Pawel Kozlowski
c7ff9dff2c
This change removes the `mutate` method from the `WritableSignal` interface and completely drops it from the public API surface. The initial API proposal for Angular signals included the mutate method, allowing in-place modification of JS objects, without changing their references (identity). This was based on the reasoning that identity change on modification is not necessary as we can send the “modified” notification through the signals graph. Unfortunately the signal-specific change notification is lost as soon as we read signal value outside of a reactive context (outside of a reactive graph). In other words - any code outside of the Angular signals library can’t know that an object is modified. Secondly, to make the mutate method work, we’ve defaulted the signal value equality function to the one that considers non-primitive values as always different. This is unfortunate for people working with immutable data structures (this is notably the case for the popular state management libraries) as the default equality function de-optimizes memoization in computed, making the application less performant. Given the above reasons we prefer to remove the mutate method in the signals library - at least for now. There are just too many sharp edges and tradeoffs that we don’t fully understand yet. BREAKING CHANGE: The `mutate` method was removed from the `WritableSignal` interface and completely dropped from the public API surface. As an alternative please use the update method and make immutable changes to the object. Example before: ```typescript items.mutate(itemsArray => itemsArray.push(newItem)); ``` Example after: ```typescript items.update(itemsArray => [itemsArray, …newItem]); ``` PR Close #51821
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