Merge "Fix incrementality bug with merged BUILD files"

bp2build/symlink_forest.go

@@ -285,6 +285,17 @@ func plantSymlinkForestRecursive(cfg android.Config, topdir string, forestDir st
 			// Neither is a directory. Merge them.
 			srcBuildFile := shared.JoinPath(topdir, srcChild)
 			generatedBuildFile := shared.JoinPath(topdir, buildFilesChild)
+			// Add the src and generated build files as dependencies so that bp2build
+			// is rerun when they change. Currently, this is only really necessary
+			// for srcBuildFile, because if we regenerate the generated build files
+			// we will always rerun the symlink forest generation as well. If that
+			// is later split up into separate, fully dependency-tracing steps, then
+			// we'll need srcBuildFile as well. Adding srcBuildFile here today
+			// technically makes it a dependency of bp2build_workspace_marker, which
+			// also implicitly outputs that file, but since bp2build_workspace_marker
+			// will always have a newer timestamp than the generatedBuildFile it
+			// shouldn't be a problem.
+			*acc = append(*acc, srcBuildFile, generatedBuildFile)
 			err = mergeBuildFiles(shared.JoinPath(topdir, forestChild), srcBuildFile, generatedBuildFile, cfg.IsEnvTrue("BP2BUILD_VERBOSE"))
 			if err != nil {
 				fmt.Fprintf(os.Stderr, "Error merging %s and %s: %s",