nix-super/src/nix/flake-check.md

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# Examples

* Evaluate the flake in the current directory, and build its checks:

  ```console
  # nix flake check
  ```

* Verify that the `patchelf` flake evaluates, but don't build its
  checks:

  ```console
  # nix flake check --no-build github:NixOS/patchelf
  ```

# Description

This command verifies that the flake specified by flake reference
*flake-url* can be evaluated successfully (as detailed below), and
that the derivations specified by the flake's `checks` output can be
built successfully.

If the `keep-going` option is set to `true`, Nix will keep evaluating as much
as it can and report the errors as it encounters them. Otherwise it will stop
at the first error.

# Evaluation checks

The following flake output attributes must be derivations:

* `checks.`*system*`.`*name*
* `defaultPackage.`*system*`
* `devShell.`*system*`
* `devShells.`*system*`.`*name*`
* `nixosConfigurations.`*name*`.config.system.build.toplevel
* `packages.`*system*`.`*name*

The following flake output attributes must be [app
definitions](./nix3-run.md):

* `apps.`*system*`.`*name*
* `defaultApp.`*system*`

The following flake output attributes must be [template
definitions](./nix3-flake-init.md):

* `defaultTemplate`
* `templates`.`*name*

The following flake output attributes must be *Nixpkgs overlays*:

* `overlay`
* `overlays`.`*name*

The following flake output attributes must be *NixOS modules*:

* `nixosModule`
* `nixosModules`.`*name*

The following flake output attributes must be
[bundlers](./nix3-bundle.md):

* `bundlers`.`*name*
* `defaultBundler`

In addition, the `hydraJobs` output is evaluated in the same way as
Hydra's `hydra-eval-jobs` (i.e. as a arbitrarily deeply nested
attribute set of derivations). Similarly, the
`legacyPackages`.*system* output is evaluated like `nix-env -qa`.

)""