feat(v2): add ability default lang for code blocks

CHANGELOG-2.x.md

@@ -14,6 +14,16 @@
 - Prioritize `@docusaurus/core` dependencies/ node_modules over user's node_modules. This fix a bug whereby if user has core-js@3 on its own node_modules but docusaurus depends on core-js@2, we previously encounter `Module not found: core-js/modules/xxxx` (because core-js@3 doesn't have that).
 Another example is if user installed webpack@3 but docusaurus depends on webpack@4.
 - Added code block line highlighting feature (thanks @lex111)! If you have previously swizzled the `CodeBlock` theme component, it is recommended to update your source code to have this feature.
+- **BREAKING** `prismTheme` is renamed to `theme` as part new `prism` object in `themeConfig` field in your `docusaurus.config.js`. Eg: 
+  ```diff
+   themeConfig: {
+  -   prismTheme: require('prism-react-renderer/themes/dracula'),
+  +   prism: {
+  +     theme: require('prism-react-renderer/themes/dracula'),
+  +   },
+  },
+  ```
+- Added new `prism` option `defaultLanguage` that is used if the language is not specified in code blocks
 
 ## 2.0.0-alpha.31
 

packages/docusaurus-theme-classic/src/theme/CodeBlock/index.js

@@ -19,7 +19,7 @@ const highlightLinesRangeRegex = /{([\d,-]+)}/;
 export default ({children, className: languageClassName, metastring}) => {
   const {
     siteConfig: {
-      themeConfig: {prismTheme},
+      themeConfig: {prism = {}},
     },
   } = useDocusaurusContext();
   const [showCopied, setShowCopied] = useState(false);
@@ -48,9 +48,13 @@ export default ({children, className: languageClassName, metastring}) => {
     };
   }, [button.current, target.current]);
 
-  const language =
+  let language =
     languageClassName && languageClassName.replace(/language-/, '');
 
+  if (language === 'undefined' && prism.defaultLanguage) {
+    language = prism.defaultLanguage;
+  }
+
   const handleCopyCode = () => {
     window.getSelection().empty();
     setShowCopied(true);
@@ -61,7 +65,7 @@ export default ({children, className: languageClassName, metastring}) => {
   return (
     <Highlight
       {...defaultProps}
-      theme={prismTheme || defaultTheme}
+      theme={prism.theme || defaultTheme}
       code={children.trim()}
       language={language}>
       {({className, style, tokens, getLineProps, getTokenProps}) => (

packages/docusaurus-theme-live-codeblock/src/theme/CodeBlock/index.js

@@ -26,7 +26,7 @@ export default ({
 }) => {
   const {
     siteConfig: {
-      themeConfig: {prismTheme},
+      themeConfig: {prism = {}},
     },
   } = useDocusaurusContext();
   const [showCopied, setShowCopied] = useState(false);
@@ -60,15 +60,19 @@ export default ({
       <Playground
         scope={{...React}}
         code={children.trim()}
-        theme={prismTheme || defaultTheme}
+        theme={prism.theme || defaultTheme}
         {...props}
       />
     );
   }
 
-  const language =
+  let language =
     languageClassName && languageClassName.replace(/language-/, '');
 
+  if (!language && prism.defaultLanguage) {
+    language = prism.defaultLanguage;
+  }
+
   const handleCopyCode = () => {
     window.getSelection().empty();
     setShowCopied(true);
@@ -79,7 +83,7 @@ export default ({
   return (
     <Highlight
       {...defaultProps}
-      theme={prismTheme || defaultTheme}
+      theme={prism.theme || defaultTheme}
       code={children.trim()}
       language={language}>
       {({className, style, tokens, getLineProps, getTokenProps}) => (

website/docs/markdown-features.mdx

@@ -201,15 +201,17 @@ Use the matching language meta string for your code block, and Docusaurus will p
 console.log('Every repo must come with a mascot.');
 ```
 
-By default, the Prism [syntax highlighting theme](https://github.com/FormidableLabs/prism-react-renderer#theming) we use is [Palenight](https://github.com/FormidableLabs/prism-react-renderer/blob/master/src/themes/palenight.js). You can change this to another theme by passing `prismTheme` as `themeConfig` in your docusaurus.config.js.
+By default, the Prism [syntax highlighting theme](https://github.com/FormidableLabs/prism-react-renderer#theming) we use is [Palenight](https://github.com/FormidableLabs/prism-react-renderer/blob/master/src/themes/palenight.js). You can change this to another theme by passing `theme` field in `prism` as `themeConfig` in your docusaurus.config.js.
 
 For example, if you prefer to use the `dracula` highlighting theme:
 
 ```js {4}
 // docusaurus.config.js
 module.exports = {
   themeConfig: {
-    prismTheme: require('prism-react-renderer/themes/dracula'),
+    prism: {
+      theme: require('prism-react-renderer/themes/dracula'),
+    },
   },
 };
 ```