Added double newline delimiters to the following functions/files:

* 'getDeclarationErrorAddendum' function of ReactDOMComponent.js
* 'getSourceInfoErrorAddendum' function of ReactElementValidator.js
* 'getDeclarationErrorAddendum' function of instantiateReactComponent.js and ReactElementValidator.js
* 'traverseAllChildrenImpl' function of traverseAllChildren.js
* 'attachRef' function of ReactRef.js
* 'mountIndeterminateComponent' function of ReactFiberBeginWork.js
* 'createFiberFromElementType' function of ReactFiber.js
* 'getDeclarationErrorAddendum' function of ReactDOMSelect.js
* 'unmountComponentAtNode' function of ReactMount.js
* 'getDeclarationErrorAddendum' function of ReactControlledValuePropTypes.js
* 'checkRenderMessage' function of CSSPropertyOperations.js
* 'getDeclarationErrorAddendum' function of ReactDomFiberSelect.js
* 'getCurrentComponentErrorInfo' function in 'ReactElementValidator'
* 'getDeclarationErrorAddendum' function in ReactDOMFiberComponent.js

Fixes #8719

src/addons/__tests__/ReactFragment-test.js

@@ -55,7 +55,7 @@ describe('ReactFragment', () => {
       'Objects are not valid as a React child (found: object with keys ' +
       '{a, b, c}). If you meant to render a collection of children, use an ' +
       'array instead or wrap the object using createFragment(object) from ' +
-      'the React add-ons. Check the render method of `Foo`.'
+      'the React add-ons.\n\nCheck the render method of `Foo`.'
     );
   });
 

src/isomorphic/classic/element/ReactElementValidator.js

@@ -33,7 +33,7 @@ function getDeclarationErrorAddendum() {
   if (ReactCurrentOwner.current) {
     var name = getComponentName(ReactCurrentOwner.current);
     if (name) {
-      return ' Check the render method of `' + name + '`.';
+      return '\n\nCheck the render method of `' + name + '`.';
     }
   }
   return '';
@@ -48,7 +48,7 @@ function getSourceInfoErrorAddendum(elementProps) {
     var source = elementProps.__source;
     var fileName = source.fileName.replace(/^.*[\\\/]/, '');
     var lineNumber = source.lineNumber;
-    return ' Check your code at ' + fileName + ':' + lineNumber + '.';
+    return '\n\nCheck your code at ' + fileName + ':' + lineNumber + '.';
   }
   return '';
 }
@@ -67,7 +67,7 @@ function getCurrentComponentErrorInfo(parentType) {
     var parentName = typeof parentType === 'string' ?
       parentType : parentType.displayName || parentType.name;
     if (parentName) {
-      info = ` Check the top-level render call using <${parentName}>.`;
+      info = `\n\nCheck the top-level render call using <${parentName}>.`;
     }
   }
   return info;

