wordpress.patch

diff U3 a/wp/wp-includes/load.php b/wp/wp-includes/load.php
--- a/wp/wp-includes/load.php	Tue Feb 02 19:38:52 2016
+++ b/wp/wp-includes/load.php	Tue Feb 02 19:58:21 2016
@@ -285,7 +285,7 @@
  */
 function wp_debug_mode() {
 	if ( WP_DEBUG ) {
-		error_reporting( E_ALL );
+		error_reporting( E_ALL  & ~E_DEPRECATED );
 
 		if ( WP_DEBUG_DISPLAY )
 			ini_set( 'display_errors', 1 );

--- web/wp/wp-includes/load.php 2016-03-12 01:51:09.000000000 -0500
+++ web/wp/wp-includes/load.php 2016-03-12 01:51:20.000000000 -0500
@@ -285,7 +285,7 @@
  */
 function wp_debug_mode() {
    if ( WP_DEBUG ) {
-       error_reporting( E_ALL );
+       error_reporting( E_ALL  & ~E_DEPRECATED );

        if ( WP_DEBUG_DISPLAY )
            ini_set( 'display_errors', 1 );

That's what worked for me. Make sure it's in your site/ dir.

@cfxd thanks!

--- web/wp/wp-includes/load.php
+++ web/wp/wp-includes/load.php
@@ -457,7 +457,7 @@ function wp_debug_mode() {
 	}

 	if ( WP_DEBUG ) {
-		error_reporting( E_ALL );
+		error_reporting( E_ALL  & ~E_DEPRECATED );

 		if ( WP_DEBUG_DISPLAY ) {
 			ini_set( 'display_errors', 1 );

Copied @cfxd path fix + updated diff for WP v5.9.1

--- web/wp/wp-includes/load.php
+++ web/wp/wp-includes/load.php
@@ -569,7 +569,7 @@ function wp_debug_mode() {
	}

	if ( WP_DEBUG ) {
-		error_reporting( E_ALL );
+		error_reporting( E_ALL & ~E_DEPRECATED );

		if ( WP_DEBUG_DISPLAY ) {
			ini_set( 'display_errors', 1 );

Line number updated for WP 6.4.1 & 6.3.1, possibly earlier versions.

If you get errors like Could not apply patch! Skipping. The error was: Cannot apply patch wordpress.patch, make sure the patch is targeting roots/wordpress-no-content and make your editor isn't converting tabs to spaces or otherwise changing the indentation in your patch file.

    "wordpress-install-dir": "web/wp",
    "patches": {
      "roots/wordpress-no-content": {
        "Prevent E_DEPRECATED error messages when debug is enabled": "wordpress.patch"
      }
    }

--- wp/wp-includes/load.php
+++ wp/wp-includes/load.php
@@ -582,7 +582,7 @@ function wp_debug_mode() {
	}

	if ( WP_DEBUG ) {
-		error_reporting( E_ALL );
+		error_reporting( E_ALL & ~E_DEPRECATED );

		if ( WP_DEBUG_DISPLAY ) {
			ini_set( 'display_errors', 1 );

Line number updated for WP 6.7.1. I've also dropped web/ from the path so the patch is picked up on the -p1 patch level, previously it would cycle through -p1, -p0 and then finally succeed on -p2.

Use composer update --verbose to give more info if you hit any issues.