frameworks_base/tools/lint

Android Framework Lint Checker

Custom lint checks written here are going to be executed for modules that opt in to those (e.g. any services.XXX module) and results will be automatically reported on CLs on gerrit.

How to add new lint checks

1. Write your detector with its issues and put it into checks/src/main/java/com/google/android/lint.
2. Add your detector's issues into AndroidFrameworkIssueRegistry's issues field.
3. Write unit tests for your detector in one file and put it into checks/test/java/com/google/android/lint.
4. Done! Your lint checks should be applied in lint report builds for modules that include AndroidFrameworkLintChecker.

How to run lint against your module

1. Add the following lint attribute to the module definition, e.g. services.autofill:

java_library_static {
    name: "services.autofill",
    ...
    lint: {
        extra_check_modules: ["AndroidFrameworkLintChecker"],
    },
}

2. Run the following command to verify that the report is being correctly built:

m out/soong/.intermediates/frameworks/base/services/autofill/services.autofill/android_common/lint/lint-report.html

(Lint report can be found in the same path, i.e. out/../lint-report.html)

3. Now lint issues should appear on gerrit!

Notes:

• Lint report will not be produced if you just build the module, i.e. m services.autofill will not build the lint report.
• If you want to build lint reports for more than 1 module and they include a common module in their defaults field, e.g. platform_service_defaults, you can add the lint property to that common module instead of adding it in every module.
• If you want to run a single lint type, use the ANDROID_LINT_CHECK environment variable with the id of the lint. For example: ANDROID_LINT_CHECK=UnusedTokenOfOriginalCallingIdentity m out/[...]/lint-report.html

How to apply automatic fixes suggested by lint

See lint_fix

Create or update a baseline

Baseline files can be used to silence known errors (and warnings) that are deemed to be safe. When there is a lint-baseline.xml file in the root folder of the java library, soong will automatically use it. You can override the file using lint properties too.

java_library {
    lint: {
        baseline_filename: "my-baseline.xml", // default: lint-baseline.xml;
    }
}

When using soong to create a lint report (as described above), it also creates a reference baseline file. This contains all lint errors and warnings that were found. So the next time you run lint, if you use this baseline file, there should be 0 findings.

After the previous invocation, you can find the baseline here:

out/soong/.intermediates/frameworks/base/services/autofill/services.autofill/android_common/lint/lint-baseline.xml

As noted above, this baseline file contains warnings too, which might be undesirable. For example, CI tools might surface these warnings in code reviews. In order to create this file without warnings, we need to pass another flag to lint: --nowarn. The easiest way to do this is to locally change the soong code in lint.go adding cmd.Flag("--nowarn") and running lint again.

Documentation

• Android Lint Docs
• Lint Check Unit Testing
• Android Lint source files
• PSI source files
• UAST source files
• IntelliJ plugin for viewing PSI tree of files