Add pygments_lexer key to kernelspec

IPython/html/static/notebook/js/notebook.js

@@ -208,9 +208,9 b' define(['
         
         this.events.on('spec_changed.Kernel', function(event, data) {
             that.set_kernelspec_metadata(data);
-            if (data.codemirror_mode) {
-                that.set_codemirror_mode(data.codemirror_mode);
-            }
+            // Mode 'null' should be plain, unhighlighted text.
+            cm_mode = data.codemirror_mode || data.language || 'null'
+            that.set_codemirror_mode(cm_mode);
         });
 
         var collapse_time = function (time) {

IPython/kernel/kernelspec.py

@@ -38,11 +38,15 b' class KernelSpec(HasTraits):'
     display_name = Unicode()
     language = Unicode()
     codemirror_mode = Any() # can be unicode or dict
+    pygments_lexer = Unicode()
     env = Dict()
     resource_dir = Unicode()
     
     def _codemirror_mode_default(self):
         return self.language
+
+    def _pygments_lexer_default(self):
+        return self.language
     
     @classmethod
     def from_resource_dir(cls, resource_dir):
@@ -56,12 +60,17 b' class KernelSpec(HasTraits):'
         return cls(resource_dir=resource_dir, **kernel_dict)
     
     def to_dict(self):
-        return dict(argv=self.argv,
-                    env=self.env,
-                    display_name=self.display_name,
-                    language=self.language,
-                    codemirror_mode=self.codemirror_mode,
-                   )
+        d = dict(argv=self.argv,
+                 env=self.env,
+                 display_name=self.display_name,
+                 language=self.language,
+                )
+        if self.codemirror_mode != self.language:
+            d['codemirror_mode'] = self.codemirror_mode
+        if self.pygments_lexer != self.language:
+            d['pygments_lexer'] = self.pygment_lexer
+
+        return d
 
     def to_json(self):
         return json.dumps(self.to_dict())
@@ -114,6 +123,7 b' class KernelSpecManager(HasTraits):'
                'language': 'python',
                'codemirror_mode': {'name': 'ipython',
                                    'version': sys.version_info[0]},
+               'pygments_lexer': 'ipython'
               }
 
     @property

docs/source/development/kernels.rst

@@ -120,6 +120,9 b' JSON serialised dictionary containing the following keys and values:'
   to use for code in this language. This can be a string or a dictionary, as
   passed to codemirror config. The string from *language* will be used if this is
   not provided.
+- **pygments_lexer** (optional): The name of a `Pygments lexer <http://pygments.org/docs/lexers/>`_
+  to use for code in this language, as a string. The value of *language* will be
+  used if this is not provided.
 - **env** (optional): A dictionary of environment variables to set for the kernel.
   These will be added to the current environment variables before the kernel is
   started.