How does "data" attribute work in java_war and appengine_war

[jiaqi]

In an exploratory project I'm trying to run an Java application that serves some static resource. I tried to add static resources to the war file using the data attribute.
https://github.com/jiaqi/angular-on-java/blob/seattle/java/org/cyclopsgroup/aoj/server/BUILD

It seems the setting is effective and after some work files do end up in the war file as expected.

$ bazel build java/org/cyclopsgroup/aoj/server
INFO: Analyzed target //java/org/cyclopsgroup/aoj/server:server (0 packages loaded, 0 targets configured).
INFO: Found 1 target...
Target //java/org/cyclopsgroup/aoj/server:server up-to-date:
  bazel-bin/java/org/cyclopsgroup/aoj/server/server.war
  bazel-bin/java/org/cyclopsgroup/aoj/server/server_deploy.sh
  bazel-bin/java/org/cyclopsgroup/aoj/server/server
  ...
$ jar -tvf bazel-bin/java/org/cyclopsgroup/aoj/server/server.war
    94 Fri Jan 01 00:00:00 PST 2010 ./webapp/aoj/styles.css
5628103 Fri Jan 01 00:00:00 PST 2010 ./webapp/aoj/js_bundle.js
   141 Fri Jan 01 00:00:00 PST 2010 ./webapp/aoj/styles.css.map
 11413 Fri Jan 01 00:00:00 PST 2010 ./favicon.png
 ...

Then I ran the war target with bazel run and found that only favicon.png is served and none of the others is.

After reading appengine_runner.sh.template I realized the root directory of web application at runtime has nothing to do with the files in the war file.

bazel-out/darwin-fastbuild/bin/java/org/cyclopsgroup/aoj/server/server.runfiles/angular_on_java/java/org/cyclopsgroup/aoj/server
├── WEB-INF
│   ├── appengine-generated
│   │   └── local_db.bin
│   ├── appengine-web.xml -> /Users/jguo/github/jiaqi/angular-on-java/java/org/cyclopsgroup/aoj/server/WEB-INF/appengine-web.xml
│   ├── jsp
│   │   └── index.jsp -> /Users/jguo/github/jiaqi/angular-on-java/java/org/cyclopsgroup/aoj/server/WEB-INF/jsp/index.jsp
│   └── lib
│       ├── appengine-api.jar -> /private/var/tmp/_bazel_jguo/239a5101fa986e10f8c504b3e6b8e624/execroot/angular_on_java/bazel-out/darwin-fastbuild/bin/java/org/cyclopsgroup/aoj/server/server.runfiles/angular_on_java/../com_google_appengine_java/lib/impl/appengine-api.jar
...
├── server -> /private/var/tmp/_bazel_jguo/239a5101fa986e10f8c504b3e6b8e624/execroot/angular_on_java/bazel-out/darwin-fastbuild/bin/java/org/cyclopsgroup/aoj/server/server
└── server.war -> /private/var/tmp/_bazel_jguo/239a5101fa986e10f8c504b3e6b8e624/execroot/angular_on_java/bazel-out/darwin-fastbuild/bin/java/org/cyclopsgroup/aoj/server/server.war

4 directories, 31 files

None of the webapp/aoj/* files we saw in the war file exists under runfiles. With file structure like this in runfiles, the running application actually serves server.war by mistake.

Unless I miss anything, this doesn't make sense to me at all. What the data attribute specifies is correctly honored when creating a war file, but completely ignored when running it. Is it by design? What's the right way to specify data attribute so it matters at runtime?

[jiaqi]

Looks like the referenced data files are under the working directory(.../server.runfiles), but not under the webapp root directory, which is the directory that matters at runtime. To fix it I think there are 2 options

1. Link data files to webapp root directory in appengine_runner.sh.template similar to how it links jar files to WEB-INF/lib
2. Use working directory(.../server.runfiles) as webapp root directory and link jars and other resources accordingly.

Does it make sense?