pyrox.dev
Merge pull request #274022 from hercules-ci/doc-attrsets-operators
lib/attrsets: Document and link Nix language operators
authored by Silvan Mosberger and committed by GitHub 5027eafc a931a220
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lib/attrsets.nix
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lib/attrsets.nix
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/* Return an attribute from nested attribute sets.
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Example:
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x = { a = { b = 3; }; }
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# ["a" "b"] is equivalent to x.a.b
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attrByPath' 0 set;
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/* Return if an attribute from nested attribute set exists.
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**Laws**:
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1. ```nix
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/* Like `attrByPath`, but without a default value. If it doesn't find the
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path it will throw an error.
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Example:
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x = { a = { b = 3; }; }
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/* Return an attribute from nested attribute sets.
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Nix has an [attribute selection operator `. or`](https://nixos.org/manual/nix/stable/language/operators#attribute-selection) which is sufficient for such queries, as long as the number of attributes is static. For example:
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```nix
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(x.a.b or 6) == attrByPath ["a" "b"] 6 x
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# and
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(x.${f p}."example.com" or 6) == attrByPath [ (f p) "example.com" ] 6 x
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```
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Example:
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x = { a = { b = 3; }; }
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# ["a" "b"] is equivalent to x.a.b
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attrByPath' 0 set;
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/* Return if an attribute from nested attribute set exists.
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Nix has a [has attribute operator `?`](https://nixos.org/manual/nix/stable/language/operators#has-attribute), which is sufficient for such queries, as long as the number of attributes is static. For example:
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```nix
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(x?a.b) == hasAttryByPath ["a" "b"] x
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# and
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(x?${f p}."example.com") == hasAttryByPath [ (f p) "example.com" ] x
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```
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**Laws**:
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1. ```nix
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/* Like `attrByPath`, but without a default value. If it doesn't find the
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path it will throw an error.
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Nix has an [attribute selection operator](https://nixos.org/manual/nix/stable/language/operators#attribute-selection) which is sufficient for such queries, as long as the number of attributes is static. For example:
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```nix
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x.a.b == getAttrByPath ["a" "b"] x
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# and
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x.${f p}."example.com" == getAttrByPath [ (f p) "example.com" ] x
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```
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Example:
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x = { a = { b = 3; }; }