Add unit test for parsing build files in bp2build

This involves some minor changes to testing infrastructure.

Bug: 285631638
Fixes: 286545783
Test: unit test
Change-Id: If64ba29308d99e63a1cc5526feaf077f2cb14478
diff --git a/cmd/soong_build/main.go b/cmd/soong_build/main.go
index 989dd7f..6975677 100644
--- a/cmd/soong_build/main.go
+++ b/cmd/soong_build/main.go
@@ -21,7 +21,6 @@
 	"fmt"
 	"os"
 	"path/filepath"
-	"regexp"
 	"strings"
 	"time"
 
@@ -737,43 +736,6 @@
 	return excluded
 }
 
-// buildTargetsByPackage parses Bazel BUILD.bazel and BUILD files under
-// the workspace, and returns a map containing names of Bazel targets defined in
-// these BUILD files.
-// For example, maps "//foo/bar" to ["baz", "qux"] if `//foo/bar:{baz,qux}` exist.
-func buildTargetsByPackage(ctx *android.Context) map[string][]string {
-	existingBazelFiles, err := getExistingBazelRelatedFiles(topDir)
-	maybeQuit(err, "Error determining existing Bazel-related files")
-
-	result := map[string][]string{}
-
-	// Search for instances of `name = "$NAME"` (with arbitrary spacing).
-	targetNameRegex := regexp.MustCompile(`(?m)^\s*name\s*=\s*\"([^\"]+)\"`)
-
-	for _, path := range existingBazelFiles {
-		if !ctx.Config().Bp2buildPackageConfig.ShouldKeepExistingBuildFileForDir(filepath.Dir(path)) {
-			continue
-		}
-		fullPath := shared.JoinPath(topDir, path)
-		sourceDir := filepath.Dir(path)
-		fileInfo, err := os.Stat(fullPath)
-		maybeQuit(err, "Error accessing Bazel file '%s'", fullPath)
-
-		if !fileInfo.IsDir() &&
-			(fileInfo.Name() == "BUILD" || fileInfo.Name() == "BUILD.bazel") {
-			// Process this BUILD file.
-			buildFileContent, err := os.ReadFile(fullPath)
-			maybeQuit(err, "Error reading Bazel file '%s'", fullPath)
-
-			matches := targetNameRegex.FindAllStringSubmatch(string(buildFileContent), -1)
-			for _, match := range matches {
-				result[sourceDir] = append(result[sourceDir], match[1])
-			}
-		}
-	}
-	return result
-}
-
 // Run Soong in the bp2build mode. This creates a standalone context that registers
 // an alternate pipeline of mutators and singletons specifically for generating
 // Bazel BUILD files instead of Ninja files.
@@ -782,7 +744,11 @@
 	ctx.EventHandler.Do("bp2build", func() {
 
 		ctx.EventHandler.Do("read_build", func() {
-			ctx.Config().SetBazelBuildFileTargets(buildTargetsByPackage(ctx))
+			existingBazelFiles, err := getExistingBazelRelatedFiles(topDir)
+			maybeQuit(err, "Error determining existing Bazel-related files")
+
+			err = ctx.ParseBuildFiles(topDir, existingBazelFiles)
+			maybeQuit(err, "Error parsing existing Bazel-related files")
 		})
 
 		// Propagate "allow misssing dependencies" bit. This is normally set in