Adding a directory to catapult

Where should the code live?

Catapult is intended to be a set of performance tools, mostly based on tracing, for developers of Chromium and other software to analyze that software’s performance. It has a lot of supporting libraries and tooling to make this happen. We’d like to create an organizational structure that makes it easy to find the performance tooling developers want, and hard to accidentally depend on something internal. Furthermore, we’d like to make it easy for code in catapult to eventually grow to its own repo, when possible. To that end, we use these guidelines to decide where code should live.

  • Is it a performance product? Meant be used by external developers for performance analysis? Some examples include telemetry, perf dashboard. If so, it should be at toplevel.
  • Is it used only by our buildbot or build process? Put it in catapult_build.
  • If it's neither of the above, it should go in common/
  • If it is aspiring to be its own repo someday, that doesn't affect where it goes. You should follow the above rules for directory placement. Third party must only be real third party repos to conform to rules of repos which include catapult.
  • If something is experimental, then talk with the catapult admins to build the best guess of where it should go.

How should directories be structured?

We have some rules on directory structure to add consistency and avoid overloaded python imports.

  • Toplevel directories are not modules. E.g. if x is a toplevel directory, x/ does not exist. Directories in common/ do not have this restriction.
  • Toplevel directories and directories in common should centralize all their path computation and sys.path manipulation in their master init file (example).
  • Projects using web server should provide a module which defines all the search paths to their html & javascript resources in their top directory (example).
  • Build code should be separate from production code. Build scripts for projects should be in x/x_build/
  • If you have a feature that has an implementation in JS and Py, then it should be in the same folder.
  • HTML search paths are arranged such that they have the same name as they would in python. E.g. tracing/tracing/base/math.html is /tracing/base/math.html for an HTML import, and tracing/tracing/base/ is tracing.base.math in python.
  • Executable files (e.g. files chmodded to +x) must live in x/bin. bin/ must not be a module, e.g. contain, as such a name would create namespace conflicts. Executable files should not have a .py extension.
  • We use a single dev server, $catapult/bin/run_dev_server; and have per-project bin/run_dev_server_tests scripts.
  • All python modules should have unique names. $catpult/catapult_build instead of $catapult/build.

How to add tests

Catapult supports two types of tests:

  • dev_server tests allow for UI testing and JavaScript testing. You can read more about adding them in the dev_server tests guide. If you want to run dev_server tests, please create a bin/run_dev_server_tests python executable like this.
  • python tests use the python unit testing framework. If you want to run python tests, please create a bin/run_py_tests executable like this.

Both types of tests should be added to the configuration in Please see the comments in that file for full documentation on specifying test commands, arguments, disabled platforms, and required environment variables.