Lint

Android's lint is a static analysis tool that Chromium uses to catch possible issues in Java code.

How Chromium uses lint

Chromium runs lint on a per-target basis for all targets using any of the following templates if they are marked as Chromium code (i.e., chromium_code = true):

• android_apk
• android_library
• instrumentation_test_apk
• unittest_apk

Chromium also runs lint on a per-target basis for all targets using any of the following templates if they are marked as Chromium code and they support Android (i.e., supports_android = true):

• java_library

This is implemented in the android_lint gn template.

My code has a lint error

If lint reports an issue in your code, there are several possible remedies. In descending order of preference:

Fix it

While this isn't always the right response, fixing the lint error or warning should be the default.

Suppress it in code

Android provides an annotation, @SuppressLint, that tells lint to ignore the annotated element. It can be used on classes, constructors, methods, parameters, fields, or local variables, though usage in Chromium is typically limited to the first three.

Like many suppression annotations, @SuppressLint takes a value that tells lint what to ignore. It can be a single String:

@SuppressLint("NewApi")
public void foo() {
    a.methodThatRequiresHighSdkLevel();
}

It can also be a list of Strings:

@SuppressLint({
        "NewApi",
        "UseSparseArrays"
        })
public Map<Integer, FakeObject> bar() {
    Map<Integer, FakeObject> shouldBeASparseArray = new HashMap<Integer, FakeObject>();
    another.methodThatRequiresHighSdkLevel(shouldBeASparseArray);
    return shouldBeASparseArray;
}

This is the preferred way of suppressing warnings in a limited scope.

Suppress it in the suppressions XML file

lint can be given an XML configuration containing warnings or errors that should be ignored. Chromium's lint suppression XML file can be found in build/android/lint/suppressions.xml. It can be updated to suppress current warnings by running:

$ python build/android/lint/suppress.py <result.xml file>

e.g., to suppress lint errors found in media_java:

$ python build/android/lint/suppress.py out/Debug/gen/media/base/android/media_java__lint/result.xml

This mechanism should only be used for disabling warnings across the entire code base; class-specific lint warnings should be disabled inline.