feat: Allow for HTML elements in dropdown field menus.

core/field_dropdown.ts

@@ -334,11 +334,11 @@ export class FieldDropdown extends Field<string> {
 
       const [label, value] = option;
       const content = (() => {
-        if (typeof label === 'object') {
+        if (isImageProperties(label)) {
           // Convert ImageProperties to an HTMLImageElement.
-          const image = new Image(label['width'], label['height']);
-          image.src = label['src'];
-          image.alt = label['alt'] || '';
+          const image = new Image(label.width, label.height);
+          image.src = label.src;
+          image.alt = label.alt;
           return image;
         }
         return label;
@@ -499,7 +499,7 @@ export class FieldDropdown extends Field<string> {
 
     // Show correct element.
     const option = this.selectedOption && this.selectedOption[0];
-    if (option && typeof option === 'object') {
+    if (isImageProperties(option)) {
       this.renderSelectedImage(option);
     } else {
       this.renderSelectedText();
@@ -637,8 +637,10 @@ export class FieldDropdown extends Field<string> {
       return null;
     }
     const option = this.selectedOption[0];
-    if (typeof option === 'object') {
-      return option['alt'];
+    if (isImageProperties(option)) {
+      return option.alt;
+    } else if (option instanceof HTMLElement) {
+      return option.title ?? option.ariaLabel ?? option.innerText;
     }
     return option;
   }
@@ -687,10 +689,9 @@ export class FieldDropdown extends Field<string> {
       hasImages = true;
       // Copy the image properties so they're not influenced by the original.
       // NOTE: No need to deep copy since image properties are only 1 level deep.
-      const imageLabel =
-        label.alt !== null
-          ? {...label, alt: parsing.replaceMessageReferences(label.alt)}
-          : {...label};
+      const imageLabel = isImageProperties(label)
+        ? {...label, alt: parsing.replaceMessageReferences(label.alt)}
+        : {...label};
       return [imageLabel, value];
     });
 
@@ -776,12 +777,13 @@ export class FieldDropdown extends Field<string> {
       } else if (
         option[0] &&
         typeof option[0] !== 'string' &&
-        typeof option[0].src !== 'string'
+        !isImageProperties(option[0]) &&
+        !(option[0] instanceof HTMLElement)
       ) {
         foundError = true;
         console.error(
           `Invalid option[${i}]: Each FieldDropdown option must have a string 
-          label or image description. Found ${option[0]} in: ${option}`,
+          label, image description, or HTML element. Found ${option[0]} in: ${option}`,
         );
       }
     }
@@ -791,6 +793,27 @@ export class FieldDropdown extends Field<string> {
   }
 }
 
+/**
+ * Returns whether or not an object conforms to the ImageProperties interface.
+ *
+ * @param obj The object to test.
+ * @returns True if the object conforms to ImageProperties, otherwise false.
+ */
+function isImageProperties(obj: any): obj is ImageProperties {
+  return (
+    obj &&
+    typeof obj === 'object' &&
+    'src' in obj &&
+    typeof obj.src === 'string' &&
+    'alt' in obj &&
+    typeof obj.alt === 'string' &&
+    'width' in obj &&
+    typeof obj.width === 'number' &&
+    'height' in obj &&
+    typeof obj.height === 'number'
+  );
+}
+
 /**
  * Definition of a human-readable image dropdown option.
  */
@@ -805,9 +828,12 @@ export interface ImageProperties {
  * An individual option in the dropdown menu. Can be either the string literal
  * `separator` for a menu separator item, or an array for normal action menu
  * items. In the latter case, the first element is the human-readable value
- * (text or image), and the second element is the language-neutral value.
+ * (text, ImageProperties object, or HTML element), and the second element is
+ * the language-neutral value.
  */
-export type MenuOption = [string | ImageProperties, string] | 'separator';
+export type MenuOption =
+  | [string | ImageProperties | HTMLElement, string]
+  | 'separator';
 
 /**
  * A function that generates an array of menu options for FieldDropdown

tests/mocha/field_dropdown_test.js

@@ -92,9 +92,9 @@ suite('Dropdown Fields', function () {
       expectedText: 'a',
       args: [
         [
-          [{src: 'scrA', alt: 'a'}, 'A'],
-          [{src: 'scrB', alt: 'b'}, 'B'],
-          [{src: 'scrC', alt: 'c'}, 'C'],
+          [{src: 'scrA', alt: 'a', width: 10, height: 10}, 'A'],
+          [{src: 'scrB', alt: 'b', width: 10, height: 10}, 'B'],
+          [{src: 'scrC', alt: 'c', width: 10, height: 10}, 'C'],
         ],
       ],
     },
@@ -121,9 +121,9 @@ suite('Dropdown Fields', function () {
       args: [
         () => {
           return [
-            [{src: 'scrA', alt: 'a'}, 'A'],
-            [{src: 'scrB', alt: 'b'}, 'B'],
-            [{src: 'scrC', alt: 'c'}, 'C'],
+            [{src: 'scrA', alt: 'a', width: 10, height: 10}, 'A'],
+            [{src: 'scrB', alt: 'b', width: 10, height: 10}, 'B'],
+            [{src: 'scrC', alt: 'c', width: 10, height: 10}, 'C'],
           ];
         },
       ],

tests/mocha/json_test.js

@@ -256,12 +256,6 @@ suite('JSON Block Definitions', function () {
         'alt': '%{BKY_ALT_TEXT}',
       };
       const VALUE1 = 'VALUE1';
-      const IMAGE2 = {
-        'width': 90,
-        'height': 123,
-        'src': 'http://image2.src',
-      };
-      const VALUE2 = 'VALUE2';
 
       Blockly.defineBlocksWithJsonArray([
         {
@@ -274,7 +268,6 @@ suite('JSON Block Definitions', function () {
               'options': [
                 [IMAGE0, VALUE0],
                 [IMAGE1, VALUE1],
-                [IMAGE2, VALUE2],
               ],
             },
           ],
@@ -305,11 +298,6 @@ suite('JSON Block Definitions', function () {
       assertImageEquals(IMAGE1, image1);
       assert.equal(image1.alt, IMAGE1_ALT_TEXT); // Via Msg reference
       assert.equal(VALUE1, options[1][1]);
-
-      const image2 = options[2][0];
-      assertImageEquals(IMAGE1, image1);
-      assert.notExists(image2.alt); // No alt specified.
-      assert.equal(VALUE2, options[2][1]);
     });
   });
 });