Mercurial > hg
view mercurial/help/hg.1.txt @ 29375:fcaf20175b1b
demandimport: delay loading for "from a import b" with absolute_import
Before this patch, "from a import b" doesn't delay loading module "b",
if absolute_import is enabled, even though "from . import b" does.
For example:
- it is assumed that extension X has "from P import M" for module M
under package P with absolute_import feature
- if importing module M is already delayed before loading extension
X, loading module M in extension X is delayed until actually
referring
util, cmdutil, scmutil or so of Mercurial itself should be
imported by "from . import M" style before loading extension X
- otherwise, module M is loaded immediately at loading extension X,
even if extension X itself isn't used at that "hg" command invocation
Some minor modules (e.g. filemerge or so) of Mercurial itself
aren't imported by "from . import M" style before loading
extension X. And of course, external libraries aren't, too.
This might cause startup performance problem of hg command, because
many bundled extensions already enable absolute_import feature.
To delay loading module for "from a import b" with absolute_import
feature, this patch does below in "from a (or .a) import b" with
absolute_import case:
1. import root module of "name" by system built-in __import__
(referred as _origimport)
2. recurse down the module chain for hierarchical "name"
This logic can be shared with non absolute_import
case. Therefore, this patch also centralizes it into chainmodules().
3. and fall through to process elements in "fromlist" for the leaf
module of "name"
Processing elements in "fromlist" is executed in the code path
after "if _pypy: .... else: ..." clause. Therefore, this patch
replaces "if _pypy:" with "elif _pypy:" to share it.
At 4f1144c3c72b introducing original "work around" for "from a import
b" case, elements in "fromlist" were imported with "level=level". But
"level" might be grater than 1 (e.g. level=2 in "from .. import b"
case) at demandimport() invocation, and importing direct sub-module in
"fromlist" with level grater than 1 causes unexpected result.
IMHO, this seems main reason of "errors for unknown reason" described
in 4f1144c3c72b, and we don't have to worry about it, because this
issue was already fixed by 78d05778907b.
This is reason why this patch removes "errors for unknown reasons"
comment.
author | FUJIWARA Katsunori <foozy@lares.dti.ne.jp> |
---|---|
date | Sun, 19 Jun 2016 02:17:33 +0900 |
parents | f6d73c8756e2 |
children | 4e934804cafe |
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==== hg ==== --------------------------------------- Mercurial source code management system --------------------------------------- :Author: Matt Mackall <mpm@selenic.com> :Organization: Mercurial :Manual section: 1 :Manual group: Mercurial Manual .. contents:: :backlinks: top :class: htmlonly :depth: 1 Synopsis """""""" **hg** *command* [*option*]... [*argument*]... Description """"""""""" The **hg** command provides a command line interface to the Mercurial system. Command Elements """""""""""""""" files... indicates one or more filename or relative path filenames; see `File Name Patterns`_ for information on pattern matching path indicates a path on the local machine revision indicates a changeset which can be specified as a changeset revision number, a tag, or a unique substring of the changeset hash value repository path either the pathname of a local repository or the URI of a remote repository. .. include:: hg.1.gendoc.txt Files """"" ``/etc/mercurial/hgrc``, ``$HOME/.hgrc``, ``.hg/hgrc`` This file contains defaults and configuration. Values in ``.hg/hgrc`` override those in ``$HOME/.hgrc``, and these override settings made in the global ``/etc/mercurial/hgrc`` configuration. See |hgrc(5)|_ for details of the contents and format of these files. ``.hgignore`` This file contains regular expressions (one per line) that describe file names that should be ignored by **hg**. For details, see |hgignore(5)|_. ``.hgsub`` This file defines the locations of all subrepositories, and tells where the subrepository checkouts came from. For details, see :hg:`help subrepos`. ``.hgsubstate`` This file is where Mercurial stores all nested repository states. *NB: This file should not be edited manually.* ``.hgtags`` This file contains changeset hash values and text tag names (one of each separated by spaces) that correspond to tagged versions of the repository contents. The file content is encoded using UTF-8. ``.hg/last-message.txt`` This file is used by :hg:`commit` to store a backup of the commit message in case the commit fails. ``.hg/localtags`` This file can be used to define local tags which are not shared among repositories. The file format is the same as for ``.hgtags``, but it is encoded using the local system encoding. Some commands (e.g. revert) produce backup files ending in ``.orig``, if the ``.orig`` file already exists and is not tracked by Mercurial, it will be overwritten. Bugs """" Probably lots, please post them to the mailing list (see Resources_ below) when you find them. See Also """""""" |hgignore(5)|_, |hgrc(5)|_ Author """""" Written by Matt Mackall <mpm@selenic.com> Resources """"""""" Main Web Site: https://mercurial-scm.org/ Source code repository: http://selenic.com/hg Mailing list: http://selenic.com/mailman/listinfo/mercurial Copying """"""" Copyright (C) 2005-2016 Matt Mackall. Free use of this software is granted under the terms of the GNU General Public License version 2 or any later version. .. include:: common.txt