Improve "empty" Schema handling

src/Dev/Build.php

@@ -64,6 +64,17 @@ public function buildSchema($key = null, $clear = false): void
             if ($clear) {
                 $schema->getStore()->clear();
             }
+            $schema->process();
+
+            // Allow for "empty" schemas which don't have any types defined.
+            // This enables baseline configuration of the "default" schema.
+            if ($schema->exists()) {
+
+            } else {
+                Schema::message('No types defined, skipping');
+                continue;
+            }
+
             $schema->save();
 
             Schema::message(

src/Schema/Schema.php

@@ -41,9 +41,11 @@
 use TypeError;
 
 /**
- * The main Schema definition. A docking station for all type, model, interface, etc., abstractions.
+ * The main Schema definition. A docking station for all type, model and interface abstractions.
  * Applies plugins, validates, and persists to code.
  *
+ * Use {@link SchemaFactory} to create functional instances of this type
+ * based on YAML configuration.
  */
 class Schema implements ConfigurationApplier, SchemaValidator
 {
@@ -131,16 +133,11 @@ class Schema implements ConfigurationApplier, SchemaValidator
     private $schemaContext;
 
     /**
-     * @var bool See constructor for details about booting.
+     * @var boolean
      */
-    private $_booted = false;
+    private $_isProcessed = false;
 
     /**
-     * In order to trigger auto-discovery of the schema configuration
-     * in Silverstripe's config system, call {@link boot()} before using.
-     * Since booting has a performance impact, some functionality is
-     * available without booting (e.g. fetching an already persisted schema).
-     *
      * @param string $schemaKey
      * @param SchemaContext|null $schemaContext
      */
@@ -537,9 +534,14 @@ private function collectSchemaUpdaters(array $components): array
     }
 
     /**
-     * @throws SchemaBuilderException
+     * Process any lazy defined properties (types and modules),
+     * and execute plugins. This step is automatically taken during {@link save()},
+     * but can be useful to execute separately in order to determine if the schema
+     * is valid before saving.
+     *
+     * @return void
      */
-    public function save(): void
+    public function process(): void
     {
         // Fill in lazily defined type properties, e.g. fields with a classname as a type
         $this->processTypes();
@@ -561,6 +563,18 @@ public function save(): void
         // Resolver discovery
         $this->processFields();
 
+        $this->_isProcessed = true;
+    }
+
+    /**
+     * @throws SchemaBuilderException
+     */
+    public function save(): void
+    {
+        if (!$this->_isProcessed) {
+            $this->process();
+        }
+
         $this->validate();
         $this->getStore()->persistSchema($this);
 

src/Schema/SchemaFactory.php

@@ -19,6 +19,14 @@ class SchemaFactory
 {
     use Injectable;
 
+    /**
+     * Retrieves an already stored schema
+     * which does not require booting.
+     * Returns null when no stored schema can be found.
+     *
+     * @param string $key
+     * @return Schema|null
+     */
     public function get(string $key): ?Schema
     {
         $schema = Schema::create($key);
@@ -27,6 +35,11 @@ public function get(string $key): ?Schema
     }
 
     /**
+     * Retrieves an already stored schema
+     * which does not require booting.
+     * Throws when the schema can either not be found,
+     * or when it has not been stored yet.
+     *
      * @param string $key
      * @return Schema
      * @throws SchemaNotFoundException
@@ -52,6 +65,10 @@ public function require(string $key): Schema
      * An instance can only be booted once to avoid conflicts with further
      * instance level modifications such as {@link addType()}.
      *
+     * This method should only be used on schemas which have not been stored,
+     * and is usually only needed for the process of storing them
+     * (through {@link Schema->save()}).
+     *
      * @param string $key
      * @throws SchemaBuilderException
      */