view tests/test-install.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

hg debuginstall
  $ hg debuginstall
  checking encoding (ascii)...
  checking Python executable (*) (glob)
  checking Python version (2.*) (glob) (no-py3 !)
  checking Python version (3.*) (glob) (py3 !)
  checking Python lib (.*[Ll]ib.*)... (re)
  checking Python security support (*) (glob)
    TLS 1.2 not supported by Python install; network connections lack modern security (?)
    SNI not supported by Python install; may have connectivity issues with some servers (?)
  checking Mercurial version (*) (glob)
  checking Mercurial custom build (*) (glob)
  checking module policy (*) (glob)
  checking installed modules (*mercurial)... (glob)
  checking registered compression engines (*zlib*) (glob)
  checking available compression engines (*zlib*) (glob)
  checking available compression engines for wire protocol (*zlib*) (glob)
  checking "re2" regexp engine \((available|missing)\) (re)
  checking templates (*mercurial?templates)... (glob)
  checking default template (*mercurial?templates?map-cmdline.default) (glob)
  checking commit editor... (*) (glob)
  checking username (test)
  no problems detected

hg debuginstall JSON
  $ hg debuginstall -Tjson | sed 's|\\\\|\\|g'
  [
   {
    "compengines": ["bz2", "bz2truncated", "none", "zlib"*], (glob)
    "compenginesavail": ["bz2", "bz2truncated", "none", "zlib"*], (glob)
    "compenginesserver": [*"zlib"*], (glob)
    "defaulttemplate": "*mercurial?templates?map-cmdline.default", (glob)
    "defaulttemplateerror": null,
    "defaulttemplatenotfound": "default",
    "editor": "*", (glob)
    "editornotfound": false,
    "encoding": "ascii",
    "encodingerror": null,
    "extensionserror": null, (no-pure !)
    "hgmodulepolicy": "*", (glob)
    "hgmodules": "*mercurial", (glob)
    "hgver": "*", (glob)
    "hgverextra": "*", (glob)
    "problems": 0,
    "pythonexe": "*", (glob)
    "pythonlib": "*", (glob)
    "pythonsecurity": [*], (glob)
    "pythonver": "*.*.*", (glob)
    "re2": (true|false), (re)
    "templatedirs": "*mercurial?templates", (glob)
    "username": "test",
    "usernameerror": null,
    "vinotfound": false
   }
  ]

hg debuginstall with no username
  $ HGUSER= hg debuginstall
  checking encoding (ascii)...
  checking Python executable (*) (glob)
  checking Python version (2.*) (glob) (no-py3 !)
  checking Python version (3.*) (glob) (py3 !)
  checking Python lib (.*[Ll]ib.*)... (re)
  checking Python security support (*) (glob)
    TLS 1.2 not supported by Python install; network connections lack modern security (?)
    SNI not supported by Python install; may have connectivity issues with some servers (?)
  checking Mercurial version (*) (glob)
  checking Mercurial custom build (*) (glob)
  checking module policy (*) (glob)
  checking installed modules (*mercurial)... (glob)
  checking registered compression engines (*zlib*) (glob)
  checking available compression engines (*zlib*) (glob)
  checking available compression engines for wire protocol (*zlib*) (glob)
  checking "re2" regexp engine \((available|missing)\) (re)
  checking templates (*mercurial?templates)... (glob)
  checking default template (*mercurial?templates?map-cmdline.default) (glob)
  checking commit editor... (*) (glob)
  checking username...
   no username supplied
   (specify a username in your configuration file)
  1 problems detected, please check your install!
  [1]

hg debuginstall with invalid encoding
  $ HGENCODING=invalidenc hg debuginstall | grep encoding
  checking encoding (invalidenc)...
   unknown encoding: invalidenc

exception message in JSON

  $ HGENCODING=invalidenc HGUSER= hg debuginstall -Tjson | grep error
    "defaulttemplateerror": null,
    "encodingerror": "unknown encoding: invalidenc",
    "extensionserror": null, (no-pure !)
    "usernameerror": "no username supplied",

