title formatter

packages/docusaurus-theme-common/src/utils/__tests__/generalUtils.test.tsx

@@ -1,33 +0,0 @@
-/**
- * Copyright (c) Facebook, Inc. and its affiliates.
- *
- * This source code is licensed under the MIT license found in the
- * LICENSE file in the root directory of this source tree.
- */
-
-import React from 'react';
-import {renderHook} from '@testing-library/react-hooks';
-import {Context} from '@docusaurus/core/src/client/docusaurusContext';
-import {useTitleFormatter} from '../generalUtils';
-import type {DocusaurusContext} from '@docusaurus/types';
-
-describe('useTitleFormatter', () => {
-  const createUseTitleFormatterMock =
-    (context: DocusaurusContext) => (title?: string) =>
-      renderHook(() => useTitleFormatter(title), {
-        wrapper: ({children}) => (
-          <Context.Provider value={context}>{children}</Context.Provider>
-        ),
-      }).result.current;
-  it('works', () => {
-    const mockUseTitleFormatter = createUseTitleFormatterMock({
-      siteConfig: {
-        title: 'my site',
-        titleDelimiter: '·',
-      },
-    } as DocusaurusContext);
-    expect(mockUseTitleFormatter('a page')).toBe('a page · my site');
-    expect(mockUseTitleFormatter(undefined)).toBe('my site');
-    expect(mockUseTitleFormatter('    ')).toBe('my site');
-  });
-});

packages/docusaurus-theme-common/src/utils/__tests__/titleFormatter.test.tsx

@@ -0,0 +1,43 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+import {DefaultTitleFormatter} from '../generalUtils';
+
+describe('DefaultTitleFormatter', () => {
+  it('works', () => {
+    expect(
+      DefaultTitleFormatter({
+        title: 'a page',
+        siteTitle: 'my site',
+        titleDelimiter: '·',
+      }),
+    ).toBe('a page · my site');
+  });
+
+  it('ignores empty title', () => {
+    expect(
+      DefaultTitleFormatter({
+        title: '    ',
+        siteTitle: 'my site',
+        titleDelimiter: '·',
+      }),
+    ).toBe('my site');
+  });
+
+  it('does not duplicate site title', () => {
+    // Users may pass <Layout title={siteTitle}> leading to duplicate titles
+    // By default it's preferable to avoid duplicate siteTitle
+    // See also https://github.com/facebook/docusaurus/issues/5878#issuecomment-961505856
+    expect(
+      DefaultTitleFormatter({
+        title: 'my site',
+        siteTitle: 'my site',
+        titleDelimiter: '·',
+      }),
+    ).toBe('my site');
+  });
+});

packages/docusaurus-theme-common/src/utils/generalUtils.ts

@@ -1,19 +0,0 @@
-/**
- * Copyright (c) Facebook, Inc. and its affiliates.
- *
- * This source code is licensed under the MIT license found in the
- * LICENSE file in the root directory of this source tree.
- */
-
-import useDocusaurusContext from '@docusaurus/useDocusaurusContext';
-
-/**
- * Formats the page's title based on relevant site config and other contexts.
- */
-export function useTitleFormatter(title?: string | undefined): string {
-  const {siteConfig} = useDocusaurusContext();
-  const {title: siteTitle, titleDelimiter} = siteConfig;
-  return title?.trim().length
-    ? `${title.trim()} ${titleDelimiter} ${siteTitle}`
-    : siteTitle;
-}

packages/docusaurus-theme-common/src/utils/titleFormatter.tsx

@@ -0,0 +1,42 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+import useDocusaurusContext from '@docusaurus/useDocusaurusContext';
+
+type TitleFormatterParams = {
+  title: string | undefined;
+  siteTitle: string;
+  titleDelimiter: string;
+};
+
+type TitleFormatterFn = (params: TitleFormatterParams) => string;
+
+export const DefaultTitleFormatter: TitleFormatterFn = ({
+  title,
+  siteTitle,
+  titleDelimiter,
+}: TitleFormatterParams): string => {
+  const trimmedTitle = title?.trim();
+  if (!trimmedTitle || trimmedTitle === siteTitle) {
+    return siteTitle;
+  }
+  return `${trimmedTitle} ${titleDelimiter} ${siteTitle}`;
+};
+
+type TitleFormatter = {format: (title?: string) => string};
+
+/**
+ * Returns a function to format the page title
+ */
+export function useTitleFormatter(): TitleFormatter {
+  const {siteConfig} = useDocusaurusContext();
+  const formatter = DefaultTitleFormatter;
+  const {title: siteTitle, titleDelimiter} = siteConfig;
+  return {
+    format: (title) => formatter({title, siteTitle, titleDelimiter}),
+  };
+}