Plugins: Add support for external CodeMirror plugins (#4015)

packages/lib/services/plugins/utils/loadContentScripts.ts

@@ -0,0 +1,43 @@
+import { PluginStates } from '../reducer';
+import { ContentScriptType } from '../api/types';
+import { dirname } from '@joplin/renderer/pathUtils';
+
+export interface ExtraContentScript {
+	id: string;
+	module: any;
+	assetPath: string;
+}
+
+export function contentScriptsToRendererRules(plugins: PluginStates): ExtraContentScript[] {
+	return loadContentScripts(plugins, ContentScriptType.MarkdownItPlugin);
+}
+
+export function contentScriptsToCodeMirrorPlugin(plugins: PluginStates): ExtraContentScript[] {
+	return loadContentScripts(plugins, ContentScriptType.CodeMirrorPlugin);
+}
+
+function loadContentScripts(plugins: PluginStates, scriptType: ContentScriptType): ExtraContentScript[] {
+	const output: ExtraContentScript[] = [];
+
+	for (const pluginId in plugins) {
+		const plugin = plugins[pluginId];
+		const contentScripts = plugin.contentScripts[scriptType];
+		if (!contentScripts) continue;
+
+		for (const contentScript of contentScripts) {
+			const module = require(contentScript.path);
+			if (!module.default || typeof module.default !== 'function') throw new Error(`Content script must export a function under the "default" key: Plugin: ${pluginId}: Script: ${contentScript.id}`);
+
+			const loadedModule = module.default({});
+			if (!loadedModule.plugin && !loadedModule.codeMirrorResources && !loadedModule.codeMirrorOptions) throw new Error(`Content script must export a "plugin" key or a list of CodeMirror assets or define a CodeMirror option: Plugin: ${pluginId}: Script: ${contentScript.id}`);
+
+			output.push({
+				id: contentScript.id,
+				module: loadedModule,
+				assetPath: dirname(contentScript.path),
+			});
+		}
+	}
+
+	return output;
+}