src/isomorphic/classic/element/__tests__/ReactElementValidator-test.js

@@ -76,8 +76,8 @@ describe('ReactElementValidator', () => {
 
     expectDev(console.error.calls.count()).toBe(1);
     expectDev(console.error.calls.argsFor(0)[0]).toContain(
-      'Each child in an array or iterator should have a unique "key" prop. ' +
-      'Check the render method of `InnerClass`. ' +
+      'Each child in an array or iterator should have a unique "key" prop.' +
+      '\n\nCheck the render method of `InnerClass`. ' +
       'It was passed a child from ComponentWrapper. '
     );
   });
@@ -118,7 +118,7 @@ describe('ReactElementValidator', () => {
     expectDev(console.error.calls.count()).toBe(1);
     expectDev(normalizeCodeLocInfo(console.error.calls.argsFor(0)[0])).toBe(
       'Warning: Each child in an array or iterator should have a unique ' +
-      '"key" prop. Check the top-level render call using <div>. See ' +
+      '"key" prop.\n\nCheck the top-level render call using <div>. See ' +
       'https://fb.me/react-warning-keys for more information.\n' +
       '    in div (at **)'
     );
@@ -150,7 +150,7 @@ describe('ReactElementValidator', () => {
     expectDev(console.error.calls.count()).toBe(1);
     expectDev(normalizeCodeLocInfo(console.error.calls.argsFor(0)[0])).toBe(
       'Warning: Each child in an array or iterator should have a unique ' +
-      '"key" prop. Check the render method of `Component`. See ' +
+      '"key" prop.\n\nCheck the render method of `Component`. See ' +
       'https://fb.me/react-warning-keys for more information.\n' +
       '    in div (at **)\n' +
       '    in Component (at **)\n' +
@@ -342,14 +342,14 @@ describe('ReactElementValidator', () => {
       ReactTestUtils.renderIntoDocument(React.createElement(ParentComp));
     }).toThrowError(
       'Element type is invalid: expected a string (for built-in components) ' +
-      'or a class/function (for composite components) but got: null. Check ' +
+      'or a class/function (for composite components) but got: null.\n\nCheck ' +
       'the render method of `ParentComp`.'
     );
     expectDev(console.error.calls.count()).toBe(1);
     expectDev(console.error.calls.argsFor(0)[0]).toBe(
       'Warning: React.createElement: type is invalid -- expected a string ' +
       '(for built-in components) or a class/function (for composite ' +
-      'components) but got: null. Check the render method of `ParentComp`.' +
+      'components) but got: null.\n\nCheck the render method of `ParentComp`.' +
       '\n    in ParentComp'
     );
   });
@@ -551,7 +551,7 @@ describe('ReactElementValidator', () => {
       'Warning: React.createElement: type is invalid -- expected a string ' +
       '(for built-in components) or a class/function (for composite ' +
       'components) but got: undefined. You likely forgot to export your ' +
-      'component from the file it\'s defined in. Check your code at **.'
+      'component from the file it\'s defined in.\n\nCheck your code at **.'
     );
   });
 

src/isomorphic/modern/element/__tests__/ReactJSXElementValidator-test.js

@@ -82,8 +82,8 @@ describe('ReactJSXElementValidator', () => {
 
     expectDev(console.error.calls.count()).toBe(1);
     expectDev(console.error.calls.argsFor(0)[0]).toContain(
-      'Each child in an array or iterator should have a unique "key" prop. ' +
-      'Check the render method of `InnerComponent`. ' +
+      'Each child in an array or iterator should have a unique "key" prop.' +
+      '\n\nCheck the render method of `InnerComponent`. ' +
       'It was passed a child from ComponentWrapper. '
     );
   });
@@ -260,26 +260,26 @@ describe('ReactJSXElementValidator', () => {
       'Warning: React.createElement: type is invalid -- expected a string ' +
       '(for built-in components) or a class/function (for composite ' +
       'components) but got: undefined. You likely forgot to export your ' +
-      'component from the file it\'s defined in. ' +
-      'Check your code at **.'
+      'component from the file it\'s defined in.' +
+      '\n\nCheck your code at **.'
     );
     expectDev(normalizeCodeLocInfo(console.error.calls.argsFor(1)[0])).toBe(
       'Warning: React.createElement: type is invalid -- expected a string ' +
       '(for built-in components) or a class/function (for composite ' +
-      'components) but got: null. ' +
-      'Check your code at **.'
+      'components) but got: null.' +
+      '\n\nCheck your code at **.'
     );
     expectDev(normalizeCodeLocInfo(console.error.calls.argsFor(2)[0])).toBe(
       'Warning: React.createElement: type is invalid -- expected a string ' +
       '(for built-in components) or a class/function (for composite ' +
-      'components) but got: boolean. ' +
-      'Check your code at **.'
+      'components) but got: boolean.' +
+      '\n\nCheck your code at **.'
     );
     expectDev(normalizeCodeLocInfo(console.error.calls.argsFor(3)[0])).toBe(
       'Warning: React.createElement: type is invalid -- expected a string ' +
       '(for built-in components) or a class/function (for composite ' +
-      'components) but got: number. ' +
-      'Check your code at **.'
+      'components) but got: number.' +
+      '\n\nCheck your code at **.'
     );
     void <Div />;
     expectDev(console.error.calls.count()).toBe(4);

src/renderers/dom/fiber/ReactDOMFiberComponent.js

@@ -68,7 +68,7 @@ function getDeclarationErrorAddendum() {
   var ownerName = getCurrentFiberOwnerName();
   if (ownerName) {
     // TODO: also report the stack.
-    return ' This DOM node was rendered by `' + ownerName + '`.';
+    return '\n\nThis DOM node was rendered by `' + ownerName + '`.';
   }
   return '';
 }

src/renderers/dom/fiber/wrappers/ReactDOMFiberSelect.js

@@ -28,7 +28,7 @@ var didWarnValueDefaultValue = false;
 function getDeclarationErrorAddendum() {
   var ownerName = getCurrentFiberOwnerName();
   if (ownerName) {
-    return ' Check the render method of `' + ownerName + '`.';
+    return '\n\nCheck the render method of `' + ownerName + '`.';
   }
   return '';
 }

