Support constants and non instantiate prop in json module

docs/api-reference/json/json-converter.md

@@ -72,7 +72,7 @@ and used to resolve this JSON object:
 }
 ```
 
-will replace the layers discriptor with
+will replace the layers descriptor with
 
 ```js
 {
@@ -140,3 +140,44 @@ and used to resolve this JSON object:
   ]
 }
 ```
+
+### Constants Catalogs
+
+A map of constants that should be made available to the JSON string resolver. This is also helpful to evaluate a prop that does not need to be instantiated. For example, when this configuration is passed to `JSONConverter`:
+
+```js
+import {MapController} from '@deck.gl/core';
+
+const configuration = {
+  ...
+  constants: {
+    MapController
+  }
+};
+```
+
+and used to resolve in this JSON object:
+
+```json
+{
+  "layers": [
+    {
+      "type": "Tile3DLayer",
+      "controller": "MapController"
+    }
+  ]
+}
+```
+
+will replace the constants' value with the value provided in configuration declaration:
+
+```js
+{
+  controller: MapController, // MapController class from '@deck.gl/core' 
+  layers: [
+    new ScatterplotLayer({
+      ...
+    })
+  ]
+}
+``

examples/playground/json-examples/3d-heatmap.json

@@ -1,6 +1,7 @@
 {
   "description": "The deck.gl website hexagonlayer example in JSON format",
   "websiteUrl": "https://deck.gl/#/examples/core-layers/hexagon-layer",
+  "controller": "MapController",
   "initialViewState": {
     "longitude": -1.4157267858730052,
     "latitude": 52.232395363869415,

modules/json/src/json-configuration.js

@@ -14,6 +14,7 @@ export default class JSONConfiguration {
     this.classes = {};
     this.reactComponents = {};
     this.enumerations = {};
+    this.constants = {};
     // TODO - this needs to be simpler, function conversion should be built in
     this.convertFunction = convertFunction;
     this.preProcessClassProps = (Class, props) => props;
@@ -27,7 +28,7 @@ export default class JSONConfiguration {
   _merge(configuration) {
     for (const key in configuration) {
       switch (key) {
-        // DEPRECATED = For backwards compatibility, add views and layers to classe;
+        // DEPRECATED = For backwards compatibility, add views and layers to classes;
         case 'layers':
         case 'views':
           Object.assign(this.classes, configuration[key]);

modules/json/src/json-converter.js

@@ -139,13 +139,16 @@ function convertPlainObject(json, configuration) {
 
 // TODO - We could also support string syntax for hydrating other types, like regexps...
 // But no current use case
-function convertString(json, key, configuration) {
-  if (configuration.enumerations[json]) {
+function convertString(string, key, configuration) {
+  if (configuration.constants[string]) {
+    return configuration.constants[string];
+  }
+  if (configuration.enumerations[string]) {
     // TODO - look up
-    return json;
+    return string;
   }
   if (configuration.convertFunction) {
-    return configuration.convertFunction(json, key, configuration);
+    return configuration.convertFunction(string, key, configuration);
   }
-  return json;
+  return string;
 }

test/modules/json/data/deck-props.json

@@ -20,6 +20,7 @@
   "layers": [
     {
       "type": "ScatterplotLayer",
+      "MapController": "MapController",
       "data": [{"position": [-122.45, 37.8]}],
       "getPosition": "position",
       "getFillColor": [255, 0, 0, 255],

test/modules/json/json-configuration-for-deck.js

@@ -1,8 +1,10 @@
-import {COORDINATE_SYSTEM, MapView, FirstPersonView} from '@deck.gl/core';
+import {COORDINATE_SYSTEM, MapView, FirstPersonView, MapController} from '@deck.gl/core';
 import GL from '@luma.gl/constants';
 
 export const log = console; // eslint-disable-line
 
+export const SCATTER_PLOT_LAYER_ID = 'scatter-plot-layer-test';
+
 export default {
   log,
   // a map of all layers that should be exposes as JSONLayers
@@ -12,5 +14,8 @@ export default {
   enumerations: {
     COORDINATE_SYSTEM,
     GL
+  },
+  constants: {
+    MapController
   }
 };

test/modules/json/json-converter.spec.js

@@ -1,6 +1,7 @@
 import test from 'tape-catch';
 import {makeSpy} from '@probe.gl/test-utils';
 
+import {MapController} from '@deck.gl/core';
 import {JSONConverter} from '@deck.gl/json';
 import configuration, {log} from './json-configuration-for-deck';
 import JSON_DATA from './data/deck-props.json';
@@ -24,6 +25,7 @@ test('JSONConverter#convert', t => {
   t.ok(deckProps, 'JSONConverter converted correctly');
 
   t.is(deckProps.views.length, 2, 'JSONConverter converted views');
+  t.is(deckProps.layers[0].props.MapController, MapController, 'Should evaluate constants.');
 
   t.end();
 });