tests/test-close-head.t

worker: avoid potential partial write of pickled data

Previously, the code wrote the pickled data using os.write(). However,
os.write() can write less bytes than passed to it. To trigger the problem, the
pickled data had to be larger than 2147479552 bytes on my system.

Instead, open a file object and pass it to pickle.dump(). This also has the
advantage that it doesn’t buffer the whole pickled data in memory.

Note that the opened file must be buffered because pickle doesn’t support
unbuffered streams because unbuffered streams’ write() method might write less
bytes than passed to it (like os.write()) but pickle.dump() relies on that all
bytes are written (see https://github.com/python/cpython/issues/93050).

The side effect of using a file object and a with statement is that wfd is
explicitly closed now while it seems like before it was implicitly closed by
process exit.

  $ hg init test-content
  $ cd test-content
  $ hg debugbuilddag '+2*2*3*4+7'
  $ hg bookmark -r 1 @
  $ hg log -G --template '{rev}:{node|short}'
  o  11:1d876b1f862c
  |
  o  10:ea5f71948eb8
  |
  o  9:f1b0356d867a
  |
  o  8:e8d1253fb0d7
  |
  o  7:d423bbba4459
  |
  o  6:a2f58e9c1e56
  |
  o  5:3a367db1fabc
  |
  o  4:e7bd5218ca15
  |
  | o  3:6100d3090acf
  |/
  | o  2:fa942426a6fd
  |/
  | o  1:66f7d451a68b
  |/
  o  0:1ea73414a91b
  
  $ hg --config extensions.closehead= close-head -m 'Not a head' 0 1
  abort: revision is not an open head: 0
  [255]
  $ hg --config extensions.closehead= close-head -m 'Not a head' -r 0 1
  abort: revision is not an open head: 0
  [255]
  $ hg id
  000000000000
  $ hg --config extensions.closehead= close-head -m 'Close old heads' -r 1 2
  $ hg id
  000000000000
  $ hg bookmark
     @                         1:66f7d451a68b
  $ hg heads
  changeset:   11:1d876b1f862c
  user:        debugbuilddag
  date:        Thu Jan 01 00:00:11 1970 +0000
  summary:     r11
  
  changeset:   3:6100d3090acf
  parent:      0:1ea73414a91b
  user:        debugbuilddag
  date:        Thu Jan 01 00:00:03 1970 +0000
  summary:     r3
  
  $ hg --config extensions.closehead= close-head -m 'Close more old heads' -r 11
  $ hg heads
  changeset:   3:6100d3090acf
  parent:      0:1ea73414a91b
  user:        debugbuilddag
  date:        Thu Jan 01 00:00:03 1970 +0000
  summary:     r3
  
  $ hg --config extensions.closehead= close-head -m 'Not a head' 0
  abort: revision is not an open head: 0
  [255]
  $ hg --config extensions.closehead= close-head -m 'Already closed head' 1
  abort: revision is not an open head: 1
  [255]

  $ hg init ../test-empty
  $ cd ../test-empty
  $ hg debugbuilddag '+1'
  $ hg log -G --template '{rev}:{node|short}'
  o  0:1ea73414a91b
  
  $ hg --config extensions.closehead= close-head -m 'Close initial revision' 0
  $ hg heads
  [1]