templatekw: add new-style template expansion to {manifest}...
templatekw: add new-style template expansion to {manifest}
The goal is to allow us to easily access to nested data. The dot operator
will be introduced later so we can write '{p1.files}' instead of
'{revset("p1()") % "{files}"}' for example.
In the example above, 'p1' needs to carry a mapping dict along with its
string representation. If it were a list or a dict, it could be wrapped
semi-transparently with the _hybrid class, but for non-list/dict types,
it would be difficult to proxy all necessary functions to underlying value
type because several core operations may conflict with the ones of the
underlying value:
- hash(value) should be different from hash(wrapped(value)), which means
dict[wrapped(value)] would be invalid
- 'value == wrapped(value)' would be false, breaks 'ifcontains'
- len(wrapped(value)) may be either len(value) or len(iter(wrapped(value)))
So the wrapper has no proxy functions and its scope designed to be minimal.
It's unwrapped at eval*() functions so we don't have to care for a wrapped
object unless it's really needed:
# most template functions just call evalfuncarg()
unwrapped_value = evalfuncarg(context, mapping, args[n])
# if wrapped value is needed, use evalrawexp()
maybe_wrapped_value = evalrawexp(context, mapping, args[n])
Another idea was to wrap every template variable with a tagging class, but
which seemed uneasy without a static type checker.
This patch updates {manifest} to a mappable as an example.
