view tests/test-url-rev.t @ 44950:f9734b2d59cc

py3: make stdout line-buffered if connected to a TTY

Status messages that are to be shown on the terminal should be written to the
file descriptor before anything further is done, to keep the user updated.

One common way to achieve this is to make stdout line-buffered if it is
connected to a TTY. This is done on Python 2 (except on Windows, where libc,
which the CPython 2 streams depend on, does not properly support this).

Python 3 rolls it own I/O streams. On Python 3, buffered binary streams can't be
set line-buffered. The previous code (added in 227ba1afcb65) incorrectly
assumed that on Python 3, pycompat.stdout (sys.stdout.buffer) is already
line-buffered. However the interpreter initializes it with a block-buffered
stream or an unbuffered stream (when the -u option or the PYTHONUNBUFFERED
environment variable is set), never with a line-buffered stream.

One example where the current behavior is unacceptable is when running
`hg pull https://www.mercurial-scm.org/repo/hg` on Python 3, where the line
"pulling from https://www.mercurial-scm.org/repo/hg" does not appear on the
terminal before the hg process blocks while waiting for the server.

Various approaches to fix this problem are possible, including:

1. Weaken the contract of procutil.stdout to not give any guarantees about
   buffering behavior. In this case, users of procutil.stdout need to be
   changed to do enough flushes. In particular,
  1. either ui must insert enough flushes for ui.write() and friends, or
  2. ui.write() and friends get split into flushing and fully buffered
     methods, or
  3. users of ui.write() and friends must flush explicitly.
2. Make stdout unbuffered.
3. Make stdout line-buffered. Since Python 3 does not natively support that for
   binary streams, we must implement it ourselves.

(2.) is problematic because using unbuffered I/O changes the performance
characteristics significantly compared to line-buffered (which is used on
Python 2) and this would be a regression.

(1.2.) and (1.3) are a substantial amount of work. It’s unclear whether the
added complexity would be justified, given that raw performance doesn’t matter
that much when writing to a terminal much faster than the user could read it.

(1.1.) pushes complexity into the ui class instead of separating the concern of
how stdout is buffered. Other users of procutil.stdout would still need to take
care of the flushes.

This patch implements (3.). The general performance considerations are very
similar to (1.1.). The extra method invocation and method forwarding add a
little more overhead if the class is used. In exchange, it doesn’t add overhead
if not used.


For the benchmarks, I compared the previous implementation (incorrect on Python
3), (1.1.), (3.) and (2.). The command was chosen so that the streams were
configured as if they were writing to a TTY, but actually write to a pager,
which is also the default:
HGRCPATH=/dev/null python3 ./hg --cwd ~/vcs/mozilla-central --time --pager yes --config pager.pager='cat > /dev/null' status --all

previous:
time: real 7.880 secs (user 7.290+0.050 sys 0.580+0.170)
time: real 7.830 secs (user 7.220+0.070 sys 0.590+0.140)
time: real 7.800 secs (user 7.210+0.050 sys 0.570+0.170)

(1.1.) using Yuya Nishihara’s patch:
time: real 9.860 secs (user 8.670+0.350 sys 1.160+0.830)
time: real 9.540 secs (user 8.430+0.370 sys 1.100+0.770)
time: real 9.830 secs (user 8.630+0.370 sys 1.180+0.840)

(3.) using this patch:
time: real 9.580 secs (user 8.480+0.350 sys 1.090+0.770)
time: real 9.670 secs (user 8.480+0.330 sys 1.170+0.860)
time: real 9.640 secs (user 8.500+0.350 sys 1.130+0.810)

(2.) using a previous patch by me:
time: real 10.480 secs (user 8.850+0.720 sys 1.590+1.500)
time: real 10.490 secs (user 8.750+0.750 sys 1.710+1.470)
time: real 10.240 secs (user 8.600+0.700 sys 1.590+1.510)


