view tests/test-empty-file.t @ 35190:bd8875b6473c

run-tests: mechanism to report exceptions during test execution

Sometimes when running tests you introduce a ton of exceptions.
The most extreme example of this is running Mercurial with Python 3,
which currently spews thousands of exceptions when running the test
harness.

This commit adds an opt-in feature to run-tests.py to aggregate
exceptions encountered by `hg` when running tests.

When --exceptions is used, the test harness enables the
"logexceptions" extension in the test environment. This extension
wraps the Mercurial function to handle exceptions and writes
information about the exception to a random filename in a directory
defined by the test harness via an environment variable. At the
end of the test harness, these files are parsed, aggregated, and
a list of all unique Mercurial frames triggering exceptions is
printed in order of frequency.

This feature is intended to aid Python 3 development. I've only
really tested it on Python 3. There is no shortage of improvements
that could be made. e.g. we could write a separate file containing
the exception report - maybe even an HTML report. We also don't
capture which tests demonstrate the exceptions, so there's no turnkey
way to test whether a code change made an exception disappear.
Perfect is the enemy of good. I think the current patch is useful
enough to land. Whoever uses it can send patches to imprve its
usefulness.

Differential Revision: https://phab.mercurial-scm.org/D1477

  $ hg init a
  $ cd a
  $ touch empty1
  $ hg add empty1
  $ hg commit -m 'add empty1'

  $ touch empty2
  $ hg add empty2
  $ hg commit -m 'add empty2'

  $ hg up -C 0
  0 files updated, 0 files merged, 1 files removed, 0 files unresolved
  $ touch empty3
  $ hg add empty3
  $ hg commit -m 'add empty3'
  created new head

  $ hg heads
  changeset:   2:a1cb177e0d44
  tag:         tip
  parent:      0:1e1d9c4e5b64
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     add empty3
  
  changeset:   1:097d2b0e17f6
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     add empty2
  

  $ hg merge 1
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)

Before changeset 05257fd28591, we didn't notice the
empty file that came from rev 1:

  $ hg status
  M empty2
  $ hg commit -m merge
  $ hg manifest --debug tip
  b80de5d138758541c5f05265ad144ab9fa86d1db 644   empty1
  b80de5d138758541c5f05265ad144ab9fa86d1db 644   empty2
  b80de5d138758541c5f05265ad144ab9fa86d1db 644   empty3

  $ cd ..