lazy assign connections to dependencies

in many cases we don't need the assignment

lib/ModuleGraph.js

@@ -79,6 +79,8 @@ class ModuleGraphModule {
 		this.profile = undefined;
 		/** @type {boolean} */
 		this.async = false;
+		/** @type {ModuleGraphConnection[]} */
+		this._unassignedConnections = undefined;
 	}
 }
 
@@ -169,14 +171,21 @@ class ModuleGraph {
 			dependency.weak,
 			dependency.getCondition(this)
 		);
-		this._dependencyMap.set(dependency, connection);
 		const connections = this._getModuleGraphModule(module).incomingConnections;
 		connections.add(connection);
-		const mgm = this._getModuleGraphModule(originModule);
-		if (mgm.outgoingConnections === undefined) {
-			mgm.outgoingConnections = new Set();
+		if (originModule) {
+			const mgm = this._getModuleGraphModule(originModule);
+			if (mgm._unassignedConnections === undefined) {
+				mgm._unassignedConnections = [];
+			}
+			mgm._unassignedConnections.push(connection);
+			if (mgm.outgoingConnections === undefined) {
+				mgm.outgoingConnections = new Set();
+			}
+			mgm.outgoingConnections.add(connection);
+		} else {
+			this._dependencyMap.set(dependency, connection);
 		}
-		mgm.outgoingConnections.add(connection);
 	}
 
 	/**
@@ -185,7 +194,7 @@ class ModuleGraph {
 	 * @returns {void}
 	 */
 	updateModule(dependency, module) {
-		const connection = this._dependencyMap.get(dependency);
+		const connection = this.getConnection(dependency);
 		if (connection.module === module) return;
 		const newConnection = connection.clone();
 		newConnection.module = module;
@@ -202,12 +211,12 @@ class ModuleGraph {
 	 * @returns {void}
 	 */
 	removeConnection(dependency) {
-		const connection = this._dependencyMap.get(dependency);
+		const connection = this.getConnection(dependency);
 		const targetMgm = this._getModuleGraphModule(connection.module);
 		targetMgm.incomingConnections.delete(connection);
 		const originMgm = this._getModuleGraphModule(connection.originModule);
 		originMgm.outgoingConnections.delete(connection);
-		this._dependencyMap.delete(dependency);
+		this._dependencyMap.set(dependency, null);
 	}
 
 	/**
@@ -216,7 +225,7 @@ class ModuleGraph {
 	 * @returns {void}
 	 */
 	addExplanation(dependency, explanation) {
-		const connection = this._dependencyMap.get(dependency);
+		const connection = this.getConnection(dependency);
 		connection.addExplanation(explanation);
 	}
 
@@ -342,7 +351,7 @@ class ModuleGraph {
 	 * @returns {Module} the referenced module
 	 */
 	getResolvedModule(dependency) {
-		const connection = this._dependencyMap.get(dependency);
+		const connection = this.getConnection(dependency);
 		return connection !== undefined ? connection.resolvedModule : null;
 	}
 
@@ -352,15 +361,38 @@ class ModuleGraph {
 	 */
 	getConnection(dependency) {
 		const connection = this._dependencyMap.get(dependency);
-		return connection;
+		if (connection === undefined) {
+			const module = this.getParentModule(dependency);
+			if (module !== undefined) {
+				const mgm = this._getModuleGraphModule(module);
+				if (
+					mgm._unassignedConnections &&
+					mgm._unassignedConnections.length !== 0
+				) {
+					let foundConnection;
+					for (const connection of mgm._unassignedConnections) {
+						this._dependencyMap.set(connection.dependency, connection);
+						if (connection.dependency === dependency)
+							foundConnection = connection;
+					}
+					mgm._unassignedConnections.length = 0;
+					if (foundConnection !== undefined) {
+						return foundConnection;
+					}
+				}
+			}
+			this._dependencyMap.set(dependency, null);
+			return undefined;
+		}
+		return connection === null ? undefined : connection;
 	}
 
 	/**
 	 * @param {Dependency} dependency the dependency to look for a referenced module
 	 * @returns {Module} the referenced module
 	 */
 	getModule(dependency) {
-		const connection = this._dependencyMap.get(dependency);
+		const connection = this.getConnection(dependency);
 		return connection !== undefined ? connection.module : null;
 	}
 
@@ -369,7 +401,7 @@ class ModuleGraph {
 	 * @returns {Module} the referencing module
 	 */
 	getOrigin(dependency) {
-		const connection = this._dependencyMap.get(dependency);
+		const connection = this.getConnection(dependency);
 		return connection !== undefined ? connection.originModule : null;
 	}
 
@@ -378,7 +410,7 @@ class ModuleGraph {
 	 * @returns {Module} the original referencing module
 	 */
 	getResolvedOrigin(dependency) {
-		const connection = this._dependencyMap.get(dependency);
+		const connection = this.getConnection(dependency);
 		return connection !== undefined ? connection.resolvedOriginModule : null;
 	}