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unsafeDiscardReferences

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Adds a new boolean structured attribute
`outputChecks.<output>.unsafeDiscardReferences` which disables scanning
an output for runtime references.

    __structuredAttrs = true;
    outputChecks.out.unsafeDiscardReferences = true;

This is useful when creating filesystem images containing their own embedded Nix
store: they are self-contained blobs of data with no runtime dependencies.

Setting this attribute requires the experimental feature
`discard-references` to be enabled.
This commit is contained in:
Naïm Favier 2022-09-23 23:30:29 +02:00
parent 15341334b5
commit 15f7fa59be
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7 changed files with 58 additions and 7 deletions
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6
doc/manual/src/language/advanced-attributes.md
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@ -207,13 +207,13 @@ Derivations can declare some infrequently used optional attributes.
the hash in either hexadecimal or base-32 notation. (See the
[`nix-hash` command](../command-ref/nix-hash.md) for information
about converting to and from base-32 notation.)
- [`__contentAddressed`]{#adv-attr-__contentAddressed}
If this **experimental** attribute is set to true, then the derivation
outputs will be stored in a content-addressed location rather than the
traditional input-addressed one.
This only has an effect if the `ca-derivation` experimental feature is enabled.
This only has an effect if the `ca-derivations` experimental feature is enabled.
Setting this attribute also requires setting `outputHashMode` and `outputHashAlgo` like for *fixed-output derivations* (see above).
- [`passAsFile`]{#adv-attr-passAsFile}\

12
doc/manual/src/release-notes/rl-next.md
View file

@ -21,3 +21,15 @@
* Error traces have been reworked to provide detailed explanations and more
accurate error locations. A short excerpt of the trace is now shown by
default when an error occurs.
* In derivations that use structured attributes, you can now use `unsafeDiscardReferences`
to disable scanning a given output for runtime dependencies:
```nix
__structuredAttrs = true;
outputChecks.out.unsafeDiscardReferences = true;
```
This is useful e.g. when generating self-contained filesystem images with
their own embedded Nix store: hashes found inside such an image refer
to the embedded store and not to the host's Nix store.
This requires the `discard-references` experimental feature.