Tweak invalid Hook warning and error

packages/react-dom/src/server/ReactPartialRendererHooks.js

@@ -57,13 +57,15 @@ let currentHookNameInDev: ?string;
 function resolveCurrentlyRenderingComponent(): Object {
   invariant(
     currentlyRenderingComponent !== null,
-    'Hooks can only be called inside the body of a function component.',
+    'Hooks can only be called inside the body of a function component. ' +
+      '(https://fb.me/react-invalid-hook-call)',
   );
   if (__DEV__) {
     warning(
       !isInHookUserCodeInDev,
-      'Hooks can only be called inside the body of a function component. ' +
-        'Do not call Hooks inside other Hooks. For more information, see ' +
+      'Do not call Hooks inside useEffect(...), useMemo(...), or other built-in Hooks. ' +
+        'You can only call Hooks at the top level of your React function. ' +
+        'For more information, see ' +
         'https://fb.me/rules-of-hooks',
     );
   }

packages/react-reconciler/src/ReactFiberHooks.js

@@ -235,7 +235,8 @@ function warnOnHookMismatchInDev() {
 function throwInvalidHookError() {
   invariant(
     false,
-    'Hooks can only be called inside the body of a function component.',
+    'Hooks can only be called inside the body of a function component. ' +
+      '(https://fb.me/react-invalid-hook-call)',
   );
 }
 
@@ -1188,8 +1189,9 @@ if (__DEV__) {
   const warnInvalidHookAccess = () => {
     warning(
       false,
-      'Hooks can only be called inside the body of a function component. ' +
-        'Do not call Hooks inside other Hooks. For more information, see ' +
+      'Do not call Hooks inside useEffect(...), useMemo(...), or other built-in Hooks. ' +
+        'You can only call Hooks at the top level of your React function. ' +
+        'For more information, see ' +
         'https://fb.me/rules-of-hooks',
     );
   };

packages/react-reconciler/src/__tests__/ReactHooks-test.internal.js

@@ -665,7 +665,7 @@ describe('ReactHooks', () => {
       return null;
     }
     expect(() => ReactTestRenderer.create(<App />)).toWarnDev(
-      'Hooks can only be called inside the body of a function component',
+      'Do not call Hooks inside useEffect(...), useMemo(...), or other built-in Hooks.',
     );
   });
 
@@ -835,12 +835,12 @@ describe('ReactHooks', () => {
     if (__DEV__) {
       expect(console.error).toHaveBeenCalledTimes(3);
       expect(console.error.calls.argsFor(0)[0]).toContain(
-        'Hooks can only be called inside the body of a function component',
+        'Do not call Hooks inside useEffect(...), useMemo(...), or other built-in Hooks',
       );
     }
   });
 
-  it("throws when calling hooks inside useState's initialize function", () => {
+  it("warns when calling hooks inside useState's initialize function", () => {
     const {useState, useRef} = React;
     function App() {
       useState(() => {
@@ -850,7 +850,7 @@ describe('ReactHooks', () => {
       return null;
     }
     expect(() => ReactTestRenderer.create(<App />)).toWarnDev(
-      'Hooks can only be called inside the body of a function component',
+      'Do not call Hooks inside useEffect(...), useMemo(...), or other built-in Hooks.',
     );
   });
 
@@ -892,9 +892,9 @@ describe('ReactHooks', () => {
     }).toWarnDev([
       // We see it twice due to replay
       'Context can only be read while React is rendering',
-      'Hooks can only be called inside the body of a function component',
+      'Do not call Hooks inside useEffect(...), useMemo(...), or other built-in Hooks',
       'Context can only be read while React is rendering',
-      'Hooks can only be called inside the body of a function component',
+      'Do not call Hooks inside useEffect(...), useMemo(...), or other built-in Hooks',
     ]);
 
     function Valid() {
@@ -925,9 +925,9 @@ describe('ReactHooks', () => {
     }).toWarnDev([
       // We see it twice due to replay
       'Context can only be read while React is rendering',
-      'Hooks can only be called inside the body of a function component',
+      'Do not call Hooks inside useEffect(...), useMemo(...), or other built-in Hooks',
       'Context can only be read while React is rendering',
-      'Hooks can only be called inside the body of a function component',
+      'Do not call Hooks inside useEffect(...), useMemo(...), or other built-in Hooks',
     ]);
   });
 

packages/react-test-renderer/src/ReactShallowRenderer.js

@@ -218,7 +218,8 @@ class ReactShallowRenderer {
   _validateCurrentlyRenderingComponent() {
     invariant(
       this._currentlyRenderingComponent !== null,
-      'Hooks can only be called inside the body of a function component.',
+      'Hooks can only be called inside the body of a function component. ' +
+        '(https://fb.me/react-invalid-hook-call)',
     );
   }
 

packages/react/src/ReactHooks.js

@@ -17,7 +17,8 @@ function resolveDispatcher() {
   const dispatcher = ReactCurrentDispatcher.current;
   invariant(
     dispatcher !== null,
-    'Hooks can only be called inside the body of a function component.',
+    'Hooks can only be called inside the body of a function component. ' +
+      '(https://fb.me/react-invalid-hook-call)',
   );
   return dispatcher;
 }