Random newlines inserted in test output

[dabrahams]

Description

These excerpts were produced with swift test (non-parallel):

Test Case '-[UtilsTests.SequenceExtensionsTests testElementCount]' started.
Test Case '-[UtilsTests.SequenceExtensionsTests testElementCount]' passed (0.000 seconds).
Test Suite 'SequenceExtensionsTests' passed at 2023-05-16 13:
57:15.569.
	 Executed 1 test, with 0 failures (0 unexpected) in 0.000 (0.000) seconds
Test Suite 'SourceFileTests' started at 2023-05-16 13:57:15.569

Test Suite 'TypeCheckerTests' started at 2023-05-16 13:57:15.572
Test Case '-[ValTests.TypeCheckerTests testTypeChecker]' started.
/Users/dave/src/val/Tests/ValTests/TestCases/TypeChecking/CallOperator.val:4: error: -[ValTests.TypeCheckerTests testTypeChecker] : unexpected diagnostic: 'cannot pass value of type 'Strin
g' to parameter 'let Int''
Test Case '-[ValTests.TypeCheckerTests testTypeChecker]' failed (6.244 seconds).
Test Suite 'TypeCheckerTests' failed at 2023-05-16 13:57:21.816.

The first one especially is problematic as the line starting with 57 gets interpreted by Emacs as an error.

Expected behavior

Test Case '-[UtilsTests.SequenceExtensionsTests testElementCount]' started.
Test Case '-[UtilsTests.SequenceExtensionsTests testElementCount]' passed (0.000 seconds).
Test Suite 'SequenceExtensionsTests' passed at 2023-05-16 13:57:15.569.
	 Executed 1 test, with 0 failures (0 unexpected) in 0.000 (0.000) seconds
Test Suite 'SourceFileTests' started at 2023-05-16 13:57:15.569

Test Suite 'TypeCheckerTests' started at 2023-05-16 13:57:15.572
Test Case '-[ValTests.TypeCheckerTests testTypeChecker]' started.
/Users/dave/src/val/Tests/ValTests/TestCases/TypeChecking/CallOperator.val:4: error: -[ValTests.TypeCheckerTests testTypeChecker] : unexpected diagnostic: 'cannot pass value of type 'String' to parameter 'let Int''
Test Case '-[ValTests.TypeCheckerTests testTypeChecker]' failed (6.244 seconds).
Test Suite 'TypeCheckerTests' failed at 2023-05-16 13:57:21.816.

Actual behavior

No response

Steps to reproduce

It's not reliably reproducible but if you run the Val tests enough times in a row you'll see it. Happens maybe 1 in 10 times.

https://github.com/val-lang/val

Swift Package Manager version/commit hash

Swift Package Manager - Swift 5.8.0

Swift & OS version (output of swift --version ; uname -a)

swift-driver version: 1.75.2 Apple Swift version 5.8 (swiftlang-5.8.0.124.2 clang-1403.0.22.11.100)
Target: arm64-apple-macosx13.0
Darwin DaveA-MBP14.local 22.4.0 Darwin Kernel Version 22.4.0: Mon Mar 6 20:59:28 PST 2023; root:xnu-8796.101.5~3/RELEASE_ARM64_T6000 arm64

[grynspan]

I counted and they're getting inserted at 1KB intervals, which suggests to me buffering is happening and the newline is inserted when the buffer reaches its capacity.

[grynspan]

Looking at the implementation, test output is "chuzzled" (whitespace is trimmed) but then is passed to outputHandler which… calls print() which inserts a newline. So if the output already has a newline, it's removed then added back, but if the output has no newline (e.g. it's buffered and the buffer is flushed) then one is inserted. @neonichu @MaxDesiatov Sounds to me like the correct fix is to get rid of the call to spm_chuzzle() and to pass terminator: "" to print()?

[tomerd]

@grynspan that sounds correct to me!

[tomerd]

#7126

[sjavora]

@tomerd so can this be closed?