It is parameterized by a function that takes a name and evaluates to the
option type for the attribute of that name. Together with
submoduleWithExtraArgs, this subsumes nixosSubmodule.
E.g.
The unique option `fileSystems./.device' is defined multiple times, in `/etc/nixos/configuration.nix' and `/etc/nixos/foo.nix'.
This requires passing file/value tuples to the merge functions.
An annoying and dangerous property of "types.string" is that it merges
multiple definitions by concatenating them, which almost never
produces a sensible result. (Those options for which it does make
sense typically should use "types.lines" instead, and things only work
because the option definitions already end in a newline.) Of course,
you can use "types.uniq types.string", but that's rather verbose, and
inconsistent with other basic types like "types.int".
Changing the behaviour of "types.string" to be unique by default is
not an option, given the large number of options that use it. So
instead, we now have "types.str", which is equivalent to "types.uniq
types.string".
For instance, if time.timeZone is defined multiple times, you now get
the error message:
error: user-thrown exception: The unique option `time.timeZone' is defined multiple times, in `/etc/nixos/configurations/misc/eelco/x11vnc.nix' and `/etc/nixos/configuration.nix'.
while previously you got:
error: user-thrown exception: Multiple definitions of string. Only one is allowed for this option.
and only an inspection of the stack trace gave a clue as to what
option caused the problem.
The major changes are:
* The evaluation is now driven by the declared options. In
particular, this fixes the long-standing problem with lack of
laziness of disabled option definitions. Thus, a configuration like
config = mkIf false {
environment.systemPackages = throw "bla";
};
will now evaluate without throwing an error. This also improves
performance since we're not evaluating unused option definitions.
* The implementation of properties is greatly simplified.
* There is a new type constructor "submodule" that replaces
"optionSet". Unlike "optionSet", "submodule" gets its option
declarations as an argument, making it more like "listOf" and other
type constructors. A typical use is:
foo = mkOption {
type = type.attrsOf (type.submodule (
{ config, ... }:
{ bar = mkOption { ... };
xyzzy = mkOption { ... };
}));
};
Existing uses of "optionSet" are automatically mapped to
"submodule".
* Modules are now checked for unsupported attributes: you get an error
if a module contains an attribute other than "config", "options" or
"imports".
* The new implementation is faster and uses much less memory.
This breaks NixOS, and I don't actually need it, so someone who needs it
can bring this back without breaking NixOS :)
This reverts commit 2742087bdd.
Signed-off-by: Shea Levy <shea@shealevy.com>
This is like types.string, but values are merged by putting a newline
in between them. This is mostly useful for configuration file
options, where we don't want values accidentally ending up on the same
line.
Note that almost all options with string type in NixOS should either
be unmergable (i.e. should be marked with ‘types.uniq’) or should
actually be of type ‘lines’. So it might make sense to remove the
merge function for the ‘string’ type eventually.
Eelco Dolstra