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doc: fixup 7714 #7768

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Feb 7, 2023
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doc: fixup 7714 #7768

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25 changes: 18 additions & 7 deletions doc/manual/src/language/advanced-attributes.md
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Expand Up @@ -260,7 +260,7 @@ Derivations can declare some infrequently used optional attributes.
If the special attribute `__structuredAttrs` is set to `true`, the other derivation
attributes are serialised in JSON format and made available to the
builder via the file `.attrs.json` in the builder’s temporary
directory. This obviates the need for `passAsFile` since JSON files
directory. This obviates the need for [`passAsFile`](#adv-attr-passAsFile) since JSON files
have no size restrictions, unlike process environments.

It also makes it possible to tweak derivation settings in a structured way; see
Expand All @@ -282,11 +282,13 @@ Derivations can declare some infrequently used optional attributes.
[`disallowedReferences`](#adv-attr-disallowedReferences) and [`disallowedRequisites`](#adv-attr-disallowedRequisites),
the following attributes are available:

- `maxSize` defines the maximum size of the output path.
- `maxSize` defines the maximum size of the resulting [store object](../glossary.md#gloss-store-object).
- `maxClosureSize` defines the maximum size of the output's closure.
- `ignoreSelfRefs` controls whether self-references should be considered when
checking for allowed references/requisites.

Example:

```nix
__structuredAttrs = true;

Expand All @@ -305,9 +307,20 @@ Derivations can declare some infrequently used optional attributes.
```

- [`unsafeDiscardReferences`]{#adv-attr-unsafeDiscardReferences}\
When using [structured attributes](#adv-attr-structuredAttrs), the **experimental**
attribute `unsafeDiscardReferences` is a per-output boolean which, if set to `true`,
disables scanning the build output for runtime dependencies altogether.
> **Warning**
> This is an experimental feature.
>
> To enable it, add the following to [nix.conf](../command-ref/conf-file.md):
>
> ```
> extra-experimental-features = discard-references
> ```

When using [structured attributes](#adv-attr-structuredAttrs), the
attribute `unsafeDiscardReferences` is an attribute set with a boolean value for each output name.
If set to `true`, it disables scanning the output for runtime dependencies.

Example:

```nix
__structuredAttrs = true;
Expand All @@ -317,5 +330,3 @@ Derivations can declare some infrequently used optional attributes.
This is useful, for example, 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 is only allowed if the `discard-references` experimental feature is enabled.