Merged PR 1192: Adopted @anpaz's suggestion for a serialization workflow.

This PR abstracts execution result and display data formatting into a new interface `IDisplaySerializer` that formats objects for displaying to clients. To demonstrate functionality that will be needed with IQ#, this PR also modifies the `moon-kernel` example to serialize all appropriate Lua objects to JSON. Using this mechanism, clients have full access to the structured output of kernels that opt-in to this behavior, making for a pretty generic way of interoperating different languages together.

Author: Chris Granade

Diff for: examples/echo-kernel/Echo Kernel.ipynb

@@ -12,7 +12,9 @@
       ]
      },
      "execution_count": 1,
-     "metadata": {},
+     "metadata": {
+      "text/plain": null
+     },
      "output_type": "execute_result"
     }
    ],
@@ -22,40 +24,73 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 2,
    "metadata": {},
-   "outputs": [],
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "bar"
+      ]
+     },
+     "execution_count": 2,
+     "metadata": {
+      "text/plain": null
+     },
+     "output_type": "execute_result"
+    }
+   ],
    "source": [
     "bar"
    ]
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 3,
    "metadata": {},
-   "outputs": [],
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "baz"
+      ]
+     },
+     "execution_count": 3,
+     "metadata": {
+      "text/plain": null
+     },
+     "output_type": "execute_result"
+    }
+   ],
    "source": [
     "baz"
    ]
   },
   {
    "cell_type": "code",
-   "execution_count": 2,
+   "execution_count": 4,
    "metadata": {},
    "outputs": [
     {
      "data": {
       "text/html": [
        "<ul><li>%dne</li>\n",
+       "<li>bar</li>\n",
+       "<li>baz</li>\n",
        "<li>%history</li></ul>"
       ],
       "text/plain": [
        "%dne\n",
+       "bar\n",
+       "baz\n",
        "%history"
       ]
      },
-     "execution_count": 2,
-     "metadata": {},
+     "execution_count": 4,
+     "metadata": {
+      "text/html": null,
+      "text/plain": null
+     },
      "output_type": "execute_result"
     }
    ],
@@ -66,9 +101,7 @@
   {
    "cell_type": "code",
    "execution_count": null,
-   "metadata": {
-    "collapsed": true
-   },
+   "metadata": {},
    "outputs": [],
    "source": []
   }

Diff for: examples/echo-kernel/KernelProperties.cs

@@ -26,7 +26,7 @@ internal static class Constants
             // The MIME type of the language implemented by the kernel.
             // This property is used mainly for providing "plain" downloads from
             // Jupyter clients.
-            LanguageMimeType = "text/plain",
+            LanguageMimeType = MimeTypes.PlainText,
             // The file extension for source files written in the language
             // implemented by the kernel.
             // This property is used mainly for providing "plain" downloads from

Diff for: examples/moon-kernel/DynValueConverter.cs

@@ -0,0 +1,39 @@
+using System;
+using System.Collections.Generic;
+using MoonSharp.Interpreter;
+using Newtonsoft.Json;
+using Newtonsoft.Json.Linq;
+
+namespace Microsoft.Jupyter.Core
+{
+    public class DynValueConverter : JsonConverter<DynValue>
+    {
+        public override DynValue ReadJson(JsonReader reader, Type objectType, DynValue existingValue, bool hasExistingValue, JsonSerializer serializer)
+        {
+            throw new NotImplementedException();
+        }
+
+        public override void WriteJson(JsonWriter writer, DynValue value, JsonSerializer serializer)
+        {
+            var obj = value.ToObject();
+            JToken token;
+            switch (obj)
+            {
+                case MoonSharp.Interpreter.Closure closure:
+                    token = JToken.FromObject(new Dictionary<string, object>
+                    {
+                        ["@closure"] = closure.ToString()
+                    });
+                    token.WriteTo(writer);
+                    return;
+
+                default:
+                    // See https://github.com/JamesNK/Newtonsoft.Json/issues/386#issuecomment-421161191
+                    // for why this works to pass through.
+                    token = JToken.FromObject(obj);
+                    token.WriteTo(writer);
+                    return;
+            }
+        }
+    }
+}

Diff for: examples/moon-kernel/MoonEngine.cs

@@ -8,6 +8,7 @@
 using MoonSharp.Interpreter.REPL;
 using Microsoft.Extensions.Options;
 using Microsoft.Extensions.Logging;
+using Newtonsoft.Json;
 
 namespace Microsoft.Jupyter.Core
 {
@@ -23,6 +24,9 @@ public MoonEngine(
             ILogger<MoonEngine> logger
         ) : base(shell, context, logger)
         {
+            RegisterJsonEncoder(
+                new DynValueConverter()
+            );
             var script = new Script();
             script.Options.DebugPrint = str => printFn?.Invoke(str);
             interp = new ReplInterpreter(script);
@@ -42,7 +46,7 @@ public override ExecutionResult ExecuteMundane(string input, Action<string> stdo
                 }
                 else if (result.ToObject() != null)
                 {
-                    return result.ToDebugPrintString().ToExecutionResult();
+                    return result.ToExecutionResult();
                 }
                 else
                 {

Diff for: examples/moon-kernel/MoonScript Kernel.ipynb

@@ -7,12 +7,16 @@
    "outputs": [
     {
      "data": {
+      "application/json": "4.0",
       "text/plain": [
        "4"
       ]
      },
      "execution_count": 1,
-     "metadata": {},
+     "metadata": {
+      "application/json": null,
+      "text/plain": null
+     },
      "output_type": "execute_result"
     }
    ],
@@ -27,12 +31,16 @@
    "outputs": [
     {
      "data": {
+      "application/json": "120.0",
       "text/plain": [
        "120"
       ]
      },
      "execution_count": 2,
-     "metadata": {},
+     "metadata": {
+      "application/json": null,
+      "text/plain": null
+     },
      "output_type": "execute_result"
     }
    ],
@@ -56,12 +64,16 @@
    "outputs": [
     {
      "data": {
+      "application/json": "{\"@closure\":\"MoonSharp.Interpreter.Closure\"}",
       "text/plain": [
-       "function: 00000099"
+       "(Function 00000074)"
       ]
      },
      "execution_count": 3,
-     "metadata": {},
+     "metadata": {
+      "application/json": null,
+      "text/plain": null
+     },
      "output_type": "execute_result"
     }
    ],
@@ -76,6 +88,7 @@
    "outputs": [
     {
      "data": {
+      "application/json": "[\"return 1 + 3\",\"-- defines a factorial function\\n    function fact (n)\\n        if (n == 0) then\\n            return 1\\n        else\\n            return n*fact(n - 1)\\n        end\\n    end\\n\\n    return fact(5)\",\"return fact\",\"%history\"]",
       "text/html": [
        "<ul><li>return 1 + 3</li>\n",
        "<li>-- defines a factorial function\n",
@@ -108,7 +121,11 @@
       ]
      },
      "execution_count": 4,
-     "metadata": {},
+     "metadata": {
+      "application/json": null,
+      "text/html": null,
+      "text/plain": null
+     },
      "output_type": "execute_result"
     }
    ],
@@ -123,12 +140,16 @@
    "outputs": [
     {
      "data": {
+      "application/json": "720.0",
       "text/plain": [
        "720"
       ]
      },
      "execution_count": 5,
-     "metadata": {},
+     "metadata": {
+      "application/json": null,
+      "text/plain": null
+     },
      "output_type": "execute_result"
     }
    ],
@@ -152,6 +173,13 @@
    "source": [
     "print('Hello, world')"
    ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
+   "source": []
   }
  ],
  "metadata": {