CSF3: Handle auto-title redundant filename

MIGRATION.md

@@ -1,5 +1,7 @@
 <h1>Migration</h1>
 
+- [From version 6.4.x to 6.5.0](#from-version-64x-to-650)
+  - [CSF3 auto-title redundant filename](#csf3-auto-title-redundant-filename)
 - [From version 6.3.x to 6.4.0](#from-version-63x-to-640)
   - [Automigrate](#automigrate)
   - [CRA5 upgrade](#cra5-upgrade)
@@ -188,6 +190,23 @@
   - [Packages renaming](#packages-renaming)
   - [Deprecated embedded addons](#deprecated-embedded-addons)
 
+## From version 6.4.x to 6.5.0
+
+### CSF3 auto-title redundant filename
+
+SB 6.4 introduced experimental "auto-title", in which a story's location in the sidebar (aka `title`) can be automatically inferred from its location on disk. For example, the file `atoms/Button.stories.js` might result in the title `Atoms/Button`.
+
+The heuristic failed in the common scenario in which each component gets its own directory, e.g. `atoms/Button/Button.stories.js`, which would result in the redundant title `Atoms/Button/Button`. Alternatively, `atoms/Button/index.stories.js` would result in `Atoms/Button/Index`.
+
+To address this problem, 6.5 introduces a new heuristic to removes the filename if it matches the directory name (case insensitive) or `index`. So `atoms/Button/Button.stories.js` and `atoms/Button/index.stories.js` would both result in the title `Atoms/Button`.
+
+Since CSF3 is experimental, we are introducing this technically breaking change in a minor release. If you desire the old structure, you can manually specify the title in file. For example:
+
+```js
+// atoms/Button/Button.stories.js
+export default { title: 'Atoms/Button/Button' };
+```
+
 ## From version 6.3.x to 6.4.0
 
 ### Automigrate

lib/store/src/autoTitle.test.ts

@@ -40,6 +40,24 @@ describe('autoTitle', () => {
       ).toMatchInlineSnapshot(`Atoms/To/File`);
     });
 
+    it('match with trailing duplicate', () => {
+      expect(
+        auto(
+          './path/to/button/button.stories.js',
+          normalizeStoriesEntry({ directory: './path' }, options)
+        )
+      ).toMatchInlineSnapshot(`To/Button`);
+    });
+
+    it('match with trailing index', () => {
+      expect(
+        auto(
+          './path/to/button/index.stories.js',
+          normalizeStoriesEntry({ directory: './path' }, options)
+        )
+      ).toMatchInlineSnapshot(`To/Button`);
+    });
+
     it('match with hyphen path', () => {
       expect(
         auto(

lib/store/src/autoTitle.ts

@@ -10,8 +10,8 @@ interface NormalizedStoriesSpecifier {
   importPathMatcher: RegExp;
 }
 
-const stripExtension = (titleWithExtension: string) => {
-  let parts = titleWithExtension.split('/');
+const stripExtension = (path: string[]) => {
+  let parts = [...path];
   const last = parts[parts.length - 1];
   const dotIndex = last.indexOf('.');
   const stripped = dotIndex > 0 ? last.substr(0, dotIndex) : last;
@@ -20,11 +20,19 @@ const stripExtension = (titleWithExtension: string) => {
   if (first === '') {
     parts = rest;
   }
-  return parts.join('/');
+  return parts;
 };
 
-const startCaseTitle = (title: string) => {
-  return title.split('/').map(startCase).join('/');
+// deal with files like "atoms/button/{button,index}.stories.js"
+const removeRedundantFilename = (paths: string[]) => {
+  let prevVal: string;
+  return paths.filter((val, index) => {
+    if (index === paths.length - 1 && (val === prevVal || val === 'Index')) {
+      return false;
+    }
+    prevVal = val;
+    return true;
+  });
 };
 
 /**
@@ -48,7 +56,10 @@ export const autoTitleFromSpecifier = (fileName: string, entry: NormalizedStorie
   if (importPathMatcher.exec(normalizedFileName)) {
     const suffix = normalizedFileName.replace(directory, '');
     const titleAndSuffix = slash(pathJoin([titlePrefix, suffix]));
-    return startCaseTitle(stripExtension(titleAndSuffix));
+    let path = titleAndSuffix.split('/');
+    path = stripExtension(path).map(startCase);
+    path = removeRedundantFilename(path);
+    return path.join('/');
   }
   return undefined;
 };