This had very bad interactions with ccache, often leading to rebuilds
with 100% cache misses, etc. Ali says it wasn't that big of a speedup
in the end anyway, so let's not bother with it.
We can always bring it back in the future if it seems like a good idea.
Almost a year after first working on this, it's finally done: an
implementation of Promises for LibJS! :^)
The core functionality is working and closely following the spec [1].
I mostly took the pseudo code and transformed it into C++ - if you read
and understand it, you will know how the spec implements Promises; and
if you read the spec first, the code will look very familiar.
Implemented functions are:
- Promise() constructor
- Promise.prototype.then()
- Promise.prototype.catch()
- Promise.prototype.finally()
- Promise.resolve()
- Promise.reject()
For the tests I added a new function to test-js's global object,
runQueuedPromiseJobs(), which calls vm.run_queued_promise_jobs().
By design, queued jobs normally only run after the script was fully
executed, making it improssible to test handlers in individual test()
calls by default [2].
Subsequent commits include integrations into LibWeb and js(1) -
pretty-printing, running queued promise jobs when necessary.
This has an unusual amount of dbgln() statements, all hidden behind the
PROMISE_DEBUG flag - I'm leaving them in for now as they've been very
useful while debugging this, things can get quite complex with so many
asynchronously executed functions.
I've not extensively explored use of these APIs for promise-based
functionality in LibWeb (fetch(), Notification.requestPermission()
etc.), but we'll get there in due time.
[1]: https://tc39.es/ecma262/#sec-promise-objects
[2]: https://tc39.es/ecma262/#sec-jobs-and-job-queues
This is a little bit messy but the basic idea is:
Syntax::Highlighter now has a Syntax::HighlighterClient to talk to the
outside world. It mostly communicates in LibGUI primitives that are
available in headers, so inlineable.
GUI::TextEditor inherits from Syntax::HighlighterClient.
This let us to move GUI::JSSyntaxHighlighter to JS::SyntaxHighlighter
and remove LibGUI's dependency on LibJS.
