view tests/test-narrow-trackedcmd.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

#testcases flat tree
  $ . "$TESTDIR/narrow-library.sh"

#if tree
  $ cat << EOF >> $HGRCPATH
  > [experimental]
  > treemanifest = 1
  > EOF
#endif

  $ hg init master
  $ cd master
  $ cat >> .hg/hgrc <<EOF
  > [narrow]
  > serveellipses=True
  > EOF

  $ mkdir inside
  $ echo 'inside' > inside/f
  $ hg add inside/f
  $ hg commit -m 'add inside'

  $ mkdir widest
  $ echo 'widest' > widest/f
  $ hg add widest/f
  $ hg commit -m 'add widest'

  $ mkdir outside
  $ echo 'outside' > outside/f
  $ hg add outside/f
  $ hg commit -m 'add outside'

  $ cd ..

narrow clone the inside file

  $ hg clone --narrow ssh://user@dummy/master narrow --include inside
  requesting all changes
  adding changesets
  adding manifests
  adding file changes
  added 2 changesets with 1 changes to 1 files
  new changesets *:* (glob)
  updating to branch default
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ cd narrow
  $ hg tracked
  I path:inside
  $ ls
  inside
  $ cat inside/f
  inside
  $ cd ..

add more upstream files which we will include in a wider narrow spec

  $ cd master

  $ mkdir wider
  $ echo 'wider' > wider/f
  $ hg add wider/f
  $ echo 'widest v2' > widest/f
  $ hg commit -m 'add wider, update widest'

  $ echo 'widest v3' > widest/f
  $ hg commit -m 'update widest v3'

  $ echo 'inside v2' > inside/f
  $ hg commit -m 'update inside'

  $ mkdir outside2
  $ echo 'outside2' > outside2/f
  $ hg add outside2/f
  $ hg commit -m 'add outside2'

  $ echo 'widest v4' > widest/f
  $ hg commit -m 'update widest v4'

  $ hg log -T "{if(ellipsis, '...')}{rev}: {desc}\n"
  7: update widest v4
  6: add outside2
  5: update inside
  4: update widest v3
  3: add wider, update widest
  2: add outside
  1: add widest
  0: add inside

  $ cd ..

Testing the --import-rules flag of `hg tracked` command

  $ cd narrow
  $ hg tracked --import-rules
  hg tracked: option --import-rules requires argument
  hg tracked [OPTIONS]... [REMOTE]
  
  show or change the current narrowspec
  
  options ([+] can be repeated):
  
      --addinclude VALUE [+]       new paths to include
      --removeinclude VALUE [+]    old paths to no longer include
      --auto-remove-includes       automatically choose unused includes to
                                   remove
      --addexclude VALUE [+]       new paths to exclude
      --import-rules VALUE         import narrowspecs from a file
      --removeexclude VALUE [+]    old paths to no longer exclude
      --clear                      whether to replace the existing narrowspec
      --force-delete-local-changes forces deletion of local changes when
                                   narrowing
      --update-working-copy        update working copy when the store has
                                   changed
   -e --ssh CMD                    specify ssh command to use
      --remotecmd CMD              specify hg command to run on the remote side
      --insecure                   do not verify server certificate (ignoring
                                   web.cacerts config)
  
  (use 'hg tracked -h' to show more help)
  [255]
  $ hg tracked --import-rules doesnotexist
  abort: cannot read narrowspecs from '$TESTTMP/narrow/doesnotexist': $ENOENT$
  [255]

  $ cat > specs <<EOF
  > %include foo
  > [include]
  > path:widest/
  > [exclude]
  > path:inside/
  > EOF

  $ hg tracked --import-rules specs
  abort: including other spec files using '%include' is not supported in narrowspec
  [255]

  $ cat > specs <<EOF
  > [include]
  > outisde
  > [exclude]
  > inside
  > EOF

  $ hg tracked --import-rules specs
  comparing with ssh://user@dummy/master
  searching for changes
  looking for local changes to affected paths
  deleting data/inside/f.i
  deleting meta/inside/00manifest.i (tree !)
  saved backup bundle to $TESTTMP/narrow/.hg/strip-backup/*-widen.hg (glob)
  adding changesets
  adding manifests
  adding file changes
  added 2 changesets with 0 changes to 0 files
  $ hg tracked
  I path:outisde
  X path:inside

Testing the --import-rules flag with --addinclude and --addexclude

  $ cat > specs <<EOF
  > [include]
  > widest
  > EOF

  $ hg tracked --import-rules specs --addinclude 'wider/'
  comparing with ssh://user@dummy/master
  searching for changes
  saved backup bundle to $TESTTMP/narrow/.hg/strip-backup/*-widen.hg (glob)
  adding changesets
  adding manifests
  adding file changes
  added 3 changesets with 1 changes to 1 files
  $ hg tracked
  I path:outisde
  I path:wider
  I path:widest
  X path:inside

  $ cat > specs <<EOF
  > [exclude]
  > outside2
  > EOF

  $ hg tracked --import-rules specs --addexclude 'widest'
  comparing with ssh://user@dummy/master
  searching for changes
  looking for local changes to affected paths
  deleting data/widest/f.i
  deleting meta/widest/00manifest.i (tree !)
  $ hg tracked
  I path:outisde
  I path:wider
  X path:inside
  X path:outside2
  X path:widest

  $ hg tracked --import-rules specs --clear
  abort: the --clear option is not yet supported
  [255]

Testing with passing a out of wdir file

  $ cat > ../nspecs <<EOF
  > [include]
  > widest
  > EOF

  $ hg tracked --import-rules ../nspecs
  comparing with ssh://user@dummy/master
  searching for changes
  saved backup bundle to $TESTTMP/narrow/.hg/strip-backup/*-widen.hg (glob)
  adding changesets
  adding manifests
  adding file changes
  added 3 changesets with 0 changes to 0 files

  $ cd ..

Testing tracked command on a non-narrow repo

  $ hg init non-narrow
  $ cd non-narrow
  $ hg tracked --addinclude foobar
  abort: the tracked command is only supported on repositories cloned with --narrow
  [255]