For the implementation of input signals, we want to extend the signal
primitive. The basic methods exposed here are not suitable as we'd like
to store additional metadata on the reactive node, and also have a
custom getter (for required inputs and throwing).
To enable this, one small piece was missing. This commit exposes it and
also improves type safety, now that `SignalNode` is typed properly after
the previous commit.
PR Close#53571
The `SignalNode` interface, describing the reactive node for a `Signal`,
seemingly exposes the `SIGNAL` symbol as a class member. This is not
true as the `SIGNAL` reactive node only exists on the getter function,
as a way to retrieve the signal underlying reactive node.
This commit fixes this, enabling improved type-safety later, in a
follow-up commit where `SIGNAL_NODE` can now be typed to match the
`SignalNode` interface (unlike now where it's typed as just `object`).
PR Close#53571
Producers represent values which can deliver change notifications.
When a producer value is changed, a change notification is propagated through the graph,
notifying live consumers which depend on the producer of the potential update.
Note here that this is a _potential_ update.
A producer may not have actually "changed" based on its equality function. With
this commit, before refreshing a view that is only marked for refresh
because its consumer is dirty, we poll producers for change to see if
they really have. If not, we can skip the refresh. The example test in this commit
shows that a `computed` which depends on a `signal` that is updated but
produces a value that is the same as before will _not_ cause the
component's template to refresh.
fixes#51797
PR Close#52476
This commit adds a global epoch to the reactive graph, which can optimize
non-live reads.
When a non-live read occurs, a computed must poll its dependencies to check
if they've changed, and this operation is transitive and not cacheable.
Since non-live computeds don't receive dirty notifications, they're forced
to assume potential dirtiness on each and every read.
Using a global epoch, we can add an important optimization: if *no* signals
have been set globally since the last time it polled its dependencies, then
we *can* assume a clean state. This significantly improves performance of
large unwatched graphs when repeatedly reading values.
PR Close#52420
This commit reorganizes the Angular code a bit, and moves signals into a
newly defined `@angular/core/primitives` location. This will be used inside
g3 to allow non-Angular targets to depend on the signals core without
incurring a dependency on the whole framework.
PR Close#51986
Matthieu Riegler