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Differential D4711

localrepo: automatically load lfs extension when required (BC)
ClosedPublic

Authored by indygreg on Sep 24 2018, 12:12 PM.

Details

Reviewers
mharbison72
Group Reviewers
hg-reviewers
Commits
rHG2c2fadbc9851: localrepo: automatically load lfs extension when required (BC)
Summary

If an unrecognized requirement is present (possibly due to an unloaded
extension), the user will get an error message telling them to go to
https://mercurial-scm.org/wiki/MissingRequirement for more info.

And some requirements clearly map to known extensions shipped by
Mercurial.

This commit teaches repository loading to automatically map
requirements to extensions. We implement support for loading the
lfs extension when the "lfs" requirement is present.

This behavior feels more user-friendly to me and I'm having trouble
coming up with a compelling reason to not do it. The strongest
argument I have against is that - strictly speaking - requirements
are general repository features and there could be N providers of that
feature. e.g. in the case of LFS, there could be another extension
implementing LFS support. And the user would want to use this
non-official extension rather than the built-in one. The way this
patch implements things, the non-official extension could be
missing and Mercurial would load the official lfs extension, leading
to unexpected behavior. But this feels like a highly marginal use
case to me and doesn't outweigh the user benefit of "it just works."
If someone really wanted to e.g. use a custom LFS extension, they
could prevent the built-in one from being loaded by either defining
"extensions.lfs=/path/to/custom/extension" or "extensions.lfs=!",
as the automatic extension loading only occurs if there is no config
entry for that extension.

Diff Detail

Repository
rHG Mercurial
Lint
Automatic diff as part of commit; lint not applicable.
Unit
Automatic diff as part of commit; unit tests not applicable.

Event Timeline

indygreg created this revision.Sep 24 2018, 12:12 PM
mharbison72 accepted this revision.Sep 25 2018, 12:23 AM
mharbison72 added a subscriber: mharbison72.

I agree with the rationale. Thanks for this.

I guess we need to figure out how to handle push/pull upgrades before doing the same to clone, because all 3 need a wire protocol capability to work. And if we unconditionally register that in core, we bypass the nice error message that comes out (and the early failure I think).

indygreg added a comment.Sep 25 2018, 12:04 PM

I actually wrote the patch to add the lfs requirement on clone. However, the way lfs is advertised on the server is a bit buggy. See https://hg.mozilla.org/users/gszorc_mozilla.com/hg/rev/d39bf70535a5.

I could solve this problem if I wanted to. But I have other aspects of the code I'd prefer to work on.

mharbison72 added a comment.Sep 25 2018, 12:27 PM
In D4711#71787, @indygreg wrote:

I actually wrote the patch to add the lfs requirement on clone. However, the way lfs is advertised on the server is a bit buggy. See https://hg.mozilla.org/users/gszorc_mozilla.com/hg/rev/d39bf70535a5.
I could solve this problem if I wanted to. But I have other aspects of the code I'd prefer to work on.

Maybe that got rewritten? I get this error:

An error occurred while processing your request

filtered revision 'd39bf70535a5' (not in 'served' subset)

I can take a look at it so you don’t get too far off track.

indygreg added a comment.Sep 25 2018, 12:30 PM

It did. https://hg.mozilla.org/users/gszorc_mozilla.com/hg/rev/65175a0 is the new version. (It probably won't last through the day though.)

(Maybe hgweb could link obsolescence changesets to their successors...)

Closed by commit rHG2c2fadbc9851: localrepo: automatically load lfs extension when required (BC) (authored by indygreg). · Explain WhySep 26 2018, 1:23 PM
This revision was automatically updated to reflect the committed changes.

