[PATCH WIP] formatter: add option to redirect output to file object (WORK IN PROGRESS)

[Yuya Nishihara]

# HG changeset patch
# User Yuya Nishihara <yuya at tcha.org>
# Date 1421571884 -32400
#      Sun Jan 18 18:04:44 2015 +0900
# Node ID 9eb6cdad8f41f2e20274a20ee10130706639a47c
# Parent  b647b923486f38d83b92089eafa9faafaa79785d
formatter: add option to redirect output to file object (WORK IN PROGRESS)

Maybe this could be used when porting 'export' to formatter. I tried to port
'cat' as an example, but the result was a bit mess because I had to manage
closable file and formatter resources carefully. Maybe we'll need some helper
functions in cmdutil.

diff --git a/mercurial/formatter.py b/mercurial/formatter.py
--- a/mercurial/formatter.py
+++ b/mercurial/formatter.py
@@ -237,24 +237,28 @@ class _plainconverter(object):
 
 class plainformatter(baseformatter):
     '''the default text output scheme'''
-    def __init__(self, ui, topic, opts):
+    def __init__(self, ui, out, topic, opts):
         baseformatter.__init__(self, ui, topic, opts, _plainconverter)
         if ui.debugflag:
             self.hexfunc = hex
         else:
             self.hexfunc = short
+        if ui is out:
+            self._write = ui.write
+        else:
+            self._write = lambda s, **opts: out.write(s)
     def startitem(self):
         pass
     def data(self, **data):
         pass
     def write(self, fields, deftext, *fielddata, **opts):
-        self._ui.write(deftext % fielddata, **opts)
+        self._write(deftext % fielddata, **opts)
     def condwrite(self, cond, fields, deftext, *fielddata, **opts):
         '''do conditional write'''
         if cond:
-            self._ui.write(deftext % fielddata, **opts)
+            self._write(deftext % fielddata, **opts)
     def plain(self, text, **opts):
-        self._ui.write(text, **opts)
+        self._write(text, **opts)
     def isplain(self):
         return True
     def nested(self, field):
@@ -411,20 +415,20 @@ def maketemplater(ui, topic, tmpl, cache
         t.cache[topic] = tmpl
     return t
 
-def formatter(ui, topic, opts):
+def formatter(ui, out, topic, opts):
     template = opts.get("template", "")
     if template == "json":
-        return jsonformatter(ui, ui, topic, opts)
+        return jsonformatter(ui, out, topic, opts)
     elif template == "pickle":
-        return pickleformatter(ui, ui, topic, opts)
+        return pickleformatter(ui, out, topic, opts)
     elif template == "debug":
-        return debugformatter(ui, ui, topic, opts)
+        return debugformatter(ui, out, topic, opts)
     elif template != "":
-        return templateformatter(ui, ui, topic, opts)
+        return templateformatter(ui, out, topic, opts)
     # developer config: ui.formatdebug
     elif ui.configbool('ui', 'formatdebug'):
-        return debugformatter(ui, ui, topic, opts)
+        return debugformatter(ui, out, topic, opts)
     # deprecated config: ui.formatjson
     elif ui.configbool('ui', 'formatjson'):
-        return jsonformatter(ui, ui, topic, opts)
-    return plainformatter(ui, topic, opts)
+        return jsonformatter(ui, out, topic, opts)
+    return plainformatter(ui, out, topic, opts)
diff --git a/mercurial/ui.py b/mercurial/ui.py
--- a/mercurial/ui.py
+++ b/mercurial/ui.py
@@ -262,8 +262,10 @@ class ui(object):
             self._blockedtimes[key + '_blocked'] += \
                 (util.timer() - starttime) * 1000
 
-    def formatter(self, topic, opts):
-        return formatter.formatter(self, topic, opts)
+    def formatter(self, topic, opts, out=None):
+        if out is None:
+            out = self
+        return formatter.formatter(self, out, topic, opts)
 
     def _trusted(self, fp, f):
         st = util.fstat(fp)