polish(theme-classic): guard against potential definition mistakes in Tabs (#5674)

jest.config.js

@@ -33,11 +33,14 @@ module.exports = {
   },
   setupFiles: ['./jest/stylelint-rule-test.js', './jest/polyfills.js'],
   moduleNameMapper: {
+    // Jest can't resolve CSS imports
+    '^.+\\.css$': '<rootDir>/jest/emptyModule.js',
     // TODO we need to allow Jest to resolve core Webpack aliases automatically
-    '@docusaurus/router': 'react-router-dom',
-    '@docusaurus/Translate': '@docusaurus/core/lib/client/exports/Translate',
-    '@docusaurus/Interpolate':
-      '@docusaurus/core/lib/client/exports/Interpolate',
-    '@generated/codeTranslations': '<rootDir>/jest/emptyModule.js',
+    '@docusaurus/(browserContext|BrowserOnly|ComponentCreator|constants|docusaurusContext|ExecutionEnvironment|Head|Interpolate|isInternalUrl|Link|Noop|renderRoutes|router|Translate|use.*)':
+      '@docusaurus/core/lib/client/exports/$1',
+    // Maybe point to a fixture?
+    '@generated/.*': '<rootDir>/jest/emptyModule.js',
+    // TODO maybe use "projects" + multiple configs if we plan to add tests to another theme?
+    '@theme/(.*)': '@docusaurus/theme-classic/lib-next/theme/$1',
   },
 };

package.json

@@ -81,6 +81,7 @@
     "@types/react-helmet": "^6.0.0",
     "@types/react-loadable": "^5.5.3",
     "@types/react-router-config": "^5.0.1",
+    "@types/react-test-renderer": "^17.0.1",
     "@types/semver": "^7.1.0",
     "@types/shelljs": "^0.8.6",
     "@types/wait-on": "^5.2.0",
@@ -110,6 +111,7 @@
     "prettier": "^2.4.1",
     "react": "^17.0.1",
     "react-dom": "^17.0.1",
+    "react-test-renderer": "^17.0.2",
     "rimraf": "^3.0.2",
     "serve": "^12.0.1",
     "stylelint": "^13.10.0",

packages/docusaurus-theme-classic/package.json

@@ -54,6 +54,7 @@
     "@types/mdx-js__react": "^1.5.4",
     "@types/parse-numeric-range": "^0.0.1",
     "@types/rtlcss": "^3.1.1",
+    "react-test-renderer": "^17.0.2",
     "utility-types": "^3.10.0"
   },
   "peerDependencies": {

