view tests/test-mq-eol.t @ 44118:f81c17ec303c

hgdemandimport: apply lazy module loading to sys.meta_path finders

Python's `sys.meta_path` finders are the primary objects whose job it
is to find a module at import time. When `import` is called, Python
iterates objects in this list and calls `o.find_spec(...)` to find
a `ModuleSpec` (or None if the module couldn't be found by that
finder). If no meta path finder can find a module, import fails.

One of the default meta path finders is `PathFinder`. Its job is to
import modules from the filesystem and is probably the most important
importer. This finder looks at `sys.path` and `sys.path_hooks` to do
its job.

The `ModuleSpec` returned by `MetaPathImporter.find_spec()` has a
`loader` attribute, which defines the concrete module loader to use.
`sys.path_hooks` is a hook point for teaching `PathFinder` to
instantiate custom loader types.

Previously, we injected a custom `sys.path_hook` that told `PathFinder`
to wrap the default loaders with a loader that creates a module object
that is lazy.

This approach worked. But its main limitation was that it only applied
to the `PathFinder` meta path importer. There are other meta path
importers that are registered. And in the case of PyOxidizer loading
modules from memory, `PathFinder` doesn't come into play since
PyOxidizer's own meta path importer was handling all imports.

This commit changes our approach to lazy module loading by proxying
all meta path importers. Specifically, we overload the `find_spec()`
method to swap in a wrapped loader on the `ModuleSpec` before it
is returned. The end result of this is all meta path importers should
be lazy.

As much as I would have loved to utilize .__class__ manipulation to
achieve this, some meta path importers are implemented in C/Rust
in such a way that they cannot be monkeypatched. This is why we
use __getattribute__ to define a proxy.

Also, this change could theoretically open us up to regressions in
meta path importers whose loader is creating module objects which
can't be monkeypatched. But I'm not aware of any of these in the
wild. So I think we'll be safe.

According to hyperfine, this change yields a decent startup time win of
5-6ms:

```
Benchmark #1: ~/.pyenv/versions/3.6.10/bin/python ./hg version
  Time (mean ± σ):      86.8 ms ±   0.5 ms    [User: 78.0 ms, System: 8.7 ms]
  Range (min … max):    86.0 ms …  89.1 ms    50 runs

  Time (mean ± σ):      81.1 ms ±   2.7 ms    [User: 74.5 ms, System: 6.5 ms]
  Range (min … max):    77.8 ms …  90.5 ms    50 runs

Benchmark #2: ~/.pyenv/versions/3.7.6/bin/python ./hg version
  Time (mean ± σ):      78.9 ms ±   0.6 ms    [User: 70.2 ms, System: 8.7 ms]
  Range (min … max):    78.1 ms …  81.2 ms    50 runs

  Time (mean ± σ):      73.4 ms ±   0.6 ms    [User: 65.3 ms, System: 8.0 ms]
  Range (min … max):    72.4 ms …  75.7 ms    50 runs

Benchmark #3: ~/.pyenv/versions/3.8.1/bin/python ./hg version
  Time (mean ± σ):      78.1 ms ±   0.6 ms    [User: 70.2 ms, System: 7.9 ms]
  Range (min … max):    77.4 ms …  80.9 ms    50 runs

  Time (mean ± σ):      72.1 ms ±   0.4 ms    [User: 64.4 ms, System: 7.6 ms]
  Range (min … max):    71.4 ms …  74.1 ms    50 runs
```

Differential Revision: https://phab.mercurial-scm.org/D7954

Test interactions between mq and patch.eol


  $ cat <<EOF >> $HGRCPATH
  > [extensions]
  > mq =
  > [diff]
  > nodates = 1
  > EOF

  $ cat > makepatch.py <<EOF
  > f = open('eol.diff', 'wb')
  > w = f.write
  > w(b'test message\n')
  > w(b'diff --git a/a b/a\n')
  > w(b'--- a/a\n')
  > w(b'+++ b/a\n')
  > w(b'@@ -1,5 +1,5 @@\n')
  > w(b' a\n')
  > w(b'-b\r\n')
  > w(b'+y\r\n')
  > w(b' c\r\n')
  > w(b' d\n')
  > w(b'-e\n')
  > w(b'\\\\ No newline at end of file\n')
  > w(b'+z\r\n')
  > w(b'\\\\ No newline at end of file\r\n')
  > EOF

  $ cat > cateol.py <<EOF
  > import sys
  > try:
  >     stdout = sys.stdout.buffer
  > except AttributeError:
  >     stdout = sys.stdout
  > for line in open(sys.argv[1], 'rb'):
  >     line = line.replace(b'\r', b'<CR>')
  >     line = line.replace(b'\n', b'<LF>')
  >     stdout.write(line + b'\n')
  > EOF

