From f7fd3684f2be3633746153b1301e26e3231b69e1 Mon Sep 17 00:00:00 2001
From: Mario Santos <34552881+SantosGuillamot@users.noreply.github.com>
Date: Thu, 5 Sep 2024 16:14:31 +0200
Subject: [PATCH] Block Bindings: Fix empty strings placeholders in post meta
 bindings (#65089)

* Contemplate empty strings as truthy

* Add e2e test for empty values

Co-authored-by: zaguiini <zaguiini@git.wordpress.org>
Co-authored-by: SantosGuillamot <santosguillamot@git.wordpress.org>
---
 packages/e2e-tests/plugins/block-bindings.php | 10 ++++++
 packages/editor/src/bindings/post-meta.js     |  2 +-
 .../editor/various/block-bindings.spec.js     | 32 +++++++++++++++++++
 3 files changed, 43 insertions(+), 1 deletion(-)

diff --git a/packages/e2e-tests/plugins/block-bindings.php b/packages/e2e-tests/plugins/block-bindings.php
index b2eb9d797610d..143feb240ac2e 100644
--- a/packages/e2e-tests/plugins/block-bindings.php
+++ b/packages/e2e-tests/plugins/block-bindings.php
@@ -41,6 +41,16 @@ function gutenberg_test_block_bindings_registration() {
 			'default'      => '#url-custom-field',
 		)
 	);
+	register_meta(
+		'post',
+		'empty_field',
+		array(
+			'show_in_rest' => true,
+			'type'         => 'string',
+			'single'       => true,
+			'default'      => '',
+		)
+	);
 	register_meta(
 		'post',
 		'_protected_field',
diff --git a/packages/editor/src/bindings/post-meta.js b/packages/editor/src/bindings/post-meta.js
index 4de8396d4c13b..7618ba6c36023 100644
--- a/packages/editor/src/bindings/post-meta.js
+++ b/packages/editor/src/bindings/post-meta.js
@@ -22,7 +22,7 @@ export default {
 		for ( const [ attributeName, source ] of Object.entries( bindings ) ) {
 			// Use the key if the value is not set.
 			newValues[ attributeName ] =
-				meta?.[ source.args.key ] || source.args.key;
+				meta?.[ source.args.key ] ?? source.args.key;
 		}
 		return newValues;
 	},
diff --git a/test/e2e/specs/editor/various/block-bindings.spec.js b/test/e2e/specs/editor/various/block-bindings.spec.js
index 2799315a10b22..6e36b6ad5dd33 100644
--- a/test/e2e/specs/editor/various/block-bindings.spec.js
+++ b/test/e2e/specs/editor/various/block-bindings.spec.js
@@ -1278,6 +1278,38 @@ test.describe( 'Block bindings', () => {
 				).toHaveText( 'fallback value' );
 			} );
 
+			test( 'should show the prompt placeholder in field with empty value', async ( {
+				editor,
+			} ) => {
+				await editor.insertBlock( {
+					name: 'core/paragraph',
+					attributes: {
+						content: 'paragraph default content',
+						metadata: {
+							bindings: {
+								content: {
+									source: 'core/post-meta',
+									args: { key: 'empty_field' },
+								},
+							},
+						},
+					},
+				} );
+
+				const paragraphBlock = editor.canvas.getByRole( 'document', {
+					// Aria-label is changed for empty paragraphs.
+					name: 'Add empty_field',
+				} );
+
+				await expect( paragraphBlock ).toBeEmpty();
+
+				const placeholder = paragraphBlock.locator( 'span' );
+				await expect( placeholder ).toHaveAttribute(
+					'data-rich-text-placeholder',
+					'Add empty_field'
+				);
+			} );
+
 			test( 'should not show the value of a protected meta field', async ( {
 				editor,
 			} ) => {