From b0f6bcc8f3cb7622fe0eb74ec3adf981e637fcd1 Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Sun, 1 Feb 2026 19:32:28 +0000
Subject: [PATCH 1/3] Initial plan


From a265c7d10eebd12d3f5ce2c33db0be45fc1cc30a Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Sun, 1 Feb 2026 19:35:24 +0000
Subject: [PATCH 2/3] Fix empty character set parameter issue in mysqlcheck
 commands

Co-authored-by: swissspidy <841956+swissspidy@users.noreply.github.com>
---
 features/db-check.feature | 26 ++++++++++++++++++++++++++
 src/DB_Command.php        |  9 +++++++++
 2 files changed, 35 insertions(+)

diff --git a/features/db-check.feature b/features/db-check.feature
index aa5ce47b..7d14a4f7 100644
--- a/features/db-check.feature
+++ b/features/db-check.feature
@@ -136,3 +136,29 @@ Feature: Check the database
     When I try `wp db check --no-defaults --debug`
     Then STDERR should match #Debug \(db\): Running shell command: /usr/bin/env (mysqlcheck|mariadb-check) --no-defaults %s#
 
+  Scenario: Empty DB credentials should not cause empty parameter errors
+    Given a WP install
+    And a wp-config.php file:
+      """
+      <?php
+      define( 'DB_NAME', 'wp_cli_test' );
+      define( 'DB_USER', 'wp_cli_test' );
+      define( 'DB_PASSWORD', 'password1' );
+      define( 'DB_HOST', 'localhost' );
+      define( 'DB_CHARSET', '' );
+      define( 'DB_COLLATE', '' );
+      $table_prefix = 'wp_';
+      require_once ABSPATH . 'wp-settings.php';
+      """
+
+    When I run `wp db check --debug`
+    Then STDERR should not contain:
+      """
+      --default-character-set=
+      """
+    And the return code should be 0
+    And STDOUT should contain:
+      """
+      Success: Database checked.
+      """
+
diff --git a/src/DB_Command.php b/src/DB_Command.php
index 77676172..2096a0a9 100644
--- a/src/DB_Command.php
+++ b/src/DB_Command.php
@@ -1827,6 +1827,15 @@ private static function run( $cmd, $assoc_args = [], $send_to_shell = true, $int
 			unset( $assoc_args['dbpass'], $assoc_args['password'] );
 		}
 
+		// Filter out empty string values to avoid passing empty parameters to MySQL commands
+		// which can cause errors like "Character set '' is not a compiled character set"
+		$required = array_filter(
+			$required,
+			static function ( $value ) {
+				return '' !== $value;
+			}
+		);
+
 		$final_args = array_merge( $required, $assoc_args );
 
 		// Adapt ordering of arguments.

From 878e3e9ff46c73c9289b1891392f63a13bedaa14 Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Sun, 1 Feb 2026 19:38:21 +0000
Subject: [PATCH 3/3] Address code review feedback: handle null values and
 improve test

Co-authored-by: swissspidy <841956+swissspidy@users.noreply.github.com>
---
 features/db-check.feature | 10 +++++++++-
 src/DB_Command.php        |  2 +-
 2 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/features/db-check.feature b/features/db-check.feature
index 7d14a4f7..c98b3786 100644
--- a/features/db-check.feature
+++ b/features/db-check.feature
@@ -152,7 +152,15 @@ Feature: Check the database
       """
 
     When I run `wp db check --debug`
-    Then STDERR should not contain:
+    Then STDERR should contain:
+      """
+      Debug (db): Final MySQL command:
+      """
+    And STDERR should not contain:
+      """
+      --default-character-set=''
+      """
+    And STDERR should not contain:
       """
       --default-character-set=
       """
diff --git a/src/DB_Command.php b/src/DB_Command.php
index 2096a0a9..b136169c 100644
--- a/src/DB_Command.php
+++ b/src/DB_Command.php
@@ -1832,7 +1832,7 @@ private static function run( $cmd, $assoc_args = [], $send_to_shell = true, $int
 		$required = array_filter(
 			$required,
 			static function ( $value ) {
-				return '' !== $value;
+				return null !== $value && '' !== $value;
 			}
 		);