packages/docusaurus-theme-classic/src/theme/Tabs/__tests__/index.test.tsx

@@ -0,0 +1,106 @@
+/**
+ * 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 renderer from 'react-test-renderer';
+import Tabs from '../index';
+import TabItem from '../../TabItem';
+
+describe('Tabs', () => {
+  test('Should reject bad Tabs child', () => {
+    expect(() => {
+      renderer.create(
+        <Tabs>
+          <div>Naughty</div>
+          <TabItem value="good">Good</TabItem>
+        </Tabs>,
+      );
+    }).toThrowErrorMatchingInlineSnapshot(
+      `"Docusaurus error: Bad <Tabs> child <div>: all children of the <Tabs> component should be <TabItem>, and every <TabItem> should have a unique \\"value\\" prop."`,
+    );
+  });
+  test('Should reject bad Tabs defaultValue', () => {
+    expect(() => {
+      renderer.create(
+        <Tabs defaultValue="bad">
+          <TabItem value="v1">Tab 1</TabItem>
+          <TabItem value="v2">Tab 2</TabItem>
+        </Tabs>,
+      );
+    }).toThrowErrorMatchingInlineSnapshot(
+      `"Docusaurus error: The <Tabs> has a defaultValue \\"bad\\" but none of its children has the corresponding value. Available values are: v1, v2. If you intend to show no default tab, use defaultValue={null} instead."`,
+    );
+  });
+  test('Should reject duplicate values', () => {
+    expect(() => {
+      renderer.create(
+        <Tabs>
+          <TabItem value="v1">Tab 1</TabItem>
+          <TabItem value="v2">Tab 2</TabItem>
+          <TabItem value="v3">Tab 3</TabItem>
+          <TabItem value="v4">Tab 4</TabItem>
+          <TabItem value="v1">Tab 5</TabItem>
+          <TabItem value="v2">Tab 6</TabItem>
+        </Tabs>,
+      );
+    }).toThrowErrorMatchingInlineSnapshot(
+      `"Docusaurus error: Duplicate values \\"v1, v2\\" found in <Tabs>. Every value needs to be unique."`,
+    );
+  });
+  test('Should accept valid Tabs config', () => {
+    expect(() => {
+      renderer.create(
+        <>
+          <Tabs>
+            <TabItem value="v1">Tab 1</TabItem>
+            <TabItem value="v2">Tab 2</TabItem>
+          </Tabs>
+          <Tabs>
+            <TabItem value="v1">Tab 1</TabItem>
+            <TabItem value="v2" default>
+              Tab 2
+            </TabItem>
+          </Tabs>
+          <Tabs defaultValue="v1">
+            <TabItem value="v1" label="V1">
+              Tab 1
+            </TabItem>
+            <TabItem value="v2" label="V2">
+              Tab 2
+            </TabItem>
+          </Tabs>
+          <Tabs
+            defaultValue="v1"
+            values={[
+              {value: 'v1', label: 'V1'},
+              {value: 'v2', label: 'V2'},
+            ]}>
+            <TabItem>Tab 1</TabItem>
+            <TabItem>Tab 2</TabItem>
+          </Tabs>
+          <Tabs
+            defaultValue={null}
+            values={[
+              {value: 'v1', label: 'V1'},
+              {value: 'v2', label: 'V2'},
+            ]}>
+            <TabItem>Tab 1</TabItem>
+            <TabItem>Tab 2</TabItem>
+          </Tabs>
+          <Tabs defaultValue={null}>
+            <TabItem value="v1" label="V1">
+              Tab 1
+            </TabItem>
+            <TabItem value="v2" label="V2">
+              Tab 2
+            </TabItem>
+          </Tabs>
+        </>,
+      );
+    }).toMatchInlineSnapshot(`[Function]`); // This is just a check that the function returns. We don't care about the actual DOM.
+  });
+});

packages/docusaurus-theme-classic/src/theme/Tabs/index.tsx

@@ -5,10 +5,16 @@
  * LICENSE file in the root directory of this source tree.
  */
 
-import React, {useState, cloneElement, Children, ReactElement} from 'react';
+import React, {
+  useState,
+  cloneElement,
+  Children,
+  isValidElement,
+  ReactElement,
+} from 'react';
 import useIsBrowser from '@docusaurus/useIsBrowser';
 import useUserPreferencesContext from '@theme/hooks/useUserPreferencesContext';
-import {useScrollPositionBlocker} from '@docusaurus/theme-common';
+import {useScrollPositionBlocker, duplicates} from '@docusaurus/theme-common';
 import type {Props} from '@theme/Tabs';
 import type {Props as TabItemProps} from '@theme/TabItem';
 
@@ -16,6 +22,12 @@ import clsx from 'clsx';
 
 import styles from './styles.module.css';
 
+// A very rough duck type, but good enough to guard against mistakes while
+// allowing customization
+function isTabItem(comp: ReactElement): comp is ReactElement<TabItemProps> {
+  return typeof comp.props.value === 'string';
+}
+
 function TabsComponent(props: Props): JSX.Element {
   const {
     lazy,
@@ -25,21 +37,48 @@ function TabsComponent(props: Props): JSX.Element {
     groupId,
     className,
   } = props;
-  const children = Children.toArray(
-    props.children,
-  ) as ReactElement<TabItemProps>[];
+  const children = Children.map(props.children, (child) => {
+    if (isValidElement(child) && isTabItem(child)) {
+      return child;
+    }
+    // child.type.name will give non-sensical values in prod because of
+    // minification, but we assume it won't throw in prod.
+    throw new Error(
+      `Docusaurus error: Bad <Tabs> child <${
+        // @ts-expect-error: guarding against unexpected cases
+        typeof child.type === 'string' ? child.type : child.type.name
+      }>: all children of the <Tabs> component should be <TabItem>, and every <TabItem> should have a unique "value" prop.`,
+    );
+  });
   const values =
     valuesProp ??
-    children.map((child) => {
-      return {
-        value: child.props.value,
-        label: child.props.label,
-      };
+    children.map(({props: {value, label}}) => {
+      return {value, label};
     });
+  const dup = duplicates(values, (a, b) => a.value === b.value);
+  if (dup.length > 0) {
+    throw new Error(
+      `Docusaurus error: Duplicate values "${dup
+        .map((a) => a.value)
+        .join(', ')}" found in <Tabs>. Every value needs to be unique.`,
+    );
+  }
+  // When defaultValueProp is null, don't show a default tab
   const defaultValue =
-    defaultValueProp ??
+    defaultValueProp === null
+      ? defaultValueProp
+      : defaultValueProp ??
         children.find((child) => child.props.default)?.props.value ??
         children[0]?.props.value;
+  if (defaultValue !== null && !values.some((a) => a.value === defaultValue)) {
+    throw new Error(
+      `Docusaurus error: The <Tabs> has a defaultValue "${defaultValue}" but none of its children has the corresponding value. Available values are: ${values
+        .map((a) => a.value)
+        .join(
+          ', ',
+        )}. If you intend to show no default tab, use defaultValue={null} instead.`,
+    );
+  }
 
