The current directory structure in Drake is organized to (1) group functional components, (2) limit dependencies, and (3) prevent circular dependencies.

Dev Directories

All code in Drake must adhere to the code standards described in the notes For Developers and must be covered by tests, unless the code lives in a subdirectory named dev.

To promote rapid development of research ideas, experimental code may be placed in a subdirectory named dev. We do not enforce code standards nor test coverage within dev directories. For pull requests that affect only dev directories, one feature review is sufficient; platform review is not required. If build or test targets in dev directories break, the response from the on-call build cop will be to disable the offending targets.

The BUILD.bazel file for dev directories must live within the directory itself, not a parent directory. (For example, foo/BUILD.bazel must not say srcs = ["dev/bar.cc"],; instead, foo/dev/BUILD.bazel must exist and must say srcs = ["bar.cc"],.) This ensures that all dev code has a package name (//foo/dev) that clearly denotes it as such.

Controlling Dependencies

We would like to avoid circular dependencies in the source code tree. For example, some code in drake/systems depends on code in drake/solvers, so code in drake/solvers should not depend on drake/systems.

The drake/examples directories are logically after all of the core libraries in drake. test directories located throughout the code are logically last in the dependency tree – they are allowed to depend on any of the other directories. For example, test code is allowed to use models/code from the examples directories to test core functionality, as long as that dependency is explicitly declared in the build system rules for that test.