Bail out of the block-mutating subcommands before doing any work

The previous approach routed the seven mutating subcommands through a private
`serialize_blocks()` wrapper, which meant the WordPress 5.3.1 check only ran
after the command had already fetched the post, parsed every block and applied
the requested changes. For `wp post block update` that also fired the
`wp_cli_post_block_update_html` filter, so third-party callbacks loaded through
`--require` ran for a command that was always going to fail.

Drop the wrapper and check for `serialize_blocks()` as the first statement of
`update`, `insert`, `remove`, `move`, `replace`, `clone` and `import` instead,
so they abort before touching anything. The read-only subcommands keep working
on WordPress 5.0 - 5.3.0, and wp-compat still sees the guard, so no PHPStan
ignore is needed.

Co-authored-by: Pascal Birchler <pascal.birchler@gmail.com>

Author: claude

src/Post_Block_Command.php

@@ -224,6 +224,10 @@ public function get( $args, $assoc_args ) {
 	 * @subcommand update
 	 */
 	public function update( $args, $assoc_args ) {
+		if ( ! function_exists( 'serialize_blocks' ) ) {
+			WP_CLI::error( 'Requires WordPress 5.3.1 or greater.' );
+		}
+
 		$post   = $this->fetcher->get_check( $args[0] );
 		$index  = (int) $args[1];
 		$blocks = parse_blocks( $post->post_content );
@@ -280,7 +284,7 @@ public function update( $args, $assoc_args ) {
 		$blocks[ $original_idx ] = $block;
 
 		// @phpstan-ignore argument.type
-		$new_content = $this->serialize_blocks( $blocks );
+		$new_content = serialize_blocks( $blocks );
 		$result      = wp_update_post(
 			[
 				'ID'           => $post->ID,
@@ -340,6 +344,10 @@ public function update( $args, $assoc_args ) {
 	 * @subcommand move
 	 */
 	public function move( $args, $assoc_args ) {
+		if ( ! function_exists( 'serialize_blocks' ) ) {
+			WP_CLI::error( 'Requires WordPress 5.3.1 or greater.' );
+		}
+
 		$post       = $this->fetcher->get_check( $args[0] );
 		$from_index = (int) $args[1];
 		$to_index   = (int) $args[2];
@@ -398,7 +406,7 @@ public function move( $args, $assoc_args ) {
 		// Insert at new position.
 		array_splice( $blocks, $insert_pos, 0, [ $block_to_move ] );
 
-		$new_content = $this->serialize_blocks( $blocks );
+		$new_content = serialize_blocks( $blocks );
 		$result      = wp_update_post(
 			[
 				'ID'           => $post->ID,
@@ -607,6 +615,10 @@ function ( $block ) {
 	 * @subcommand import
 	 */
 	public function import( $args, $assoc_args ) {
+		if ( ! function_exists( 'serialize_blocks' ) ) {
+			WP_CLI::error( 'Requires WordPress 5.3.1 or greater.' );
+		}
+
 		$post     = $this->fetcher->get_check( $args[0] );
 		$file     = Utils\get_flag_value( $assoc_args, 'file', null );
 		$position = Utils\get_flag_value( $assoc_args, 'position', 'end' );
@@ -691,7 +703,7 @@ function ( $block ) {
 			}
 		}
 
-		$new_content = $this->serialize_blocks( $blocks );
+		$new_content = serialize_blocks( $blocks );
 		$result      = wp_update_post(
 			[
 				'ID'           => $post->ID,
@@ -914,6 +926,10 @@ public function count( $args, $assoc_args ) {
 	 * @subcommand clone
 	 */
 	public function clone_block( $args, $assoc_args ) {
+		if ( ! function_exists( 'serialize_blocks' ) ) {
+			WP_CLI::error( 'Requires WordPress 5.3.1 or greater.' );
+		}
+
 		$post         = $this->fetcher->get_check( $args[0] );
 		$source_index = (int) $args[1];
 		$position     = Utils\get_flag_value( $assoc_args, 'position', 'after' );
@@ -975,7 +991,7 @@ public function clone_block( $args, $assoc_args ) {
 		array_splice( $blocks, (int) $insert_pos, 0, [ $cloned_block ] );
 
