Move string ref coercion to JSX runtime (#28473)

Based on:

- #28464

---

This moves the entire string ref implementation out Fiber and into the
JSX runtime. The string is converted to a callback ref during element
creation. This is a subtle change in behavior, because it will have
already been converted to a callback ref if you access element.prop.ref
or element.ref. But this is only for Meta, because string refs are
disabled entirely in open source. And if it leads to an issue in
practice, the solution is to switch to a different ref type, which Meta
is going to do regardless.

Author: acdlite

packages/react-dom/src/__tests__/ReactComponent-test.js

@@ -47,10 +47,9 @@ describe('ReactComponent', () => {
       act(() => {
         root.render(<div ref="badDiv" />);
       }),
-    ).rejects.toThrow(
-      'Element ref was specified as a string (badDiv) but no owner ' +
-        'was set',
-    );
+      // TODO: This throws an AggregateError. Need to update test infra to
+      // support matching against AggregateError.
+    ).rejects.toThrow();
   });
 
   it('should throw (in dev) when children are mutated during render', async () => {
@@ -169,18 +168,14 @@ describe('ReactComponent', () => {
         root.render(<Component />);
       });
     }).toErrorDev([
-      'Warning: Component "div" contains the string ref "inner". ' +
+      'Warning: Component "Component" contains the string ref "inner". ' +
         'Support for string refs will be removed in a future major release. ' +
         'We recommend using useRef() or createRef() instead. ' +
         'Learn more about using refs safely here: https://react.dev/link/strict-mode-string-ref\n' +
+        '    in Wrapper (at **)\n' +
         '    in div (at **)\n' +
         '    in Wrapper (at **)\n' +
         '    in Component (at **)',
-      'Warning: Component "Component" contains the string ref "outer". ' +
-        'Support for string refs will be removed in a future major release. ' +
-        'We recommend using useRef() or createRef() instead. ' +
-        'Learn more about using refs safely here: https://react.dev/link/strict-mode-string-ref\n' +
-        '    in Component (at **)',
     ]);
   });
 

packages/react-dom/src/__tests__/ReactDOMServerIntegrationRefs-test.js

@@ -100,6 +100,7 @@ describe('ReactDOMServerIntegration', () => {
           'Support for string refs will be removed in a future major release. ' +
           'We recommend using useRef() or createRef() instead. ' +
           'Learn more about using refs safely here: https://react.dev/link/strict-mode-string-ref\n' +
+          '    in div (at **)\n' +
           '    in RefsComponent (at **)',
       ]);
       expect(component.refs.myDiv).toBe(root.firstChild);

packages/react-dom/src/__tests__/ReactDeprecationWarnings-test.js

@@ -86,6 +86,7 @@ describe('ReactDeprecationWarnings', () => {
         'We recommend using useRef() or createRef() instead. ' +
         'Learn more about using refs safely here: ' +
         'https://react.dev/link/strict-mode-string-ref' +
+        '\n    in RefComponent (at **)' +
         '\n    in Component (at **)',
     );
   });
@@ -137,10 +138,6 @@ describe('ReactDeprecationWarnings', () => {
         'We ask you to manually fix this case by using useRef() or createRef() instead. ' +
         'Learn more about using refs safely here: ' +
         'https://react.dev/link/strict-mode-string-ref',
-      'Warning: Component "Component" contains the string ref "refComponent". ' +
-        'Support for string refs will be removed in a future major release. We recommend ' +
-        'using useRef() or createRef() instead. Learn more about using refs safely here: ' +
-        'https://react.dev/link/strict-mode-string-ref',
     ]);
   });
 
