demandimport: allow extensions to import own modules by absolute name

demandimport: allow extensions to import own modules by absolute name

Before this patch, python modules of each extensions can't import
another one in own extension by absolute name, because root modules of
each extensions are loaded with "hgext_" prefix.

For example, "import extroot.bar" in "extroot/foo.py" of "extroot"
extension fails, even though "import bar" in it succeeds.

Installing extensions into site-packages of python library path can
avoid this problem, but this solution is not reasonable in some cases:
using binary package of Mercurial on Windows, for example.

This patch retries to import with "hgext_" prefix after ImportError,
if the module in the extension may try to import another one in own
extension.

This patch doesn't change some "_import()"/"_origimport()" invocations
below, because ordinary extensions shouldn't cause such invocations.

    - invocation of "_import()" when root module imports sub-module by
      absolute path without "fromlist"

      for example, "import a.b" in "a.__init__.py".

      extensions are loaded with "hgext_" prefix, and this causes
      execution of another (= fixed by this patch) code path.

    - invocation of "_origimport()" when "level != -1" with "fromlist"

      for example, importing after "from __future__ import
      absolute_import" (level == 0), or "from . import b" or "from .a
      import b" (0 < level),

      for portability between python versions and environments,
      extensions shouldn't cause "level != -1".

--- a/mercurial/demandimport.py	Sat Oct 05 01:02:22 2013 +0900
+++ b/mercurial/demandimport.py	Sat Oct 05 01:02:22 2013 +0900
@@ -38,6 +38,21 @@
 else:
     _import = _origimport
 
+def _hgextimport(importfunc, name, globals, *args):
+    try:
+        return importfunc(name, globals, *args)
+    except ImportError:
+        if not globals:
+            raise
+        # extensions are loaded with "hgext_" prefix
+        hgextname = 'hgext_%s' % name
+        nameroot = hgextname.split('.', 1)[0]
+        contextroot = globals.get('__name__', '').split('.', 1)[0]
+        if nameroot != contextroot:
+            raise
+        # retry to import with "hgext_" prefix
+        return importfunc(hgextname, globals, *args)
+
 class _demandmod(object):
     """module demand-loader and proxy"""
     def __init__(self, name, globals, locals, level=-1):
@@ -56,7 +71,7 @@
     def _load(self):
         if not self._module:
             head, globals, locals, after, level = self._data
-            mod = _import(head, globals, locals, None, level)
+            mod = _hgextimport(_import, head, globals, locals, None, level)
             # load submodules
             def subload(mod, p):
                 h, t = p, None
@@ -93,7 +108,7 @@
 def _demandimport(name, globals=None, locals=None, fromlist=None, level=-1):
     if not locals or name in ignore or fromlist == ('*',):
         # these cases we can't really delay
-        return _import(name, globals, locals, fromlist, level)
+        return _hgextimport(_import, name, globals, locals, fromlist, level)
     elif not fromlist:
         # import a [as b]
         if '.' in name: # a.b
@@ -112,7 +127,7 @@
             # from . import b,c,d or from .a import b,c,d
             return _origimport(name, globals, locals, fromlist, level)
         # from a import b,c,d
-        mod = _origimport(name, globals, locals)
+        mod = _hgextimport(_origimport, name, globals, locals)
         # recurse down the module chain
         for comp in name.split('.')[1:]:
             if getattr(mod, comp, nothing) is nothing:

--- a/tests/test-extension.t	Sat Oct 05 01:02:22 2013 +0900
+++ b/tests/test-extension.t	Sat Oct 05 01:02:22 2013 +0900
@@ -168,6 +168,97 @@
   $TESTTMP/a
 #endif
 
+Check absolute/relative import of extension specific modules
+
+  $ mkdir $TESTTMP/extroot
+  $ cat > $TESTTMP/extroot/bar.py <<EOF
+  > s = 'this is extroot.bar'
+  > EOF
+  $ mkdir $TESTTMP/extroot/sub1
+  $ cat > $TESTTMP/extroot/sub1/__init__.py <<EOF
+  > s = 'this is extroot.sub1.__init__'
+  > EOF
+  $ cat > $TESTTMP/extroot/sub1/baz.py <<EOF
+  > s = 'this is extroot.sub1.baz'
+  > EOF
+  $ cat > $TESTTMP/extroot/__init__.py <<EOF
+  > s = 'this is extroot.__init__'
+  > import foo
+  > def extsetup(ui):
+  >     ui.write('(extroot) ', foo.func(), '\n')
+  > EOF
+
+  $ cat > $TESTTMP/extroot/foo.py <<EOF
+  > # test absolute import
+  > buf = []
+  > def func():
+  >     # "not locals" case
+  >     import extroot.bar
+  >     buf.append('import extroot.bar in func(): %s' % extroot.bar.s)
+  > 
+  >     return '\n(extroot) '.join(buf)
+  > 
+  > # "fromlist == ('*',)" case
+  > from extroot.bar import *
+  > buf.append('from extroot.bar import *: %s' % s)
+  > 
+  > # "not fromlist" and "if '.' in name" case
+  > import extroot.sub1.baz
+  > buf.append('import extroot.sub1.baz: %s' % extroot.sub1.baz.s)
+  > 
+  > # "not fromlist" and NOT "if '.' in name" case
+  > import extroot
+  > buf.append('import extroot: %s' % extroot.s)
+  > 
+  > # NOT "not fromlist" and NOT "level != -1" case
+  > from extroot.bar import s
+  > buf.append('from extroot.bar import s: %s' % s)
+  > EOF
+  $ hg --config extensions.extroot=$TESTTMP/extroot root
+  (extroot) from extroot.bar import *: this is extroot.bar
+  (extroot) import extroot.sub1.baz: this is extroot.sub1.baz
+  (extroot) import extroot: this is extroot.__init__
+  (extroot) from extroot.bar import s: this is extroot.bar
+  (extroot) import extroot.bar in func(): this is extroot.bar
+  $TESTTMP/a
+
+#if no-py3k
+  $ rm -f $TESTTMP/extroot/foo.*
+  $ cat > $TESTTMP/extroot/foo.py <<EOF
+  > # test relative import
+  > buf = []
+  > def func():
+  >     # "not locals" case
+  >     import bar
+  >     buf.append('import bar in func(): %s' % bar.s)
+  > 
+  >     return '\n(extroot) '.join(buf)
+  > 
+  > # "fromlist == ('*',)" case
+  > from bar import *
+  > buf.append('from bar import *: %s' % s)
+  > 
+  > # "not fromlist" and "if '.' in name" case
+  > import sub1.baz
+  > buf.append('import sub1.baz: %s' % sub1.baz.s)
+  > 
+  > # "not fromlist" and NOT "if '.' in name" case
+  > import sub1
+  > buf.append('import sub1: %s' % sub1.s)
+  > 
+  > # NOT "not fromlist" and NOT "level != -1" case
+  > from bar import s
+  > buf.append('from bar import s: %s' % s)
+  > EOF
+  $ hg --config extensions.extroot=$TESTTMP/extroot root
+  (extroot) from bar import *: this is extroot.bar
+  (extroot) import sub1.baz: this is extroot.sub1.baz
+  (extroot) import sub1: this is extroot.sub1.__init__
+  (extroot) from bar import s: this is extroot.bar
+  (extroot) import bar in func(): this is extroot.bar
+  $TESTTMP/a
+#endif
+
   $ cd ..
 
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