Document builtins.derivation

This commit is contained in:
Robert Hensing 2024-07-10 13:34:42 +02:00
parent 9c6678da0e
commit 74698d54c8
2 changed files with 39 additions and 14 deletions

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@ -1,6 +1,31 @@
/* This is the implementation of the derivation builtin function.
It's actually a wrapper around the derivationStrict primop. */
# This is the implementation of the derivation builtin function.
# It's actually a wrapper around the derivationStrict primop.
# Note that the following comment will be shown in :doc in the repl, but not in the manual.
/**
Create a derivation.
# Inputs
The single argument is an attribute set that describes what to build and how to build it.
See https://nix.dev/manual/nix/2.23/language/derivations
# Output
The result is an attribute set that describes the derivation.
Notably it contains the outputs, which in the context of the Nix language are special strings that refer to the output paths, which may not yet exist.
The realisation of these outputs only occurs when needed; for example
* When `nix-build` or a similar command is run, it realises the outputs that were requested on its command line.
See https://nix.dev/manual/nix/2.23/command-ref/nix-build
* When `import`, `readFile`, `readDir` or some other functions are called, they have to realise the outputs they depend on.
This is referred to as "import from derivation".
See https://nix.dev/manual/nix/2.23/language/import-from-derivation
Note that `derivation` is very bare-bones, and provides almost no commands during the build.
Most likely, you'll want to use functions like `stdenv.mkDerivation` in Nixpkgs to set up a basic environment.
*/
drvAttrs @ { outputs ? [ "out" ], ... }:
let

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error:
… while evaluating the attribute 'outPath'
at <nix/derivation-internal.nix>:19:9:
18| value = commonAttrs // {
19| outPath = builtins.getAttr outputName strict;
at <nix/derivation-internal.nix>:44:9:
43| value = commonAttrs // {
44| outPath = builtins.getAttr outputName strict;
| ^
20| drvPath = strict.drvPath;
45| drvPath = strict.drvPath;
… while calling the 'getAttr' builtin
at <nix/derivation-internal.nix>:19:19:
18| value = commonAttrs // {
19| outPath = builtins.getAttr outputName strict;
at <nix/derivation-internal.nix>:44:19:
43| value = commonAttrs // {
44| outPath = builtins.getAttr outputName strict;
| ^
20| drvPath = strict.drvPath;
45| drvPath = strict.drvPath;
… while calling the 'derivationStrict' builtin
at <nix/derivation-internal.nix>:9:12:
8|
9| strict = derivationStrict drvAttrs;
at <nix/derivation-internal.nix>:34:12:
33|
34| strict = derivationStrict drvAttrs;
| ^
10|
35|
… while evaluating derivation '~jiggle~'
whose name attribute is located at /pwd/lang/eval-fail-derivation-name.nix:2:3