Revision Contents
Changeset List

PathPackages
Mmercurial/localrepo.py (27 lines)
Mtests/test-lfs.t (47 lines)

Diff 11383

mercurial/localrepo.py

raise raise
requirements = set() requirements = set()
# The .hg/hgrc file may load extensions or contain config options # The .hg/hgrc file may load extensions or contain config options
# that influence repository construction. Attempt to load it and # that influence repository construction. Attempt to load it and
# process any new extensions that it may have pulled in. # process any new extensions that it may have pulled in.
try: try:
ui.readconfig(hgvfs.join(b'hgrc'), root=wdirvfs.base) ui.readconfig(hgvfs.join(b'hgrc'), root=wdirvfs.base)
# Run this before extensions.loadall() so extensions can be
# automatically enabled.
afterhgrcload(ui, wdirvfs, hgvfs, requirements)
except IOError: except IOError:
pass pass
else: else:
extensions.loadall(ui) extensions.loadall(ui)
# Set of module names of extensions loaded for this repository. # Set of module names of extensions loaded for this repository.
extensionmodulenames = {m.__name__ for n, m in extensions.extensions(ui)} extensionmodulenames = {m.__name__ for n, m in extensions.extensions(ui)}
requirements=requirements, requirements=requirements,
supportedrequirements=supportedrequirements, supportedrequirements=supportedrequirements,
sharedpath=storebasepath, sharedpath=storebasepath,
store=store, store=store,
cachevfs=cachevfs, cachevfs=cachevfs,
features=features, features=features,
intents=intents) intents=intents)
def afterhgrcload(ui, wdirvfs, hgvfs, requirements):
"""Perform additional actions after .hg/hgrc is loaded.
This function is called during repository loading immediately after
the .hg/hgrc file is loaded and before per-repo extensions are loaded.
The function can be used to validate configs, automatically add
options (including extensions) based on requirements, etc.
"""
# Map of requirements to list of extensions to load automatically when
# requirement is present.
autoextensions = {
b'lfs': [b'lfs'],
}
for requirement, names in sorted(autoextensions.items()):
if requirement not in requirements:
continue
for name in names:
if not ui.hasconfig(b'extensions', name):
ui.setconfig(b'extensions', name, b'', source='autoload')
def gathersupportedrequirements(ui): def gathersupportedrequirements(ui):
"""Determine the complete set of recognized requirements.""" """Determine the complete set of recognized requirements."""
# Start with all requirements supported by this file. # Start with all requirements supported by this file.
supported = set(localrepository._basesupported) supported = set(localrepository._basesupported)
# Execute ``featuresetupfuncs`` entries if they belong to an extension # Execute ``featuresetupfuncs`` entries if they belong to an extension
# relevant to this ui instance. # relevant to this ui instance.
modules = {m.__name__ for n, m in extensions.extensions(ui)} modules = {m.__name__ for n, m in extensions.extensions(ui)}

tests/test-lfs.t

#require no-reposimplestore no-chg #require no-reposimplestore no-chg
$ hg init requirements
$ cd requirements
# LFS not loaded by default.
$ hg config extensions
[1]
# Adding lfs to requires file will auto-load lfs extension.
$ echo lfs >> .hg/requires
$ hg config extensions
extensions.lfs=
# But only if there is no config entry for the extension already.
$ cat > .hg/hgrc << EOF
> [extensions]
> lfs=!
> EOF
$ hg config extensions
abort: repository requires features unknown to this Mercurial: lfs!
(see https://mercurial-scm.org/wiki/MissingRequirement for more information)
[255]
$ cat > .hg/hgrc << EOF
> [extensions]
> lfs=
> EOF
$ hg config extensions
extensions.lfs=
$ cat > .hg/hgrc << EOF
> [extensions]
> lfs = missing.py
> EOF
$ hg config extensions
*** failed to import extension lfs from missing.py: [Errno 2] $ENOENT$: 'missing.py'
abort: repository requires features unknown to this Mercurial: lfs!
(see https://mercurial-scm.org/wiki/MissingRequirement for more information)
[255]
$ cd ..
# Initial setup # Initial setup
$ cat >> $HGRCPATH << EOF $ cat >> $HGRCPATH << EOF
> [extensions] > [extensions]
> lfs= > lfs=
> [lfs] > [lfs]
> # Test deprecated config > # Test deprecated config
> threshold=1000B > threshold=1000B