bundletool leaves 100s of KB of META-INF metadata in output APKs

[ChrisCraik]

Describe the bug

Bundletool version(s) affected
Version: 1.15.6

To Reproduce

1. Build an android app release bundle with gradle, and create release APKs. For my testing I'm in the androidx repository and built a sample app into a release app bundle:

> ./gradlew benchmark:i-t:mac-target:bundleRelease
> java -jar ~/Downloads/bundletool-all-1.15.6.jar build-apks --bundle=../../out/androidx/benchmark/integration-tests/macrobenchmark-target/build/outputs/bundle/release/macrobenchmark-target-release.aab --output=no-local-testing.apks --overwrite --ks=/home/ccraik/androidx/frameworks/support/development/keystore/debug.keystore --connected-device --ks-key-alias=AndroidDebugKey --ks-pass=pass:android
> ls -lh *.apks
-rw-r--r-- 1 ccraik primarygroup 2252680 Feb 13 07:03 no-local-testing.apks

2. Then, look at the amount of metadata included in output APKs:

> unzip no-local-testing.apks
> unzip -vl splits/base-master.apk | grep META-INF
      63  Defl:N       58   8% 1981-01-01 01:01 2996938b  META-INF/com/android/build/gradle/app-metadata.properties
       6  Stored        6   0% 1981-01-01 01:01 4e6c51a2  META-INF/com.google.android.material_material.version
       5  Stored        5   0% 1981-01-01 01:01 8f7d2509  META-INF/kotlinx_coroutines_android.version
       5  Stored        5   0% 1981-01-01 01:01 8f7d2509  META-INF/kotlinx_coroutines_core.version
       5  Stored        5   0% 1981-01-01 01:01 294be821  META-INF/services/A1.u
       5  Stored        5   0% 1981-01-01 01:01 0266bbe2  META-INF/services/F1.o
     120  Defl:N      118   2% 1981-01-01 01:01 0dcd0bf7  META-INF/version-control-info.textproto
   39788  Defl:N    15177  62% 1981-01-01 01:01 2bf94a2f  META-INF/BNDLTOOL.SF
     773  Defl:N      601  22% 1981-01-01 01:01 e6735010  META-INF/BNDLTOOL.RSA
   39661  Defl:N    14723  63% 1981-01-01 01:01 37e23612  META-INF/MANIFEST.MF

There's 30KB of compressed bundletool and manifest metadata (3rd column), even though I'm not passing --local-testing (which appears to do very little at changing quantities of metadata)

Knowing that I'm using debug keys, and that this is a trivial sample, I took to dumping metadata from production apps on my device, and found most apps retaining much more. Note that this affects 1P google apps, so it wouldn't be an issue with what AGP puts into the bundle.

I wrote a script to capture the amount on apps on my device, to remove any issue with me configuring bundletool incorrectly which shows e.g. 200KB of metadata for nexuslauncher and 100KB for discord
dumpMetadataCost.zip

Google internal equivalent links: script sample output

Expected behavior

Minimal amounts of metadata ends up in output APKs, e.g. 1KB

Known workaround

Manually removing metadata from bundle before running

Environment:
OS: glinux

Additional context
Add any other context about the problem here.