fix code and add test

code/lib/core-server/src/presets/common-preset.ts

@@ -1,4 +1,4 @@
-import fs, { pathExists } from 'fs-extra';
+import { pathExists, readFile } from 'fs-extra';
 import { deprecate, logger } from '@storybook/node-logger';
 import {
   getDirectoryFromWorkingDir,
@@ -21,7 +21,10 @@ import { parseStaticDir } from '../utils/server-statics';
 
 const defaultFavicon = require.resolve('@storybook/core-server/public/favicon.svg');
 
-export const favicon = async (value: string, options: Options) => {
+export const favicon = async (
+  value: string,
+  options: Pick<Options, 'presets' | 'configDir' | 'staticDir'>
+) => {
   if (value) {
     return value;
   }
@@ -42,6 +45,7 @@ export const favicon = async (value: string, options: Options) => {
               directory: dir,
             })
           : dir;
+
         const { staticPath, targetEndpoint } = await parseStaticDir(relativeDir);
 
         if (targetEndpoint === '/') {
@@ -58,16 +62,17 @@ export const favicon = async (value: string, options: Options) => {
             results.push(path);
           }
         }
+
+        return results;
       })
     );
-
     const flatlist = lists.reduce((l1, l2) => l1.concat(l2), []);
 
     if (flatlist.length > 1) {
       logger.warn(dedent`
         Looks like multiple favicons were detected. Using the first one.
         
-        ${flatlist.map((f) => f.path).join(', ')}
+        ${flatlist.join(', ')}
         `);
     }
 
@@ -170,7 +175,7 @@ export const features = async (
 
 export const storyIndexers = async (indexers?: StoryIndexer[]) => {
   const csfIndexer = async (fileName: string, opts: IndexerOptions) => {
-    const code = (await fs.readFile(fileName, 'utf-8')).toString();
+    const code = (await readFile(fileName, 'utf-8')).toString();
     return loadCsf(code, { ...opts, fileName }).parse();
   };
   return [

code/lib/core-server/src/presets/favicon.test.ts

@@ -0,0 +1,127 @@
+/// <reference types="@types/jest" />;
+
+import { join } from 'path';
+import * as fs from 'fs-extra';
+import { logger } from '@storybook/node-logger';
+import * as m from './common-preset';
+
+const defaultFavicon = require.resolve('@storybook/core-server/public/favicon.svg');
+
+const createPath = (...p: string[]) => join(process.cwd(), ...p);
+const createOptions = (locations: string[]): Parameters<typeof m.favicon>[1] => ({
+  configDir: '',
+  presets: {
+    apply: async (extension: string, config: any) => {
+      switch (extension) {
+        case 'staticDirs': {
+          return locations.map((location) => ({ from: location, to: '/' }));
+        }
+        default: {
+          return config as any;
+        }
+      }
+    },
+  },
+});
+
+jest.mock('fs-extra', () => {
+  return {
+    pathExists: jest.fn((p: string) => {
+      return false;
+    }),
+  };
+});
+
+jest.mock('@storybook/node-logger', () => {
+  return {
+    logger: {
+      warn: jest.fn(() => {}),
+    },
+  };
+});
+
+const pathExists = fs.pathExists as jest.Mock;
+
+test('with no staticDirs favicon should return default', async () => {
+  const options = createOptions([]);
+
+  expect(await m.favicon(undefined, options)).toBe(defaultFavicon);
+});
+
+test('with staticDirs containing a single favicon.ico should return the found favicon', async () => {
+  const location = 'static';
+  pathExists.mockImplementation((p: string) => {
+    if (p === createPath(location)) {
+      return true;
+    }
+    if (p === createPath(location, 'favicon.ico')) {
+      return true;
+    }
+    return false;
+  });
+  const options = createOptions([location]);
+
+  expect(await m.favicon(undefined, options)).toBe(createPath(location, 'favicon.ico'));
+});
+
+test('with staticDirs containing a single favicon.svg should return the found favicon', async () => {
+  const location = 'static';
+  pathExists.mockImplementation((p: string) => {
+    if (p === createPath(location)) {
+      return true;
+    }
+    if (p === createPath(location, 'favicon.svg')) {
+      return true;
+    }
+    return false;
+  });
+  const options = createOptions([location]);
+
+  expect(await m.favicon(undefined, options)).toBe(createPath(location, 'favicon.svg'));
+});
+
+test('with staticDirs containing a multiple favicons should return the first favicon and warn', async () => {
+  const location = 'static';
+  pathExists.mockImplementation((p: string) => {
+    if (p === createPath(location)) {
+      return true;
+    }
+    if (p === createPath(location, 'favicon.ico')) {
+      return true;
+    }
+    if (p === createPath(location, 'favicon.svg')) {
+      return true;
+    }
+    return false;
+  });
+  const options = createOptions([location]);
+
+  expect(await m.favicon(undefined, options)).toBe(createPath(location, 'favicon.svg'));
+
+  expect(logger.warn).toHaveBeenCalledWith(expect.stringContaining('multiple favicons'));
+});
+
+test('with multiple staticDirs containing a multiple favicons should return the first favicon and warn', async () => {
+  const locationA = 'static-a';
+  const locationB = 'static-b';
+  pathExists.mockImplementation((p: string) => {
+    if (p === createPath(locationA)) {
+      return true;
+    }
+    if (p === createPath(locationB)) {
+      return true;
+    }
+    if (p === createPath(locationA, 'favicon.ico')) {
+      return true;
+    }
+    if (p === createPath(locationB, 'favicon.svg')) {
+      return true;
+    }
+    return false;
+  });
+  const options = createOptions([locationA, locationB]);
+
+  expect(await m.favicon(undefined, options)).toBe(createPath(locationA, 'favicon.ico'));
+
+  expect(logger.warn).toHaveBeenCalledWith(expect.stringContaining('multiple favicons'));
+});