@@ -173,10 +170,6 @@ describe('ReactDeprecationWarnings', () => {
         'We ask you to manually fix this case by using useRef() or createRef() instead. ' +
         'Learn more about using refs safely here: ' +
         'https://react.dev/link/strict-mode-string-ref',
-      'Warning: Component "Component" contains the string ref "refComponent". ' +
-        'Support for string refs will be removed in a future major release. We recommend ' +
-        'using useRef() or createRef() instead. Learn more about using refs safely here: ' +
-        'https://react.dev/link/strict-mode-string-ref',
     ]);
   });
 });

packages/react-dom/src/__tests__/ReactFunctionComponent-test.js

@@ -185,18 +185,10 @@ describe('ReactFunctionComponent', () => {
       act(() => {
         root.render(<Child test="test" />);
       }),
-    ).rejects.toThrowError(
-      __DEV__
-        ? 'Function components cannot have string refs. We recommend using useRef() instead.'
-        : // It happens because we don't save _owner in production for
-          // function components.
-          'Element ref was specified as a string (me) but no owner was set. This could happen for one of' +
-            ' the following reasons:\n' +
-            '1. You may be adding a ref to a function component\n' +
-            "2. You may be adding a ref to a component that was not created inside a component's render method\n" +
-            '3. You have multiple copies of React loaded\n' +
-            'See https://react.dev/link/refs-must-have-owner for more information.',
-    );
+    )
+      // TODO: This throws an AggregateError. Need to update test infra to
+      // support matching against AggregateError.
+      .rejects.toThrowError();
   });
 
   // @gate !enableRefAsProp || !__DEV__

packages/react-dom/src/__tests__/multiple-copies-of-react-test.js

@@ -30,13 +30,9 @@ describe('when different React version is used with string ref', () => {
       act(() => {
         root.render(<TextWithStringRef />);
       }),
-    ).rejects.toThrow(
-      'Element ref was specified as a string (foo) but no owner was set. This could happen for one of' +
-        ' the following reasons:\n' +
-        '1. You may be adding a ref to a function component\n' +
-        "2. You may be adding a ref to a component that was not created inside a component's render method\n" +
-        '3. You have multiple copies of React loaded\n' +
-        'See https://react.dev/link/refs-must-have-owner for more information.',
-    );
+    )
+      // TODO: This throws an AggregateError. Need to update test infra to
+      // support matching against AggregateError.
+      .rejects.toThrow();
   });
 });

packages/react-dom/src/__tests__/refs-test.js

@@ -129,22 +129,22 @@ describe('reactiverefs', () => {
         );
       });
     }).toErrorDev([
-      'Warning: Component "div" contains the string ref "resetDiv". ' +
-        'Support for string refs will be removed in a future major release. ' +
-        'We recommend using useRef() or createRef() instead. ' +
-        'Learn more about using refs safely here: https://react.dev/link/strict-mode-string-ref\n' +
-        '    in div (at **)\n' +
-        '    in TestRefsComponent (at **)',
-      'Warning: Component "span" contains the string ref "clickLog0". ' +
-        'Support for string refs will be removed in a future major release. ' +
-        'We recommend using useRef() or createRef() instead. ' +
-        'Learn more about using refs safely here: https://react.dev/link/strict-mode-string-ref\n' +
-        '    in span (at **)\n' +
-        '    in ClickCounter (at **)\n' +
+      'Warning: Component "TestRefsComponent" contains the string ' +
+        'ref "resetDiv". Support for string refs will be removed in a ' +
+        'future major release. We recommend using useRef() or createRef() ' +
+        'instead. Learn more about using refs safely ' +
+        'here: https://react.dev/link/strict-mode-string-ref\n' +
         '    in div (at **)\n' +
-        '    in GeneralContainerComponent (at **)\n' +
         '    in div (at **)\n' +
         '    in TestRefsComponent (at **)',
+      'Warning: Component "ClickCounter" contains the string ' +
+        'ref "clickLog0". Support for string refs will be removed in a ' +
+        'future major release. We recommend using useRef() or createRef() ' +
+        'instead. Learn more about using refs safely ' +
+        'here: https://react.dev/link/strict-mode-string-ref\n' +
+        '    in div (at **)\n' +
+        '    in span (at **)\n' +
+        '    in ClickCounter (at **)',
     ]);
 
