From 9930fc7ed1dc7b5308a496a8c9205834b243dc62 Mon Sep 17 00:00:00 2001
From: Him188 <Him188@mamoe.net>
Date: Sun, 26 Dec 2021 18:55:19 +0000
Subject: [PATCH] Extend `AbstractSingletonExtensionPoint` and
 `AbstractInstanceExtensionPoint`, support lazy instance computation

---
 .../src/extension/ExtensionPoint.kt           | 47 +++++++++++++++++--
 .../extensions/CommandCallResolverProvider.kt |  2 +-
 .../extensions/PermissionServiceProvider.kt   |  2 +-
 .../extension/ComponentStorageInternal.kt     | 14 +++---
 4 files changed, 51 insertions(+), 14 deletions(-)

diff --git a/mirai-console/backend/mirai-console/src/extension/ExtensionPoint.kt b/mirai-console/backend/mirai-console/src/extension/ExtensionPoint.kt
index 07afb9f83..f861b92ed 100644
--- a/mirai-console/backend/mirai-console/src/extension/ExtensionPoint.kt
+++ b/mirai-console/backend/mirai-console/src/extension/ExtensionPoint.kt
@@ -51,25 +51,62 @@ public interface FunctionExtensionPoint<T : FunctionExtension> : ExtensionPoint<
 
 
 public abstract class AbstractInstanceExtensionPoint<E : InstanceExtension<T>, T>
-@ConsoleExperimentalApi constructor(
+/**
+ * @since 2.10
+ */
+@ConsoleExperimentalApi
+constructor(
     extensionType: KClass<E>,
     /**
      * 内建的实现列表.
      */
     @ConsoleExperimentalApi
-    public vararg val builtinImplementations: E,
-) : AbstractExtensionPoint<E>(extensionType)
+    public vararg val builtinImplementations: () -> E,
+) : AbstractExtensionPoint<E>(extensionType) {
+
+    /**
+     * @since 2.10
+     */
+    @ConsoleExperimentalApi
+    public constructor(extensionType: KClass<E>) : this(
+        extensionType,
+        builtinImplementations = arrayOf<() -> E>() as Array<out () -> E>
+    ) // to avoid resolution ambiguity
+
+    /**
+     * @since 2.0
+     */
+    @ConsoleExperimentalApi
+    public constructor(extensionType: KClass<E>, vararg builtinImplementations: E) : this(
+        extensionType,
+        builtinImplementations = builtinImplementations.map { { it } }.toTypedArray()
+    )
+}
 
 public abstract class AbstractSingletonExtensionPoint<E : SingletonExtension<T>, T>
-@ConsoleExperimentalApi constructor(
+/**
+ * @since 2.10
+ */
+@ConsoleExperimentalApi
+constructor(
     extensionType: KClass<E>,
     /**
      * 内建的实现.
      */
     @ConsoleExperimentalApi
-    public val builtinImplementation: T,
+    public val builtinImplementation: () -> T,
 ) : AbstractExtensionPoint<E>(extensionType), SingletonExtensionPoint<E> {
 
+    /**
+     * @since 2.0
+     */
+    @Suppress("USELESS_CAST") // compiler bug
+    @ConsoleExperimentalApi
+    public constructor(extensionType: KClass<E>, builtinImplementation: T) : this(
+        extensionType,
+        { builtinImplementation } as () -> T
+    )
+
     /**
      * 由 [SingletonExtensionSelector] 选择后的实例.
      */
diff --git a/mirai-console/backend/mirai-console/src/extensions/CommandCallResolverProvider.kt b/mirai-console/backend/mirai-console/src/extensions/CommandCallResolverProvider.kt
index e88519539..3181a9045 100644
--- a/mirai-console/backend/mirai-console/src/extensions/CommandCallResolverProvider.kt
+++ b/mirai-console/backend/mirai-console/src/extensions/CommandCallResolverProvider.kt
@@ -20,7 +20,7 @@ public interface CommandCallResolverProvider : SingletonExtension<CommandCallRes
     public companion object ExtensionPoint :
         AbstractSingletonExtensionPoint<CommandCallResolverProvider, CommandCallResolver>(
             CommandCallResolverProvider::class,
-            BuiltInCommandCallResolver
+            { BuiltInCommandCallResolver }
         )
 }
 
diff --git a/mirai-console/backend/mirai-console/src/extensions/PermissionServiceProvider.kt b/mirai-console/backend/mirai-console/src/extensions/PermissionServiceProvider.kt
index 3a4806c48..2d0618180 100644
--- a/mirai-console/backend/mirai-console/src/extensions/PermissionServiceProvider.kt
+++ b/mirai-console/backend/mirai-console/src/extensions/PermissionServiceProvider.kt
@@ -26,7 +26,7 @@ public interface PermissionServiceProvider : SingletonExtension<PermissionServic
     public companion object ExtensionPoint :
         AbstractSingletonExtensionPoint<PermissionServiceProvider, PermissionService<*>>(
             PermissionServiceProvider::class,
-            BuiltInPermissionService
+            { BuiltInPermissionService }
         ) {
         internal var permissionServiceOk = false
 
diff --git a/mirai-console/backend/mirai-console/src/internal/extension/ComponentStorageInternal.kt b/mirai-console/backend/mirai-console/src/internal/extension/ComponentStorageInternal.kt
index 96d44922d..5e8d4a755 100644
--- a/mirai-console/backend/mirai-console/src/internal/extension/ComponentStorageInternal.kt
+++ b/mirai-console/backend/mirai-console/src/internal/extension/ComponentStorageInternal.kt
@@ -57,10 +57,10 @@ internal abstract class AbstractConcurrentComponentStorage : ComponentStorage {
         val userDefined = instances.getOrPut(this, ::CopyOnWriteArraySet) as Set<ExtensionRegistry<T>>
 
         val builtins = if (this is AbstractInstanceExtensionPoint<*, *>) {
-            this.builtinImplementations.mapTo(HashSet()) {
+            this.builtinImplementations.mapTo(HashSet()) { instance ->
                 DataExtensionRegistry(
                     null,
-                    it
+                    instance()
                 )
             } as Set<ExtensionRegistry<T>>
         } else null
@@ -116,18 +116,18 @@ internal abstract class AbstractConcurrentComponentStorage : ComponentStorage {
         }
     }
 
-    internal inline fun <reified E : SingletonExtension<T>, T> ExtensionPoint<out E>.findSingletonInstance(builtin: T): T =
-        findSingletonInstance(E::class, builtin)
+    internal inline fun <reified E : SingletonExtension<T>, T> ExtensionPoint<out E>.findSingletonInstance(noinline default: () -> T): T =
+        findSingletonInstance(E::class, default)
 
     internal fun <E : SingletonExtension<T>, T> ExtensionPoint<out E>.findSingletonInstance(
         type: KClass<E>,
-        builtin: T,
+        default: () -> T,
     ): T {
         val candidates = this.getExtensions()
         return when (candidates.size) {
-            0 -> builtin
+            0 -> default()
             1 -> candidates.single().extension.instance
-            else -> SingletonExtensionSelector.instance.selectSingleton(type, candidates)?.instance ?: builtin
+            else -> SingletonExtensionSelector.instance.selectSingleton(type, candidates)?.instance ?: default()
         }
     }