   const {tabGroupChoices, setTabGroupChoices} = useUserPreferencesContext();
   const [selectedValue, setSelectedValue] = useState(defaultValue);
@@ -80,12 +119,12 @@ function TabsComponent(props: Props): JSX.Element {
 
     switch (event.key) {
       case 'ArrowRight': {
-        const nextTab = tabRefs.indexOf(event.target as HTMLLIElement) + 1;
+        const nextTab = tabRefs.indexOf(event.currentTarget) + 1;
         focusElement = tabRefs[nextTab] || tabRefs[0];
         break;
       }
       case 'ArrowLeft': {
-        const prevTab = tabRefs.indexOf(event.target as HTMLLIElement) - 1;
+        const prevTab = tabRefs.indexOf(event.currentTarget) - 1;
         focusElement = tabRefs[prevTab] || tabRefs[tabRefs.length - 1];
         break;
       }

packages/docusaurus-theme-classic/src/types.d.ts

@@ -529,7 +529,7 @@ declare module '@theme/Tabs' {
     readonly lazy?: boolean;
     readonly block?: boolean;
     readonly children: readonly ReactElement<TabItemProps>[];
-    readonly defaultValue?: string;
+    readonly defaultValue?: string | null;
     readonly values?: readonly {value: string; label?: string}[];
     readonly groupId?: string;
     readonly className?: string;

packages/docusaurus-theme-common/src/index.ts

@@ -59,6 +59,8 @@ export {
   useDocsPreferredVersionByPluginId,
 } from './utils/docsPreferredVersion/useDocsPreferredVersion';
 
+export {duplicates} from './utils/jsUtils';
+
 export {DocsPreferredVersionContextProvider} from './utils/docsPreferredVersion/DocsPreferredVersionProvider';
 
 export {ThemeClassNames} from './utils/ThemeClassNames';

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

@@ -0,0 +1,23 @@
+/**
+ * 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.
+ */
+
+// A replacement of lodash in client code
+
+/**
+ * Gets the duplicate values in an array.
+ * @param arr The array.
+ * @param comparator Compares two values and returns `true` if they are equal (duplicated).
+ * @returns Value of the elements `v` that have a preceding element `u` where `comparator(u, v) === true`. Values within the returned array are not guaranteed to be unique.
+ */
+export function duplicates<T>(
+  arr: readonly T[],
+  comparator: (a: T, b: T) => boolean = (a, b) => a === b,
+): T[] {
+  return arr.filter(
+    (v, vIndex) => arr.findIndex((u) => comparator(u, v)) !== vIndex,
+  );
+}

website/docs/guides/markdown-features/markdown-features-tabs.mdx

@@ -131,7 +131,7 @@ It is possible to only render the default tab with `<Tabs lazy />`.
 
 The first tab is displayed by default, and to override this behavior, you can specify a default tab by adding `default` to one of the tab items. You can also set the `defaultValue` prop of the `Tabs` component to the label value of your choice. For example, in the example above, either setting `default` for the `value="apple"` tab or setting `defaultValue="apple"` for the tabs forces the "Apple" tab to be open by default.
 
-If `defaultValue` is provided for the `Tabs`, but it refers to an non-existing value, only the tab headings will appear until the user clicks on a tab.
+Docusaurus will throw an error if a `defaultValue` is provided for the `Tabs` but it refers to an non-existing value. If you want none of the tabs to be shown by default, use `defaultValue={null}`.
 
