view tests/test-exchange-obsmarkers-case-C3.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

============================================
Testing obsolescence markers push: Cases C.3
============================================

Mercurial pushes obsolescences markers relevant to the "pushed-set", the set of
all changesets that requested to be "in sync" after the push (even if they are
already on both side).

This test belongs to a series of tests checking such set is properly computed
and applied. This does not tests "obsmarkers" discovery capabilities.

Category C: advanced case
TestCase 3: Pruned changeset on precursors of another pruned one
Variants:
# a: explicite push
# b: bare push

C.3 Pruned changeset on precursors of another pruned one
========================================================

.. {{{
..   B ⊗
..     |
..   A ø⇠⊗ A'
..     |/
..     ● O
.. }}}
..
.. Marker exist from:
..
..  * A' succeed to A
..  * A' (prune
..  * B (prune)
..
.. Command run:
..
..  * hg push -r A'
..  * hg push
..
.. Expected exchange:
..
..  * `A ø⇠⊗ A'`
..  * A (prune)
..  * B (prune)

Setup
-----

  $ . $TESTDIR/testlib/exchange-obsmarker-util.sh

Initial

  $ setuprepos C.3
  creating test repo for test case C.3
  - pulldest
  - main
  - pushdest
  cd into `main` and proceed with env setup
  $ cd main
  $ mkcommit A0
  $ mkcommit B
  $ hg prune -qd '0 0' .
  $ hg update -q 0
  $ mkcommit A1
  created new head
  $ hg debugobsolete `getid 'desc(A0)'` `getid 'desc(A1)'`
  1 new obsolescence markers
  obsoleted 1 changesets
  $ hg prune -qd '0 0' .
  $ hg log -G --hidden
  x  e5ea8f9c7314 (draft): A1
  |
  | x  06055a7959d4 (draft): B
  | |
  | x  28b51eb45704 (draft): A0
  |/
  @  a9bdc8b26820 (public): O
  
  $ inspect_obsmarkers
  obsstore content
  ================
  06055a7959d4128e6e3bccfd01482e83a2db8a3a 0 {28b51eb45704506b5c603decd6bf7ac5e0f6a52f} (Thu Jan 01 00:00:00 1970 +0000) {'user': 'test'}
  28b51eb45704506b5c603decd6bf7ac5e0f6a52f e5ea8f9c73143125d36658e90ef70c6d2027a5b7 0 (Thu Jan 01 00:00:00 1970 +0000) {'user': 'test'}
  e5ea8f9c73143125d36658e90ef70c6d2027a5b7 0 {a9bdc8b26820b1b87d585b82eb0ceb4a2ecdbc04} (Thu Jan 01 00:00:00 1970 +0000) {'user': 'test'}
  $ cd ..
  $ cd ..

