[PATCH V4] ui: add new config flag for interface selection

[Laurent Charignon]

# HG changeset patch
# User Laurent Charignon <lcharignon at fb.com>
# Date 1455210657 28800
#      Thu Feb 11 09:10:57 2016 -0800
# Node ID 53494a3e515b7744759dfa064685b1b8299fffb7
# Parent  01a5143cd25f285f8c745a92986cd7186bb32c90
ui: add new config flag for interface selection

This patch introduces a new config flag ui.interface to select the interface
for interactive commands. It currently only applies to chunks selection.
The config can be overridden on a per feature basis with the flag
ui.interface.<feature>.

features for the moment can only be 'chunkselector', moving forward we expect
to have 'histedit' and other commands there.

If an incorrect value is given to ui.interface we print a warning and use the
default interface: text. If HGPLAIN is specified we also use the default
interface: text.

diff --git a/mercurial/help/config.txt b/mercurial/help/config.txt
--- a/mercurial/help/config.txt
+++ b/mercurial/help/config.txt
@@ -1587,6 +1587,17 @@
 ``interactive``
     Allow to prompt the user. (default: True)
 
+``interface``
+    Select the default interface for interactive features (default: text).
+    Possible values are 'text' and 'curses'.
+
+``interface.chunkselector``
+    Select the interface for chunkselection.
+    Possible values are 'text' and 'curses'.
+    This config overrides the interface specified by ui.interface.
+    If ui.interface and ui.interface.chunkselector aren't set, we use the text
+    interface.
+
 ``logtemplate``
     Template string for commands that print changesets.
 
diff --git a/mercurial/ui.py b/mercurial/ui.py
--- a/mercurial/ui.py
+++ b/mercurial/ui.py
@@ -699,6 +699,73 @@
             return False
         return util.isatty(fh)
 
+    def interface(self, feature):
+        '''what interface to use for interactive console features?
+
+        The interface is controlled by the value of `ui.interface` but also by
+        the value of feature-specific configuration. For example:
+
+        ui.interface.histedit = text
+        ui.interface.chunkselector = curses
+
+        Here the features are "histedit" and "chunkselector".
+
+        The configuration above means that the default interfaces for commands
+        is curses, the interface for histedit is text and the interface for
+        selecting chunk is crecord (the best curses interface available).
+
+        Consider the following exemple:
+        ui.interface = curses
+        ui.interface.histedit = text
+
+        Then histedit will use the text interface and chunkselector will use
+        the default curses interface (crecord at the moment).
+        '''
+        if self.plain():
+            return "text"
+
+        alloweddefaultinterfaces = ("text", "curses")
+        defaultfeaturesinterfaces = {
+            "chunkselector": {
+                "text": "text",
+                "curses": "crecord"
+            }
+        }
+
+        # Default interface for all the features
+        defaultinterface = "text"
+        i = self.config("ui", "interface", None)
+        if i is not None:
+            if i not in alloweddefaultinterfaces:
+                self.warn(_("invalid value for ui.interface: %s\n") % i)
+                self.warn(_("(using default interface instead %s)\n")
+                          % defaultinterface)
+            else:
+                defaultinterface = i
+
+
+        # Feature-specific interface
+        if feature not in defaultfeaturesinterfaces.keys():
+            # Programming error, not user error
+            raise ValueError("Unknown feature requested %s" % feature)
+
+
+        availablefeatureinterfaces = defaultfeaturesinterfaces[feature].keys()
+        defaultinterface = defaultfeaturesinterfaces[feature][defaultinterface]
+
+        f = self.config("ui", "interface.%s" % feature, None)
+        if f is None:
+            return defaultinterface
+        else:
+            if f not in availablefeatureinterfaces:
+                self.warn(_("invalid value for ui.interface.%s: %s\n")
+                          % (feature, f))
+                self.warn(_("(using default interface instead: %s)\n")
+                          % defaultinterface)
+                return defaultinterface
+            else:
+                return defaultfeaturesinterfaces[feature][f]
+
     def interactive(self):
         '''is interactive input allowed?
 
diff --git a/tests/test-commit-interactive-curses.t b/tests/test-commit-interactive-curses.t
--- a/tests/test-commit-interactive-curses.t
+++ b/tests/test-commit-interactive-curses.t
@@ -223,3 +223,58 @@
   hello world
 
 
+Check ui.interface logic for the chunkselector
+
+The default interface is text
+  $ chunkselectorinterface() {
+  > python <<EOF
+  > from mercurial import hg, ui, parsers;\
+  > repo = hg.repository(ui.ui(), ".");\
+  > print repo.ui.interface("chunkselector")
+  > EOF
+  > }
+  $ chunkselectorinterface
+  text
+
+The default curses interface is crecord
+  $ cat <<EOF >> $HGRCPATH
+  > [ui]
+  > interface = curses
+  > EOF
+  $ chunkselectorinterface
+  crecord
+
+It is possible to override the default interface with a feature specific
+interface
+  $ cat <<EOF >> $HGRCPATH
+  > [ui]
+  > interface = text
+  > interface.chunkselector = curses
+  > EOF
+
+  $ chunkselectorinterface
+  crecord
+
+If a bad interface name is given, we use the default value:
+  $ cat <<EOF >> $HGRCPATH
+  > [ui]
+  > interface = curses
+  > interface.chunkselector = blah
+  > EOF
+
+  $ chunkselectorinterface
+  invalid value for ui.interface.chunkselector: blah
+  (using default interface instead: crecord)
+  crecord
+  $ cat <<EOF >> $HGRCPATH
+  > [ui]
+  > interface = blah
+  > interface.chunkselector = blah
+  > EOF
+
+  $ chunkselectorinterface
+  invalid value for ui.interface: blah
+  (using default interface instead text)
+  invalid value for ui.interface.chunkselector: blah
+  (using default interface instead: text)
+  text