We expect the vast majority of requirements and features to be defined
in services as possible. However, there are some "complex" requirements
that require additional application/HTTP request state. Unfortunately,
service wiring is done before some of that state is available.
I65702426 attempted to work around this by requiring clients of the
Feature Manager to pass that additional state on every interaction with
the system. Those complex requirements would then select the parts of
the state that they required when it was required. However
implementations of \IContextSource are God objects and their use should
be limited.
Whilst reviewing I65702426, Stephen Niedzielski mentioned that the
application state being available is a requirement. This remarkably
simple solution:
- Keeps the Requirement interface and FeatureManager API free of God
objects;
- Is true to the nature of the Feature Manager - it makes clear and
centralizes the various checks for application state being available
across the codebase; and
- Inject a Requirement implementations' dependencies at construction
time
It just so happens that the $wgFullyInitialised variable flags whether
the application state is available...
Changes:
- Add the the FeatureManager\Requirements\DynamicConfigRequirement class
and tests. The DynamicConfigRequirement lazily evaluates a single
configuration value whenever ::isMet is invoked
- Register an DynamicConfigRequirement instance, configured to evaluate
$wgFullyInitialised while constructing the Vector.FeatureManager
service
Bug: T244481
Change-Id: I7a2cdc2dfdf20d78e4548f07cf53994563b234b3
As was noted in https://phabricator.wikimedia.org/T244481#5859513, the
term "set" doesn't seem natural. Piotr Miazga (polishdeveloper, pmiazga)
and Nicholas Ray (nray) suggested a number of good replacements,
including "requirement." Serendipitously, this term is already used in
FeatureManager's documentation.
Bug: T244481
Change-Id: I559c2d4149db69235cdd4bb880697deb1a145743
With complex additions to Vector's codebase like the Desktop Improvement
Program upcoming, it's important that we have a shared, intuitive
language to talk about features and their requirements. Centralising
the registration of features and creating an API satisfies does exactly
this.
This change introduces a greatly-reduced version of Piotr Miazga's
(polishdeveloper, pmiazga) original proposed API and associated
scaffolding classes for feature management in Vector, which itself was
based upon his work in MobileFrontend/MinervaNeue. This is done to
establish a foundation upon which we can build the more sophisticated
parts of Piotr's proposal in a piecemeal basis, thereby minimising risk.
Distinct from Piotr's proposed API is the ability to register sets and
features that are always enabled or disabled.
Additionally:
- A Vector.FeatureManager service is registered but not used
- A list of proposed immediate next steps is included
Bug: T244481
Change-Id: Ie53c41d479eaf15559d5bb00f269774760360bde
Sam Smith