[pluginDiscovery] fail early if multiple plugins have conflicting ids (#17311) (#17445)

src/plugin_discovery/__tests__/find_plugin_specs.js

@@ -5,6 +5,7 @@ import { findPluginSpecs } from '../find_plugin_specs';
 import { PluginSpec } from '../plugin_spec';
 
 const PLUGIN_FIXTURES = resolve(__dirname, 'fixtures/plugins');
+const CONFLICT_FIXTURES = resolve(__dirname, 'fixtures/conflicts');
 
 describe('plugin discovery', () => {
   describe('findPluginSpecs()', function () {
@@ -92,5 +93,26 @@ describe('plugin discovery', () => {
       expect(specs.map(s => s.getId()).sort())
         .to.eql(['bar:one', 'bar:two', 'foo']);
     });
+
+    describe('conflicting plugin spec ids', () => {
+      it('fails with informative message', async () => {
+        const { spec$ } = findPluginSpecs({
+          plugins: {
+            scanDirs: [],
+            paths: [
+              resolve(CONFLICT_FIXTURES, 'foo'),
+            ],
+          }
+        });
+
+        try {
+          await spec$.toArray().toPromise();
+          throw new Error('expected spec$ to throw an error');
+        } catch (error) {
+          expect(error.message).to.contain('Multple plugins found with the id "foo"');
+          expect(error.message).to.contain(CONFLICT_FIXTURES);
+        }
+      });
+    });
   });
 });

src/plugin_discovery/__tests__/fixtures/conflicts/foo/index.js

@@ -0,0 +1,8 @@
+export default function (kibana) {
+  return [
+    // two plugins exported without ids will both inherit
+    // the id of the pack and conflict
+    new kibana.Plugin({}),
+    new kibana.Plugin({}),
+  ];
+}

src/plugin_discovery/__tests__/fixtures/conflicts/foo/package.json

@@ -0,0 +1,4 @@
+{
+  "name": "foo",
+  "version": "kibana"
+}

src/plugin_discovery/find_plugin_specs.js

@@ -53,6 +53,19 @@ function getDistinctKeyForFindResult(result) {
   return result;
 }
 
+function groupSpecsById(specs) {
+  const specsById = new Map();
+  for (const spec of specs) {
+    const id = spec.getId();
+    if (specsById.has(id)) {
+      specsById.get(id).push(spec);
+    } else {
+      specsById.set(id, [spec]);
+    }
+  }
+  return specsById;
+}
+
 /**
  *  Creates a collection of observables for discovering pluginSpecs
  *  using Kibana's defaults, settings, and config service
@@ -76,6 +89,22 @@ export function findPluginSpecs(settings, config = defaultConfig(settings)) {
     .mergeMap(({ pack }) => (
       pack ? pack.getPluginSpecs() : []
     ))
+    // make sure that none of the plugin specs have conflicting ids, fail
+    // early if conflicts detected or merge the specs back into the stream
+    .toArray()
+    .mergeMap(allSpecs => {
+      for (const [id, specs] of groupSpecsById(allSpecs)) {
+        if (specs.length > 1) {
+          throw new Error(
+            `Multple plugins found with the id "${id}":\n${
+              specs.map(spec => `  - ${id} at ${spec.getPath()}`).join('\n')
+            }`
+          );
+        }
+      }
+
+      return allSpecs;
+    })
     .mergeMap(async (spec) => {
       // extend the config service with this plugin spec and
       // collect its deprecations messages if some of its