- Improve extractItem error messages: distinguish non-attrset elements
from multi-key attrsets, and include the faulty definition via showDefs.
- Use isType instead of raw _type access for order detection.
- Disable type merging (typeMerge = t: null) instead of providing a
functor-based merge. Add test confirming duplicate declarations fail.
This allows the type's return value to be accessed more easily.
Motivating use case:
- Built-in module provides CLI functionality by declaring
an `attrListWith { asAttrs = true; }`, extracting the ordered list
from `valueMeta` for the purpose of creating the `argv`.
- User modules can read the command line's flags directly without
having to parse the list of attrs.
This adds a type for name-value mappings that preserve ordering.
Motivating use case: command line flags for package modules /
wrappers / modular services.
The option value can be transformed into a command line in the
correct order.
Additionally, a convenience readOnly option could be provided
to give easy introspection access to the values in an ad hoc
manner.
`emptyValue` for `types.submodule` was `{ value = { }; }`, i.e. none
of the type-declared options or their defaults.
Previously submodules without defs would simply fail for lack of a default,
but since PR #500104 repurposed `emptyValue` as the fallback when no
definitions exist, submodule options without an explicit `default = { }`
(new additions) silently lost their sub-option defaults
(e.g. `requiredFeatures.devnet` in the nixos-test-driver, #511413).
Main change: `emptyValue`: `{ }` -> `{ value = base.config; }`
Additionally, skip `emptyValue`-based default rendering in docs for
types with submodules, because their sub-options are already documented
individually, and forcing evaluation here can break on modules with
invalid or incomplete definitions.
Downstream types that want to use `lib.types.defaultTypeMerge` must include
`wrapped` even though it is deprecated or the internal
`wrappedDeprecationMessage`. This is caused by accessing the
`wrapped` attr in `lib.types.defaultTypeMerge`. The logic should first check
if the attr exists and then if it does check if it is null.
This change introduces the suggesting of possible valid option names for
a given invalid option, based on the keys of said invalid option's
parent attrset. That is, `foo.bar.baz` will only be suggested keys from
`foo.bar`, while `(config).baz` will only be suggested keys from the
toplevel.
