Turn missing jarjar output files into errors

Jarjar doesn't exit with a nonzero return code when there is a syntax
error in a rules file and doesn't write the output file.  Without a
nonzero return code ninja prints a warning but continues, which leads
to stale results on incremental builds where the output file already
exists, or delayed errors on clean builds whre the output file didn't
exist.

Delete the output file before running jarjar, and then check if it
exists after running jarjar.

Fixes: 119516143
Test: m out/target/common/obj/APPS/TeleService_intermediates/classes.jar
Change-Id: I7e9f7ff34de565a986ab0dc6e375f606c91c3846

1 files changed, 9 insertions, 2 deletions

diff --git a/java/builder.go b/java/builder.go
index 995160d0e..22a891ae1 100644
--- a/java/builder.go
+++ b/java/builder.go
@@ -193,12 +193,19 @@ var (
 
 	jarjar = pctx.AndroidStaticRule("jarjar",
 		blueprint.RuleParams{
-			Command: "${config.JavaCmd} ${config.JavaVmFlags}" +
+			Command: "" +
+				// Jarjar doesn't exit with an error when the rules file contains a syntax error,
+				// leading to stale or missing files later in the build.  Remove the output file
+				// before running jarjar.
+				"rm -f ${out} && " +
+				"${config.JavaCmd} ${config.JavaVmFlags}" +
 				// b/146418363 Enable Android specific jarjar transformer to drop compat annotations
 				// for newly repackaged classes. Dropping @UnsupportedAppUsage on repackaged classes
 				// avoids adding new hiddenapis after jarjar'ing.
 				" -DremoveAndroidCompatAnnotations=true" +
-				" -jar ${config.JarjarCmd} process $rulesFile $in $out",
+				" -jar ${config.JarjarCmd} process $rulesFile $in $out && " +
+				// Turn a missing output file into a ninja error
+				`[ -e ${out} ] || (echo "Missing output file"; exit 1)`,
 			CommandDeps: []string{"${config.JavaCmd}", "${config.JarjarCmd}", "$rulesFile"},
 		},
 		"rulesFile")