Add a new attachment property for cells.

docs/format_description.rst

@@ -155,6 +155,7 @@ stream output
     The ``stream`` key was changed to ``name`` to match
     the stream message.
 
+.. _display-data:
 
 display_data
 ************
@@ -291,6 +292,28 @@ regardless of format.
       "source" : "[some nbformat output text]"
     }
 
+
+Cell attachments
+----------------
+Markdown and raw cells can have a number of attachments, typically inline
+images that can be referenced in the markdown content of a cell. The attachment
+dictionary of a cell contains a set of mime-bundles (see :ref:`display_data`)
+keyed by filename that represents the files attached to the cell.
+
+
+.. sourcecode:: python
+
+    {
+      "cell_type" : "markdown",
+      "metadata" : {},
+      "source" : ["Here is an *inline* image ![inline image](attachment:test.png)"],
+      "attachments" : {
+        "test.png": {
+            "image/png" : ["base64-encoded-png-data"],
+        },
+      },
+    }
+
 Backward-compatible changes
 ===========================
 

nbformat/v4/nbbase.py

@@ -13,7 +13,7 @@
 
 # Change this when incrementing the nbformat version
 nbformat = 4
-nbformat_minor = 0
+nbformat_minor = 1
 nbformat_schema = 'nbformat.v4.schema.json'
 
 

nbformat/v4/nbformat.v4.schema.json

@@ -113,6 +113,7 @@
                         "tags": {"$ref": "#/definitions/misc/metadata_tags"}
                     }
                 },
+                "attachments": {"$ref": "#/definitions/misc/attachments"},
                 "source": {"$ref": "#/definitions/misc/source"}
             }
         },
@@ -136,6 +137,7 @@
                     },
                     "additionalProperties": true
                 },
+                "attachments": {"$ref": "#/definitions/misc/attachments"},
                 "source": {"$ref": "#/definitions/misc/source"}
             }
         },
@@ -327,6 +329,16 @@
                     "pattern": "^[^,]+$"
                 }
             },
+            "attachments": {
+                "description": "Media attachments (e.g. inline images), stored as mimebundle keyed by filename.",
+                "type": "object",
+                "patternProperties": {
+                    ".*": {
+                        "description": "The attachment's data stored as a mimebundle.",
+                        "$ref": "#/definitions/misc/mimebundle"
+                    }
+                }
+            },
             "source": {
                 "description": "Contents of the cell, represented as an array of lines.",
                 "$ref": "#/definitions/misc/multiline_string"