tests/test-fix-metadata.t

fix: allow fixer tools to return metadata in addition to the file content

With this change, fixer tools can be configured to output a JSON object that
will be parsed and passed to hooks that can be used to print summaries of what
code was formatted or perform other post-fixing work.

The motivation for this change is to allow parallel executions of a
"meta-formatter" tool to report back statistics, which are then aggregated and
processed after all formatting has completed. Providing an extensible mechanism
inside fix.py is far simpler, and more portable, than trying to make a tool
like this communicate through some other channel.

Differential Revision: https://phab.mercurial-scm.org/D6167

A python hook for "hg fix" that prints out the number of files and revisions
that were affected, along with which fixer tools were applied. Also checks how
many times it sees a specific key generated by one of the fixer tools defined
below.

  $ cat >> $TESTTMP/postfixhook.py <<EOF
  > import collections
  > def file(ui, repo, rev=None, path='', metadata=None, **kwargs):
  >   ui.status('fixed %s in revision %d using %s\n' %
  >             (path, rev, ', '.join(metadata.keys())))
  > def summarize(ui, repo, replacements=None, wdirwritten=False,
  >               metadata=None, **kwargs):
  >     counts = collections.defaultdict(int)
  >     keys = 0
  >     for fixername, metadatalist in metadata.items():
  >         for metadata in metadatalist:
  >             if metadata is None:
  >                 continue
  >             counts[fixername] += 1
  >             if 'key' in metadata:
  >                 keys += 1
  >     ui.status('saw "key" %d times\n' % (keys,))
  >     for name, count in sorted(counts.items()):
  >         ui.status('fixed %d files with %s\n' % (count, name))
  >     if replacements:
  >         ui.status('fixed %d revisions\n' % (len(replacements),))
  >     if wdirwritten:
  >         ui.status('fixed the working copy\n')
  > EOF

Some mock output for fixer tools that demonstrate what could go wrong with
expecting the metadata output format.

  $ printf 'new content\n' > $TESTTMP/missing
  $ printf 'not valid json\0new content\n' > $TESTTMP/invalid
  $ printf '{"key": "value"}\0new content\n' > $TESTTMP/valid

Configure some fixer tools based on the output defined above, and enable the
hooks defined above. Disable parallelism to make output of the parallel file
processing phase stable.

  $ cat >> $HGRCPATH <<EOF
  > [extensions]
  > fix =
  > [fix]
  > missing:command=cat $TESTTMP/missing
  > missing:pattern=missing
  > missing:metadata=true
  > invalid:command=cat $TESTTMP/invalid
  > invalid:pattern=invalid
  > invalid:metadata=true
  > valid:command=cat $TESTTMP/valid
  > valid:pattern=valid
  > valid:metadata=true
  > [hooks]
  > postfixfile = python:$TESTTMP/postfixhook.py:file
  > postfix = python:$TESTTMP/postfixhook.py:summarize
  > [worker]
  > enabled=false
  > EOF

See what happens when we execute each of the fixer tools. Some print warnings,
some write back to the file.

  $ hg init repo
  $ cd repo

  $ printf "old content\n" > invalid
  $ printf "old content\n" > missing
  $ printf "old content\n" > valid
  $ hg add -q

  $ hg fix -w
  ignored invalid output from fixer tool: invalid
  ignored invalid output from fixer tool: missing
  fixed valid in revision 2147483647 using valid
  saw "key" 1 times
  fixed 1 files with valid
  fixed the working copy

  $ cat missing invalid valid
  old content
  old content
  new content

  $ cd ..