//chrome/android/java/*.expected files

Proguard flags

Proguard is used in the build to obfuscate and minify Java code.

Proguard flags (also known as configs or rules) are used to specify which parts of Java code should not be optimized/obfuscated/modified by Proguard.

For example, the following rule specifies that all public classes with a public static void main(java.lang.String[]) method should not be modifed.

-keepclasseswithmembers public class * {
    public static void main(java.lang.String[]);
}

What are *.proguard_flags.expected files?

monochrome_public_apk.proguard_flags.expected contains all proguard configs used when building MonochromePublic.apk, and is generated by the proguard() build step.

Why do we care about Proguard flag discrepancies?

Some configs are explicitly added (ex) while others are pulled in implicitly by GN deps (ex. aar_prebuilt() deps). In the later case, these config changes aren't reviewed and can sometimes result in crashes and/or size regressions. Example of where this has happened before:

  • Updating a prebuilt that supplies a Proguard config with a rule that is too broad (i.e. a rule that matches more classes than the intended ones)

Having checked-in versions of the Proguard configs used allows us to identify and address these issues earlier.

AndroidManifest.xml

Each Android application has a manifest that contains information about the app (ex. permissions required, services exposed, etc).

What are *.AndroidManifest.expected files?

monochrome_public_apk.AndroidManifest.expected contains the contents of the final merged manifest used when building MonochromePublic.apk.

Why do we care about AndroidManifest discrepancies?

While most manifest changes are reviewed when the manifest template file changes, manifest entries that are pulled in via. deps (through manifest merging) can cause real bugs (permissions issues, security vulnerabilities).

Build failures caused by *.expected files

What is the build error telling me?

The build error is indicating that your CL has caused a mismatch between the expected file and the generated file and that either the issue requires attention or the expected file needs updating.

Fixing build failures

  1. Ensure your args.gn contains these args:
enable_chrome_android_internal = false
is_java_debug = false
  1. Run:
autoninja -C $CHROMIUM_OUTPUT_DIR monochrome_public_apk

  1. Run the command suggested in the error message to copy the contents of the generated file to the expected file path

  2. Add the updated .expected file to your CL

  3. Afterwards, you can revert the args.gn changes suggested above and build normally

Trybot failures

On the android-binary-size trybot we set check_android_configuration=true which causes any differences between the expected and generated files to fail the build.

Without this argument the error message is shown but doesn't fail the build.

Troubleshooting

Trybots fail but you can't reproduce locally

  • If a public target is failing, double check to make sure you've set enable_chrome_android_internal=false

Can't find the file suggested by the error message

  • Make sure is_java_debug=false

Updating the file doesn't fix the error

  • Make sure you're building monochrome_public_apk

Otherwise, please file a bug at crbug.com/new and/or message estevenson@.