view tests/test-arbitraryfilectx.t @ 38526:313a940d49a3

ui: add an uninterruptable context manager that can block SIGINT

The blocking of SIGINT is not done by default, but my hope is that we
will one day. This was inspired by Facebook's "nointerrupt" extension,
which is a bit more heavy-handed than this (whole commands are treated
as unsafe to interrupt). A future patch will enable this for varying
bits of Mercurial that are performing unsafe operations.

It's intentional that the KeyboardInterrupt is raised as the context
manager exits: during the span of the context manager interrupting
Mercurial could lead to data loss, but typically those spans are
fairly narrow, so we can let the unsafe block complete and then
terminate hg (which will leave the repo in a consistent state, even if
it's not the user's desired state).

.. api::

   New context manager ``ui.uninterruptable()`` to mark portions of a command
   as potentially unsafe places to interrupt Mercurial with Control-C or
   similar.

Differential Revision: https://phab.mercurial-scm.org/D3716

Setup:
  $ cat > eval.py <<EOF
  > from __future__ import absolute_import
  > import filecmp
  > from mercurial import commands, context, pycompat, registrar
  > cmdtable = {}
  > command = registrar.command(cmdtable)
  > @command(b'eval', [], b'hg eval CMD')
  > def eval_(ui, repo, *cmds, **opts):
  >     cmd = b" ".join(cmds)
  >     res = pycompat.bytestr(eval(cmd, globals(), locals()))
  >     ui.warn(b"%s" % res)
  > EOF

  $ echo "[extensions]" >> $HGRCPATH
  $ echo "eval=`pwd`/eval.py" >> $HGRCPATH

Arbitraryfilectx.cmp does not follow symlinks:
  $ mkdir case1
  $ cd case1
  $ hg init
#if symlink
  $ printf "A" > real_A
  $ printf "foo" > A
  $ printf "foo" > B
  $ ln -s A sym_A
  $ hg add .
  adding A
  adding B
  adding real_A
  adding sym_A
  $ hg commit -m "base"
#else
  $ hg import -q --bypass - <<EOF
  > # HG changeset patch
  > # User test
  > # Date 0 0
  > base
  > 
  > diff --git a/A b/A
  > new file mode 100644
  > --- /dev/null
  > +++ b/A
  > @@ -0,0 +1,1 @@
  > +foo
  > \ No newline at end of file
  > diff --git a/B b/B
  > new file mode 100644
  > --- /dev/null
  > +++ b/B
  > @@ -0,0 +1,1 @@
  > +foo
  > \ No newline at end of file
  > diff --git a/real_A b/real_A
  > new file mode 100644
  > --- /dev/null
  > +++ b/real_A
  > @@ -0,0 +1,1 @@
  > +A
  > \ No newline at end of file
  > diff --git a/sym_A b/sym_A
  > new file mode 120000
  > --- /dev/null
  > +++ b/sym_A
  > @@ -0,0 +1,1 @@
  > +A
  > \ No newline at end of file
  > EOF
  $ hg up -q
#endif

These files are different and should return True (different):
(Note that filecmp.cmp's return semantics are inverted from ours, so we invert
for simplicity):
  $ hg eval "context.arbitraryfilectx('A', repo).cmp(repo[None]['real_A'])"
  True (no-eol)
  $ hg eval "not filecmp.cmp('A', 'real_A')"
  True (no-eol)

These files are identical and should return False (same):
  $ hg eval "context.arbitraryfilectx('A', repo).cmp(repo[None]['A'])"
  False (no-eol)
  $ hg eval "context.arbitraryfilectx('A', repo).cmp(repo[None]['B'])"
  False (no-eol)
  $ hg eval "not filecmp.cmp('A', 'B')"
  False (no-eol)

This comparison should also return False, since A and sym_A are substantially
the same in the eyes of ``filectx.cmp``, which looks at data only.
  $ hg eval "context.arbitraryfilectx('real_A', repo).cmp(repo[None]['sym_A'])"
  False (no-eol)

A naive use of filecmp on those two would wrongly return True, since it follows
the symlink to "A", which has different contents.
#if symlink
  $ hg eval "not filecmp.cmp('real_A', 'sym_A')"
  True (no-eol)
#else
  $ hg eval "not filecmp.cmp('real_A', 'sym_A')"
  False (no-eol)
#endif