diff --git a/mercurial/commands.py b/mercurial/commands.py
--- a/mercurial/commands.py
+++ b/mercurial/commands.py
@@ -1804,8 +1804,11 @@ def config(ui, repo, *values, **opts):
         return
     ui.pager('config')
     fm = ui.formatter('config', opts)
-    for f in rcutil.rccomponents():
-        ui.debug('read config from: %s\n' % f)
+    for t, f in rcutil.rccomponents():
+        if t == 'path':
+            ui.debug('read config from: %s\n' % f)
+        else:
+            raise error.ProgrammingError('unknown rctype: %s' % t)
     untrusted = bool(opts.get('untrusted'))
     if values:
         sections = [v for v in values if '.' not in v]
diff --git a/mercurial/rcutil.py b/mercurial/rcutil.py
--- a/mercurial/rcutil.py
+++ b/mercurial/rcutil.py
@@ -43,11 +43,17 @@ def defaultrcpath():
 _rccomponents = None
 
 def rccomponents():
-    '''return hgrc search path. if env var HGRCPATH is set, use it.
-    for each item in path, if directory, use files ending in .rc,
-    else use item.
-    make HGRCPATH empty to only look in .hg/hgrc of current repo.
-    if no HGRCPATH, use default os-specific path.'''
+    '''return an ordered [(type, obj)] about where to load configs.
+
+    respect $HGRCPATH. if $HGRCPATH is empty, only .hg/hgrc of current repo is
+    used. if $HGRCPATH is not set, the platform default will be used.
+
+    if a directory is provided, *.rc files under it will be used.
+
+    type could be either 'path' or 'items', if type is 'path', obj is a string,
+    and is the config file path. if type is 'items', obj is a list of (section,
+    name, value, source) that should fill the config directly.
+    '''
     global _rccomponents
     if _rccomponents is None:
         if 'HGRCPATH' in encoding.environ:
@@ -55,8 +61,8 @@ def rccomponents():
             for p in encoding.environ['HGRCPATH'].split(pycompat.ospathsep):
                 if not p:
                     continue
-                _rccomponents.extend(_expandrcpath(p))
+                _rccomponents.extend(('path', p) for p in _expandrcpath(p))
         else:
             paths = defaultrcpath() + systemrcpath() + userrcpath()
-            _rccomponents = pycompat.maplist(os.path.normpath, paths)
+            _rccomponents = [('path', os.path.normpath(p)) for p in paths]
     return _rccomponents
diff --git a/mercurial/ui.py b/mercurial/ui.py
--- a/mercurial/ui.py
+++ b/mercurial/ui.py
@@ -212,8 +212,11 @@ class ui(object):
         """Create a ui and load global and user configs"""
         u = cls()
         # we always trust global config files
-        for f in rcutil.rccomponents():
-            u.readconfig(f, trust=True)
+        for t, f in rcutil.rccomponents():
+            if t == 'path':
+                u.readconfig(f, trust=True)
+            else:
+                raise error.ProgrammingError('unknown rctype: %s' % t)
         return u
 
     def copy(self):