From ecc3fd0ff3ec91da0c14d798a69f877a5c297325 Mon Sep 17 00:00:00 2001
From: Matt Tingen <matt.tingen@gmail.com>
Date: Tue, 12 Mar 2019 22:27:11 -0400
Subject: [PATCH] Fix optionality of inferred props

---
 types/react/index.d.ts                 | 16 +++++++++-------
 types/react/test/managedAttributes.tsx | 23 +++++++++++++++++++++++
 2 files changed, 32 insertions(+), 7 deletions(-)

diff --git a/types/react/index.d.ts b/types/react/index.d.ts
index d7fcb51d61..554d05fc70 100644
--- a/types/react/index.d.ts
+++ b/types/react/index.d.ts
@@ -2732,16 +2732,18 @@ declare namespace React {
 // so boolean is only resolved for T = any
 type IsExactlyAny<T> = boolean extends (T extends never ? true : false) ? true : false;
 
+// Pick properties for which the value is `any`
+type PickAny<T> = Pick<T, { [K in keyof T]: IsExactlyAny<T[K]> extends true ? K : never }[keyof T]>;
+
 // Try to resolve ill-defined props like for JS users: props can be any, or sometimes objects with properties of type any
 // If props is type any, use propTypes definitions, otherwise for each `any` property of props, use the propTypes type
 // If declared props have indexed properties, ignore inferred props entirely as keyof gets widened
-type MergePropTypes<P, T> = IsExactlyAny<P> extends true ? T : ({
-    [K in keyof P]: IsExactlyAny<P[K]> extends true
-        ? K extends keyof T
-        ? T[K]
-        : P[K]
-        : P[K]
-} & Pick<T, Exclude<keyof T, keyof P>>);
+type MergePropTypes<P, T> = IsExactlyAny<P> extends true ? T : string extends keyof P ? P : (
+    // From declared props, pick properties which are either not `any` or are missing on `propTypes`.
+    & Pick<P, Exclude<keyof P, keyof PickAny<P>> | Exclude<keyof P, keyof T>>
+    // From inferred props, pick all properties except those which are not `any` on `Props`
+    & Pick<T, Exclude<keyof T, Exclude<keyof P, keyof PickAny<P>>>>
+);
 
 // Any prop that has a default prop becomes optional, but its type is unchanged
 // Undeclared default props are augmented into the resulting allowable attributes
diff --git a/types/react/test/managedAttributes.tsx b/types/react/test/managedAttributes.tsx
index 9939cffb15..d60e75e5a0 100644
--- a/types/react/test/managedAttributes.tsx
+++ b/types/react/test/managedAttributes.tsx
@@ -235,17 +235,40 @@ interface LeaveMeAloneDtslint { foo: string; }
 //     foo: string;
 //     bar: any;
 // }
+// interface WeakComponentProps3 {
+//     foo: any;
+//     bar: any;
+// }
 
 // // $ExpectType true
 // type weakComponentTest1 = JSX.LibraryManagedAttributes<{ propTypes: typeof weakComponentPropTypes }, any> extends {
 //     foo?: string | null
 //     bar: boolean
 // } ? true : false;
+// // $ExpectType true
 // type weakComponentTest2 = JSX.LibraryManagedAttributes<{ propTypes: typeof weakComponentPropTypes }, WeakComponentProps1> extends {
 //     foo?: string | null
 //     bar: number
 // } ? true : false;
+// // $ExpectType true
 // type weakComponentTest3 = JSX.LibraryManagedAttributes<{ propTypes: typeof weakComponentPropTypes }, WeakComponentProps2> extends {
 //     foo: string
 //     bar: boolean
 // } ? true : false;
+
+// // $ExpectError
+// const weakComponentOptionalityTest1: JSX.LibraryManagedAttributes<{ propTypes: typeof weakComponentPropTypes }, WeakComponentProps3> = { foo: '' };
+// const weakComponentOptionalityTest2: JSX.LibraryManagedAttributes<{ propTypes: typeof weakComponentPropTypes }, WeakComponentProps3> = { bar: true };
+
+// interface IndexedComponentProps {
+//     [K: string]: boolean;
+// }
+// interface WeakIndexedComponentProps {
+//     [K: string]: any;
+// }
+
+// const weakComponentIndexedTest1: JSX.LibraryManagedAttributes<{ propTypes: typeof weakComponentPropTypes }, IndexedComponentProps> = { };
+// // $ExpectError
+// const weakComponentIndexedTest2: JSX.LibraryManagedAttributes<{ propTypes: typeof weakComponentPropTypes }, IndexedComponentProps> = { foo: '' };
+// const weakComponentIndexedTest3: JSX.LibraryManagedAttributes<{ propTypes: typeof weakComponentPropTypes }, WeakIndexedComponentProps> = { foo: '' };
+// const weakComponentIndexedTest4: JSX.LibraryManagedAttributes<{ propTypes: typeof weakComponentPropTypes }, WeakIndexedComponentProps> = { foo: 4 };