Emit each deprecation warning only once

src/deprecated.js

@@ -1,11 +1,23 @@
 import warning from 'warning';
 
+let warned = {};
+
 export default function deprecated(propType, explanation) {
   return function validate(props, propName, componentName) {
     if (props[propName] != null) {
-      warning(false, `"${propName}" property of "${componentName}" has been deprecated.\n${explanation}`);
+      const message = `"${propName}" property of "${componentName}" has been deprecated.\n${explanation}`;
+      if (!warned[message]) {
+        warning(false, message);
+        warned[message] = true;
+      }
     }
 
     return propType(props, propName, componentName);
   };
 }
+
+function _resetWarned() {
+  warned = {};
+}
+
+deprecated._resetWarned = _resetWarned;

test/deprecatedSpec.js

@@ -10,6 +10,8 @@ export function shouldError(about) {
 
 describe('deprecated', function() {
   beforeEach(function() {
+    deprecated._resetWarned();
+
     // because 'warning' package uses console.error instead of console.warn
     sinon.stub(console, 'error');
   });
@@ -22,16 +24,23 @@ describe('deprecated', function() {
     return deprecated(React.PropTypes.string, 'Read more at link')({pName: prop}, 'pName', 'ComponentName');
   }
 
-  it('Should warn about deprecation and validate OK', function() {
+  it('should warn about deprecation and validate OK', function() {
     const err = validate('value');
     shouldError('"pName" property of "ComponentName" has been deprecated.\nRead more at link');
     assert.notInstanceOf(err, Error);
   });
 
-  it('Should warn about deprecation and throw validation error when property value is not OK', function() {
+  it('should warn about deprecation and throw validation error when property value is not OK', function() {
     const err = validate({});
     shouldError('"pName" property of "ComponentName" has been deprecated.\nRead more at link');
     assert.instanceOf(err, Error);
     assert.include(err.message, 'Invalid undefined `pName` of type `object` supplied to `ComponentName`');
   });
+
+  it('should not emit the same warning more than once', function() {
+    validate('value');
+    validate('value');
+    console.error.should.have.been.calledOnce;
+    shouldError('deprecated');
+  });
 });