//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_bundle.proguard_flags.expected contains all proguard configs used when building MonochromePublic.aab, 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, or any target that specifies proguard_configs = [...]).

Since proguard configs are global in nature, it is important that all configs go through code review. We use these .expected files to ensure that they do.


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

What are *.AndroidManifest.expected files?

They contain the pretty-printed contents of the final merged manifest used when building their associated targets.

What are *.AndroidManifest.diff.expected files?

For internal targets, we don‘t want to check that the generated manifest are identical to a specified expectation file. Instead, we want to ensure that the differences between the target’s AndroidManifest and an expectation file are as expected. In this case, we specify a *.AndroidManifest.diff.expected file to store the expected differences.

The contents of the *.AndroidManifest.diff.expected file are lines that start with ‘+’. We use ndiff diff format to diff the 2 manifests, which represents differences by prepending ‘+’ before new lines, ‘-’ before deleted lines, and keeping all common lines. To create a *.AndroidManifest.diff.expected, we filter out all lines that don't start with ‘+’ to avoid irrelevant upstream changes to break downstream checks.

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).

AndroidManfiest.xml entries create a contract between Chrome and Android, and so its important that all changes to this contract go through code review.

Native Libraries and Assets

Some of our apk and aab files contain native library files (under lib/) and assets files (under assets/).

What are *.native_libs_and_assets.expected files?

*.native_libs_and_assets.expected files store in a text format the list of native libraries & assets, and their related information (whether it‘s compressed, how it’s aligned).

Why do we care about native libraries and assets discrepancies?

When we change build gn files, the native libraries and assets can sometimes be changed in an unexpected way.

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

Option A: Copy the expected file generated by the trybot

  1. Click on the android-binary-size trybot failure in your CL

  2. Click on the stdout link of the compile step

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

Option B: Update expected files with a local build

  1. Ensure that your args.gn contain:

    # For arm32:
    is_debug = false
    enable_chrome_android_internal = false
    android_channel = "stable"
    # For arm64:
    is_debug = false
    enable_chrome_android_internal = false
  2. Run:

    autoninja -C $CHROMIUM_OUTPUT_DIR validate_expectations
  3. Run the command suggested in the error message to copy the contents of the generated file to the expected file path

  4. Add the updated .expected file to your CL

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

Trybot failures

The android-binary-size trybot fails when expectations do not match. The one exception is that arm64 native libs and assets expectations are checked by android-pie-arm64-rel.


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_bundle

Otherwise, please file a bug at crbug.com/new and/or message clank-build@google.com.