Addon-docs: Document dynamic source snippets

addons/docs/docs/multiframework.md

@@ -6,6 +6,7 @@ Storybook Docs [provides basic support for all non-RN Storybook view layers](../
 - [Arg tables](#arg-tables)
 - [Component descriptions](#component-descriptions)
 - [Inline story rendering](#inline-story-rendering)
+- [Dynamic source rendering](#dynamic-source-rendering)
 - [More resources](#more-resources)
 
 ## Framework-specific configuration
@@ -103,6 +104,59 @@ addParameters({
 
 The input is the story function and the story context (id, parameters, args, etc.), and the output is a React element, because we render docs pages in react. In the case of Vue, all of the work is done by the `@egoist/vue-to-react` library. If there's no analogous library for your framework, you may need to figure it out yourself!
 
+## Dynamic source rendering
+
+With the release of Storybook 6.0, we've improved how stories are rendered in the [Source doc block](https://storybook.js.org/docs/react/writing-docs/doc-blocks#source). One of such improvements is the `dynamic` source type, which renders a snippet based on the output the story function. 
+
+This dynamic rendering is framework-specific, meaning it needs a custom implementation for each framework.
+
+Let's take a look at the React framework implementation of `dynamic` snippets as a reference for implementing this feature in other frameworks:
+
+```tsx
+import { addons, StoryContext } from '@storybook/addons';
+import { SNIPPET_RENDERED } from '../../shared';
+
+export const jsxDecorator = (storyFn: any, context: StoryContext) => {
+  const story = storyFn();
+
+  // We only need to render JSX if the source block is actually going to
+  // consume it. Otherwise it's just slowing us down.
+  if (skipJsxRender(context)) {
+    return story;
+  }
+
+  const channel = addons.getChannel();
+
+  const options = {}; // retrieve from story parameters
+  const jsx = renderJsx(story, options);
+  channel.emit(SNIPPET_RENDERED, (context || {}).id, jsx);
+
+  return story;
+};
+```
+
+A few key points from the above snippet:
+
+- The **renderJsx** function call is responsible for transforming the output of a story function into a string specific to the framework (in this case React).
+- The returned snippet string is emitted on Storybook's channel through **channel.emit()** and subsequently consumed up by the Source block for any given story, if it exists.
+
+<div class="aside">
+ To learn more and see how it's implemented in context, check out <a href="https://github.com/storybookjs/storybook/blob/next/addons/docs/src/frameworks/react/jsxDecorator.tsx">the code</a> .
+</div>
+
+Now we need a way to configure how it's displayed in the UI:
+
+```tsx
+import { jsxDecorator } from './jsxDecorator';
+export const decorators = [jsxDecorator];
+```
+
+This configures the `jsxDecorator` to be run on every story. 
+
+<div class="aside">
+ To learn more and see how it's implemented in context, check out <a href="https://github.com/storybookjs/storybook/blob/next/addons/docs/src/frameworks/react/jsxDecorator.tsx">the code</a> .
+</div>
+
 ## More resources
 
 - References: [README](../README.md) / [DocsPage](docspage.md) / [MDX](mdx.md) / [FAQ](faq.md) / [Recipes](recipes.md) / [Theming](theming.md) / [Props](props-tables.md)

docs/frameworks.js

@@ -109,6 +109,11 @@ module.exports = {
           unsupported: [],
           path: 'writing-docs/doc-blocks#source',
         },
+        {
+          name: 'Dynamic source',
+          supported: ['react'],
+          path: 'writing-docs/doc-blocks#source',
+        },
         {
           name: 'Args Table',
           supported: ['react', 'vue', 'angular', 'html', 'ember', 'web-components'],

docs/writing-docs/doc-blocks.md

@@ -4,7 +4,6 @@ title: 'Doc Blocks'
 
 Doc Blocks are the building blocks of Storybook documentation pages. By default, [DocsPage](./docs-page.md) uses a combination of the blocks below to build a page for each of your components automatically.
 
-
 Custom [addons](../api/addons.md) can also provide their own doc blocks.
 
 ## ArgsTable
@@ -150,6 +149,14 @@ To customize the source snippet that’s displayed for a story, set the `docs.so
 
 <!-- prettier-ignore-end -->
 
+There is also a `docs.source.type` parameter that controls how source is auto-generated. Valid values include:
+
+| Value              | Description                                                                                                         |                   Support                    |
+| :----------------- | :------------------------------------------------------------------------------------------------------------------ | :------------------------------------------: |
+| **auto** (default) | Use `dynamic` snippets if the story is written using [Args](../writing-stories/args) and the framework supports it. |                     All                      |
+| **dynamic**        | Dynamically generated snippet based on the output of the story function, e.g. JSX code for react.                   | [Limited](../api/frameworks-feature-support) |
+| **code**           | Use the raw story source as written in the story file.                                                              |                     All                      |
+
 ### MDX
 
 You can also use the `Source` block in MDX. It accepts either a story ID or `code` snippet. Use the `language` for syntax highlighting.