If none of the jars have a spring.components file, it fails

spring_image.bzl

@@ -129,13 +129,14 @@ def tar_jars(ctx, files, out):
     ctx.actions.run_shell(
         inputs = ctx.files._jdk + files,
         outputs = [spring_components_file],
-        command = "touch {file}; for i in {all_paths}; do {jar} xf $i && cat META-INF/spring.components >> {file}; done".format(file = spring_components_file.path, jar = jar_path, all_paths = " ".join(paths)),
+        command = "touch {file}; for i in {all_paths}; do {jar} xf $i && if [-s META-INF/spring.components ]; then cat META-INF/spring.components >> {file}; fi; done".format(file = spring_components_file.path, jar = jar_path, all_paths = " ".join(paths)),
     )
 
     ctx.actions.run_shell(
         inputs = ctx.files._jdk + files + [spring_components_file],
         outputs = [out],
         # Create an empty tarball, then extract all the jars and append the contents into it.
+        # TODO: get rid of the hardcoded bazel-out path in the first transform.
         command = 'tar cf {out} -T /dev/null && if [ -s {scf} ]; then tar rhf {out} --transform "s,bazel-out/k8-fastbuild/bin/,BOOT-INF/classes/META-INF/," {scf}; fi && for i in {all_paths}; do {jar} xf $i && {jar} tf $i | tar rf {out} --transform "s,^,BOOT-INF/classes/," -T -; done'.format(out = out.path, all_paths = " ".join(paths), jar = jar_path, scf = spring_components_file.path),
     )