[PATCH 2 of 2 v4] configitems: add alias support in config

[David Demelier]

# HG changeset patch
# User David Demelier <demelier.david at gmail.com>
# Date 1499409190 -7200
#      Fri Jul 07 08:33:10 2017 +0200
# Node ID 936ce124293ab334d10239c9088c74f47fc55212
# Parent  d32ff523e0219b48b119d9dc44d9d07638153a72
configitems: add alias support in config

Aliases define optional alternatives to existing options. For example the old
option ui.user was deprecated and replaced by ui.username. With this mechanism,
it's even possible to create an alias to an option in a different section.

Add ui.user as alias to ui.username as an example of this concept.

The old alternates principle in ui.config is removed as it was used only for
this option.

diff -r d32ff523e021 -r 936ce124293a mercurial/configitems.py
--- a/mercurial/configitems.py	Mon Jul 03 13:04:35 2017 +0200
+++ b/mercurial/configitems.py	Fri Jul 07 08:33:10 2017 +0200
@@ -32,12 +32,14 @@
     :section: the official config section where to find this item,
        :name: the official name within the section,
     :default: default value for this item,
+    :alias: optional list of tuples as alternatives.
     """
 
-    def __init__(self, section, name, default=None):
+    def __init__(self, section, name, default=None, alias=()):
         self.section = section
         self.name = name
         self.default = default
+        self.alias = list(alias)
 
 coreitems = {}
 
@@ -95,3 +97,6 @@
 coreconfigitem('ui', 'quiet',
     default=False,
 )
+coreconfigitem('ui', 'username',
+    alias=[('ui', 'user')]
+)
diff -r d32ff523e021 -r 936ce124293a mercurial/ui.py
--- a/mercurial/ui.py	Mon Jul 03 13:04:35 2017 +0200
+++ b/mercurial/ui.py	Fri Jul 07 08:33:10 2017 +0200
@@ -448,38 +448,39 @@
 
     def _config(self, section, name, default=_unset, untrusted=False):
         value = default
-        if isinstance(name, list):
-            alternates = name
-        else:
-            item = self._knownconfig.get(section, {}).get(name)
-            if default is _unset:
-                if item is None:
-                    value = default
-                elif callable(item.default):
+        item = self._knownconfig.get(section, {}).get(name)
+        alternates = [(section, name)]
+
+        if item is not None:
+            alternates.extend(item.alias)
+
+        if default is _unset:
+            if item is None:
+                value = default
+            elif callable(item.default):
                     value = item.default()
-                else:
-                    value = item.default
-            elif item is not None:
-                msg = ("specifying a default value for a registered "
-                       "config item: '%s.%s' '%s'")
-                msg %= (section, name, default)
-                self.develwarn(msg, 2, 'warn-config-default')
+            else:
+                value = item.default
+        elif item is not None:
+            msg = ("specifying a default value for a registered "
+                   "config item: '%s.%s' '%s'")
+            msg %= (section, name, default)
+            self.develwarn(msg, 2, 'warn-config-default')
 
-            alternates = [name]
-
-        for n in alternates:
-            candidate = self._data(untrusted).get(section, n, None)
+        for s, n in alternates:
+            candidate = self._data(untrusted).get(s, n, None)
             if candidate is not None:
                 value = candidate
+                section = s
                 name = n
                 break
 
         if self.debugflag and not untrusted and self._reportuntrusted:
-            for n in alternates:
-                uvalue = self._ucfg.get(section, n)
+            for s, n in alternates:
+                uvalue = self._ucfg.get(s, n)
                 if uvalue is not None and uvalue != value:
                     self.debug("ignoring untrusted configuration option "
-                               "%s.%s = %s\n" % (section, n, uvalue))
+                               "%s.%s = %s\n" % (s, n, uvalue))
         return value
 
     def configsuboptions(self, section, name, default=_unset, untrusted=False):
@@ -744,7 +745,7 @@
         """
         user = encoding.environ.get("HGUSER")
         if user is None:
-            user = self.config("ui", ["username", "user"])
+            user = self.config("ui", "username")
             if user is not None:
                 user = os.path.expandvars(user)
         if user is None:
diff -r d32ff523e021 -r 936ce124293a tests/test-config.t
--- a/tests/test-config.t	Mon Jul 03 13:04:35 2017 +0200
+++ b/tests/test-config.t	Fri Jul 07 08:33:10 2017 +0200
@@ -178,3 +178,36 @@
 
   $ PAGER=p1 hg config --debug --config pager.pager=p2 | grep 'pager\.pager'
   --config: pager.pager=p2
+
+verify that aliases are evaluated as well
+
+  $ hg init aliastest
+  $ cd aliastest
+  $ cat > .hg/hgrc << EOF
+  > [ui]
+  > user = repo user
+  > EOF
+  $ touch index
+  $ unset HGUSER
+  $ hg ci -Am test
+  adding index
+  $ hg log --template '{author}\n'
+  repo user
+  $ cd ..
+
+alias has lower priority
+
+  $ hg init aliaspriority
+  $ cd aliaspriority
+  $ cat > .hg/hgrc << EOF
+  > [ui]
+  > user = alias user
+  > username = repo user
+  > EOF
+  $ touch index
+  $ unset HGUSER
+  $ hg ci -Am test
+  adding index
+  $ hg log --template '{author}\n'
+  repo user
+  $ cd ..