src/renderers/dom/shared/CSSPropertyOperations.js

@@ -128,7 +128,7 @@ if (__DEV__) {
       // TODO: also report the stack.
     }
     if (ownerName) {
-      return ' Check the render method of `' + ownerName + '`.';
+      return '\n\nCheck the render method of `' + ownerName + '`.';
     }
     return '';
   };

src/renderers/dom/shared/__tests__/CSSPropertyOperations-test.js

@@ -121,8 +121,8 @@ describe('CSSPropertyOperations', () => {
     ReactDOM.render(<Comp />, root);
     expectDev(console.error.calls.count()).toBe(1);
     expectDev(console.error.calls.argsFor(0)[0]).toEqual(
-      'Warning: Unsupported style property background-color. Did you mean backgroundColor? ' +
-      'Check the render method of `Comp`.'
+      'Warning: Unsupported style property background-color. Did you mean backgroundColor?' +
+      '\n\nCheck the render method of `Comp`.'
     );
   });
 
@@ -146,12 +146,12 @@ describe('CSSPropertyOperations', () => {
 
     expectDev(console.error.calls.count()).toBe(2);
     expectDev(console.error.calls.argsFor(0)[0]).toEqual(
-      'Warning: Unsupported style property -ms-transform. Did you mean msTransform? ' +
-      'Check the render method of `Comp`.'
+      'Warning: Unsupported style property -ms-transform. Did you mean msTransform?' +
+      '\n\nCheck the render method of `Comp`.'
     );
     expectDev(console.error.calls.argsFor(1)[0]).toEqual(
-      'Warning: Unsupported style property -webkit-transform. Did you mean WebkitTransform? ' +
-      'Check the render method of `Comp`.'
+      'Warning: Unsupported style property -webkit-transform. Did you mean WebkitTransform?' +
+      '\n\nCheck the render method of `Comp`.'
     );
   });
 
@@ -175,11 +175,11 @@ describe('CSSPropertyOperations', () => {
     expectDev(console.error.calls.count()).toBe(2);
     expectDev(console.error.calls.argsFor(0)[0]).toEqual(
       'Warning: Unsupported vendor-prefixed style property oTransform. ' +
-      'Did you mean OTransform? Check the render method of `Comp`.'
+      'Did you mean OTransform?\n\nCheck the render method of `Comp`.'
     );
     expectDev(console.error.calls.argsFor(1)[0]).toEqual(
       'Warning: Unsupported vendor-prefixed style property webkitTransform. ' +
-      'Did you mean WebkitTransform? Check the render method of `Comp`.'
+      'Did you mean WebkitTransform?\n\nCheck the render method of `Comp`.'
     );
   });
 
@@ -202,12 +202,12 @@ describe('CSSPropertyOperations', () => {
     ReactDOM.render(<Comp />, root);
     expectDev(console.error.calls.count()).toBe(2);
     expectDev(console.error.calls.argsFor(0)[0]).toEqual(
-      'Warning: Style property values shouldn\'t contain a semicolon. ' +
-      'Check the render method of `Comp`. Try "backgroundColor: blue" instead.',
+      'Warning: Style property values shouldn\'t contain a semicolon.' +
+      '\n\nCheck the render method of `Comp`. Try "backgroundColor: blue" instead.',
     );
     expectDev(console.error.calls.argsFor(1)[0]).toEqual(
-      'Warning: Style property values shouldn\'t contain a semicolon. ' +
-      'Check the render method of `Comp`. Try "color: red" instead.',
+      'Warning: Style property values shouldn\'t contain a semicolon.' +
+      '\n\nCheck the render method of `Comp`. Try "color: red" instead.',
     );
   });
 
@@ -226,8 +226,8 @@ describe('CSSPropertyOperations', () => {
 
     expectDev(console.error.calls.count()).toBe(1);
     expectDev(console.error.calls.argsFor(0)[0]).toEqual(
-      'Warning: `NaN` is an invalid value for the `fontSize` css style property. ' +
-      'Check the render method of `Comp`.'
+      'Warning: `NaN` is an invalid value for the `fontSize` css style property.' +
+      '\n\nCheck the render method of `Comp`.'
     );
   });
 });

src/renderers/dom/shared/__tests__/ReactDOMComponent-test.js

@@ -871,7 +871,7 @@ describe('ReactDOMComponent', () => {
           container
         );
       }).toThrowError(
-        'This DOM node was rendered by `Owner`.'
+        '\n\nThis DOM node was rendered by `Owner`.'
       );
     });
 
