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Add best pratice for how to check in generated files #16405

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epage merged 1 commit into from
Dec 16, 2025
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Add best pratice for how to check in generated files #16405

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7 changes: 7 additions & 0 deletions src/doc/src/reference/build-script-examples.md
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Expand Up @@ -86,6 +86,13 @@ There’s a couple of points of note here:
such crate as a dependency, because there's an *implicit* invariant that
sources in `.cargo/registry` should be immutable. `cargo` won't allow such
scripts when packaging.
* Sometimes, projects want to check in a generated file, and treat it as
source code. However, in this case, the file shouldn't be generated from
`build.rs`. Instead, have a test or similar which checks that the file
precisely matches the generated version *and fails if the result doesn't
match*, and run that test as part of your CI. (The test can generate a
temporary file to compare to, and if you want to update the generated file,
you can replace the checked-in file with that temporary file.)
Comment on lines +89 to +95
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@epage epage Dec 16, 2025

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non-blocking: should we point people to libraries like expect-test ad snapbox for doing this?

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@joshtriplett joshtriplett Dec 18, 2025

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I'd love to point people to snapbox and insta and expect-test, yes.

* This script is relatively simple as it just writes out a small generated file.
One could imagine that other more complex operations could take place such as
generating a Rust module from a C header file or another language definition,
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