Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Use null for computing rather than undefined #235

Merged
merged 2 commits into from
Aug 6, 2024
Merged

Use null for computing rather than undefined #235

Changes from all commits
Commits
Show all changes
2 commits
Select commit Hold shift + click to select a range
81774c7
Use `null` rather than `undefined` on `computing`
prophile Aug 1, 2024
e20c88a
Specify the (trivial) semantics of `currentComputed()`
prophile Aug 1, 2024
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
10 changes: 7 additions & 3 deletions README.md
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -442,7 +442,7 @@ Some aspects of the algorithm:

Signal algorithms need to reference certain global state. This state is global for the entire thread, or "agent".

- `computing`: The innermost computed or effect Signal currently being reevaluated due to a `.get` or `.run` call, or `undefined`. Initially `undefined`.
- `computing`: The innermost computed or effect Signal currently being reevaluated due to a `.get` or `.run` call, or `null`. Initially `null`.
- `frozen`: Boolean denoting whether there is a callback currently executing which requires that the graph not be modified. Initially `false`.
- `generation`: An incrementing integer, starting at 0, used to track how current a value is while avoiding circularities.

Expand Down Expand Up @@ -549,7 +549,7 @@ With [AsyncContext](https://github.com/tc39/proposal-async-context), the callbac
#### Method: `Signal.Computed.prototype.get`

1. If the current execution context is `frozen` or if this Signal has the state `~computing~`, or if this signal is an Effect and `computing` a computed Signal, throw an exception.
1. If `computing` is not `undefined`, add this Signal to `computing`'s `sources` set.
1. If `computing` is not `null`, add this Signal to `computing`'s `sources` set.
1. NOTE: We do not add `computing` to this Signal's `sinks` set until/unless it becomes watched by a Watcher.
1. If this Signal's state is `~dirty~` or `~checked~`: Repeat the following steps until this Signal is `~clean~`:
1. Recurse up via `sources` to find the deepest, left-most (i.e. earliest observed) recursive source which is marked `~dirty~` (cutting off search when hitting a `~clean~` Signal, and including this Signal as the last thing to search).
Expand Down Expand Up @@ -632,13 +632,17 @@ With [AsyncContext](https://github.com/tc39/proposal-async-context), the callbac
### Method: `Signal.subtle.untrack(cb)`

1. Let `c` be the execution context's current `computing` state.
1. Set `computing` to undefined.
1. Set `computing` to null.
1. Call `cb`.
1. Restore `computing` to `c` (even if `cb` threw an exception).
1. Return the return value of `cb` (rethrowing any exception).

Note: untrack doesn't get you out of the `frozen` state, which is maintained strictly.

### Method: `Signal.subtle.currentComputed()`

1. Return the current `computing` value.

### Common algorithms

##### Algorithm: recalculate dirty computed Signal
Expand Down
Loading