  $ hg init repo
  $ cd repo
  $ echo '\.diff' > .hgignore
  $ echo '\.rej' >> .hgignore


Test different --eol values

  $ "$PYTHON" -c 'open("a", "wb").write(b"a\nb\nc\nd\ne")'
  $ hg ci -Am adda
  adding .hgignore
  adding a
  $ "$PYTHON" ../makepatch.py
  $ hg qimport eol.diff
  adding eol.diff to series file

should fail in strict mode

  $ hg qpush
  applying eol.diff
  patching file a
  Hunk #1 FAILED at 0
  1 out of 1 hunks FAILED -- saving rejects to file a.rej
  patch failed, unable to continue (try -v)
  patch failed, rejects left in working directory
  errors during apply, please fix and qrefresh eol.diff
  [2]
  $ hg qpop
  popping eol.diff
  patch queue now empty

invalid eol

  $ hg --config patch.eol='LFCR' qpush
  applying eol.diff
  patch failed, unable to continue (try -v)
  patch failed, rejects left in working directory
  errors during apply, please fix and qrefresh eol.diff
  [2]
  $ hg qpop
  popping eol.diff
  patch queue now empty

force LF

  $ hg --config patch.eol='CRLF' qpush
  applying eol.diff
  now at: eol.diff
  $ hg qrefresh
  $ "$PYTHON" ../cateol.py .hg/patches/eol.diff
  # HG changeset patch<LF>
  # Parent  0d0bf99a8b7a3842c6f8ef09e34f69156c4bd9d0<LF>
  test message<LF>
  <LF>
  diff -r 0d0bf99a8b7a a<LF>
  --- a/a<LF>
  +++ b/a<LF>
  @@ -1,5 +1,5 @@<LF>
  -a<LF>
  -b<LF>
  -c<LF>
  -d<LF>
  -e<LF>
  \ No newline at end of file<LF>
  +a<CR><LF>
  +y<CR><LF>
  +c<CR><LF>
  +d<CR><LF>
  +z<LF>
  \ No newline at end of file<LF>
  $ "$PYTHON" ../cateol.py a
  a<CR><LF>
  y<CR><LF>
  c<CR><LF>
  d<CR><LF>
  z
  $ hg qpop
  popping eol.diff
  patch queue now empty

push again forcing LF and compare revisions

  $ hg --config patch.eol='CRLF' qpush
  applying eol.diff
  now at: eol.diff
  $ "$PYTHON" ../cateol.py a
  a<CR><LF>
  y<CR><LF>
  c<CR><LF>
  d<CR><LF>
  z
  $ hg qpop
  popping eol.diff
  patch queue now empty

push again without LF and compare revisions

  $ hg qpush
  applying eol.diff
  now at: eol.diff
  $ "$PYTHON" ../cateol.py a
  a<CR><LF>
  y<CR><LF>
  c<CR><LF>
  d<CR><LF>
  z
  $ hg qpop
  popping eol.diff
  patch queue now empty
  $ cd ..


Test .rej file EOL are left unchanged

  $ hg init testeol
  $ cd testeol
  $ "$PYTHON" -c "open('a', 'wb').write(b'1\r\n2\r\n3\r\n4')"
  $ hg ci -Am adda
  adding a
  $ "$PYTHON" -c "open('a', 'wb').write(b'1\r\n2\r\n33\r\n4')"
  $ hg qnew patch1
  $ hg qpop
  popping patch1
  patch queue now empty
  $ "$PYTHON" -c "open('a', 'wb').write(b'1\r\n22\r\n33\r\n4')"
  $ hg ci -m changea

  $ hg --config 'patch.eol=LF' qpush
  applying patch1
  patching file a
  Hunk #1 FAILED at 0
  1 out of 1 hunks FAILED -- saving rejects to file a.rej
  patch failed, unable to continue (try -v)
  patch failed, rejects left in working directory
  errors during apply, please fix and qrefresh patch1
  [2]
  $ hg qpop
  popping patch1
  patch queue now empty
  $ cat a.rej
  --- a
  +++ a
  @@ -1,4 +1,4 @@
   1\r (esc)
   2\r (esc)
  -3\r (esc)
  +33\r (esc)
   4
  \ No newline at end of file

  $ hg --config 'patch.eol=auto' qpush
  applying patch1
  patching file a
  Hunk #1 FAILED at 0
  1 out of 1 hunks FAILED -- saving rejects to file a.rej
  patch failed, unable to continue (try -v)
  patch failed, rejects left in working directory
  errors during apply, please fix and qrefresh patch1
  [2]
  $ hg qpop
  popping patch1
  patch queue now empty
  $ cat a.rej
  --- a
  +++ a
  @@ -1,4 +1,4 @@
   1\r (esc)
   2\r (esc)
  -3\r (esc)
  +33\r (esc)
   4
  \ No newline at end of file
  $ cd ..