  $ cp -R C.3 C.3.a
  $ cp -R C.3 C.3.b

Actual Test (explicit push)
---------------------------

  $ dotest C.3.a O
  ## Running testcase C.3.a
  # testing echange of "O" (a9bdc8b26820)
  ## initial state
  # obstore: main
  06055a7959d4128e6e3bccfd01482e83a2db8a3a 0 {28b51eb45704506b5c603decd6bf7ac5e0f6a52f} (Thu Jan 01 00:00:00 1970 +0000) {'user': 'test'}
  28b51eb45704506b5c603decd6bf7ac5e0f6a52f e5ea8f9c73143125d36658e90ef70c6d2027a5b7 0 (Thu Jan 01 00:00:00 1970 +0000) {'user': 'test'}
  e5ea8f9c73143125d36658e90ef70c6d2027a5b7 0 {a9bdc8b26820b1b87d585b82eb0ceb4a2ecdbc04} (Thu Jan 01 00:00:00 1970 +0000) {'user': 'test'}
  # obstore: pushdest
  # obstore: pulldest
  ## pushing "O" from main to pushdest
  pushing to pushdest
  searching for changes
  no changes found
  remote: 3 new obsolescence markers
  ## post push state
  # obstore: main
  06055a7959d4128e6e3bccfd01482e83a2db8a3a 0 {28b51eb45704506b5c603decd6bf7ac5e0f6a52f} (Thu Jan 01 00:00:00 1970 +0000) {'user': 'test'}
  28b51eb45704506b5c603decd6bf7ac5e0f6a52f e5ea8f9c73143125d36658e90ef70c6d2027a5b7 0 (Thu Jan 01 00:00:00 1970 +0000) {'user': 'test'}
  e5ea8f9c73143125d36658e90ef70c6d2027a5b7 0 {a9bdc8b26820b1b87d585b82eb0ceb4a2ecdbc04} (Thu Jan 01 00:00:00 1970 +0000) {'user': 'test'}
  # obstore: pushdest
  06055a7959d4128e6e3bccfd01482e83a2db8a3a 0 {28b51eb45704506b5c603decd6bf7ac5e0f6a52f} (Thu Jan 01 00:00:00 1970 +0000) {'user': 'test'}
  28b51eb45704506b5c603decd6bf7ac5e0f6a52f e5ea8f9c73143125d36658e90ef70c6d2027a5b7 0 (Thu Jan 01 00:00:00 1970 +0000) {'user': 'test'}
  e5ea8f9c73143125d36658e90ef70c6d2027a5b7 0 {a9bdc8b26820b1b87d585b82eb0ceb4a2ecdbc04} (Thu Jan 01 00:00:00 1970 +0000) {'user': 'test'}
  # obstore: pulldest
  ## pulling "a9bdc8b26820" from main into pulldest
  pulling from main
  no changes found
  3 new obsolescence markers
  ## post pull state
  # obstore: main
  06055a7959d4128e6e3bccfd01482e83a2db8a3a 0 {28b51eb45704506b5c603decd6bf7ac5e0f6a52f} (Thu Jan 01 00:00:00 1970 +0000) {'user': 'test'}
  28b51eb45704506b5c603decd6bf7ac5e0f6a52f e5ea8f9c73143125d36658e90ef70c6d2027a5b7 0 (Thu Jan 01 00:00:00 1970 +0000) {'user': 'test'}
  e5ea8f9c73143125d36658e90ef70c6d2027a5b7 0 {a9bdc8b26820b1b87d585b82eb0ceb4a2ecdbc04} (Thu Jan 01 00:00:00 1970 +0000) {'user': 'test'}
  # obstore: pushdest
  06055a7959d4128e6e3bccfd01482e83a2db8a3a 0 {28b51eb45704506b5c603decd6bf7ac5e0f6a52f} (Thu Jan 01 00:00:00 1970 +0000) {'user': 'test'}
  28b51eb45704506b5c603decd6bf7ac5e0f6a52f e5ea8f9c73143125d36658e90ef70c6d2027a5b7 0 (Thu Jan 01 00:00:00 1970 +0000) {'user': 'test'}
  e5ea8f9c73143125d36658e90ef70c6d2027a5b7 0 {a9bdc8b26820b1b87d585b82eb0ceb4a2ecdbc04} (Thu Jan 01 00:00:00 1970 +0000) {'user': 'test'}
  # obstore: pulldest
  06055a7959d4128e6e3bccfd01482e83a2db8a3a 0 {28b51eb45704506b5c603decd6bf7ac5e0f6a52f} (Thu Jan 01 00:00:00 1970 +0000) {'user': 'test'}
  28b51eb45704506b5c603decd6bf7ac5e0f6a52f e5ea8f9c73143125d36658e90ef70c6d2027a5b7 0 (Thu Jan 01 00:00:00 1970 +0000) {'user': 'test'}
  e5ea8f9c73143125d36658e90ef70c6d2027a5b7 0 {a9bdc8b26820b1b87d585b82eb0ceb4a2ecdbc04} (Thu Jan 01 00:00:00 1970 +0000) {'user': 'test'}

