Migrate to Swift concurrency. #675
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This replaces `Dispatch.concurrentPerform` with a task group. One benefit of this approach is that we don't need to know the number of iterations that we want ahead of time. We can start tasks during the initial iteration over the `FileIterator` instead of eagerly expanding it first; this should potentially improve behavior for invocations that cover very large directories recursively, especially when they're on slower storage like a network drive.
Instead of having `StderrDiagnosticPrinter` internally manage its own synchronization (which currently uses a Dispatch queue), turn `DiagnosticsEngine` into an actor that processes diagnostics from an `AsyncStream`. When rules emit findings, they are enqueued in the stream, and a single task iterates over them to ensure that individual diagnostic handlers don't need to synchronize their own activity.
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@allevato Just curious, is there any reason why swift-format hasn't migrated to Swift concurrency yet? |
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Mainly just that I wanted to do further testing to make sure that the new implementation didn't try to overcommit the thread pool when the number of files is significantly higher than the number of cores. That doesn't come automatically with Swift concurrency whereas Dispatch's |
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How hard would it be to conditionally switch to Swift Concurrency only when |
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We must have very different definitions of "small" 🙂 I'm very uninterested in maintaining both implementations simultaneously for any period of time. This really just needs me to carve out a little bit more time to do some further testing. |
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I ran the old version and the new version in release mode for 15 iterations over about 400 source files and got the following mean wall times:
lint: 9.71 sec (Dispatch) vs. 9.83 sec (Concurrency)format: 20.61 sec (Dispatch) vs. 20.79 (Concurrency)Even though the means for Concurrency are slightly higher, Student's t-test yielded p = 0.416 (lint) and p = 0.439 (format) which aren't low enough to claim they're significant.