templater: make label() take unknown symbol as color literal

Instead of the mapping hack introduced by b775a2029e8d, this patch changes the
way how a label symbol is evaluated. This is still hackish, but should be more
predictable in that it doesn't depend on the known color effects.

This change is intended to eliminate the reference to color._effects so that
color.templatelabel() can be merged with templater.label().

hgext/color.py

@@ -485,10 +485,6 def templatelabel(context, mapping, args
         # i18n: "label" is a keyword
         raise error.ParseError(_("label expects two arguments"))
 
-    # add known effects to the mapping so symbols like 'red', 'bold',
-    # etc. don't need to be quoted
-    mapping.update(dict([(k, k) for k in _effects]))
-
     thing = templater.evalstring(context, mapping, args[1])
 
     # apparently, repo could be a string that is the favicon?
@@ -496,7 +492,9 def templatelabel(context, mapping, args
     if isinstance(repo, str):
         return thing
 
-    label = templater.evalstring(context, mapping, args[0])
+    # preserve unknown symbol as literal so effects like 'red', 'bold',
+    # etc. don't need to be quoted
+    label = templater.evalstringliteral(context, mapping, args[0])
 
     return repo.ui.label(thing, label)
 

mercurial/templater.py

@@ -231,6 +231,16 def evalstring(context, mapping, arg):
     func, data = arg
     return stringify(func(context, mapping, data))
 
+def evalstringliteral(context, mapping, arg):
+    """Evaluate given argument as string template, but returns symbol name
+    if it is unknown"""
+    func, data = arg
+    if func is runsymbol:
+        thing = func(context, mapping, data, default=data)
+    else:
+        thing = func(context, mapping, data)
+    return stringify(thing)
+
 def runinteger(context, mapping, data):
     return int(data)
 
@@ -245,7 +255,7 def _recursivesymbolblocker(key):
 def _runrecursivesymbol(context, mapping, key):
     raise error.Abort(_("recursive reference '%s' in template") % key)
 
-def runsymbol(context, mapping, key):
+def runsymbol(context, mapping, key, default=''):
     v = mapping.get(key)
     if v is None:
         v = context._defaults.get(key)
@@ -257,7 +267,7 def runsymbol(context, mapping, key):
         try:
             v = context.process(key, safemapping)
         except TemplateNotFound:
-            v = ''
+            v = default
     if callable(v):
         return v(**mapping)
     return v

tests/test-command-template.t

@@ -3178,6 +3178,11 Test recursive evaluation:
   $ hg log --color=always -l 1 --template '{label("text.{rev}", "text\n")}'
   \x1b[0;32mtext\x1b[0m (esc)
 
+color effect can be specified without quoting:
+
+  $ hg log --color=always -l 1 --template '{label(red, "text\n")}'
+  \x1b[0;31mtext\x1b[0m (esc)
+
 Test branches inside if statement:
 
   $ hg log -r 0 --template '{if(branches, "yes", "no")}\n'