procutil: make stream detection in make_line_buffered more correct and strict In make_line_buffered(), we don’t want to wrap the stream if we know that lines get flushed to the underlying raw stream already. Previously, the heuristic was too optimistic. It assumed that any stream which is not an instance of io.BufferedIOBase doesn’t need wrapping. However, there are buffered streams that aren’t instances of io.BufferedIOBase, like Mercurial’s own winstdout. The new logic is different in two ways: First, only for the check, if unwraps any combination of WriteAllWrapper and winstdout. Second, it skips wrapping the stream only if it is an instance of io.RawIOBase (or already wrapped). If it is an instance of io.BufferedIOBase, it gets wrapped. In any other case, the function raises an exception. This ensures that, if an unknown stream is passed or we add another wrapper in the future, we don’t wrap the stream if it’s already line buffered or not wrap the stream if it’s not line buffered. In fact, this was already helpful during development of this change. Without it, I possibly would have forgot that WriteAllWrapper needs to be ignored for the check, leading to unnecessary wrapping if stdout is unbuffered. The alternative would have been to always wrap unknown streams. However, I don’t think that anyone would benefit from being less strict. We can expect streams from the standard library to be subclassing either io.RawIOBase or io.BufferedIOBase, so running Mercurial in the standard way should not regress by this change. Py2exe might replace sys.stdout and sys.stderr, but that currently breaks Mercurial anyway and also these streams don’t claim to be interactive, so this function is not called for them.

     1

Define helpers.

     2

     3

  $ hg_log () { hg log -G -T "{rev}:{node|short}"; }

     4

  $ commit () { echo "foo - ${2:-$1}" > $1; hg commit -Aqm "Edited $1"; }

     5

  $ strip() { hg --config extensions.strip= strip -q -r "$1" ; }

     6

     7

Setup hg repo.

     8

     9

  $ hg init repo

    10

  $ cd repo

    11

  $ touch x; hg add x; hg commit -m "initial"

    12

  $ hg clone -q . ../clone

    13

  $ commit a

    14

    15

  $ cd ../clone

    16

    17

  $ commit b

    18

    19

  $ hg pull -q ../repo

    20

    21

  $ cat .hg/cache/branch2-visible

    22

  222ae9789a75703f9836e44de7db179cbfd420ee 2

    23

  a3498d6e39376d2456425dd8c692367bdbf00fa2 o default

    24

  222ae9789a75703f9836e44de7db179cbfd420ee o default

    25

    26

  $ hg_log

    27

  o  2:222ae9789a75

    28

  |

    29

  | @  1:a3498d6e3937

    30

  |/

    31

  o  0:7ab0a3bd758a

    32

    33

    34

  $ strip '1:'

    35

    36

The branchmap cache is not adjusted on strip.

    37

Now mentions a changelog entry that has been stripped.

    38

    39

  $ cat .hg/cache/branch2-visible

    40

  222ae9789a75703f9836e44de7db179cbfd420ee 2

    41

  a3498d6e39376d2456425dd8c692367bdbf00fa2 o default

    42

  222ae9789a75703f9836e44de7db179cbfd420ee o default

    43

    44

  $ commit c

    45

    46

Not adjusted on commit, either.

    47

    48

  $ cat .hg/cache/branch2-visible

    49

  222ae9789a75703f9836e44de7db179cbfd420ee 2

    50

  a3498d6e39376d2456425dd8c692367bdbf00fa2 o default

    51

  222ae9789a75703f9836e44de7db179cbfd420ee o default

    52

    53

On pull we end up with the same tip, and so wrongly reuse the invalid cache and crash.

    54

    55

  $ hg pull ../repo 2>&1 | grep 'ValueError:'

    56

  ValueError: node a3498d6e39376d2456425dd8c692367bdbf00fa2 does not exist (known-bad-output !)