Actual Test (bare push)
-------------------------------------

  $ dotest C.3.b
  ## Running testcase C.3.b
  ## initial state
  # obstore: main
  06055a7959d4128e6e3bccfd01482e83a2db8a3a 0 {28b51eb45704506b5c603decd6bf7ac5e0f6a52f} (Thu Jan 01 00:00:00 1970 +0000) {'user': 'test'}
  28b51eb45704506b5c603decd6bf7ac5e0f6a52f e5ea8f9c73143125d36658e90ef70c6d2027a5b7 0 (Thu Jan 01 00:00:00 1970 +0000) {'user': 'test'}
  e5ea8f9c73143125d36658e90ef70c6d2027a5b7 0 {a9bdc8b26820b1b87d585b82eb0ceb4a2ecdbc04} (Thu Jan 01 00:00:00 1970 +0000) {'user': 'test'}
  # obstore: pushdest
  # obstore: pulldest
  ## pushing from main to pushdest
  pushing to pushdest
  searching for changes
  no changes found
  remote: 3 new obsolescence markers
  ## post push state
  # obstore: main
  06055a7959d4128e6e3bccfd01482e83a2db8a3a 0 {28b51eb45704506b5c603decd6bf7ac5e0f6a52f} (Thu Jan 01 00:00:00 1970 +0000) {'user': 'test'}
  28b51eb45704506b5c603decd6bf7ac5e0f6a52f e5ea8f9c73143125d36658e90ef70c6d2027a5b7 0 (Thu Jan 01 00:00:00 1970 +0000) {'user': 'test'}
  e5ea8f9c73143125d36658e90ef70c6d2027a5b7 0 {a9bdc8b26820b1b87d585b82eb0ceb4a2ecdbc04} (Thu Jan 01 00:00:00 1970 +0000) {'user': 'test'}
  # obstore: pushdest
  06055a7959d4128e6e3bccfd01482e83a2db8a3a 0 {28b51eb45704506b5c603decd6bf7ac5e0f6a52f} (Thu Jan 01 00:00:00 1970 +0000) {'user': 'test'}
  28b51eb45704506b5c603decd6bf7ac5e0f6a52f e5ea8f9c73143125d36658e90ef70c6d2027a5b7 0 (Thu Jan 01 00:00:00 1970 +0000) {'user': 'test'}
  e5ea8f9c73143125d36658e90ef70c6d2027a5b7 0 {a9bdc8b26820b1b87d585b82eb0ceb4a2ecdbc04} (Thu Jan 01 00:00:00 1970 +0000) {'user': 'test'}
  # obstore: pulldest
  ## pulling from main into pulldest
  pulling from main
  searching for changes
  no changes found
  3 new obsolescence markers
  ## post pull state
  # obstore: main
  06055a7959d4128e6e3bccfd01482e83a2db8a3a 0 {28b51eb45704506b5c603decd6bf7ac5e0f6a52f} (Thu Jan 01 00:00:00 1970 +0000) {'user': 'test'}
  28b51eb45704506b5c603decd6bf7ac5e0f6a52f e5ea8f9c73143125d36658e90ef70c6d2027a5b7 0 (Thu Jan 01 00:00:00 1970 +0000) {'user': 'test'}
  e5ea8f9c73143125d36658e90ef70c6d2027a5b7 0 {a9bdc8b26820b1b87d585b82eb0ceb4a2ecdbc04} (Thu Jan 01 00:00:00 1970 +0000) {'user': 'test'}
  # obstore: pushdest
  06055a7959d4128e6e3bccfd01482e83a2db8a3a 0 {28b51eb45704506b5c603decd6bf7ac5e0f6a52f} (Thu Jan 01 00:00:00 1970 +0000) {'user': 'test'}
  28b51eb45704506b5c603decd6bf7ac5e0f6a52f e5ea8f9c73143125d36658e90ef70c6d2027a5b7 0 (Thu Jan 01 00:00:00 1970 +0000) {'user': 'test'}
  e5ea8f9c73143125d36658e90ef70c6d2027a5b7 0 {a9bdc8b26820b1b87d585b82eb0ceb4a2ecdbc04} (Thu Jan 01 00:00:00 1970 +0000) {'user': 'test'}
  # obstore: pulldest
  06055a7959d4128e6e3bccfd01482e83a2db8a3a 0 {28b51eb45704506b5c603decd6bf7ac5e0f6a52f} (Thu Jan 01 00:00:00 1970 +0000) {'user': 'test'}
  28b51eb45704506b5c603decd6bf7ac5e0f6a52f e5ea8f9c73143125d36658e90ef70c6d2027a5b7 0 (Thu Jan 01 00:00:00 1970 +0000) {'user': 'test'}
  e5ea8f9c73143125d36658e90ef70c6d2027a5b7 0 {a9bdc8b26820b1b87d585b82eb0ceb4a2ecdbc04} (Thu Jan 01 00:00:00 1970 +0000) {'user': 'test'}