Interactivity API: Allow missing state negation on server

Aligns on the behavior of the negation operator with directives to missing paths in client and in server.

With a directive like the following:
{{{
<div data-wp-bind--hidden="!state.missing.property">
	This should be hidden by the <code>hidden</code> attribute.
</div>
}}}

Both server and client will return with this fix:
{{{
<div data-wp-bind--hidden="!state.missing.property" hidden="">
	This should be hidden by the <code>hidden</code> attribute.
</div>
}}}

Props jonsurrell, luisherranz.
Fixes #62374.



git-svn-id: https://develop.svn.wordpress.org/trunk@59398 602fd350-edb4-49c9-b593-d223f7449a82

Author: cbravobernal

Diff for: src/wp-includes/interactivity-api/class-wp-interactivity-api.php

@@ -584,7 +584,8 @@ private function evaluate( $directive_value ) {
 			} elseif ( is_object( $current ) && isset( $current->$path_segment ) ) {
 				$current = $current->$path_segment;
 			} else {
-				return null;
+				$current = null;
+				break;
 			}
 
 			if ( $current instanceof Closure ) {

Diff for: tests/phpunit/tests/interactivity-api/wpInteractivityAPI.php

@@ -1079,6 +1079,38 @@ public function test_evaluate_value_negation() {
 		$this->assertFalse( $result );
 	}
 
+	/**
+	 * Tests that the `evaluate` method operates correctly when used with the
+	 * negation operator (!) with non-existent paths.
+	 *
+	 * @ticket 62374
+	 *
+	 * @covers ::evaluate
+	 */
+	public function test_evaluate_value_negation_non_existent_path() {
+		$this->interactivity->state( 'myPlugin', array() );
+		$this->interactivity->state( 'otherPlugin', array() );
+		$this->set_internal_context_stack(
+			array(
+				'myPlugin'    => array(),
+				'otherPlugin' => array(),
+			)
+		);
+		$this->set_internal_namespace_stack( 'myPlugin' );
+
+		$result = $this->evaluate( '!state.missing' );
+		$this->assertTrue( $result );
+
+		$result = $this->evaluate( '!context.missing' );
+		$this->assertTrue( $result );
+
+		$result = $this->evaluate( 'otherPlugin::!state.deeply.nested.missing' );
+		$this->assertTrue( $result );
+
+		$result = $this->evaluate( 'otherPlugin::!context.deeply.nested.missing' );
+		$this->assertTrue( $result );
+	}
+
 	/**
 	 * Tests the `evaluate` method with non-existent paths.
 	 *