Mercurial > hg
view mercurial/help/environment.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 | 77e566fe31ec |
children | 40785ccab410 |
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HG Path to the 'hg' executable, automatically passed when running hooks, extensions or external tools. If unset or empty, this is the hg executable's name if it's frozen, or an executable named 'hg' (with %PATHEXT% [defaulting to COM/EXE/BAT/CMD] extensions on Windows) is searched. HGEDITOR This is the name of the editor to run when committing. See EDITOR. (deprecated, use configuration file) HGENCODING This overrides the default locale setting detected by Mercurial. This setting is used to convert data including usernames, changeset descriptions, tag names, and branches. This setting can be overridden with the --encoding command-line option. HGENCODINGMODE This sets Mercurial's behavior for handling unknown characters while transcoding user input. The default is "strict", which causes Mercurial to abort if it can't map a character. Other settings include "replace", which replaces unknown characters, and "ignore", which drops them. This setting can be overridden with the --encodingmode command-line option. HGENCODINGAMBIGUOUS This sets Mercurial's behavior for handling characters with "ambiguous" widths like accented Latin characters with East Asian fonts. By default, Mercurial assumes ambiguous characters are narrow, set this variable to "wide" if such characters cause formatting problems. HGMERGE An executable to use for resolving merge conflicts. The program will be executed with three arguments: local file, remote file, ancestor file. (deprecated, use configuration file) HGRCPATH A list of files or directories to search for configuration files. Item separator is ":" on Unix, ";" on Windows. If HGRCPATH is not set, platform default search path is used. If empty, only the .hg/hgrc from the current repository is read. For each element in HGRCPATH: - if it's a directory, all files ending with .rc are added - otherwise, the file itself will be added HGPLAIN When set, this disables any configuration settings that might change Mercurial's default output. This includes encoding, defaults, verbose mode, debug mode, quiet mode, tracebacks, and localization. This can be useful when scripting against Mercurial in the face of existing user configuration. Equivalent options set via command line flags or environment variables are not overridden. HGPLAINEXCEPT This is a comma-separated list of features to preserve when HGPLAIN is enabled. Currently the following values are supported: ``alias`` Don't remove aliases. ``i18n`` Preserve internationalization. ``revsetalias`` Don't remove revset aliases. ``templatealias`` Don't remove template aliases. ``progress`` Don't hide progress output. Setting HGPLAINEXCEPT to anything (even an empty string) will enable plain mode. HGUSER This is the string used as the author of a commit. If not set, available values will be considered in this order: - HGUSER (deprecated) - configuration files from the HGRCPATH - EMAIL - interactive prompt - LOGNAME (with ``@hostname`` appended) (deprecated, use configuration file) EMAIL May be used as the author of a commit; see HGUSER. LOGNAME May be used as the author of a commit; see HGUSER. VISUAL This is the name of the editor to use when committing. See EDITOR. EDITOR Sometimes Mercurial needs to open a text file in an editor for a user to modify, for example when writing commit messages. The editor it uses is determined by looking at the environment variables HGEDITOR, VISUAL and EDITOR, in that order. The first non-empty one is chosen. If all of them are empty, the editor defaults to 'vi'. PYTHONPATH This is used by Python to find imported modules and may need to be set appropriately if this Mercurial is not installed system-wide.