It didn't do what I thought it did with a RevertableProperty; it always
returned Nothing because even if the input properties to <!> are NoInfo, it
casts them to HasInfo.
Even if it had worked, it lost type safety. Better to export the
Property NoInfo that is used in a RevertableProperty, so it can be used
directly.
The old one caused the actions to run in the right order, but with the
wrong description.
This problem was found by comparing the [Host] between this branch and
current joeyconfig, and printing out their properties, info, and also their
list of child properties.
The only other difference found is that onChange orders the child property
list differently. That does not have any real effect and would be difficult
to change, so I've left it as-is.
* Property has been converted to a GADT, and will be Property NoInfo
or Property HasInfo.
This was done to make sure that ensureProperty is only used on
properties that do not have Info.
Transition guide:
- Change all "Property" to "Property NoInfo" or "Property WithInfo"
(The compiler can tell you if you got it wrong!)
- To construct a RevertableProperty, it is useful to use the new
(<!>) operator
- Constructing a list of properties can be problimatic, since
Property NoInto and Property WithInfo are different types and cannot
appear in the same list. To deal with this, "props" has been added,
and can built up a list of properties of different types,
using the same (&) and (!) operators that are used to build
up a host's properties.
Joey Hess