Multiple apps don't work anymore

[sergibondarenko]

Kibana version:
7.6.0

Elasticsearch version:
7.6.0

Server OS version:
Mac OS 10.15.3

Browser version:
Chrome 79

Browser OS version:
Mac OS 10.15.3

Original install method (e.g. download page, yum, from source, etc.):
From git branch: https://github.com/elastic/kibana/tree/7.6

Describe the bug:
Multiple apps registration doesn't work anymore. The code snippet:

index.js

...
    uiExports: {
      apps: [
        {
          id: 'app_a',
          title: 'app_a',
          description: 'An awesome Kibana plugin',
          main: 'plugins/aplugin/apps/app_a/app',
        },
        {
          id: 'app_b',
          title: 'app_b',
          description: 'An awesome Kibana plugin',
          main: 'plugins/aplugin/apps/app_b/app',
        },
      ],

The demo plugin can be found here https://github.com/sergibondarenko/kibana_multi_app_plugin_FAILS

Steps to reproduce:

1. Install and run Elasticsearch 7.6.0 and Kibana 7.6.0
2. Clone the demo plugin https://github.com/sergibondarenko/kibana_multi_app_plugin_FAILS
3. Put it into "kibana/plugins" folder
4. Wait until Kibana restarts. Then put the following string to your browser URL: http://localhost:5601
5. See an error page saying

An application is already registered with the id "aplugin"

Expected behavior:
I should access Kibana with no error and see two new apps in the left nav bar: app_a and app_b.

Screenshots (if relevant):

Errors in browser console (if relevant):

Uncaught (in promise) Error: An application is already registered with the id "aplugin"
    at Object.registerLegacyApp (application_service.tsx:276)
    at legacy_service.ts:64
    at Array.forEach (<anonymous>)
    at LegacyPlatformService.setup (legacy_service.ts:63)
    at CoreSystem.setup$ (core_system.ts:212)
    at tryCatch (runtime.js:45)
    at Generator.invoke [as _invoke] (runtime.js:271)
    at Generator.prototype.<computed> [as next] (runtime.js:97)
    at tryCatch (runtime.js:45)
    at invoke (runtime.js:135)

[elasticmachine]

Pinging @elastic/kibana-platform (Team:Platform)

[pgayvallet]

It seems the pluginId is prevalent to the actual declared application id when gathering the legacy navlinks/apps:

kibana/src/core/server/legacy/plugins/find_legacy_plugin_specs.ts

Lines 44 to 54 in 8c29802

	function getUiAppsNavLinks({ uiAppSpecs = [] }: LegacyUiExports, pluginSpecs: LegacyPluginSpec[]) {
	return uiAppSpecs.flatMap(spec => {
	if (!spec) {
	return REMOVE_FROM_ARRAY;
	}
	const id = spec.pluginId || spec.id;
	if (!id) {
	throw new Error('Every app must specify an id');
	}

which results in multiple apps with the same 'id' being registered twice:

kibana/src/core/public/application/application_service.tsx

Lines 196 to 202 in 47d0744

	registerLegacyApp: app => {
	const appRoute = `/app/${app.id.split(':')[0]}`;
	if (this.registrationClosed) {
	throw new Error('Applications cannot be registered after "setup"');
	} else if (this.apps.has(app.id)) {
	throw new Error(`An application is already registered with the id "${app.id}"`);

need to investigate on what caused this, I'm not aware of any major changes in the way we were merging plugin specs in src/core/server/legacy/plugins/find_legacy_plugin_specs.ts

@sergibondarenko can you confirm this did work properly on a 7.5.x ?

[pgayvallet]

Also, this seems to be still working with the kibana security plugin

kibana/x-pack/legacy/plugins/security/index.js

Lines 44 to 55 in b228689

	apps: [
	{
	id: 'login',
	title: 'Login',
	main: 'plugins/security/views/login',
	hidden: true,
	},
	{
	id: 'overwritten_session',
	title: 'Overwritten Session',
	main: 'plugins/security/views/overwritten_session',
	description:

[sergibondarenko]

@pgayvallet I confirm, the app works in Kibana v7.5.x

[sergibondarenko]

The plugin is loaded as expected in Kibana v7.6 if the line

const id = spec.pluginId || spec.id; 

is substituted by

const id = spec.id || spec.pluginId; 

in kibana/src/core/server/legacy/plugins/find_legacy_plugin_specs.ts

[pgayvallet]

Reproduction confirmed on current master (c5a60b9)

Also it does work with security as all registered apps are hidden, and hidden apps are excluded from the navlink generation

kibana/src/core/server/legacy/plugins/find_legacy_plugin_specs.ts

Lines 62 to 64 in 8c29802

	if (spec.hidden || !listed) {
	return REMOVE_FROM_ARRAY;
	}

This was caused by #52161. Before that, the gathered apps were only using the id prop

kibana/src/legacy/ui/ui_apps/ui_apps_mixin.js

Lines 37 to 54 in 054ec70

	kbnServer.uiApps = uiAppSpecs.map(spec => {
	const app = new UiApp(kbnServer, spec);
	const id = app.getId();
	if (!existingIds.has(id)) {
	existingIds.add(id);
	} else {
	throw new Error(`Unable to create two apps with the id ${id}.`);
	}
	if (app.isHidden()) {
	hiddenAppsById.set(id, app);
	} else {
	appsById.set(id, app);
	}
	return app;
	});

kibana/src/legacy/ui/ui_apps/ui_app.js

Lines 81 to 83 in 8c29802

	getId() {
	return this._id;
	}

[pgayvallet]

@sergibondarenko thanks for the complete reproduction scenario. That helped a lot. On it.

[joshdover]

Removing the regression label since this is a break on an experimental, unsupported API.