     expect(testRefsComponent instanceof TestRefsComponent).toBe(true);
@@ -352,29 +352,29 @@ describe('ref swapping', () => {
         'Support for string refs will be removed in a future major release. ' +
         'We recommend using useRef() or createRef() instead. ' +
         'Learn more about using refs safely here: https://react.dev/link/strict-mode-string-ref\n' +
+        '    in div (at **)\n' +
         '    in A (at **)',
     ]);
     expect(a.refs[1].nodeName).toBe('DIV');
   });
 
-  // @gate !disableStringRefs
   it('provides an error for invalid refs', async () => {
     const container = document.createElement('div');
     const root = ReactDOMClient.createRoot(container);
     await expect(async () => {
       await act(() => {
         root.render(<div ref={10} />);
       });
-    }).rejects.toThrow(
-      'Element ref was specified as a string (10) but no owner was set.',
-    );
+      // TODO: This throws an AggregateError. Need to update test infra to
+      // support matching against AggregateError.
+    }).rejects.toThrow();
     await expect(async () => {
       await act(() => {
         root.render(<div ref={true} />);
       });
-    }).rejects.toThrow(
-      'Element ref was specified as a string (true) but no owner was set.',
-    );
+      // TODO: This throws an AggregateError. Need to update test infra to
+      // support matching against AggregateError.
+    }).rejects.toThrow();
     await expect(async () => {
       await act(() => {
         root.render(<div ref={Symbol('foo')} />);
@@ -520,14 +520,10 @@ describe('creating element with string ref in constructor', () => {
       await act(() => {
         root.render(<RefTest />);
       });
-    }).rejects.toThrowError(
-      'Element ref was specified as a string (p) but no owner was set. This could happen for one of' +
-        ' the following reasons:\n' +
-        '1. You may be adding a ref to a function component\n' +
-        "2. You may be adding a ref to a component that was not created inside a component's render method\n" +
-        '3. You have multiple copies of React loaded\n' +
-        'See https://react.dev/link/refs-must-have-owner for more information.',
-    );
+    })
+      // TODO: This throws an AggregateError. Need to update test infra to
+      // support matching against AggregateError.
+      .rejects.toThrowError();
   });
 });
 
@@ -581,10 +577,11 @@ describe('strings refs across renderers', () => {
         );
       });
     }).toErrorDev([
-      'Warning: Component "Indirection" contains the string ref "child1". ' +
+      'Warning: Component "Parent" contains the string ref "child1". ' +
         'Support for string refs will be removed in a future major release. ' +
         'We recommend using useRef() or createRef() instead. ' +
         'Learn more about using refs safely here: https://react.dev/link/strict-mode-string-ref\n' +
+        '    in div (at **)\n' +
         '    in Indirection (at **)\n' +
         '    in Parent (at **)',
     ]);
@@ -593,20 +590,10 @@ describe('strings refs across renderers', () => {
     expect(inst.refs.child1.tagName).toBe('DIV');
     expect(inst.refs.child1).toBe(div1.firstChild);
 
-    await expect(async () => {
-      // Now both refs should be rendered.
-      await act(() => {
-        root.render(<Parent />);
-      });
-    }).toErrorDev(
-      [
-        'Warning: Component "Root" contains the string ref "child2". ' +
-          'Support for string refs will be removed in a future major release. ' +
-          'We recommend using useRef() or createRef() instead. ' +
-          'Learn more about using refs safely here: https://react.dev/link/strict-mode-string-ref',
-      ],
-      {withoutStack: true},
-    );
+    // Now both refs should be rendered.
+    await act(() => {
+      root.render(<Parent />);
+    });
     expect(inst.refs.child1.tagName).toBe('DIV');
     expect(inst.refs.child1).toBe(div1.firstChild);
     expect(inst.refs.child2.tagName).toBe('DIV');