jolheiser/nixpkgs
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

lib/attrsets: Document and link Nix language operators

Browse Source
This commit is contained in:
Robert Hensing 2023-12-13 18:38:41 +01:00
parent 7d993b9521
commit a7aa95db53
1 changed files with 24 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

24
lib/attrsets.nix
View File

@ -14,6 +14,14 @@ rec {
/* Return an attribute from nested attribute sets.
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:
```nix
(x.a.b or 6) == attrByPath ["a" "b"] 6 x
# and
(x.${f p}."example.com" or 6) == attrByPath [ (f p) "example.com" ] 6 x
```
Example:
x = { a = { b = 3; }; }
# ["a" "b"] is equivalent to x.a.b
@ -51,6 +59,14 @@ rec {
/* Return if an attribute from nested attribute set exists.
Nix has a [has attribute operator `?`](https://nixos.org/manual/nix/stable/language/operators#has-attribute), which is sufficient for such queries, as long as the number of attributes is static. For example:
```nix
(x?a.b) == hasAttryByPath ["a" "b"] x
# and
(x?${f p}."example.com") == hasAttryByPath [ (f p) "example.com" ] x
```
**Laws**:
1. ```nix
hasAttrByPath [] x == true
@ -177,6 +193,14 @@ rec {
/* Like `attrByPath`, but without a default value. If it doesn't find the
path it will throw an error.
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:
```nix
x.a.b == getAttrByPath ["a" "b"] x
# and
x.${f p}."example.com" == getAttrByPath [ (f p) "example.com" ] x
```
Example:
x = { a = { b = 3; }; }
getAttrFromPath ["a" "b"] x