chromium::import! Macro

After adding :my_rust_lib to GN deps, we still need to learn how to import and use my_rust_lib from my_rust_lib_unittest.rs. We haven't provided an explicit crate_name for my_rust_lib so its crate name is computed based on the full target path and name. Fortunately we can avoid working with such an unwieldy name by using the chromium::import! macro from the automatically-imported chromium crate:

# // Copyright 2023 Google LLC
# // SPDX-License-Identifier: Apache-2.0
#
chromium::import! {
    "//ui/base:my_rust_lib";
}

use my_rust_lib::my_function_under_test;

Under the covers the macro expands to something similar to:

# // Copyright 2023 Google LLC
# // SPDX-License-Identifier: Apache-2.0
#
extern crate ui_sbase_cmy_urust_ulib as my_rust_lib;

use my_rust_lib::my_function_under_test;

More information can be found in the doc comment of the chromium::import macro.

rust_static_library supports specifying an explicit name via crate_name property, but doing this is discouraged. And it is discouraged because the crate name has to be globally unique. crates.io guarantees uniqueness of its crate names so cargo_crate GN targets (generated by the gnrt tool covered in a later section) use short crate names.