Deprecated: Log message maximum once per session (#7840)

packages/deprecated/src/index.js

@@ -1,3 +1,11 @@
+/**
+ * Object map tracking messages which have been logged, for use in ensuring a
+ * message is only logged once.
+ *
+ * @type {Object}
+ */
+export const logged = Object.create( null );
+
 /**
  * Logs a message to notify developers about a deprecated feature.
  *
@@ -17,6 +25,13 @@ export default function deprecated( feature, { version, alternative, plugin, lin
 	const hintMessage = hint ? ` Note: ${ hint }` : '';
 	const message = `${ feature } is deprecated and will be removed${ versionMessage }.${ useInsteadMessage }${ linkMessage }${ hintMessage }`;
 
+	// Skip if already logged.
+	if ( message in logged ) {
+		return;
+	}
+
 	// eslint-disable-next-line no-console
 	console.warn( message );
+
+	logged[ message ] = true;
 }

packages/deprecated/src/test/index.js

@@ -1,9 +1,15 @@
 /**
  * Internal dependencies
  */
-import deprecated from '../';
+import deprecated, { logged } from '../';
 
 describe( 'deprecated', () => {
+	afterEach( () => {
+		for ( const key in logged ) {
+			delete logged[ key ];
+		}
+	} );
+
 	it( 'should show a deprecation warning', () => {
 		deprecated( 'Eating meat' );
 
@@ -65,4 +71,13 @@ describe( 'deprecated', () => {
 			'Eating meat is deprecated and will be removed from the earth in the future. Please use vegetables instead. Note: You may find it beneficial to transition gradually.'
 		);
 	} );
+
+	it( 'should show a message once', () => {
+		deprecated( 'Eating meat' );
+		deprecated( 'Eating meat' );
+
+		expect( console ).toHaveWarned();
+		// eslint-disable-next-line no-console
+		expect( console.warn ).toHaveBeenCalledTimes( 1 );
+	} );
 } );