Fix JSONMessageStreamingParser error message formatting

[tristanlabelle]

When json parsing fails in JSONMessageStreamingParser, the error thrown was meant to include the message that failed to parse, but it referred to a buffer that had already been cleared by the buffer.removeAll() line.

This is especially useful to debug swiftc crashes when invoked through swift build, where the call stack should be in the JSON message that is not printed between the two colons : : :

error: failed parsing the Swift compiler output: unexpected JSON message: : dataCorrupted(Swift.DecodingError.Context(codingPath: [CodingKeys(stringValue: "kind", intValue: nil)], debugDescription: "invalid kind", underlyingError: nil))

[neonichu]

@swift-ci please smoke test

[compnerd]

@swift-ci please smoke test

[tristanlabelle]

Ping. Any blockers for merging this? I'm seeing that Linux/macOS tests are not running.

[compnerd]

@swift-ci please test Linux platform

[neonichu]

@swift-ci please smoke test macOS

[neonichu]

Oh I see, since this is TSC, the "smoke test" trigger doesn't do anything

[neonichu]

@swift-ci please test macOS

[compnerd]

@swift-ci please test macOS platform

[tristanlabelle]

The macOS CI appears to be hitting this unrelated failure:

/Users/ec2-user/jenkins/workspace/pr-swift-tools-support-core-macos/branch-main/swift-package-manager: error: package at '/Users/ec2-user/jenkins/workspace/pr-swift-tools-support-core-macos/branch-main/swift-package-manager' is using Swift tools version 5.7.0 but the installed version is 5.5.0

[compnerd]

@swift-ci please test macOS platform

[tomerd]

@swift-ci smoke test

[tomerd]

@shahmishal this is another CI job that needs upgrading, here this may be a more urgent need since we dont have the secondary job that uses the just-built-compiler

[compnerd]

@swift-ci please test macOS platform

[DougGregor]

It should be safe to merge this

[compnerd]

@DougGregor agreed, but that requires mighty powers (perhaps @Azoy can help with that?)

[DougGregor]

💪