 		// @phpstan-ignore argument.type
-		$new_content = $this->serialize_blocks( $blocks );
+		$new_content = serialize_blocks( $blocks );
 
 		$result = wp_update_post(
 			[
@@ -1393,6 +1409,10 @@ public function list_( $args, $assoc_args ) {
 	 * @subcommand insert
 	 */
 	public function insert( $args, $assoc_args ) {
+		if ( ! function_exists( 'serialize_blocks' ) ) {
+			WP_CLI::error( 'Requires WordPress 5.3.1 or greater.' );
+		}
+
 		$post       = $this->fetcher->get_check( $args[0] );
 		$block_name = $args[1];
 		$content    = Utils\get_flag_value( $assoc_args, 'content', '' );
@@ -1424,7 +1444,7 @@ public function insert( $args, $assoc_args ) {
 		}
 
 		// @phpstan-ignore argument.type
-		$new_content = $this->serialize_blocks( $blocks );
+		$new_content = serialize_blocks( $blocks );
 		$result      = wp_update_post(
 			[
 				'ID'           => $post->ID,
@@ -1492,6 +1512,10 @@ public function insert( $args, $assoc_args ) {
 	 * @subcommand remove
 	 */
 	public function remove( $args, $assoc_args ) {
+		if ( ! function_exists( 'serialize_blocks' ) ) {
+			WP_CLI::error( 'Requires WordPress 5.3.1 or greater.' );
+		}
+
 		$post       = $this->fetcher->get_check( $args[0] );
 		$block_name = isset( $args[1] ) ? $args[1] : null;
 		$indices    = Utils\get_flag_value( $assoc_args, 'index', null );
@@ -1567,7 +1591,7 @@ function ( $idx ) use ( $index_map ) {
 			return;
 		}
 
-		$new_content = $this->serialize_blocks( $blocks );
+		$new_content = serialize_blocks( $blocks );
 		$result      = wp_update_post(
 			[
 				'ID'           => $post->ID,
@@ -1637,6 +1661,10 @@ function ( $idx ) use ( $index_map ) {
 	 * @subcommand replace
 	 */
 	public function replace( $args, $assoc_args ) {
+		if ( ! function_exists( 'serialize_blocks' ) ) {
+			WP_CLI::error( 'Requires WordPress 5.3.1 or greater.' );
+		}
+
 		$post           = $this->fetcher->get_check( $args[0] );
 		$old_block_name = $args[1];
 		$new_block_name = $args[2];
@@ -1681,7 +1709,7 @@ public function replace( $args, $assoc_args ) {
 		}
 
 		// @phpstan-ignore argument.type
-		$new_content = $this->serialize_blocks( $blocks );
+		$new_content = serialize_blocks( $blocks );
 		$result      = wp_update_post(
 			[
 				'ID'           => $post->ID,
@@ -1702,25 +1730,6 @@ public function replace( $args, $assoc_args ) {
 		}
 	}
 
-	/**
-	 * Serializes blocks back into post content.
-	 *
-	 * The command itself requires WordPress 5.0, but `serialize_blocks()` was only
-	 * introduced in WordPress 5.3.1.
-	 *
-	 * @param array $blocks Array of blocks.
-	 * @return string Serialized post content.
-	 *
-	 * @phpstan-param array<int|string, array{blockName: string|null, attrs: array, innerBlocks: array[], innerHTML: string, innerContent: array}> $blocks
-	 */
-	private function serialize_blocks( $blocks ) {
-		if ( ! function_exists( 'serialize_blocks' ) ) {
-			WP_CLI::error( 'Requires WordPress 5.3.1 or greater.' );
-		}
-
-		return serialize_blocks( $blocks );
-	}
-
 	/**
 	 * Strips innerHTML and innerContent from blocks recursively.
 	 *