Parse comments as Story description

src/parser/collect-stories.ts

@@ -5,6 +5,7 @@ import RenderContext from '../components/RenderContext.svelte';
 import { combineParameters } from '@storybook/client-api';
 import { extractId } from './extract-id.js';
 import { logger } from '@storybook/client-logger';
+import type { StoryDef } from './extract-stories.ts';
 
 /* Called from a webpack loader and a jest transformation.
  *
@@ -35,7 +36,14 @@ const createFragment = document.createDocumentFragment
   ? () => document.createDocumentFragment()
   : () => document.createElement('div');
 
-export default (StoriesComponent, { stories = {}, allocatedIds = [] }, exportedMeta = undefined) => {
+export default (
+  StoriesComponent,
+  {
+    stories = {},
+    allocatedIds = [],
+  }: { stories: Record<string, StoryDef>; allocatedIds: string[] },
+  exportedMeta = undefined
+) => {
   const repositories = {
     meta: null as Meta | null,
     stories: [] as Story[],
@@ -145,9 +153,20 @@ export default (StoriesComponent, { stories = {}, allocatedIds = [] }, exportedM
           });
         }
 
+        const relStory = stories[storyId];
+        if (relStory?.description) {
+          storyFn.parameters = combineParameters(storyFn.parameters || {}, {
+            docs: {
+              description: {
+                story: relStory.description,
+              },
+            },
+          });
+        }
+
         // eslint-disable-next-line no-param-reassign
         all[storyId] = storyFn;
         return all;
-      }, {}) as { [key: string]: { storyName: string; parameters: string; } },
+      }, {}) as { [key: string]: { storyName: string; parameters: string } },
   };
 };

src/parser/extract-stories.test.ts

@@ -253,7 +253,6 @@ describe('extractSource', () => {
             "hasArgs": false,
             "name": "Story1",
             "source": "<div>story 1</div>",
-            "storyId": "test--story-1",
             "template": false,
           },
         },
@@ -293,7 +292,6 @@ describe('extractSource', () => {
             "hasArgs": false,
             "name": "Story1",
             "source": "<div>story 1</div>",
-            "storyId": "test--story-1",
             "template": false,
           },
         },
@@ -332,7 +330,6 @@ describe('extractSource', () => {
             "hasArgs": false,
             "name": "Story1",
             "source": "<div>story 1</div>",
-            "storyId": "test--story-1",
             "template": false,
           },
         },
@@ -396,4 +393,145 @@ describe('extractSource', () => {
       }
     `);
   });
+  test('With description', () => {
+    expect(
+      extractStories(`
+        <script>
+          import { Story } from '@storybook/svelte';
+          import Button from './Button.svelte';
+        </script>
+
+        <!-- Story Description -->
+
+        <Story name="Desc">
+          <div>a story</div>
+        </Story>
+        `)
+    ).toMatchInlineSnapshot(`
+      {
+        "allocatedIds": [
+          "default",
+          "Story",
+          "Button",
+        ],
+        "meta": {},
+        "stories": {
+          "Desc": {
+            "description": "Story Description",
+            "hasArgs": false,
+            "name": "Desc",
+            "source": "<div>a story</div>",
+            "template": false,
+          },
+        },
+      }
+    `);
+  });
+  test('With multiline description', () => {
+    expect(
+      extractStories(`
+        <script>
+          import { Story } from '@storybook/svelte';
+          import Button from './Button.svelte';
+        </script>
+
+        <!-- 
+        Story Description 
+
+        another line.
+        -->
+
+        <Story name="Desc">
+          <div>a story</div>
+        </Story>
+        `)
+    ).toMatchInlineSnapshot(`
+      {
+        "allocatedIds": [
+          "default",
+          "Story",
+          "Button",
+        ],
+        "meta": {},
+        "stories": {
+          "Desc": {
+            "description": "Story Description 
+
+      another line.",
+            "hasArgs": false,
+            "name": "Desc",
+            "source": "<div>a story</div>",
+            "template": false,
+          },
+        },
+      }
+    `);
+  });
+  test('With unrelated nested description', () => {
+    expect(
+      extractStories(`
+          <script>
+            import { Story } from '@storybook/svelte';
+            import Button from './Button.svelte';
+          </script>
+
+          <div>
+            <!-- unrelated desc -->
+          </div>
+          <Story name="Desc">
+            <div>a story</div>
+          </Story>
+          `)
+    ).toMatchInlineSnapshot(`
+        {
+          "allocatedIds": [
+            "default",
+            "Story",
+            "Button",
+          ],
+          "meta": {},
+          "stories": {
+            "Desc": {
+              "hasArgs": false,
+              "name": "Desc",
+              "source": "<div>a story</div>",
+              "template": false,
+            },
+          },
+        }
+      `);
+  });
+  test('With unrelated description', () => {
+    expect(
+      extractStories(`
+          <script>
+            import { Story } from '@storybook/svelte';
+            import Button from './Button.svelte';
+          </script>
+
+          <!-- unrelated desc -->
+          <div></div>
+          <Story name="Desc">
+            <div>a story</div>
+          </Story>
+          `)
+    ).toMatchInlineSnapshot(`
+        {
+          "allocatedIds": [
+            "default",
+            "Story",
+            "Button",
+          ],
+          "meta": {},
+          "stories": {
+            "Desc": {
+              "hasArgs": false,
+              "name": "Desc",
+              "source": "<div>a story</div>",
+              "template": false,
+            },
+          },
+        }
+      `);
+  });
 });

src/parser/extract-stories.ts

@@ -4,10 +4,11 @@ import type { Node } from 'estree';
 import dedent from 'dedent';
 import { extractId } from './extract-id.js';
 
-interface StoryDef {
+export interface StoryDef {
   name: string;
   template: boolean;
   source: string;
+  description?: string;
   hasArgs: boolean;
 }
 
@@ -187,6 +188,7 @@ export function extractStories(component: string): StoriesDef {
       }
     });
   }
+  let latestComment: string|undefined;
   svelte.walk(<Node>ast.html, {
     enter(node: any) {
       if (
@@ -224,19 +226,37 @@ export function extractStories(component: string): StoriesDef {
             // @ts-ignore
             source = dedent`${component.substr(start, end - start)}`;
           }
-          stories[isTemplate ? `tpl:${id}` : id] = {
+          const story = {
             name,
             template: isTemplate,
             source,
             hasArgs: node.attributes.find((att: any) => att.type === 'Let') != null,
           };
+          if (!isTemplate && latestComment) {
+            // throws dedent expression is not callable.
+            // @ts-ignore
+            story.description = dedent`${latestComment}`;
+          }
+          stories[isTemplate ? `tpl:${id}` : id] = story;
+          latestComment = undefined;
         }
       } else if (node.type === 'InlineComponent' && node.name === localNames.Meta) {
         this.skip();
 
         fillMetaFromAttributes(meta, node.attributes);
+        latestComment = undefined;
+      } else if (node.type === 'Comment') {
+        this.skip();
+
+        latestComment = node.data?.trim();
+        return;
       }
     },
+    leave(node: any) {
+      if (node.type !== "Comment" && node.type !== "Text") {
+        latestComment = undefined;
+      }
+    }
   });
   return {
     meta,

stories/metaexport.stories.svelte

@@ -25,6 +25,7 @@
 
 <Story name="Default"/>
 
+<!-- Story about the Rounded State -->
 <Story name="Rounded" args={{rounded: true}}/>
 
 <Story name="Square" source args={{rounded: false}}/>