@@ -1048,7 +1048,7 @@ describe('ReactDOMComponent', () => {
         ReactDOM.render(<X />, container);
       }).toThrowError(
         'input is a void element tag and must neither have `children` ' +
-        'nor use `dangerouslySetInnerHTML`. This DOM node was rendered by `X`.'
+        'nor use `dangerouslySetInnerHTML`.\n\nThis DOM node was rendered by `X`.'
       );
     });
 
@@ -1143,7 +1143,7 @@ describe('ReactDOMComponent', () => {
       }).toThrowError(
         'The `style` prop expects a mapping from style properties to values, ' +
         'not a string. For example, style={{marginRight: spacing + \'em\'}} ' +
-        'when using JSX. This DOM node was rendered by `Animal`.'
+        'when using JSX.\n\nThis DOM node was rendered by `Animal`.'
       );
     });
 

src/renderers/dom/shared/utils/ReactControlledValuePropTypes.js

@@ -61,7 +61,7 @@ var propTypes = {
 var loggedTypeFailures = {};
 function getDeclarationErrorAddendum(ownerName) {
   if (ownerName) {
-    return ' Check the render method of `' + ownerName + '`.';
+    return '\n\nCheck the render method of `' + ownerName + '`.';
   }
   return '';
 }

src/renderers/dom/stack/client/ReactDOMComponent.js

@@ -66,7 +66,7 @@ function getDeclarationErrorAddendum(internalInstance) {
     if (owner) {
       var name = owner.getName();
       if (name) {
-        return ' This DOM node was rendered by `' + name + '`.';
+        return '\n\nThis DOM node was rendered by `' + name + '`.';
       }
     }
   }

src/renderers/dom/stack/client/ReactMount.js

@@ -369,7 +369,7 @@ var ReactMount = {
       '_renderNewRootComponent(): Render methods should be a pure function ' +
       'of props and state; triggering nested component updates from ' +
       'render is not allowed. If necessary, trigger nested updates in ' +
-      'componentDidUpdate. Check the render method of %s.',
+      'componentDidUpdate.\n\nCheck the render method of %s.',
       ReactCurrentOwner.current && ReactCurrentOwner.current.getName() ||
         'ReactCompositeComponent'
     );
@@ -572,7 +572,7 @@ var ReactMount = {
       'unmountComponentAtNode(): Render methods should be a pure function ' +
       'of props and state; triggering nested component updates from render ' +
       'is not allowed. If necessary, trigger nested updates in ' +
-      'componentDidUpdate. Check the render method of %s.',
+      'componentDidUpdate.\n\nCheck the render method of %s.',
       ReactCurrentOwner.current && ReactCurrentOwner.current.getName() ||
         'ReactCompositeComponent'
     );

src/renderers/dom/stack/client/wrappers/ReactDOMSelect.js

@@ -22,7 +22,7 @@ function getDeclarationErrorAddendum(owner) {
   if (owner) {
     var name = owner.getName();
     if (name) {
-      return ' Check the render method of `' + name + '`.';
+      return '\n\nCheck the render method of `' + name + '`.';
     }
   }
   return '';

src/renderers/shared/fiber/ReactFiber.js

@@ -368,7 +368,7 @@ function createFiberFromElementType(type : mixed, key : null | string, debugOwne
       }
       const ownerName = debugOwner ? getComponentName(debugOwner) : null;
       if (ownerName) {
-        info += ' Check the render method of `' + ownerName + '`.';
+        info += '\n\nCheck the render method of `' + ownerName + '`.';
       }
     }
     invariant(

src/renderers/shared/fiber/ReactFiberBeginWork.js

@@ -463,7 +463,7 @@ module.exports = function<T, P, I, TI, PI, C, CX>(
           let info = '';
           const ownerName = ReactDebugCurrentFiber.getCurrentFiberOwnerName();
           if (ownerName) {
-            info += ' Check the render method of `' + ownerName + '`.';
+            info += '\n\nCheck the render method of `' + ownerName + '`.';
           }
 
           let warningKey = ownerName || workInProgress._debugID || '';

