[vello_shaders] Bring back the Bazel build hack #621
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Skia, an external consumer of this crate, uses Bazel rules to compile Rust code. Due to limitations in Bazel's rust support, the CARGO_MANIFEST_DIR environment variable isn't set properly for nested crates as Bazel always seems to assign the workspace root instead. Until we figure out a better way to manage the bazel integration, this PR reintroduces a recently-removed hack to work around this by allowing the crate manifest path to be assigned explicitly, using a new environment variable called `BAZEL_CRATE_MANIFEST_PATH`. This is intended to be the absolute path to `vello_shaders/Cargo.toml` within the bazel sandbox file system.
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I think a better solution going forward might be to host this bazel file directly in the vello repo, which may fix the issue with The reason Skia requires Bazel rules to build the crates (as opposed to listing them as a third-party cargo dependencies, which Bazel does support) is that I couldn't find a cleaner way to conditionally toggle crate features (particularly |
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Some of the documentation in that BUILD file suggests that this hack was needed because the shader directory is outside vello_shaders. That is no longer true since #590.
Does that change the equation here?
Approving anyway, because the actual change is fine.
That was part of the original reason for this hack. I was hoping that #590 would address it but I ran into some limitations. I'll update that comment in Skia when I roll this PR in.
Thanks! |
Skia, an external consumer of this crate, uses Bazel rules to compile Rust code. Due to limitations in Bazel's rust support, the CARGO_MANIFEST_DIR environment variable doesn't get set properly for nested crates since Bazel seems to assign the workspace root instead (as the BUILD file needs to be specified relative to the external repository root).
Until we figure out a better way to manage the bazel integration, this PR reintroduces a recently removed hack to work around this by allowing the crate manifest path to be assigned explicitly, using a new environment variable called
BAZEL_CRATE_MANIFEST_PATH. This is intended to be the absolute path tovello_shaders/Cargo.tomlwithin the bazel sandbox file system.