Realisations use regular drv paths again#15322
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Mic92 merged 2 commits intoNixOS:masterfrom Mar 2, 2026
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This reverts commit 100e7cc. Unlike the last version, this fixes `--print-out-paths` for old clients When the client lacks `featureRealisationWithPath` (worker) or version < 2.8 (serve), the daemon was sending an empty `StringMap` for `builtOutputs`, causing `--print-out-paths` to print nothing. This commit constructs the old wire format instead, using a dummy `sha256:` hash since the derivation hash no longer exists. Old clients only need the output name and path from the JSON.
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Ericson2314
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@Mic92 tested this and it is not causing problems anymore
The previous commit changed CA derivation realisations to be keyed by store path instead of hash modulo, affecting binary cache and wire protocols. Users and tool authors need to understand the impact on binary cache layout, protocol negotiation, and what migration looks like. This documents the key changes: the new build-trace-v2/ cache directory, the split key/value JSON format, worker protocol feature negotiation, serve protocol version bump, and the fact that non-CA users are unaffected.
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Realisations use regular drv paths again
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Note
This is a redo of #12464 with a bug fix applied
Motivation
Fix #11897
As described in the issue, this makes for a simpler and much more intuitive notion of a realisation key. This is better for pedagogy, and interoperability between more tools.
Context
The way the issue was written was that we would switch to only having shallow realisations first, and then do this. But going to only shallow realisations is more complex change, and it turns out we weren't even testing for the benefits that derivation hashes (modulo FODs) provided in the deep realisation case, so I now just want to do this first.
Doing this gets the binary cache data structures in order, which will unblock the Hydra fixed-output-derivation tracking work. I don't want to delay that work while I figure out the changes needed for shallow-realisations only.
Revert "Use the hash modulo in the derivation outputs"
This reverts commit bab1cda.
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