Patchwork [1,of,1,V2] demandimport: allow extensions to import own modules by absolute name

diff --git a/mercurial/demandimport.py b/mercurial/demandimport.py
--- a/mercurial/demandimport.py
+++ b/mercurial/demandimport.py
@@ -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):
@@ -55,7 +70,7 @@ 
     def _load(self):
         if not self._module:
             head, globals, locals, after = self._data
-            mod = _origimport(head, globals, locals)
+            mod = _hgextimport(_origimport, head, globals, locals)
             # load submodules
             def subload(mod, p):
                 h, t = p, None
@@ -92,7 +107,7 @@ 
 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
@@ -111,7 +126,7 @@ 
             # 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:
diff --git a/tests/test-extension.t b/tests/test-extension.t
--- a/tests/test-extension.t
+++ b/tests/test-extension.t
@@ -129,6 +129,73 @@ 
   $ echo 'foo = !' >> $HGRCPATH
   $ echo 'bar = !' >> $HGRCPATH
 
+Check absolute/relative import of extension specific modules
+
+  $ mkdir $TESTTMP/extroot
+  $ cat > $TESTTMP/extroot/__init__.py <<EOF
+  > extrootstr = 'this is extroot.extrootstr'
+  > import foo
+  > def extsetup(ui):
+  >     ui.write('(extroot) ', foo.func(), '\n')
+  > EOF
+  $ cat > $TESTTMP/extroot/foo.py <<EOF
+  > buf = []
+  > def func():
+  >     # "not locals" case
+  >     import bar         # relative
+  >     buf.append('import bar in func(): %s' % bar.barstr)
+  >     import extroot.bar # absolute
+  >     buf.append('import extroot.bar in func(): %s' % extroot.bar.barstr)
+  > 
+  >     return '\n(extroot) '.join(buf)
+  > 
+  > # "fromlist == ('*',)" case
+  > from bar import *         # relative
+  > buf.append('from bar import *: %s' % barstr)
+  > from extroot.bar import * # absolute
+  > buf.append('from extroot.bar import *: %s' % barstr)
+  > 
+  > # "not fromlist" and "if '.' in name" case
+  > import sub1.baz         # relative
+  > buf.append('import sub1.baz: %s' % sub1.baz.bazstr)
+  > import extroot.sub1.baz # absolute
+  > buf.append('import extroot.sub1.baz: %s' % extroot.sub1.baz.bazstr)
+  > 
+  > # "not fromlist" and NOT "if '.' in name" case
+  > import sub1    # relative
+  > buf.append('import sub1: %s' % sub1.sub1str)
+  > import extroot # absolute
+  > buf.append('import extroot: %s' % extroot.extrootstr)
+  > 
+  > # NOT "not fromlist" and NOT "level != -1" case
+  > from bar import barstr         # relative
+  > buf.append('from bar import barstr: %s' % barstr)
+  > from extroot.bar import barstr # absolute
+  > buf.append('from extroot.bar import barstr: %s' % barstr)
+  > EOF
+  $ cat > $TESTTMP/extroot/bar.py <<EOF
+  > barstr = 'this is extroot.bar.barstr'
+  > EOF
+  $ mkdir $TESTTMP/extroot/sub1
+  $ cat > $TESTTMP/extroot/sub1/__init__.py <<EOF
+  > sub1str = 'this is extroot.sub1.sub1str'
+  > EOF
+  $ cat > $TESTTMP/extroot/sub1/baz.py <<EOF
+  > bazstr = 'this is extroot.sub1.baz.bazstr'
+  > EOF
+  $ hg --config extensions.extroot=$TESTTMP/extroot tip --template '{rev}\n'
+  (extroot) from bar import *: this is extroot.bar.barstr
+  (extroot) from extroot.bar import *: this is extroot.bar.barstr
+  (extroot) import sub1.baz: this is extroot.sub1.baz.bazstr
+  (extroot) import extroot.sub1.baz: this is extroot.sub1.baz.bazstr
+  (extroot) import sub1: this is extroot.sub1.sub1str
+  (extroot) import extroot: this is extroot.extrootstr
+  (extroot) from bar import barstr: this is extroot.bar.barstr
+  (extroot) from extroot.bar import barstr: this is extroot.bar.barstr
+  (extroot) import bar in func(): this is extroot.bar.barstr
+  (extroot) import extroot.bar in func(): this is extroot.bar.barstr
+  0
+
   $ cd ..
 
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