Craft now ensures that installed schema versions match the schema ver…

…sions in `project.yaml` before syncing project config changes.

CHANGELOG-v3.md

@@ -8,6 +8,7 @@
 
 ### Changed
 - URLs are no longer allowed in a user’s first or last names.
+- Craft now ensures that installed schema versions match the schema versions in `project.yaml` before syncing project config changes.
 
 ### Fixed
 - Fixed a bug where `site` translations were falling back to English if the translated message was identical to the source message. ([#3692](https://github.com/craftcms/cms/issues/3692))

src/services/ProjectConfig.php

@@ -649,6 +649,8 @@ public function getPendingChangeSummary(): array
 
     /**
      * Returns whether all schema versions stored in the config are compatible with the actual codebase.
+     * The schemas must match exactly to avoid unpredictable behavior that can occur when running migrations
+     * and applying project config changes at the same time.
      *
      * @return bool
      */
@@ -659,19 +661,23 @@ public function getAreConfigSchemaVersionsCompatible(): bool
             return true;
         }
 
-        $configSchemaVersion = (string)$this->get(self::CONFIG_SCHEMA_VERSION_KEY, true);
+        $incomingSchema = (string)$this->get(self::CONFIG_SCHEMA_VERSION_KEY, true);
+        $existingSchema = (string)Craft::$app->schemaVersion;
 
-        if (version_compare((string)Craft::$app->schemaVersion, $configSchemaVersion, '<')) {
+        // Compare existing Craft schema version with the one that is being applied.
+        if (version_compare($existingSchema, $incomingSchema, '=')) {
             return false;
         }
 
         $plugins = Craft::$app->getPlugins()->getAllPlugins();
 
         foreach ($plugins as $plugin) {
             /** @var Plugin $plugin */
-            $configSchemaVersion = (string)$this->get(Plugins::CONFIG_PLUGINS_KEY . '.' . $plugin->handle . '.schemaVersion', true);
+            $incomingSchema = (string)$this->get(Plugins::CONFIG_PLUGINS_KEY . '.' . $plugin->handle . '.schemaVersion', true);
+            $existingSchema = (string)$plugin->schemaVersion;
 
-            if (version_compare((string)$plugin->schemaVersion, $configSchemaVersion, '<')) {
+            // Compare existing plugin schema version with the one that is being applied.
+            if (version_compare($existingSchema, $incomingSchema, '=')) {
                 return false;
             }
         }

src/templates/_special/incompatibleconfigs.html

@@ -2,6 +2,6 @@
 {% set title = "Unable to apply project.yaml changes"|t('app') %}
 
 {% block message %}
-<p>{{ 'Your `project.yaml` file was created for more recent versions of Craft and/or plugins than what’s currently installed.'|t('app')|md(inlineOnly=true) }}</p>
+<p>{{ 'Your `project.yaml` file was created for different versions of Craft and/or plugins than what’s currently installed.'|t('app')|md(inlineOnly=true) }}</p>
 <p>{{ 'Try running `composer install` from your terminal to resolve.'|t('app')|md(inlineOnly=true) }}</p>
 {% endblock %}