forked from mirrors/nixpkgs
65e25deb06
For programs that have a lot of (Nix-representable) configuration options, a simple way to represent this in a NixOS module is to declare an option of a type like `attrsOf str`, representing a key-value mapping which then gets generated into a config file. However with such a type, there's no way to add type checking for only some key values. On the other end of the spectrum, one can declare a single separate option for every key value that the program supports, ending up with a module with potentially 100s of options. This has the benefit that every value gets type checked, catching mistakes at evaluation time already. However the disadvantage is that the module becomes big, becomes coupled to the program version and takes a lot of effort to write and maintain. Previously there was a middle ground between these two extremes: Declare an option of a type like `attrsOf str`, but declare additional separate options for the values you wish to have type checked, and assign their values to the `attrsOf str` option. While this works decently, it has the problem of duplicated options, since now both the additional options and the `attrsOf str` option can be used to set a key value. This leads to confusion about what should happen if both are set, which defaults should apply, and more. Now with this change, a middle ground becomes available that solves above problems: The module system now supports setting a freeform type, which gets used for all definitions that don't have an associated option. This means that you can now declare all options you wish to have type checked, while for the rest a freeform type like `attrsOf str` can be used. |
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| .. | ||
| systems | ||
| tests | ||
| asserts.nix | ||
| attrsets.nix | ||
| cli.nix | ||
| customisation.nix | ||
| debug.nix | ||
| default.nix | ||
| deprecated.nix | ||
| fetchers.nix | ||
| filesystem.nix | ||
| fixed-points.nix | ||
| generators.nix | ||
| kernel.nix | ||
| licenses.nix | ||
| lists.nix | ||
| meta.nix | ||
| minver.nix | ||
| modules.nix | ||
| options.nix | ||
| sources.nix | ||
| strings-with-deps.nix | ||
| strings.nix | ||
| trivial.nix | ||
| types.nix | ||
| versions.nix | ||
| zip-int-bits.nix | ||