From 7a9a332851c1e39703365c0c3ea02948c06d2961 Mon Sep 17 00:00:00 2001
From: Sebastian Silbermann <silbermann.sebastian@gmail.com>
Date: Wed, 5 Dec 2018 12:35:32 +0100
Subject: [PATCH] [styles] Infer optional props argument for makeStyles in
 TypeScript

---
 packages/material-ui-styles/src/index.d.ts    | 19 +++++++++++++++++--
 .../material-ui-styles/test/index.spec.tsx    | 18 +++++++++++++++++-
 2 files changed, 34 insertions(+), 3 deletions(-)

diff --git a/packages/material-ui-styles/src/index.d.ts b/packages/material-ui-styles/src/index.d.ts
index 64b0ddfafbd9f0..4e4a2b9f09a574 100644
--- a/packages/material-ui-styles/src/index.d.ts
+++ b/packages/material-ui-styles/src/index.d.ts
@@ -111,10 +111,24 @@ declare module '@material-ui/styles/makeStyles' {
     WithStylesOptions,
   } from '@material-ui/styles/withStyles';
 
+  // https://stackoverflow.com/a/49928360/3406963 without generic branch types
+  type IsAny<T> = 0 extends (1 & T) ? true : false;
+
+  /**
+   * @internal
+   *
+   * `Props` are `any` either by explicit annotation or if there are no callbacks
+   * from which the typechecker could infer a type so it falls back to `any`.
+   * See the test cases for examples and implications of explicit `any` annotation
+   */
+  export type StylesHook<S extends Styles<any, any>> = IsAny<PropsOfStyles<S>> extends true
+    ? (props?: any) => ClassNameMap<ClassKeyOfStyles<S>>
+    : (props: PropsOfStyles<S>) => ClassNameMap<ClassKeyOfStyles<S>>;
+
   export default function makeStyles<S extends Styles<any, any>>(
     styles: S,
     options?: WithStylesOptions<ClassKeyOfStyles<S>>,
-  ): (props: PropsOfStyles<S>) => ClassNameMap<ClassKeyOfStyles<S>>;
+  ): StylesHook<S>;
 }
 
 declare module '@material-ui/styles/styled' {
@@ -200,9 +214,10 @@ declare module '@material-ui/styles/withStyles' {
    * @internal
    * This is basically the API of JSS. It defines a Map<string, CSS>,
    * where
-   *
    * - the `keys` are the class (names) that will be created
    * - the `values` are objects that represent CSS rules (`React.CSSProperties`).
+   *
+   * if only `CSSProperties` are matched `Props` are inferred to `any`
    */
   export type StyleRules<Props extends object, ClassKey extends string = string> = Record<
     ClassKey,
diff --git a/packages/material-ui-styles/test/index.spec.tsx b/packages/material-ui-styles/test/index.spec.tsx
index 1012e985329a62..e10ad30ade66b2 100644
--- a/packages/material-ui-styles/test/index.spec.tsx
+++ b/packages/material-ui-styles/test/index.spec.tsx
@@ -119,7 +119,23 @@ function testGetThemeProps(theme: Theme, props: AppBarProps): void {
   );
   const NoPropsComponent = () => {
     const classes = useWithoutProps();
-    const alssoClasses = useWithoutProps({});
+    const alsoClasses = useWithoutProps(5);
+  };
+
+  // unsafe any props make the param optional
+  const useUnsafeProps = makeStyles(
+    createStyles({
+      root: (props: any) => ({
+        backgroundColor: props.deep.color,
+      }),
+    }),
+  );
+
+  const UnsafeProps = (props: StyleProps) => {
+    // would be nice to have at least a compile time error because we forgot the argument
+    const classes = useUnsafeProps(); // runtime: Can't read property color of undefined
+    // but this would pass anyway
+    const alsoClasses = useUnsafeProps(undefined); // runtime: Can't read property color of undefined
   };
 }