Infinite loop is occurring in MockingBird shell script during unit test build phases

[Caleb-Bolton]

When building my unit tests, the MockingBird build phase shell script spams the logs seemingly infinitely (or at least until Xcode seizes up) with the following warning:

Ignoring unknown parameter attribute '@convention(block)' in function type declaration 'execute work: @escaping @convention(block) () -> Void'

which looks like it's coming from this line:
https://github.com/birdrides/mockingbird/blob/2108f83899745b0e08851caed10a4917757404b3/Sources/MockingbirdGenerator/Parser/Models/Function.swift#L99

Here is a picture of the logs, notice the 65535 count of warnings in the top right:

[Caleb-Bolton]

Looks like the parser fails to move forward from the '@' character in '@convention(block)' as once it encounters an unrecognized '@' attribute, it looks for the next non-letter, non-number character... which is the '@' character we're already on, so it infinitely loops.

It obviously needs to move past this attribute, I'm not familiar with this code though so I don't know what this would look like.

          var mutableComponent = component
          while (true) { // TODO: Use SwiftSyntax to properly parse this...
            if mutableComponent.starts(with: "@escaping") {
              attributes.insert(.escaping)
              mutableComponent = mutableComponent.dropFirst("@escaping".count)
            } else if mutableComponent.starts(with: "@autoclosure") {
              attributes.insert(.autoclosure)
              mutableComponent = mutableComponent.dropFirst("@autoclosure".count)
            } else if mutableComponent.hasPrefix("@") { // Unknown parameter attribute.
              logWarning("Ignoring unknown parameter attribute \(String(mutableComponent).singleQuoted) in function type declaration \(String(serialized).singleQuoted)")
              let index = mutableComponent.firstIndex(where: { !$0.isLetter && !$0.isNumber })
                ?? mutableComponent.endIndex
              mutableComponent = mutableComponent[index...]
            } else if mutableComponent == "inout" {
              attributes.insert(.inout)
              mutableComponent = mutableComponent.dropFirst("inout".count)
            } else if mutableComponent == "..." {
              attributes.insert(.variadic)
              mutableComponent = mutableComponent.dropFirst("...".count)
            } else {
              break
            }
          }

[amine2233]

have the same failure, do you have any update for it ?

[AlexanderMarchant]

Same problem here.

It can be easily reproduced by creating a protocol for the DispatchQueue method(s).

protocol DispatchQueueProtocol
{
    func async(group: DispatchGroup?, qos: DispatchQoS, flags: DispatchWorkItemFlags, execute work: @escaping @convention(block) () -> Void)
}

extension DispatchQueue: DispatchQueueProtocol {}

I think it should also be noted, this problem freezes and crashes Xcode for me when I try to run my unit tests target.

[Narayane]

Hi,
Any updates or workarounds? cc @andrewchang-bird
@fabianmuecke possible to make a PR with your fix on mockingbird repo?
Thanks

[fabianmuecke]

Sorry, @Narayane, I don't even remember what I did there and why it fixed the issue. 😬 My new employer doesn't use Mockingbird, so I doubt I'll find time to update my fork and make a PR anytime soon.

Please, feel free to make a PR with the change yourself, though. Looks like the fix itself seemed to be just adding dropFirst(). 🤔

[Narayane]

Hi,

I tried to exclude relative file but without success FYI ⬆️

[stidch]

Looks related to #310

Has anybody found a working workaround?