path variables are expanded (~ is the same as $TESTTMP)
  $ mkdir tools
  $ touch tools/testeditor.exe
#if execbit
  $ chmod 755 tools/testeditor.exe
#endif
  $ HGEDITOR="~/tools/testeditor.exe" hg debuginstall
  checking encoding (ascii)...
  checking Python executable (*) (glob)
  checking Python version (2.*) (glob) (no-py3 !)
  checking Python version (3.*) (glob) (py3 !)
  checking Python lib (.*[Ll]ib.*)... (re)
  checking Python security support (*) (glob)
    TLS 1.2 not supported by Python install; network connections lack modern security (?)
    SNI not supported by Python install; may have connectivity issues with some servers (?)
  checking Mercurial version (*) (glob)
  checking Mercurial custom build (*) (glob)
  checking module policy (*) (glob)
  checking installed modules (*mercurial)... (glob)
  checking registered compression engines (*zlib*) (glob)
  checking available compression engines (*zlib*) (glob)
  checking available compression engines for wire protocol (*zlib*) (glob)
  checking "re2" regexp engine \((available|missing)\) (re)
  checking templates (*mercurial?templates)... (glob)
  checking default template (*mercurial?templates?map-cmdline.default) (glob)
  checking commit editor... ($TESTTMP/tools/testeditor.exe)
  checking username (test)
  no problems detected

print out the binary post-shlexsplit in the error message when commit editor is
not found (this is intentionally using backslashes to mimic a windows usecase).
  $ HGEDITOR="c:\foo\bar\baz.exe -y -z" hg debuginstall
  checking encoding (ascii)...
  checking Python executable (*) (glob)
  checking Python version (2.*) (glob) (no-py3 !)
  checking Python version (3.*) (glob) (py3 !)
  checking Python lib (.*[Ll]ib.*)... (re)
  checking Python security support (*) (glob)
    TLS 1.2 not supported by Python install; network connections lack modern security (?)
    SNI not supported by Python install; may have connectivity issues with some servers (?)
  checking Mercurial version (*) (glob)
  checking Mercurial custom build (*) (glob)
  checking module policy (*) (glob)
  checking installed modules (*mercurial)... (glob)
  checking registered compression engines (*zlib*) (glob)
  checking available compression engines (*zlib*) (glob)
  checking available compression engines for wire protocol (*zlib*) (glob)
  checking "re2" regexp engine \((available|missing)\) (re)
  checking templates (*mercurial?templates)... (glob)
  checking default template (*mercurial?templates?map-cmdline.default) (glob)
  checking commit editor... (c:\foo\bar\baz.exe) (windows !)
   Can't find editor 'c:\foo\bar\baz.exe' in PATH (windows !)
  checking commit editor... (c:foobarbaz.exe) (no-windows !)
   Can't find editor 'c:foobarbaz.exe' in PATH (no-windows !)
   (specify a commit editor in your configuration file)
  checking username (test)
  1 problems detected, please check your install!
  [1]

debuginstall extension support
  $ hg debuginstall --config extensions.fsmonitor= --config fsmonitor.watchman_exe=false | grep atchman
  fsmonitor checking for watchman binary... (false)
   watchman binary missing or broken: warning: Watchman unavailable: watchman exited with code 1
Verify the json works too:
  $ hg debuginstall --config extensions.fsmonitor= --config fsmonitor.watchman_exe=false -Tjson | grep atchman
    "fsmonitor-watchman": "false",
    "fsmonitor-watchman-error": "warning: Watchman unavailable: watchman exited with code 1",

Verify that Mercurial is installable with pip. Note that this MUST be
the last test in this file, because we do some nasty things to the
shell environment in order to make the virtualenv work reliably.

On Python 3, we use the venv module, which is part of the standard library.
But some Linux distros strip out this module's functionality involving pip,
so we have to look for the ensurepip module, which these distros strip out
completely.
On Python 2, we use the 3rd party virtualenv module, if available.

