Merge "Avoid deleting bp2build directory"

bp2build/bp2build.go

@@ -17,21 +17,57 @@ package bp2build
 import (
 	"fmt"
 	"os"
+	"path/filepath"
 	"strings"
 
 	"android/soong/android"
 	"android/soong/bazel"
+	"android/soong/shared"
 )
 
+func deleteFilesExcept(ctx *CodegenContext, rootOutputPath android.OutputPath, except []BazelFile) {
+	// Delete files that should no longer be present.
+	bp2buildDirAbs := shared.JoinPath(ctx.topDir, rootOutputPath.String())
+
+	filesToDelete := make(map[string]struct{})
+	err := filepath.Walk(bp2buildDirAbs,
+		func(path string, info os.FileInfo, err error) error {
+			if err != nil {
+				return err
+			}
+			if !info.IsDir() {
+				relPath, err := filepath.Rel(bp2buildDirAbs, path)
+				if err != nil {
+					return err
+				}
+				filesToDelete[relPath] = struct{}{}
+			}
+			return nil
+		})
+	if err != nil {
+		fmt.Printf("ERROR reading %s: %s", bp2buildDirAbs, err)
+		os.Exit(1)
+	}
+
+	for _, bazelFile := range except {
+		filePath := filepath.Join(bazelFile.Dir, bazelFile.Basename)
+		delete(filesToDelete, filePath)
+	}
+	for f, _ := range filesToDelete {
+		absPath := shared.JoinPath(bp2buildDirAbs, f)
+		if err := os.RemoveAll(absPath); err != nil {
+			fmt.Printf("ERROR deleting %s: %s", absPath, err)
+			os.Exit(1)
+		}
+	}
+}
+
 // Codegen is the backend of bp2build. The code generator is responsible for
 // writing .bzl files that are equivalent to Android.bp files that are capable
 // of being built with Bazel.
 func Codegen(ctx *CodegenContext) *CodegenMetrics {
 	// This directory stores BUILD files that could be eventually checked-in.
 	bp2buildDir := android.PathForOutput(ctx, "bp2build")
-	if err := android.RemoveAllOutputDir(bp2buildDir); err != nil {
-		fmt.Printf("ERROR: Encountered error while cleaning %s: %s", bp2buildDir, err.Error())
-	}
 
 	res, errs := GenerateBazelTargets(ctx, true)
 	if len(errs) > 0 {
@@ -44,6 +80,12 @@ func Codegen(ctx *CodegenContext) *CodegenMetrics {
 	}
 	bp2buildFiles := CreateBazelFiles(ctx.Config(), nil, res.buildFileToTargets, ctx.mode)
 	writeFiles(ctx, bp2buildDir, bp2buildFiles)
+	// Delete files under the bp2build root which weren't just written. An
+	// alternative would have been to delete the whole directory and write these
+	// files. However, this would regenerate files which were otherwise unchanged
+	// since the last bp2build run, which would have negative incremental
+	// performance implications.
+	deleteFilesExcept(ctx, bp2buildDir, bp2buildFiles)
 
 	injectionFiles, err := CreateSoongInjectionDirFiles(ctx, res.metrics)
 	if err != nil {
@@ -51,7 +93,6 @@ func Codegen(ctx *CodegenContext) *CodegenMetrics {
 		os.Exit(1)
 	}
 	writeFiles(ctx, android.PathForOutput(ctx, bazel.SoongInjectionDirName), injectionFiles)
-
 	return &res.metrics
 }
 

tests/bp2build_bazel_test.sh

@@ -21,6 +21,68 @@ function test_bp2build_null_build {
   fi
 }
 
+# Tests that, if bp2build reruns due to a blueprint file changing, that
+# BUILD files whose contents are unchanged are not regenerated.
+function test_bp2build_unchanged {
+  setup
+
+  mkdir -p pkg
+  touch pkg/x.txt
+  cat > pkg/Android.bp <<'EOF'
+filegroup {
+    name: "x",
+    srcs: ["x.txt"],
+    bazel_module: {bp2build_available: true},
+  }
+EOF
+
+  run_soong bp2build
+  local -r buildfile_mtime1=$(stat -c "%y" out/soong/bp2build/pkg/BUILD.bazel)
+  local -r marker_mtime1=$(stat -c "%y" out/soong/bp2build_workspace_marker)
+
+  # Force bp2build to rerun by updating the timestamp of a blueprint file.
+  touch pkg/Android.bp
+
+  run_soong bp2build
+  local -r buildfile_mtime2=$(stat -c "%y" out/soong/bp2build/pkg/BUILD.bazel)
+  local -r marker_mtime2=$(stat -c "%y" out/soong/bp2build_workspace_marker)
+
+  if [[ "$marker_mtime1" == "$marker_mtime2" ]]; then
+    fail "Expected bp2build marker file to change"
+  fi
+  if [[ "$buildfile_mtime1" != "$buildfile_mtime2" ]]; then
+    fail "BUILD.bazel was updated even though contents are same"
+  fi
+}
+
+# Tests that blueprint files that are deleted are not present when the
+# bp2build tree is regenerated.
+function test_bp2build_deleted_blueprint {
+  setup
+
+  mkdir -p pkg
+  touch pkg/x.txt
+  cat > pkg/Android.bp <<'EOF'
+filegroup {
+    name: "x",
+    srcs: ["x.txt"],
+    bazel_module: {bp2build_available: true},
+  }
+EOF
+
+  run_soong bp2build
+  if [[ ! -e "./out/soong/bp2build/pkg/BUILD.bazel" ]]; then
+    fail "Expected pkg/BUILD.bazel to be generated"
+  fi
+
+  rm pkg/Android.bp
+
+  run_soong bp2build
+  if [[ -e "./out/soong/bp2build/pkg/BUILD.bazel" ]]; then
+    fail "Expected pkg/BUILD.bazel to be deleted"
+  fi
+}
+
 function test_bp2build_null_build_with_globs {
   setup