As expected, there’s no difference on Python 2, as exactly the same code paths
are used:

previous:
time: real 6.950 secs (user 5.870+0.330 sys 1.070+0.770)
time: real 7.040 secs (user 6.040+0.360 sys 0.980+0.750)
time: real 7.070 secs (user 5.950+0.360 sys 1.100+0.760)

this patch:
time: real 7.010 secs (user 5.900+0.390 sys 1.070+0.730)
time: real 7.000 secs (user 5.850+0.350 sys 1.120+0.760)
time: real 7.000 secs (user 5.790+0.380 sys 1.170+0.710)

Test basic functionality of url#rev syntax

  $ hg init repo
  $ cd repo
  $ echo a > a
  $ hg ci -qAm 'add a'
  $ hg branch foo
  marked working directory as branch foo
  (branches are permanent and global, did you want a bookmark?)
  $ echo >> a
  $ hg ci -m 'change a'
  $ cd ..

  $ hg clone 'repo#foo' clone
  adding changesets
  adding manifests
  adding file changes
  added 2 changesets with 2 changes to 1 files
  new changesets 1f0dee641bb7:cd2a86ecc814
  updating to branch foo
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved

  $ hg --cwd clone heads
  changeset:   1:cd2a86ecc814
  branch:      foo
  tag:         tip
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     change a
  
  changeset:   0:1f0dee641bb7
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     add a
  
  $ hg --cwd clone parents
  changeset:   1:cd2a86ecc814
  branch:      foo
  tag:         tip
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     change a
  
  $ cat clone/.hg/hgrc
  # example repository config (see 'hg help config' for more info)
  [paths]
  default = $TESTTMP/repo#foo
  
  # path aliases to other clones of this repo in URLs or filesystem paths
  # (see 'hg help config.paths' for more info)
  #
  # default:pushurl = ssh://[e-mail]/hg/jdoes-fork
  # my-fork         = ssh://[e-mail]/hg/jdoes-fork
  # my-clone        = /home/jdoe/jdoes-clone
  
  [ui]
  # name and email (local to this repository, optional), e.g.
  # username = Jane Doe <[e-mail]>

Changing original repo:

  $ cd repo

  $ echo >> a
  $ hg ci -m 'new head of branch foo'

  $ hg up -qC default
  $ echo bar > bar
  $ hg ci -qAm 'add bar'

  $ hg log
  changeset:   3:4cd725637392
  tag:         tip
  parent:      0:1f0dee641bb7
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     add bar
  
  changeset:   2:faba9097cad4
  branch:      foo
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     new head of branch foo
  
  changeset:   1:cd2a86ecc814
  branch:      foo
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     change a
  
  changeset:   0:1f0dee641bb7
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     add a
  
  $ hg -q outgoing '../clone'
  2:faba9097cad4
  3:4cd725637392
  $ hg summary --remote --config paths.default='../clone'
  parent: 3:4cd725637392 tip
   add bar
  branch: default
  commit: (clean)
  update: (current)
  phases: 4 draft
  remote: 2 outgoing
  $ hg -q outgoing '../clone#foo'
  2:faba9097cad4
  $ hg summary --remote --config paths.default='../clone#foo'
  parent: 3:4cd725637392 tip
   add bar
  branch: default
  commit: (clean)
  update: (current)
  phases: 4 draft
  remote: 1 outgoing

  $ hg -q --cwd ../clone incoming '../repo#foo'
  2:faba9097cad4
  $ hg --cwd ../clone summary --remote --config paths.default='../repo#foo'
  parent: 1:cd2a86ecc814 tip
   change a
  branch: foo
  commit: (clean)
  update: (current)
  remote: 1 or more incoming

  $ hg -q push '../clone#foo'

  $ hg --cwd ../clone heads
  changeset:   2:faba9097cad4
  branch:      foo
  tag:         tip
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     new head of branch foo
  
  changeset:   0:1f0dee641bb7
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     add a
  
  $ hg -q --cwd ../clone incoming '../repo#foo'
  [1]
  $ hg --cwd ../clone summary --remote --config paths.default='../repo#foo'
  parent: 1:cd2a86ecc814 
   change a
  branch: foo
  commit: (clean)
  update: 1 new changesets (update)
  remote: (synced)

  $ cd ..

