Let a relational field send arguments with its search

`data-search-args` was rendered, the script forwarded it, the endpoint
cleaned it and the callback took it as a third argument -- and nothing could
ever put anything in it. search_args() returned an empty array and read no
configuration, so the whole path existed and was unreachable from a field.

It reads `search_args` now. The reason to want it is context the search term
does not carry: most often which record the picker is sitting in, so the
callback can leave that one out. A product's "also suggest" offering the
product itself is a choice that looks available, and is thrown away on save.

Scalars only, matching what the endpoint reduces them to anyway -- a nested
array would reach the callback as the string "Array" and read as a filter
that had been applied.

Subclasses that build their own arguments still override; a post picker has
a post type to send and no use for anything a caller invents.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Tk8y5eZa3CHVVSM6nVxsJw

Author: arraypress

src/Types/AbstractRelationalType.php

@@ -74,12 +74,29 @@ abstract protected function resolve_labels( array $ids, Field $field ): array;
 	/**
 	 * Query arguments forwarded to the endpoint.
 	 *
+	 * Whatever the field declares under `search_args`, so a callback source
+	 * can be told something the search term does not carry -- which record
+	 * the picker is sitting in, most often, so it can leave that one out.
+	 * Without this the attribute existed and nothing could ever fill it.
+	 *
+	 * They reach the callback as its third argument, and the endpoint
+	 * reduces them to scalars before they get there.
+	 *
+	 * Subclasses that build their own arguments override this; a post picker
+	 * has a post type to send and no use for anything a caller invents.
+	 *
 	 * @param Field $field The field.
 	 *
 	 * @return array<string, scalar>
 	 */
 	protected function search_args( Field $field ): array {
-		return [];
+		$args = $field->get( 'search_args', [] );
+
+		if ( ! is_array( $args ) ) {
+			return [];
+		}
+
+		return array_filter( $args, 'is_scalar' );
 	}
 
 	/**
@@ -284,7 +301,7 @@ public function config_keys(): array {
 		// it in the list twice.
 		return array_merge(
 			parent::config_keys(),
-			[ 'min_chars', 'search_callback', 'sortable', 'min', 'max' ]
+			[ 'min_chars', 'search_callback', 'search_args', 'sortable', 'min', 'max' ]
 		);
 	}
 

tests/RelationalLimitsTest.php

@@ -243,4 +243,41 @@ public function test_config_keys_have_no_duplicates( string $type ): void {
 		$this->assertSame( array_values( array_unique( $keys ) ), $keys, "{$type} repeats a config key" );
 	}
 
+	/**
+	 * A callback source can be told something the search term does not carry.
+	 *
+	 * `search_args` reaches the endpoint, which passes it to the callback as
+	 * its third argument. The usual reason is which record the picker is
+	 * sitting in, so it can leave that one out of the results -- a product's
+	 * "also suggest" offering the product itself is a choice that looks
+	 * available and is thrown away on save.
+	 *
+	 * The attribute existed before this and nothing could fill it.
+	 */
+	public function test_search_args_reach_the_page(): void {
+		$markup = $this->render( 'ajax', [ 'search_args' => [ 'exclude' => 12 ] ] );
+
+		$this->assertStringContainsString( 'data-search-args', $markup );
+		$this->assertStringContainsString( '"exclude":12', $markup );
+	}
+
+	/**
+	 * A field that declares none gets no attribute at all.
+	 */
+	public function test_no_search_args_means_no_attribute(): void {
+		$this->assertStringNotContainsString( 'data-search-args', $this->render( 'ajax' ) );
+	}
+
+	/**
+	 * Only scalars, because the endpoint reduces them to scalars anyway.
+	 *
+	 * A nested array would arrive as the string "Array" and read as a filter
+	 * that had been applied.
+	 */
+	public function test_search_args_drop_anything_that_is_not_scalar(): void {
+		$markup = $this->render( 'ajax', [ 'search_args' => [ 'ok' => 1, 'bad' => [ 1, 2 ] ] ] );
+
+		$this->assertStringContainsString( '"ok":1', $markup );
+		$this->assertStringNotContainsString( 'bad', $markup );
+	}
 }