From 011a95ec021b0652d51e817837b1ed353c5665a0 Mon Sep 17 00:00:00 2001
From: Kasper Peulen <kasperpeulen@gmail.com>
Date: Thu, 8 Dec 2022 16:42:53 +0100
Subject: [PATCH] Fix bug with meta not working well as generic parameter for
 StoryObj

---
 src/story.test.ts | 10 ++++++++++
 src/story.ts      | 19 ++++++++++++++++++-
 2 files changed, 28 insertions(+), 1 deletion(-)

diff --git a/src/story.test.ts b/src/story.test.ts
index 07e1133..c58df9a 100644
--- a/src/story.test.ts
+++ b/src/story.test.ts
@@ -144,3 +144,13 @@ test('ArgsFromMeta will infer correct args from render/loader/decorators', () =>
     loaderArg2: number;
   }>();
 });
+
+test('You can assign a component to Meta, even when you pass a top type', () => {
+  expectTypeOf({ component: Button }).toMatchTypeOf<XMeta>();
+  expectTypeOf({ component: Button }).toMatchTypeOf<XMeta<Record<string, any>>>();
+  expectTypeOf({ component: Button }).toMatchTypeOf<XMeta<Record<string, unknown>>>();
+  expectTypeOf({ component: Button }).toMatchTypeOf<XMeta<unknown>>();
+  expectTypeOf({ component: Button }).toMatchTypeOf<XMeta<any>>();
+  expectTypeOf({ component: Button }).not.toMatchTypeOf<XMeta<{ a?: number }>>();
+  expectTypeOf({ component: Button }).not.toMatchTypeOf<XMeta<{ a: number }>>();
+});
diff --git a/src/story.ts b/src/story.ts
index f937a4a..c96eaae 100644
--- a/src/story.ts
+++ b/src/story.ts
@@ -298,7 +298,24 @@ export interface ComponentAnnotations<TRenderer extends Renderer = Renderer, TAr
    *
    * Used by addons for automatic prop table generation and display of other component metadata.
    */
-  component?: (TRenderer & { T: Args extends TArgs ? any : TArgs })['component'];
+  component?: (TRenderer & {
+    // We fall back to `any` when TArgs is missing (and so TArgs will be Args).
+    // We also fallback to `any` for any other "top" type (Record<string, any>, Record<string, unknown>, any, unknown).
+    // This is because you can not assign Component with more specific props, to a Component that accepts anything
+
+    // For example this won't compile
+    // const Button: FC<Args> = (props: {prop: number} ) => {}
+    //
+    // Note that the subtyping relationship is inversed for T and (t: T) => any. As this is fine:
+    // const args: Args = { prop: 1 };
+    // The correct way would probably to fall back to `never`, being the inverse of unknown. Or maybe `Record<string, never>`
+    //
+    // Any is really weird as it pretends to be never and unknown at the same time (so being the absolute bottom and top type at the same time)
+    // However, I don't have the guts to fallback to Record<string, never>, forgive me.
+    //
+    // If this all doesn't make sense, you may want to look at the test: You can assign a component to Meta, even when you pass a top type.
+    T: Record<string, unknown> extends Required<TArgs> ? any : TArgs;
+  })['component'];
 
   /**
    * Auxiliary subcomponents that are part of the stories.