imagebuildah: avoid empty layer in single-layer build path#6699
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jlebon wants to merge 1 commit intocontainers:mainfrom
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imagebuildah: avoid empty layer in single-layer build path#6699jlebon wants to merge 1 commit intocontainers:mainfrom
jlebon wants to merge 1 commit intocontainers:mainfrom
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In the single-layer build path (i.e. with `--layers=false`), the final commit always created a layer even when only metadata instructions were executed after `FROM`. Fix this by tracking if any instruction actually created data so we can avoid creating a layer in that case. Noticed this when looking at images passed through chunkah, where one can specify the number of layers N to output; the resulting image would have a total of N+1 layers because it's often the case that you want to add metadata after the `FROM oci-archive:...`. Signed-off-by: Jonathan Lebon <jonathan@jlebon.com> Assisted-by: Claude Opus 4.6
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nalind
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Feb 27, 2026
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I vaguely recall OpenShift having a build test that checked how many layers a test build added to its output image compared to the base image; it's why we added the stepRequiresLayer() helper function and started using it where we do in multi-layer builds. I don't think that it was a Layers==false (imageOptimizationPolicy==SkipLayers) case, though, so it's probably not going to be tripped up by this change.
Anyway, LGTM. Thanks!
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In the single-layer build path (i.e. with
--layers=false), the final commit always created a layer even when only metadata instructions were executed afterFROM.Fix this by tracking if any instruction actually created data so we can avoid creating a layer in that case.
Noticed this when looking at images passed through chunkah, where one can specify the number of layers N to output; the resulting image would have a total of N+1 layers because it's often the case that you want to add metadata after the
FROM oci-archive:....Assisted-by: Claude Opus 4.6
/kind bug