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.
import-checker: increase portability for python 2.6.x
Before this patch, fromlocalfunc() assumes that "module" attribute of
ast.ImportFrom is None for "from . import a", and Python 2.7.x
satisfies this assumption.
On the other hand, with Python 2.6.x, "module" attribute of
ast.ImportFrom is an empty string for "from . import a", and this
causes failure of test-check-module-imports.t.
scmutil: allow access to filecache descriptor on class
To make it easier to patch the wrapped function, make it possible to access the
filecache descriptor directly on the class (rather than have to use
ClassObject.__dict__['attributename']). Returning `self` when the first
argument to `__get__` is `None` makes the descriptor behave the same way
`property` objects do.
changegroup: don't send empty subdirectory manifest groups
When grafting/rebasing, it is common for multiple changesets to make
the same change to a subdirectory. When writing the revlog for the
directory, the revlog code already takes care of not writing the entry
again. In
0c2a088ffcc5 (changegroup: prune subdirectory dirlogs too,
2016-02-12), I added the corresponding code in changegroup (not
sending entries the client already has), but I forgot to avoid sending
the entire changegroup if no nodes remained in the pruned
set. Although that's harmless besides the wasted network traffic, the
receiving side was checking for it (copied from the changegroup code
for handling files). This resulted in the client crashing with:
abort: received dir revlog group is empty
Fix by simply not emitting a changegroup for the directory if there
were no changes is it. This matches how files are handled.
chg: ignore SIGINT while waiting pager termination
Otherwise the terminal would be left with unclean state. This is what
fcc4b55876c3 does.
chg: reset signal handlers to default before waiting pager
Our signal handlers forward signals to the server process, but it will
disappear soon after hgc_close(). So we should unregister handlers before
hgc_close(). Otherwise chg would abort due to kill(perrpid, sig) failure.
The problem is spotted by SIGWINCH while waiting pager termination.