[rust] Write {{sources}} ninja variable for Rust targets

Rust compiles a crate using all source files in a single command.
However, rustc only requires the source_root, and then traverses
the series of `mod` statements and `include_str!` macros to find
all the source files.

On Fuchsia, it is desired to enforce that all Rust source files
are listed explicitly in BUILD.gn files.

In order to make it possible to enforce that the list matches
the depfile rustc emits, the set of source files needs to be
accessible in the `tool` target for `rust_bin`, `rust_library`, etc.

This change writes the source files to a new ninja variable
`sources`. `inputs` are also included in this variable, since a
Rust crate can read non-rust files at build-time
(eg. `include_str!("foo.json")`).

Change-Id: I076232739c54b78508db13549a3db4894b16ea11
Reviewed-on: https://gn-review.googlesource.com/c/gn/+/9360
Reviewed-by: Tyler Mandry <tmandry@google.com>
Reviewed-by: Petr Hosek <phosek@google.com>
Commit-Queue: Petr Hosek <phosek@google.com>
5 files changed
tree: 33b466a55eca0833792cbe3eae98e85f018fb5a5
  1. build/
  2. docs/
  3. examples/
  4. infra/
  5. misc/
  6. src/
  7. tools/
  8. .clang-format
  9. .editorconfig
  10. .gitignore
  11. .style.yapf
  14. OWNERS
  15. README.md


GN is a meta-build system that generates build files for Ninja.

Related resources:

Getting a binary

You can download the latest version of GN binary for Linux, macOS and Windows.

Alternatively, you can build GN from source:

git clone https://gn.googlesource.com/gn
cd gn
python build/gen.py
ninja -C out
# To run tests:

On Windows, it is expected that cl.exe, link.exe, and lib.exe can be found in PATH, so you'll want to run from a Visual Studio command prompt, or similar.

On Linux and Mac, the default compiler is clang++, a recent version is expected to be found in PATH. This can be overridden by setting CC, CXX, and AR.


There is a simple example in examples/simple_build directory that is a good place to get started with the minimal configuration.

To build and run the simple example with the default gcc compiler:

cd examples/simple_build
../../out/gn gen -C out
ninja -C out

For a maximal configuration see the Chromium setup:

and the Fuchsia setup:

Reporting bugs

If you find a bug, you can see if it is known or report it in the bug database.

Sending patches

GN uses Gerrit for code review. The short version of how to patch is:

Register at https://gn-review.googlesource.com.

... edit code ...
ninja -C out && out/gn_unittests

Then, to upload a change for review:

git commit
git push origin HEAD:refs/for/master

The first time you do this you'll get an error from the server about a missing change-ID. Follow the directions in the error message to install the change-ID hook and run git commit --amend to apply the hook to the current commit.

When revising a change, use:

git commit --amend
git push origin HEAD:refs/for/master

which will add the new changes to the existing code review, rather than creating a new one.

We ask that all contributors sign Google's Contributor License Agreement (either individual or corporate as appropriate, select ‘any other Google project’).


You may ask questions and follow along with GN‘s development on Chromium’s gn-dev@ Google Group.