Add --plugin-path support for new platform plugins in dev (#33865)

* Add --plugin-path support for new platform plugins

* PR comments

* PR review comments

src/core/server/legacy/config/legacy_object_to_config_adapter.ts

@@ -72,10 +72,11 @@ export class LegacyObjectToConfigAdapter extends ObjectToConfigAdapter {
   }
 
   private static transformPlugins(configValue: Record<string, any>) {
-    // This property is the only one we use from the existing `plugins` config node
-    // since `scanDirs` and `paths` aren't respected by new platform plugin discovery.
+    // These properties are the only ones we use from the existing `plugins` config node
+    // since `scanDirs` isn't respected by new platform plugin discovery.
     return {
       initialize: configValue.initialize,
+      paths: configValue.paths,
     };
   }
 

src/core/server/plugins/discovery/plugin_discovery.test.ts

@@ -34,6 +34,7 @@ const TEST_PLUGIN_SEARCH_PATHS = {
   emptyPlugins: resolve(process.cwd(), 'plugins'),
   nonExistentKibanaExtra: resolve(process.cwd(), '..', 'kibana-extra'),
 };
+const TEST_EXTRA_PLUGIN_PATH = resolve(process.cwd(), 'my-extra-plugin');
 
 const logger = loggingServiceMock.create();
 beforeEach(() => {
@@ -112,9 +113,15 @@ test('properly iterates through plugin search locations', async () => {
     },
   };
 
-  const env = Env.createDefault(getEnvOptions());
+  const env = Env.createDefault(
+    getEnvOptions({
+      cliArgs: { envName: 'development' },
+    })
+  );
   const configService = new ConfigService(
-    new BehaviorSubject<Config>(new ObjectToConfigAdapter({})),
+    new BehaviorSubject<Config>(
+      new ObjectToConfigAdapter({ plugins: { paths: [TEST_EXTRA_PLUGIN_PATH] } })
+    ),
     env,
     logger
   );
@@ -126,12 +133,13 @@ test('properly iterates through plugin search locations', async () => {
   const { plugin$, error$ } = discover(pluginsConfig, { configService, env, logger });
 
   const plugins = await plugin$.pipe(toArray()).toPromise();
-  expect(plugins).toHaveLength(3);
+  expect(plugins).toHaveLength(4);
 
   for (const path of [
     resolve(TEST_PLUGIN_SEARCH_PATHS.nonEmptySrcPlugins, '1'),
     resolve(TEST_PLUGIN_SEARCH_PATHS.nonEmptySrcPlugins, '3'),
     resolve(TEST_PLUGIN_SEARCH_PATHS.nonEmptySrcPlugins, '6'),
+    TEST_EXTRA_PLUGIN_PATH,
   ]) {
     const discoveredPlugin = plugins.find(plugin => plugin.path === path)!;
     expect(discoveredPlugin).toBeInstanceOf(Plugin);
@@ -174,4 +182,12 @@ test('properly iterates through plugin search locations', async () => {
       'kibana.json'
     )})`,
   ]);
+
+  expect(loggingServiceMock.collect(logger).warn).toMatchInlineSnapshot(`
+Array [
+  Array [
+    "Explicit plugin paths [${TEST_EXTRA_PLUGIN_PATH}] are only supported in development. Relative imports will not work in production.",
+  ],
+]
+`);
 });

src/core/server/plugins/discovery/plugins_discovery.ts

@@ -19,7 +19,7 @@
 
 import { readdir, stat } from 'fs';
 import { resolve } from 'path';
-import { bindNodeCallback, from } from 'rxjs';
+import { bindNodeCallback, from, merge } from 'rxjs';
 import { catchError, filter, map, mergeMap, shareReplay } from 'rxjs/operators';
 import { CoreContext } from '../../core_context';
 import { Logger } from '../../logging';
@@ -46,7 +46,18 @@ export function discover(config: PluginsConfig, coreContext: CoreContext) {
   const log = coreContext.logger.get('plugins-discovery');
   log.debug('Discovering plugins...');
 
-  const discoveryResults$ = processPluginSearchPaths$(config.pluginSearchPaths, log).pipe(
+  if (config.additionalPluginPaths.length) {
+    log.warn(
+      `Explicit plugin paths [${
+        config.additionalPluginPaths
+      }] are only supported in development. Relative imports will not work in production.`
+    );
+  }
+
+  const discoveryResults$ = merge(
+    from(config.additionalPluginPaths),
+    processPluginSearchPaths$(config.pluginSearchPaths, log)
+  ).pipe(
     mergeMap(pluginPathOrError => {
       return typeof pluginPathOrError === 'string'
         ? createPlugin$(pluginPathOrError, log, coreContext)

src/core/server/plugins/plugins_config.ts

@@ -22,6 +22,12 @@ import { Env } from '../config';
 
 const pluginsSchema = schema.object({
   initialize: schema.boolean({ defaultValue: true }),
+
+  /**
+   * Defines an array of directories where another plugin should be loaded from.
+   * Should only be used in a development environment.
+   */
+  paths: schema.arrayOf(schema.string(), { defaultValue: [] }),
 });
 
 type PluginsConfigType = TypeOf<typeof pluginsSchema>;
@@ -40,8 +46,15 @@ export class PluginsConfig {
    */
   public readonly pluginSearchPaths: ReadonlyArray<string>;
 
+  /**
+   * Defines directories where an additional plugin exists.
+   */
+  public readonly additionalPluginPaths: ReadonlyArray<string>;
+
   constructor(config: PluginsConfigType, env: Env) {
     this.initialize = config.initialize;
     this.pluginSearchPaths = env.pluginSearchPaths;
+    // Only allow custom plugin paths in dev.
+    this.additionalPluginPaths = env.mode.dev ? config.paths : [];
   }
 }

src/core/server/plugins/plugins_service.test.ts

@@ -302,6 +302,7 @@ test('`setup` properly invokes `discover` and ignores non-critical errors.', asy
   expect(mockDiscover).toHaveBeenCalledTimes(1);
   expect(mockDiscover).toHaveBeenCalledWith(
     {
+      additionalPluginPaths: [],
       initialize: true,
       pluginSearchPaths: [
         resolve(process.cwd(), 'src', 'plugins'),