  $ cd $TESTTMP
  $ unset PYTHONPATH

#if py3 ensurepip
  $ "$PYTHON" -m venv installenv >> pip.log

Note: we use this weird path to run pip and hg to avoid platform differences,
since it's bin on most platforms but Scripts on Windows.
  $ ./installenv/*/pip install --no-index $TESTDIR/.. >> pip.log
    Failed building wheel for mercurial (?)
  $ ./installenv/*/hg debuginstall || cat pip.log
  checking encoding (ascii)...
  checking Python executable (*) (glob)
  checking Python version (3.*) (glob)
  checking Python lib (*)... (glob)
  checking Python security support (*) (glob)
  checking Mercurial version (*) (glob)
  checking Mercurial custom build (*) (glob)
  checking module policy (*) (glob)
  checking installed modules (*/mercurial)... (glob)
  checking registered compression engines (*) (glob)
  checking available compression engines (*) (glob)
  checking available compression engines for wire protocol (*) (glob)
  checking "re2" regexp engine \((available|missing)\) (re)
  checking templates ($TESTTMP/installenv/*/site-packages/mercurial/templates)... (glob)
  checking default template ($TESTTMP/installenv/*/site-packages/mercurial/templates/map-cmdline.default) (glob)
  checking commit editor... (*) (glob)
  checking username (test)
  no problems detected
#endif

#if no-py3 virtualenv

Note: --no-site-packages is deprecated, but some places have an
ancient virtualenv from their linux distro or similar and it's not yet
the default for them.

  $ "$PYTHON" -m virtualenv --no-site-packages --never-download installenv >> pip.log
  DEPRECATION: Python 2.7 will reach the end of its life on January 1st, 2020. Please upgrade your Python as Python 2.7 won't be maintained after that date. A future version of pip will drop support for Python 2.7. (?)
  DEPRECATION: Python 2.7 will reach the end of its life on January 1st, 2020. Please upgrade your Python as Python 2.7 won't be maintained after that date. A future version of pip will drop support for Python 2.7. More details about Python 2 support in pip, can be found at https://pip.pypa.io/en/latest/development/release-process/#python-2-support (?)

Note: we use this weird path to run pip and hg to avoid platform differences,
since it's bin on most platforms but Scripts on Windows.
  $ ./installenv/*/pip install --no-index $TESTDIR/.. >> pip.log
  DEPRECATION: Python 2.7 will reach the end of its life on January 1st, 2020. Please upgrade your Python as Python 2.7 won't be maintained after that date. A future version of pip will drop support for Python 2.7. (?)
  DEPRECATION: Python 2.7 will reach the end of its life on January 1st, 2020. Please upgrade your Python as Python 2.7 won't be maintained after that date. A future version of pip will drop support for Python 2.7. More details about Python 2 support in pip, can be found at https://pip.pypa.io/en/latest/development/release-process/#python-2-support (?)
  $ ./installenv/*/hg debuginstall || cat pip.log
  checking encoding (ascii)...
  checking Python executable (*) (glob)
  checking Python version (2.*) (glob)
  checking Python lib (*)... (glob)
  checking Python security support (*) (glob)
    TLS 1.2 not supported by Python install; network connections lack modern security (?)
    SNI not supported by Python install; may have connectivity issues with some servers (?)
  checking Mercurial version (*) (glob)
  checking Mercurial custom build (*) (glob)
  checking module policy (*) (glob)
  checking installed modules (*/mercurial)... (glob)
  checking registered compression engines (*) (glob)
  checking available compression engines (*) (glob)
  checking available compression engines for wire protocol (*) (glob)
  checking "re2" regexp engine \((available|missing)\) (re)
  checking templates ($TESTTMP/installenv/*/site-packages/mercurial/templates)... (glob)
  checking default template ($TESTTMP/installenv/*/site-packages/mercurial/templates/map-cmdline.default) (glob)
  checking commit editor... (*) (glob)
  checking username (test)
  no problems detected
#endif