Gemini-CLI Specific Directives

Instructions that apply only to gemini-cli.

• When using the read_file tool:
  • Always set the 'limit' parameter to 20000 to prevent truncation.
• File Not Found Errors:
  • If a file operation fails due to an incorrect path, do not retry with the same path.
  • Inform the user and search for the correct path using parts of the path or filename.

Common Directives

Instructions that are useful for chromium development, and not specific to a single agentic tool.

Paths

• All files in chromium’s source can be read by substituting chromium/src or // for the current workspace (which can be determined by running gclient root and appending /src to the output).

Building

• Do not attempt a build without first establishing the correct output directory and target. If you have not been given them, and you plan on doing a build, then stop and ask before starting on any other tasks.
• Unless otherwise instructed, build with: autoninja --quiet -C {OUT_DIR} {TARGET}
  • If given an autoninja command that is missing --quiet, add --quiet.

Testing

Unless otherwise instructed, run tests with: tools/autotest.py --quiet --run-all -C {OUT_DIR} {RELEVANT_TEST_FILENAMES}

When using tools/autotest.py:

• Do not invoke autoninja beforehand because autotest.py automatically builds relevant targets.
• Build targets containing colons (:) are not valid inputs for {RELEVANT_TEST_FILENAMES}.

Coding

• Stay on task: Do not address code health issues or TODOs in code unless it is required to achieve your given task.
• Add code comments sparingly: Focus on why something is done, not what is done.

Presubmit Checks

When you have finished validating your changes through other means, run:

git cl format
git cl presubmit -u --force

• Fix errors / warnings related to your change, but do not fix pre-existing warnings (from lines that you did not change).

JNI

Chrome on Android uses both Java and C++ frequently. Our JNI uses codegen from //third_party/jni_zero.

Identifying JNI methods:

• In Java, methods annotated with @CalledByNative are called by C++.
  • In C++, these appear as methods with a "Java_" prefix.
• In Java, methods within interfaces annotated with @NativeMethods are calls into C++.
  • In C++, these appear as methods with a "JNI_" prefix.
  • If the first parameter is of type long and has a prefix of "native", then it maps to a method of the same name on the C++ class that comes after the "native" prefix. Eg. void foo(long nativeBarImpl) means you need to find BarImpl::Foo in C++.

Finding JNI methods:

• To find the Java side of JNI: search for the file named {JavaClass}.java (where {JavaClass} is taken from the #include "{JavaClass}_jni.h".
• To find the C++ side of JNI: Search for the text {JavaClass}_jni.h in C++ files (where {JavaClass} is taken from the .java file name).

When making changes to JNI methods, always make changes to both the .java and .cc/.h files involved.