view tests/test-convert-bzr-merges.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

#require bzr

N.B. bzr 1.13 has a bug that breaks this test.  If you see this
test fail, check your bzr version.  Upgrading to bzr 1.13.1
should fix it.

  $ . "$TESTDIR/bzr-definitions"

test multiple merges at once

  $ mkdir test-multimerge
  $ cd test-multimerge
  $ bzr init -q source
  $ cd source
  $ echo content > file
  $ echo text > rename_me
  $ bzr add -q file rename_me
  $ bzr commit -q -m 'Initial add' '--commit-time=2009-10-10 08:00:00 +0100'
  $ cd ..
  $ bzr branch -q source source-branch1
  $ cd source-branch1
  $ echo morecontent >> file
  $ echo evenmorecontent > file-branch1
  $ bzr add -q file-branch1
  $ bzr commit -q -m 'Added branch1 file' '--commit-time=2009-10-10 08:00:01 +0100'
  $ cd ../source
  $ sleep 1
  $ echo content > file-parent
  $ bzr add -q file-parent
  $ bzr commit -q -m 'Added parent file' '--commit-time=2009-10-10 08:00:02 +0100'
  $ cd ..
  $ bzr branch -q source source-branch2
  $ cd source-branch2
  $ echo somecontent > file-branch2
  $ bzr add -q file-branch2
  $ bzr mv -q rename_me renamed
  $ echo change > renamed
  $ bzr commit -q -m 'Added brach2 file' '--commit-time=2009-10-10 08:00:03 +0100'
  $ sleep 1
  $ cd ../source
  $ bzr merge -q ../source-branch1
  $ bzr merge -q --force ../source-branch2
  $ bzr commit -q -m 'Merged branches' '--commit-time=2009-10-10 08:00:04 +0100'
  $ cd ..

BUG: file-branch2 should not be added in rev 4, and the rename_me -> renamed
move should be recorded in the fixup merge.
  $ hg convert --datesort --config convert.bzr.saverev=False source source-hg
  initializing destination source-hg repository
  scanning source...
  sorting...
  converting...
  4 Initial add
  3 Added branch1 file
  2 Added parent file
  1 Added brach2 file
  0 Merged branches
  warning: can't find ancestor for 'renamed' copied from 'rename_me'!
  $ glog -R source-hg
  o    5@source "(octopus merge fixup)" files+: [], files-: [], files: [renamed]
  |\
  | o    4@source "Merged branches" files+: [file-branch2 renamed], files-: [rename_me], files: []
  | |\
  o---+  3@source-branch2 "Added brach2 file" files+: [file-branch2 renamed], files-: [rename_me], files: []
   / /
  | o  2@source "Added parent file" files+: [file-parent], files-: [], files: []
  | |
  o |  1@source-branch1 "Added branch1 file" files+: [file-branch1], files-: [], files: [file]
  |/
  o  0@source "Initial add" files+: [file rename_me], files-: [], files: []
  
  $ manifest source-hg tip
  % manifest of tip
  644   file
  644   file-branch1
  644   file-branch2
  644   file-parent
  644   renamed

  $ hg convert source-hg hg2hg
  initializing destination hg2hg repository
  scanning source...
  sorting...
  converting...
  5 Initial add
  4 Added branch1 file
  3 Added parent file
  2 Added brach2 file
  1 Merged branches
  0 (octopus merge fixup)

BUG: The manifest entries should be the same for matching revisions, and
nothing should be outgoing

  $ hg -R source-hg manifest --debug -r tip | grep renamed
  67109fdebf6c556eb0a9d5696dd98c8420520405 644   renamed
  $ hg -R hg2hg manifest --debug -r tip | grep renamed
  27c968376d7c3afd095ecb9c7697919b933448c8 644   renamed
  $ hg -R source-hg manifest --debug -r 'tip^' | grep renamed
  27c968376d7c3afd095ecb9c7697919b933448c8 644   renamed
  $ hg -R hg2hg manifest --debug -r 'tip^' | grep renamed
  27c968376d7c3afd095ecb9c7697919b933448c8 644   renamed

BUG: The revisions found should be the same in both repos

  $ hg --cwd source-hg log -r 'file("renamed")' -G -Tcompact
  o    5[tip]:4,3   6652429c300a   2009-10-10 08:00 +0100   foo
  |\     (octopus merge fixup)
  | |
  | o    4:2,1   e0ae8af3503a   2009-10-10 08:00 +0100   foo
  | |\     Merged branches
  | ~ ~
  o  3   138bed2e14be   2009-10-10 08:00 +0100   foo
  |    Added brach2 file
  ~
  $ hg --cwd hg2hg log -r 'file("renamed")' -G -Tcompact
  o    4:2,1   e0ae8af3503a   2009-10-10 08:00 +0100   foo
  |\     Merged branches
  ~ ~
  o  3   138bed2e14be   2009-10-10 08:00 +0100   foo
  |    Added brach2 file
  ~

BUG(?): The move seems to be recorded in rev 4, so it should probably show up
there.  It's not recorded as a move in rev 5, even in source-hg.

