view tests/test-purge.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

  $ cat <<EOF >> $HGRCPATH
  > [extensions]
  > purge =
  > EOF

init

  $ hg init t
  $ cd t

setup

  $ echo r1 > r1
  $ hg ci -qAmr1 -d'0 0'
  $ mkdir directory
  $ echo r2 > directory/r2
  $ hg ci -qAmr2 -d'1 0'
  $ echo 'ignored' > .hgignore
  $ hg ci -qAmr3 -d'2 0'

delete an empty directory

  $ mkdir empty_dir
  $ hg purge -p -v
  empty_dir
  $ hg purge -v
  removing directory empty_dir
  $ ls
  directory
  r1

delete an untracked directory

  $ mkdir untracked_dir
  $ touch untracked_dir/untracked_file1
  $ touch untracked_dir/untracked_file2
  $ hg purge -p
  untracked_dir/untracked_file1
  untracked_dir/untracked_file2
  $ hg purge -v
  removing file untracked_dir/untracked_file1
  removing file untracked_dir/untracked_file2
  removing directory untracked_dir
  $ ls
  directory
  r1

delete an untracked file

  $ touch untracked_file
  $ touch untracked_file_readonly
  $ "$PYTHON" <<EOF
  > import os
  > import stat
  > f = 'untracked_file_readonly'
  > os.chmod(f, stat.S_IMODE(os.stat(f).st_mode) & ~stat.S_IWRITE)
  > EOF
  $ hg purge -p
  untracked_file
  untracked_file_readonly
  $ hg purge -v
  removing file untracked_file
  removing file untracked_file_readonly
  $ ls
  directory
  r1

delete an untracked file in a tracked directory

  $ touch directory/untracked_file
  $ hg purge -p
  directory/untracked_file
  $ hg purge -v
  removing file directory/untracked_file
  $ ls
  directory
  r1

delete nested directories

  $ mkdir -p untracked_directory/nested_directory
  $ hg purge -p
  untracked_directory/nested_directory
  $ hg purge -v
  removing directory untracked_directory/nested_directory
  removing directory untracked_directory
  $ ls
  directory
  r1

delete nested directories from a subdir

  $ mkdir -p untracked_directory/nested_directory
  $ cd directory
  $ hg purge -p
  untracked_directory/nested_directory
  $ hg purge -v
  removing directory untracked_directory/nested_directory
  removing directory untracked_directory
  $ cd ..
  $ ls
  directory
  r1

delete only part of the tree

  $ mkdir -p untracked_directory/nested_directory
  $ touch directory/untracked_file
  $ cd directory
  $ hg purge -p ../untracked_directory
  untracked_directory/nested_directory
  $ hg purge -v ../untracked_directory
  removing directory untracked_directory/nested_directory
  removing directory untracked_directory
  $ cd ..
  $ ls
  directory
  r1
  $ ls directory/untracked_file
  directory/untracked_file
  $ rm directory/untracked_file

skip ignored files if --all not specified

  $ touch ignored
  $ hg purge -p
  $ hg purge -v
  $ ls
  directory
  ignored
  r1
  $ hg purge -p --all
  ignored
  $ hg purge -v --all
  removing file ignored
  $ ls
  directory
  r1

abort with missing files until we support name mangling filesystems

  $ touch untracked_file
  $ rm r1

hide error messages to avoid changing the output when the text changes

  $ hg purge -p 2> /dev/null
  untracked_file
  $ hg st
  ! r1
  ? untracked_file

  $ hg purge -p
  untracked_file
  $ hg purge -v 2> /dev/null
  removing file untracked_file
  $ hg st
  ! r1

  $ hg purge -v
  $ hg revert --all --quiet
  $ hg st -a

tracked file in ignored directory (issue621)

  $ echo directory >> .hgignore
  $ hg ci -m 'ignore directory'
  $ touch untracked_file
  $ hg purge -p
  untracked_file
  $ hg purge -v
  removing file untracked_file

skip excluded files

  $ touch excluded_file
  $ hg purge -p -X excluded_file
  $ hg purge -v -X excluded_file
  $ ls
  directory
  excluded_file
  r1
  $ rm excluded_file

skip files in excluded dirs

  $ mkdir excluded_dir
  $ touch excluded_dir/file
  $ hg purge -p -X excluded_dir
  $ hg purge -v -X excluded_dir
  $ ls
  directory
  excluded_dir
  r1
  $ ls excluded_dir
  file
  $ rm -R excluded_dir

skip excluded empty dirs

  $ mkdir excluded_dir
  $ hg purge -p -X excluded_dir
  $ hg purge -v -X excluded_dir
  $ ls
  directory
  excluded_dir
  r1
  $ rmdir excluded_dir

skip patterns

  $ mkdir .svn
  $ touch .svn/foo
  $ mkdir directory/.svn
  $ touch directory/.svn/foo
  $ hg purge -p -X .svn -X '*/.svn'
  $ hg purge -p -X re:.*.svn

  $ rm -R .svn directory r1

only remove files

  $ mkdir -p empty_dir dir
  $ touch untracked_file dir/untracked_file
  $ hg purge -p --files
  dir/untracked_file
  untracked_file
  $ hg purge -v --files
  removing file dir/untracked_file
  removing file untracked_file
  $ ls
  dir
  empty_dir
  $ ls dir

only remove dirs

  $ mkdir -p empty_dir dir
  $ touch untracked_file dir/untracked_file
  $ hg purge -p --dirs
  empty_dir
  $ hg purge -v --dirs
  removing directory empty_dir
  $ ls
  dir
  untracked_file
  $ ls dir
  untracked_file

remove both files and dirs

  $ mkdir -p empty_dir dir
  $ touch untracked_file dir/untracked_file
  $ hg purge -p --files --dirs
  dir/untracked_file
  untracked_file
  empty_dir
  $ hg purge -v --files --dirs
  removing file dir/untracked_file
  removing file untracked_file
  removing directory empty_dir
  removing directory dir
  $ ls

  $ cd ..