 ## Syncing tab choices {#syncing-tab-choices}
 

yarn.lock

@@ -4465,6 +4465,13 @@
     "@types/history" "*"
     "@types/react" "*"
 
+"@types/react-test-renderer@^17.0.1":
+  version "17.0.1"
+  resolved "https://registry.yarnpkg.com/@types/react-test-renderer/-/react-test-renderer-17.0.1.tgz#3120f7d1c157fba9df0118dae20cb0297ee0e06b"
+  integrity sha512-3Fi2O6Zzq/f3QR9dRnlnHso9bMl7weKCviFmfF6B4LS1Uat6Hkm15k0ZAQuDz+UBq6B3+g+NM6IT2nr5QgPzCw==
+  dependencies:
+    "@types/react" "*"
+
 "@types/react@*", "@types/react@^17.0.2":
   version "17.0.24"
   resolved "https://registry.yarnpkg.com/@types/react/-/react-17.0.24.tgz#7e1b3f78d0fc53782543f9bce6d949959a5880bd"
@@ -16741,7 +16748,7 @@ react-is@^16.12.0, react-is@^16.6.0, react-is@^16.7.0, react-is@^16.8.1, react-i
   resolved "https://registry.yarnpkg.com/react-is/-/react-is-16.13.1.tgz#789729a4dc36de2999dc156dd6c1d9c18cea56a4"
   integrity sha512-24e6ynE2H+OKt4kqsOvNd8kBpV65zoxbA4BVsEOB3ARVWQki/DHzaUoC5KuON/BiccDaCCTZBuOcfZs70kR8bQ==
 
-react-is@^17.0.1:
+"react-is@^16.12.0 || ^17.0.0", react-is@^17.0.1, react-is@^17.0.2:
   version "17.0.2"
   resolved "https://registry.yarnpkg.com/react-is/-/react-is-17.0.2.tgz#e691d4a8e9c789365655539ab372762b0efb54f0"
   integrity sha512-w2GsyukL62IJnlaff/nRegPQR94C/XXamvMWmSHRJ4y7Ts/4ocGRmTHvOs8PSE6pB3dWOrD/nueuU5sduBsQ4w==
@@ -16824,6 +16831,14 @@ react-router@5.2.1, react-router@^5.2.0:
     tiny-invariant "^1.0.2"
     tiny-warning "^1.0.0"
 
+react-shallow-renderer@^16.13.1:
+  version "16.14.1"
+  resolved "https://registry.yarnpkg.com/react-shallow-renderer/-/react-shallow-renderer-16.14.1.tgz#bf0d02df8a519a558fd9b8215442efa5c840e124"
+  integrity sha512-rkIMcQi01/+kxiTE9D3fdS959U1g7gs+/rborw++42m1O9FAQiNI/UNRZExVUoAOprn4umcXf+pFRou8i4zuBg==
+  dependencies:
+    object-assign "^4.1.1"
+    react-is "^16.12.0 || ^17.0.0"
+
 react-side-effect@^2.1.0:
   version "2.1.1"
   resolved "https://registry.yarnpkg.com/react-side-effect/-/react-side-effect-2.1.1.tgz#66c5701c3e7560ab4822a4ee2742dee215d72eb3"
@@ -16834,6 +16849,16 @@ react-simple-code-editor@^0.10.0:
   resolved "https://registry.yarnpkg.com/react-simple-code-editor/-/react-simple-code-editor-0.10.0.tgz#73e7ac550a928069715482aeb33ccba36efe2373"
   integrity sha512-bL5W5mAxSW6+cLwqqVWY47Silqgy2DKDTR4hDBrLrUqC5BXc29YVx17l2IZk5v36VcDEq1Bszu2oHm1qBwKqBA==
 
+react-test-renderer@^17.0.2:
+  version "17.0.2"
+  resolved "https://registry.yarnpkg.com/react-test-renderer/-/react-test-renderer-17.0.2.tgz#4cd4ae5ef1ad5670fc0ef776e8cc7e1231d9866c"
+  integrity sha512-yaQ9cB89c17PUb0x6UfWRs7kQCorVdHlutU1boVPEsB8IDZH6n9tHxMacc3y0JoXOJUsZb/t/Mb8FUWMKaM7iQ==
+  dependencies:
+    object-assign "^4.1.1"
+    react-is "^17.0.2"
+    react-shallow-renderer "^16.13.1"
+    scheduler "^0.20.2"
+
 react-textarea-autosize@^8.3.2:
   version "8.3.3"
   resolved "https://registry.yarnpkg.com/react-textarea-autosize/-/react-textarea-autosize-8.3.3.tgz#f70913945369da453fd554c168f6baacd1fa04d8"