Ensure we clear the in-memory Stripe API keys for key situations (#4348)

* Ensure we clear the in-memory Stripe API keys for key situations
* Call WC_Stripe_API::set_secret_key() statically

Author: daledupreez

changelog.txt

@@ -4,6 +4,7 @@
 * Add - Implement custom database cache for persistent caching with in-memory optimization.
 * Update - Remove feature that flags 401s and proactively blocks subsequent API calls until the store has reauthenticated.
 * Fix - Disable payment settings sync when we receive unsupported payment method configurations.
+* Fix - Ensure that we use current Stripe API keys after settings updates
 
 = 9.5.1 - 2025-05-17 =
 * Fix - Add a fetch cooldown to the payment method configuration retrieval endpoint to prevent excessive requests.

readme.txt

@@ -114,5 +114,6 @@ If you get stuck, you can ask for help in the [Plugin Forum](https://wordpress.o
 * Add - Implement custom database cache for persistent caching with in-memory optimization.
 * Update - Remove feature that flags 401s and proactively blocks subsequent API calls until the store has reauthenticated.
 * Fix - Disable payment settings sync when we receive unsupported payment method configurations.
+* Fix - Ensure that we use current Stripe API keys after settings updates
 
 [See changelog for full details across versions](https://raw.githubusercontent.com/woocommerce/woocommerce-gateway-stripe/trunk/changelog.txt).

woocommerce-gateway-stripe.php

@@ -598,13 +598,48 @@ public function gateway_settings_update( $settings, $old_settings ) {
 					$settings     = array_merge( $old_settings, $settings );
 				}
 
+				// Note that we need to run these checks before we call toggle_upe() below.
+				$this->maybe_reset_stripe_in_memory_key( $settings, $old_settings );
+
 				if ( ! WC_Stripe_Feature_Flags::is_upe_preview_enabled() ) {
 					return $settings;
 				}
 
 				return $this->toggle_upe( $settings, $old_settings );
 			}
 
+			/**
+			 * Helper function that ensures we clear the in-memory Stripe API key in {@see WC_Stripe_API}
+			 * when we're making a change to our settings that impacts which secret key we should be using.
+			 *
+			 * @param array $settings     New settings that have just been saved.
+			 * @param array $old_settings Old settings that were previously saved.
+			 * @return void
+			 */
+			protected function maybe_reset_stripe_in_memory_key( $settings, $old_settings ) {
+				// If we're making a change that impacts which secret key we should be using,
+				// we need to clear the static key being used by WC_Stripe_API.
+				// Note that this also needs to run before we call toggle_upe() below.
+				$should_clear_stripe_api_key = false;
+
+				$settings_to_check = [
+					'testmode',
+					'secret_key',
+					'test_secret_key',
+				];
+
+				foreach ( $settings_to_check as $setting_to_check ) {
+					if ( isset( $settings[ $setting_to_check ] ) && isset( $old_settings[ $setting_to_check ] ) && $settings[ $setting_to_check ] !== $old_settings[ $setting_to_check ] ) {
+						$should_clear_stripe_api_key = true;
+						break;
+					}
+				}
+
+				if ( $should_clear_stripe_api_key ) {
+					WC_Stripe_API::set_secret_key( '' );
+				}
+			}
+
 			/**
 			 * Enable or disable UPE.
 			 *