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.
test children command
$ cat <<EOF >> $HGRCPATH
> [extensions]
> children =
> EOF
init
$ hg init t
$ cd t
no working directory
$ hg children
setup
$ echo 0 > file0
$ hg ci -qAm 0 -d '0 0'
$ echo 1 > file1
$ hg ci -qAm 1 -d '1 0'
$ echo 2 >> file0
$ hg ci -qAm 2 -d '2 0'
$ hg co null
0 files updated, 0 files merged, 2 files removed, 0 files unresolved
$ echo 3 > file3
$ hg ci -qAm 3 -d '3 0'
hg children at revision 3 (tip)
$ hg children
$ hg co null
0 files updated, 0 files merged, 1 files removed, 0 files unresolved
hg children at nullrev (should be 0 and 3)
$ hg children
changeset: 0:4df8521a7374
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: 0
changeset: 3:e2962852269d
tag: tip
parent: -1:000000000000
user: test
date: Thu Jan 01 00:00:03 1970 +0000
summary: 3
$ hg co 1
2 files updated, 0 files merged, 0 files removed, 0 files unresolved
hg children at revision 1 (should be 2)
$ hg children
changeset: 2:8f5eea5023c2
user: test
date: Thu Jan 01 00:00:02 1970 +0000
summary: 2
$ hg co 2
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
hg children at revision 2 (other head)
$ hg children
$ for i in null 0 1 2 3; do
> echo "hg children -r $i"
> hg children -r $i
> done
hg children -r null
changeset: 0:4df8521a7374
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: 0
changeset: 3:e2962852269d
tag: tip
parent: -1:000000000000
user: test
date: Thu Jan 01 00:00:03 1970 +0000
summary: 3
hg children -r 0
changeset: 1:708c093edef0
user: test
date: Thu Jan 01 00:00:01 1970 +0000
summary: 1
hg children -r 1
changeset: 2:8f5eea5023c2
user: test
date: Thu Jan 01 00:00:02 1970 +0000
summary: 2
hg children -r 2
hg children -r 3
hg children -r 0 file0 (should be 2)
$ hg children -r 0 file0
changeset: 2:8f5eea5023c2
user: test
date: Thu Jan 01 00:00:02 1970 +0000
summary: 2
hg children -r 1 file0 (should be 2)
$ hg children -r 1 file0
changeset: 2:8f5eea5023c2
user: test
date: Thu Jan 01 00:00:02 1970 +0000
summary: 2
$ hg co 0
1 files updated, 0 files merged, 1 files removed, 0 files unresolved
hg children file0 at revision 0 (should be 2)
$ hg children file0
changeset: 2:8f5eea5023c2
user: test
date: Thu Jan 01 00:00:02 1970 +0000
summary: 2
should be compatible with templater (don't pass fctx to displayer)
$ hg children file0 -Tdefault
changeset: 2:8f5eea5023c2
user: test
date: Thu Jan 01 00:00:02 1970 +0000
summary: 2
$ cd ..