  $ cd clone
  $ hg rollback
  repository tip rolled back to revision 1 (undo push)

  $ hg -q incoming
  2:faba9097cad4

  $ hg -q pull

  $ hg heads
  changeset:   2:faba9097cad4
  branch:      foo
  tag:         tip
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     new head of branch foo
  
  changeset:   0:1f0dee641bb7
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     add a
  
Pull should not have updated:

  $ hg parents -q
  1:cd2a86ecc814

Going back to the default branch:

  $ hg up -C 0
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved

  $ hg parents
  changeset:   0:1f0dee641bb7
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     add a
  
No new revs, no update:

  $ hg pull -qu

  $ hg parents -q
  0:1f0dee641bb7

  $ hg rollback
  repository tip rolled back to revision 1 (undo pull)

  $ hg parents -q
  0:1f0dee641bb7

Pull -u takes us back to branch foo:

  $ hg pull -qu

  $ hg parents
  changeset:   2:faba9097cad4
  branch:      foo
  tag:         tip
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     new head of branch foo
  
  $ hg rollback
  repository tip rolled back to revision 1 (undo pull)
  working directory now based on revision 0

  $ hg up -C 0
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved

  $ hg parents -q
  0:1f0dee641bb7

  $ hg heads -q
  1:cd2a86ecc814
  0:1f0dee641bb7

  $ hg pull -qur default default

  $ hg parents
  changeset:   3:4cd725637392
  tag:         tip
  parent:      0:1f0dee641bb7
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     add bar
  
  $ hg heads
  changeset:   3:4cd725637392
  tag:         tip
  parent:      0:1f0dee641bb7
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     add bar
  
  changeset:   2:faba9097cad4
  branch:      foo
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     new head of branch foo
  
Test handling of invalid urls

  $ hg id http://foo/?bar
  abort: unsupported URL component: "bar"
  [255]

  $ cd ..

Test handling common incoming revisions between "default" and
"default-push"

  $ hg -R clone rollback
  repository tip rolled back to revision 1 (undo pull)
  working directory now based on revision 0

  $ cd repo

  $ hg update -q -C default
  $ echo modified >> bar
  $ hg commit -m "new head to push current default head"
  $ hg -q push -r ".^1" '../clone'

  $ hg -q outgoing '../clone'
  2:faba9097cad4
  4:d515801a8f3d

  $ hg summary --remote --config paths.default='../clone#default' --config paths.default-push='../clone#foo'
  parent: 4:d515801a8f3d tip
   new head to push current default head
  branch: default
  commit: (clean)
  update: (current)
  phases: 1 draft
  remote: 1 outgoing

  $ hg summary --remote --config paths.default='../clone#foo' --config paths.default-push='../clone'
  parent: 4:d515801a8f3d tip
   new head to push current default head
  branch: default
  commit: (clean)
  update: (current)
  phases: 1 draft
  remote: 2 outgoing

  $ hg summary --remote --config paths.default='../clone' --config paths.default-push='../clone#foo'
  parent: 4:d515801a8f3d tip
   new head to push current default head
  branch: default
  commit: (clean)
  update: (current)
  phases: 1 draft
  remote: 1 outgoing

  $ hg clone -q -r 0 . ../another
  $ hg -q outgoing '../another#default'
  3:4cd725637392
  4:d515801a8f3d

  $ hg summary --remote --config paths.default='../another#default' --config paths.default-push='../clone#default'
  parent: 4:d515801a8f3d tip
   new head to push current default head
  branch: default
  commit: (clean)
  update: (current)
  phases: 1 draft
  remote: 1 outgoing

  $ cd ..

Test url#rev syntax of local destination path, which should be taken as
a 'url#rev' path

  $ hg clone repo '#foo'
  updating to branch default
  2 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ hg root -R '#foo'
  $TESTTMP/#foo