODO(b/215119317) This is a hack to handle the fact that we don't convert
+		// pkg_path properly right now. If the folder structure that contains this
+		// Android.bp file matches pkg_path, we can set imports to an appropriate
+		// number of ../..s to emulate moving the files under a pkg_path folder.
+		pkg_path := filepath.Clean(*m.properties.Pkg_path)
+		if strings.HasPrefix(pkg_path, "/") {
+			ctx.ModuleErrorf("pkg_path cannot start with a /: %s", pkg_path)
+			return
+		}
+
+		if !strings.HasSuffix(ctx.ModuleDir(), "/"+pkg_path) && ctx.ModuleDir() != pkg_path {
+			ctx.ModuleErrorf("Currently, bp2build only supports pkg_paths that are the same as the folders the Android.bp file is in. pkg_path: %s, module directory: %s", pkg_path, ctx.ModuleDir())
+			return
+		}
+		numFolders := strings.Count(pkg_path, "/") + 1
+		dots := make([]string, numFolders)
+		for i := 0; i < numFolders; i++ {
+			dots[i] = ".."
+		}
+		imports = strings.Join(dots, "/")
+	}
+
 	baseAttrs := m.makeArchVariantBaseAttributes(ctx)
 	attrs := &bazelPythonLibraryAttributes{
 		Srcs:         baseAttrs.Srcs,
 		Deps:         baseAttrs.Deps,
 		Srcs_version: python_version,
+		Imports:      bazel.MakeStringListAttribute([]string{imports}),
 	}
 
 	props := bazel.BazelTargetModuleProperties{
-		Rule_class:        "py_library",
-		Bzl_load_location: "//build/bazel/rules/python:library.bzl",
+		// Use the native py_library rule.
+		Rule_class: "py_library",
 	}
 
 	ctx.CreateBazelTargetModule(props, android.CommonAttributes{