Add support for combined test output (to land) #1212
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Checkpointing so I can check Windows impl on an actual windows machine
Adds basic tests for TestOutput, particularly the line iterator
While adding tests for the libtestjson output, I noticed that my assumption that stdout/stderr ordering would be _mostly_ correct except in "extreme" scenarios was...completely wrong. With even the most simple mixed stdout/stderr output (no multithreading, no unbuffered output, no huge single writes) that the ordering of the output was wrong on my machine more often than not. After playing around with the idea of using a pseudo terminal, similar to how alacritty or other terminal emulators work, I checked the even easier case of...just passing the same file descriptor for both stdout and stderr...which works. Committing this in a separate branch so that I can push and add the Windows implementation before merging this back to the combined output branch.
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Codecov ReportAttention:
Additional details and impacted files@@ Coverage Diff @@
## main #1212 +/- ##
==========================================
- Coverage 78.26% 77.39% -0.88%
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Files 69 72 +3
Lines 17464 17860 +396
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+ Hits 13668 13822 +154
- Misses 3796 4038 +242 ☔ View full report in Codecov by Sentry. |
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For libtest JSON emulation, we need to have a way to model combined stdout and stderr output. The best way to do this happens to be to use the same file descriptor (HANDLE on Windows) for stdout and stderr. This is pretty useful generally, and in the future we may enable support for combined test output even outside the libtest-json context. The main alternative considered was having separate fds, but selecting from them into a single giant buffer with tracking indexes into it. However, that doesn't quite work because reading from pipes is done asynchronously with the test process writing to them. This typically causes lines from stdout and stderr to be clumped with each other. If the same fd is used as in this PR, the test process writes to stdout and stderr *synchronously*, which means that the combined output is recorded in the exact order the test process generates it in. Enabling combined output does mean that we lose the ability to track outputs separately, but that's not a huge deal. Co-authored-by: Rain <[email protected]>
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(the last commit did not have the correct attribution, so I force-pushed one that did) |
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This is a version of #1088 that's ready for landing.
The big changes compared to #1088 are: