Desktop: Fix returning form data from plugin dialogs (#12092)

packages/app-desktop/integration-tests/resources/test-plugins/dialogs.js

@@ -0,0 +1,51 @@
+// Allows referencing the Joplin global:
+/* eslint-disable no-undef */
+
+// Allows the `joplin-manifest` block comment:
+/* eslint-disable multiline-comment-style */
+
+/* joplin-manifest:
+{
+	"id": "org.joplinapp.plugins.example.dialogs",
+	"manifest_version": 1,
+	"app_min_version": "3.1",
+	"name": "JS Bundle test",
+	"description": "JS Bundle Test plugin",
+	"version": "1.0.0",
+	"author": "",
+	"homepage_url": "https://joplinapp.org"
+}
+*/
+
+joplin.plugins.register({
+	onStart: async function() {
+		const dialogs = joplin.views.dialogs;
+		const dialogHandle = await dialogs.create('test-dialog');
+		await dialogs.setHtml(
+			dialogHandle,
+			`
+				<form name="main-form">
+					<label>Test: <input type="checkbox" name="test" checked/></label>
+				</form>
+			`,
+		);
+		await dialogs.setButtons(dialogHandle, [
+			{
+				id: 'ok',
+				title: 'Okay',
+			},
+		]);
+		await joplin.commands.register({
+			name: 'showTestDialog',
+			label: 'showTestDialog',
+			iconName: 'fas fa-drum',
+			execute: async () => {
+				const result = await joplin.views.dialogs.open(dialogHandle);
+				await joplin.commands.execute('editor.setText', JSON.stringify({
+					id: result.id,
+					hasFormData: !!result.formData,
+				}));
+			},
+		});
+	},
+});