add language_info to nbformat doc and spec

IPython/nbformat/v4/nbformat.v4.schema.json

@@ -10,25 +10,48 b''
             "type": "object",
             "additionalProperties": true,
             "properties": {
-                "kernel_info": {
+                "kernelspec": {
                     "description": "Kernel information.",
                     "type": "object",
-                    "required": ["name", "language"],
+                    "required": ["name", "display_name"],
                     "properties": {
                         "name": {
                             "description": "Name of the kernel specification.",
                             "type": "string"
                         },
-                        "language": {
-                            "description": "The programming language which this kernel runs.",
-                            "type": "string"
-                        },
-                        "codemirror_mode": {
-                            "description": "The codemirror mode to use for code in this language.",
+                        "display_name": {
+                            "description": "Name to display in UI.",
                             "type": "string"
                         }
                     }
                 },
+                "language_info": {
+                  "description": "Kernel information.",
+                  "type": "object",
+                  "required": ["name"],
+                  "properties": {
+                    "name": {
+                        "description": "The programming language which this kernel runs.",
+                        "type": "string"
+                    },
+                    "codemirror_mode": {
+                        "description": "The codemirror mode to use for code in this language.",
+                        "type": "string"
+                    },
+                    "file_extension": {
+                        "description": "The file extension for files in this language.",
+                        "type": "string"
+                    },
+                    "mimetype": {
+                        "description": "The mimetype corresponding to files in this language.",
+                        "type": "string"
+                    },
+                    "pygments_lexer": {
+                        "description": "The pygments lexer to use for code in this language.",
+                        "type": "string"
+                    }
+                  }
+                },
                 "signature": {
                     "description": "Hash of the notebook.",
                     "type": "string"

docs/source/notebook/nbformat.rst

@@ -36,11 +36,15 b' At the highest level, a Jupyter notebook is a dictionary with a few keys:'
       "metadata" : {
         "signature": "hex-digest", # used for authenticating unsafe outputs on load
         "kernel_info": {
-            # if kernel_info is defined, its name and language fields are required.
-            "name" : "the name of the kernel",
-            "language" : "the programming language of the kernel",
-            "codemirror_mode": "The name of the codemirror mode to use [optional]"
+            # if kernel_info is defined, its name field is required.
+            "name" : "the name of the kernel"
         },
+        "language_info": {
+            # if language_info is defined, its name field is required.
+            "name" : "the programming language of the kernel",
+            "version": "the version of the language",
+            "codemirror_mode": "The name of the codemirror mode to use [optional]"
+        }
       },
       "nbformat": 4,
       "nbformat_minor": 0,