  $ hg -R source-hg up -q tip
  $ hg -R hg2hg up -q tip
  $ hg --cwd source-hg log -r 'follow("renamed")' -G -Tcompact
  @    5[tip]:4,3   6652429c300a   2009-10-10 08:00 +0100   foo
  |\     (octopus merge fixup)
  | :
  o :  3   138bed2e14be   2009-10-10 08:00 +0100   foo
  :/     Added brach2 file
  :
  o  0   18b86f5df51b   2009-10-10 08:00 +0100   foo
       Initial add
  
  $ hg --cwd hg2hg log -r 'follow("renamed")' -G -Tcompact
  o  3   138bed2e14be   2009-10-10 08:00 +0100   foo
  :    Added brach2 file
  :
  o  0   18b86f5df51b   2009-10-10 08:00 +0100   foo
       Initial add
  

  $ hg -R hg2hg out source-hg -T compact
  comparing with source-hg
  searching for changes
  5[tip]:4,3   3be2299ccd31   2009-10-10 08:00 +0100   foo
    (octopus merge fixup)
  

  $ glog -R hg2hg
  @    5@source "(octopus merge fixup)" files+: [], files-: [], files: []
  |\
  | o    4@source "Merged branches" files+: [file-branch2 renamed], files-: [rename_me], files: []
  | |\
  o---+  3@source-branch2 "Added brach2 file" files+: [file-branch2 renamed], files-: [rename_me], files: []
   / /
  | o  2@source "Added parent file" files+: [file-parent], files-: [], files: []
  | |
  o |  1@source-branch1 "Added branch1 file" files+: [file-branch1], files-: [], files: [file]
  |/
  o  0@source "Initial add" files+: [file rename_me], files-: [], files: []
  

  $ hg -R source-hg log --debug -r tip
  changeset:   5:6652429c300ab66fdeaf2e730945676a00b53231
  branch:      source
  tag:         tip
  phase:       draft
  parent:      4:e0ae8af3503af9bbffb0b29268a02744cc61a561
  parent:      3:138bed2e14be415a2692b02e41405b2864f758b4
  manifest:    5:1eabd5f5d4b985784cf2c45c717ff053eca14b0d
  user:        Foo Bar <[e-mail]>
  date:        Sat Oct 10 08:00:04 2009 +0100
  files:       renamed
  extra:       branch=source
  description:
  (octopus merge fixup)
  
  
  $ hg -R hg2hg log --debug -r tip
  changeset:   5:3be2299ccd315ff9aab2b49bdb0d14e3244435e8
  branch:      source
  tag:         tip
  phase:       draft
  parent:      4:e0ae8af3503af9bbffb0b29268a02744cc61a561
  parent:      3:138bed2e14be415a2692b02e41405b2864f758b4
  manifest:    4:3ece3c7f2cc6df15b3cbbf3273c69869fc7c3ab0
  user:        Foo Bar <[e-mail]>
  date:        Sat Oct 10 08:00:04 2009 +0100
  extra:       branch=source
  description:
  (octopus merge fixup)
  
  
  $ hg -R source-hg manifest --debug -r tip
  cdf31ed9242b209cd94697112160e2c5b37a667d 644   file
  5108144f585149b29779d7c7e51d61dd22303ffe 644   file-branch1
  80753c4a9ac3806858405b96b24a907b309e3616 644   file-branch2
  7108421418404a937c684d2479a34a24d2ce4757 644   file-parent
  67109fdebf6c556eb0a9d5696dd98c8420520405 644   renamed
  $ hg -R source-hg manifest --debug -r 'tip^'
  cdf31ed9242b209cd94697112160e2c5b37a667d 644   file
  5108144f585149b29779d7c7e51d61dd22303ffe 644   file-branch1
  80753c4a9ac3806858405b96b24a907b309e3616 644   file-branch2
  7108421418404a937c684d2479a34a24d2ce4757 644   file-parent
  27c968376d7c3afd095ecb9c7697919b933448c8 644   renamed

  $ hg -R hg2hg manifest --debug -r tip
  cdf31ed9242b209cd94697112160e2c5b37a667d 644   file
  5108144f585149b29779d7c7e51d61dd22303ffe 644   file-branch1
  80753c4a9ac3806858405b96b24a907b309e3616 644   file-branch2
  7108421418404a937c684d2479a34a24d2ce4757 644   file-parent
  27c968376d7c3afd095ecb9c7697919b933448c8 644   renamed
  $ hg -R hg2hg manifest --debug -r 'tip^'
  cdf31ed9242b209cd94697112160e2c5b37a667d 644   file
  5108144f585149b29779d7c7e51d61dd22303ffe 644   file-branch1
  80753c4a9ac3806858405b96b24a907b309e3616 644   file-branch2
  7108421418404a937c684d2479a34a24d2ce4757 644   file-parent
  27c968376d7c3afd095ecb9c7697919b933448c8 644   renamed

  $ cd ..