This turns on clippy checking and also fixes all lints in the code.
Many lints are obvious improvements. Only a small number are slightly annoying, so I think overall worth having a vanilla default config.
* Bazel builds seem to fail to open relative paths to parent directories
due to hermetic sandboxing of third-party repositories. This adds a
WORKSPACE_MANIFEST_FILE environment variable that allows the caller to
optionally provide an absolute path to the workspace root manifest
file.
* The existing code processed a shader file only if
`FileType::is_file` returns true for it. This is not the case when
sources are accessed via symbolic links, which is possible in a Bazel
sandbox. The code now filters for the ".wgsl" file extension instead
of the file type which should generally be safe.
Previously the generated shader data structures were rooted in
backend-specific top-level mods (`mod wgsl`, `mod msl`, etc). This made
access to per-shader information that is common to all backends (e.g.
workgroup sizes, shader name etc) awkward to access from backend
agnostic code, especially when feature-gated conditional compilation is
used on the client side.
The data structures have been rearranged such that there is a top-level
`ComputeShader` declaration for each stage under a `gen` mod. The
`ComputeShader` struct declares feature-gated fields for backend shader
sources, such that backend specific data is now a leaf node in the
structure rather than the root. This has some additional benefits:
1. Common data doesn't have to be redeclared, saving on code size when
multiple backends are enabled.
2. The backend specific source code was previously encoded as a `[u8]`.
We can now use types that more closely match the expected format, for
example `&str` for WGSL and MSL, `[u32]` for SPIR-V, etc.
3. If we ever need to expose additional backend-specific metadata in the
future, we can bundle them alongside the source code in a
backend-specific data structure at this level of the tree.