src/renderers/shared/fiber/__tests__/ReactIncrementalErrorHandling-test.js

@@ -753,7 +753,7 @@ describe('ReactIncrementalErrorHandling', () => {
       'Element type is invalid: expected a string (for built-in components) or ' +
       'a class/function (for composite components) but got: undefined. ' +
       'You likely forgot to export your component from the file it\'s ' +
-      'defined in. Check the render method of `BrokenRender`.'
+      'defined in.\n\nCheck the render method of `BrokenRender`.'
     )]);
     expect(console.error.calls.count()).toBe(1);
   });
@@ -796,7 +796,7 @@ describe('ReactIncrementalErrorHandling', () => {
       'Element type is invalid: expected a string (for built-in components) or ' +
       'a class/function (for composite components) but got: undefined. ' +
       'You likely forgot to export your component from the file it\'s ' +
-      'defined in. Check the render method of `BrokenRender`.'
+      'defined in.\n\nCheck the render method of `BrokenRender`.'
     )]);
     expect(console.error.calls.count()).toBe(1);
   });

src/renderers/shared/fiber/__tests__/ReactIncrementalSideEffects-test.js

@@ -1135,7 +1135,7 @@ describe('ReactIncrementalSideEffects', () => {
 
     expectDev(normalizeCodeLocInfo(console.error.calls.argsFor(0)[0])).toBe(
       'Warning: Stateless function components cannot be given refs. ' +
-      'Attempts to access this ref will fail. Check the render method ' +
+      'Attempts to access this ref will fail.\n\nCheck the render method ' +
       'of `Foo`.\n' +
       '    in FunctionalComponent (at **)\n' +
       '    in div (at **)\n' +

src/renderers/shared/shared/__tests__/ReactComponent-test.js

@@ -370,7 +370,7 @@ describe('ReactComponent', () => {
       'Element type is invalid: expected a string (for built-in components) ' +
       'or a class/function (for composite components) but got: undefined. ' +
       'You likely forgot to export your component from the file it\'s ' +
-      'defined in. Check the render method of `Bar`.'
+      'defined in.\n\nCheck the render method of `Bar`.'
     );
 
     // One warning for each element creation

src/renderers/shared/shared/__tests__/ReactCompositeComponent-test.js

@@ -1033,7 +1033,7 @@ describe('ReactCompositeComponent', () => {
       'Warning: _renderNewRootComponent(): Render methods should ' +
       'be a pure function of props and state; triggering nested component ' +
       'updates from render is not allowed. If necessary, trigger nested ' +
-      'updates in componentDidUpdate. Check the render method of Outer.'
+      'updates in componentDidUpdate.\n\nCheck the render method of Outer.'
     );
   });
 

src/renderers/shared/shared/__tests__/ReactMultiChild-test.js

@@ -280,7 +280,7 @@ describe('ReactMultiChild', () => {
       expectDev(console.error.calls.argsFor(0)[0]).toBe(
         'Warning: Using Maps as children is not yet fully supported. It is an ' +
         'experimental feature that might be removed. Convert it to a sequence ' +
-        '/ iterable of keyed ReactElements instead. Check the render method of `Parent`.'
+        '/ iterable of keyed ReactElements instead.\n\nCheck the render method of `Parent`.'
       );
     });
   });

src/renderers/shared/shared/__tests__/ReactStatelessComponent-test.js

@@ -171,7 +171,7 @@ describe('ReactStatelessComponent', () => {
     expectDev(console.error.calls.count()).toBe(1);
     expectDev(normalizeCodeLocInfo(console.error.calls.argsFor(0)[0])).toBe(
       'Warning: Stateless function components cannot be given refs. ' +
-      'Attempts to access this ref will fail. Check the render method ' +
+      'Attempts to access this ref will fail.\n\nCheck the render method ' +
       'of `ParentUsingStringRef`.\n' +
       '    in StatelessComponent (at **)\n' +
       '    in div (at **)\n' +
@@ -206,7 +206,7 @@ describe('ReactStatelessComponent', () => {
     expectDev(console.error.calls.count()).toBe(1);
     expectDev(normalizeCodeLocInfo(console.error.calls.argsFor(0)[0])).toBe(
       'Warning: Stateless function components cannot be given refs. ' +
-      'Attempts to access this ref will fail. Check the render method ' +
+      'Attempts to access this ref will fail.\n\nCheck the render method ' +
       'of `ParentUsingFunctionRef`.\n' +
       '    in StatelessComponent (at **)\n' +
       '    in div (at **)\n' +