Manager: Add tags property to ComponentEntry objects

code/core/src/manager-api/lib/intersect.ts

@@ -0,0 +1,14 @@
+export default <T>(a: T[], b: T[]): T[] => {
+  // no point in intersecting if one of the input is ill-defined
+  if (!a || !b) {
+    return [];
+  }
+
+  return a.reduce((acc: T[], aValue) => {
+    if (b.includes(aValue)) {
+      acc.push(aValue);
+    }
+
+    return acc;
+  }, []);
+};

code/core/src/manager-api/lib/stories.ts

@@ -24,6 +24,7 @@ import memoize from 'memoizerific';
 import { dedent } from 'ts-dedent';
 
 import { type API, type State, combineParameters } from '../root';
+import intersect from './intersect';
 import merge from './merge';
 
 const TITLE_PATH_SEPARATOR = /\s*\/\s*/;
@@ -273,6 +274,9 @@ export const transformStoryIndexToStoriesHash = (
             children: [childId],
           }),
         });
+        // merge computes a union of arrays but we want an intersection on this
+        // specific array property, so it's easier to add it after the merge.
+        acc[id].tags = intersect(acc[id]?.tags ?? item.tags, item.tags);
       } else {
         acc[id] = merge<API_GroupEntry>((acc[id] || {}) as API_GroupEntry, {
           type: 'group',

code/core/src/manager-api/tests/intersect.test.ts

@@ -0,0 +1,44 @@
+import { describe, expect, it } from 'vitest';
+
+import intersect from '../lib/intersect';
+
+describe('Manager API utilities - intersect', () => {
+  it('returns identity when intersecting identity', () => {
+    const a = ['foo', 'bar'];
+    expect(intersect(a, a)).toEqual(a);
+  });
+
+  it('returns a when b is a superset of a', () => {
+    const a = ['foo', 'bar'];
+    const b = ['a', 'foo', 'b', 'bar', 'c', 'ter'];
+    expect(intersect(a, b)).toEqual(a);
+  });
+
+  it('returns b when a is a superset of b', () => {
+    const a = ['a', 'foo', 'b', 'bar', 'c', 'ter'];
+    const b = ['foo', 'bar'];
+    expect(intersect(a, b)).toEqual(b);
+  });
+
+  it('returns an intersection', () => {
+    const a = ['a', 'bar', 'b', 'c'];
+    const b = ['foo', 'bar', 'ter'];
+    expect(intersect(a, b)).toEqual(['bar']);
+  });
+
+  it('returns an empty set when there is no overlap', () => {
+    const a = ['a', 'b', 'c'];
+    const b = ['foo', 'bar', 'ter'];
+    expect(intersect(a, b)).toEqual([]);
+  });
+
+  it('returns an empty set if a is undefined', () => {
+    const b = ['foo', 'bar', 'ter'];
+    expect(intersect(undefined as unknown as [], b)).toEqual([]);
+  });
+
+  it('returns an empty set if b is undefined', () => {
+    const a = ['foo', 'bar', 'ter'];
+    expect(intersect(a, undefined as unknown as [])).toEqual([]);
+  });
+});

code/core/src/manager-api/tests/stories.test.ts

@@ -281,6 +281,57 @@ describe('stories API', () => {
         name: '1',
       });
     });
+    it('intersects story/docs tags to compute tags for component entries', () => {
+      const moduleArgs = createMockModuleArgs({});
+      const { api } = initStories(moduleArgs as unknown as ModuleArgs);
+      const { store } = moduleArgs;
+      api.setIndex({
+        v: 5,
+        entries: {
+          'a--1': {
+            type: 'story',
+            id: 'a--1',
+            title: 'a',
+            name: '1',
+            tags: ['shared', 'one-specific'],
+            importPath: './a.ts',
+          },
+          'a--2': {
+            type: 'story',
+            id: 'a--2',
+            title: 'a',
+            name: '2',
+            tags: ['shared', 'two-specific'],
+            importPath: './a.ts',
+          },
+        },
+      });
+      const { index } = store.getState();
+      // We need exact key ordering, even if in theory JS doesn't guarantee it
+      expect(Object.keys(index!)).toEqual(['a', 'a--1', 'a--2']);
+      expect(index!.a).toMatchObject({
+        type: 'component',
+        id: 'a',
+        tags: ['shared'],
+        children: ['a--1', 'a--2'],
+      });
+      expect(index!['a--1']).toMatchObject({
+        type: 'story',
+        id: 'a--1',
+        parent: 'a',
+        title: 'a',
+        name: '1',
+        tags: ['shared', 'one-specific'],
+      });
+      expect(index!['a--2']).toMatchObject({
+        type: 'story',
+        id: 'a--2',
+        parent: 'a',
+        title: 'a',
+        name: '2',
+        tags: ['shared', 'two-specific'],
+      });
+    });
     // Stories can get out of order for a few reasons -- see reproductions on
     //   https://github.com/storybookjs/storybook/issues/5518
     it('does the right thing for out of order stories', async () => {
@@ -1453,6 +1504,7 @@ describe('stories API', () => {
             "name": "a",
             "parent": undefined,
             "renderLabel": undefined,
+            "tags": [],
             "type": "component",
           },
           "a--1": {
@@ -1518,6 +1570,7 @@ describe('stories API', () => {
             "name": "a",
             "parent": undefined,
             "renderLabel": undefined,
+            "tags": [],
             "type": "component",
           },
           "a--1": {
@@ -1559,6 +1612,7 @@ describe('stories API', () => {
             "name": "a",
             "parent": undefined,
             "renderLabel": undefined,
+            "tags": [],
             "type": "component",
           },
           "a--1": {

code/core/src/types/modules/api-stories.ts

@@ -27,6 +27,7 @@ export interface API_ComponentEntry extends API_BaseEntry {
   type: 'component';
   parent?: StoryId;
   children: StoryId[];
+  tags: Tag[];
 }
 
 export interface API_DocsEntry extends API_BaseEntry {