Simon Jakobi pushed to branch wip/sjakobi/testsuite-atomic-output at Glasgow Haskell Compiler / GHC

Commits:

• 9dc76830
  by Simon Jakobi at 2026-06-11T08:45:04+02:00

  testsuite: Give each test's output block a header
  
  A test's output is now emitted as one contiguous block (see
  Note [Atomic test output]), but adjacent blocks had no demarcation,
  so e.g. a one-line message from a passing test visually attached
  itself to a neighbouring test's failure diff. Prefix each non-empty
  block with a header naming the test and follow it with a blank line.
  
  Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
  

1 changed file:

• testsuite/driver/testlib.py

Changes:

         output_buffer_ctx_var.reset(token)

         s = buf.getvalue()

         if s:

+            # Set the block apart from adjacent tests' output with a header

+            # naming the test and a trailing blank line. Without this,

+            # neighbouring blocks read as one interleaved mess, and output

+            # of passing tests cannot be attributed to its test at all.

+            if not s.endswith('\n'):

+                s += '\n'

+            s = '=====> output from {}:\n{}\n'.format(name, s)

             # The event loop is single-threaded and there is no await between

             # these calls, so the block is written out atomically.

             sys.stdout.write(s)