Proposed fix to module federation to stop ignoring the singleton flag when requiredVersion is false

lib/sharing/ConsumeSharedModule.js

@@ -210,6 +210,10 @@ class ConsumeSharedModule extends Module {
 			}
 			args.push(stringifyHoley(requiredVersion));
 			fn += "VersionCheck";
+		} else {
+			if (singleton) {
+				fn += "Singleton";
+			}
 		}
 		if (fallbackCode) {
 			fn += "Fallback";

lib/sharing/ConsumeSharedRuntimeModule.js

@@ -108,6 +108,13 @@ class ConsumeSharedRuntimeModule extends RuntimeModule {
 					`return "Unsatisfied version " + version + " from " + (version && scope[key][version].from) + " of shared singleton module " + key + " (required " + rangeToString(requiredVersion) + ")"`
 				]
 			)};`,
+			`var getSingleton = ${runtimeTemplate.basicFunction(
+				"scope, scopeName, key, requiredVersion",
+				[
+					"var version = findSingletonVersionKey(scope, key);",
+					"return get(scope[key][version]);"
+				]
+			)};`,
 			`var getSingletonVersion = ${runtimeTemplate.basicFunction(
 				"scope, scopeName, key, requiredVersion",
 				[
@@ -202,6 +209,13 @@ class ConsumeSharedRuntimeModule extends RuntimeModule {
 					"return get(findValidVersion(scope, key, version) || warnInvalidVersion(scope, scopeName, key, version) || findVersion(scope, key));"
 				]
 			)});`,
+			`var loadSingleton = /*#__PURE__*/ init(${runtimeTemplate.basicFunction(
+				"scopeName, scope, key",
+				[
+					"ensureExistence(scopeName, key);",
+					"return getSingleton(scope, scopeName, key);"
+				]
+			)});`,
 			`var loadSingletonVersionCheck = /*#__PURE__*/ init(${runtimeTemplate.basicFunction(
 				"scopeName, scope, key, version",
 				[
@@ -230,6 +244,13 @@ class ConsumeSharedRuntimeModule extends RuntimeModule {
 					"return get(findValidVersion(scope, key, version) || warnInvalidVersion(scope, scopeName, key, version) || findVersion(scope, key));"
 				]
 			)});`,
+			`var loadSingletonFallback = /*#__PURE__*/ init(${runtimeTemplate.basicFunction(
+				"scopeName, scope, key, fallback",
+				[
+					`if(!scope || !${RuntimeGlobals.hasOwnProperty}(scope, key)) return fallback();`,
+					"return getSingleton(scope, scopeName, key);"
+				]
+			)});`,
 			`var loadSingletonVersionCheckFallback = /*#__PURE__*/ init(${runtimeTemplate.basicFunction(
 				"scopeName, scope, key, version, fallback",
 				[

test/configCases/sharing/consume-module/index.js

@@ -196,6 +196,15 @@ it("should handle version matching correctly in strict and singleton mode", asyn
 				get: () => () => "shared singleton",
 				from: 'container-a'
 			}
+		},
+		singletonWithoutVersion: {
+			"1.0.0": {
+				get: () => () => "shared singleton v1.0.0",
+				loaded: true
+			},
+			"2.0.0": {
+				get: () => () => "shared singleton v2.0.0"
+			}
 		}
 	};
 	{
@@ -235,3 +244,21 @@ it("should handle version matching correctly in strict and singleton mode", asyn
 		);
 	}
 });
+
+it("should not instantiate multiple singletons even if a higher version exists", async () => {
+	__webpack_share_scopes__["default"] = {
+		singletonWithoutVersion: {
+			"1.0.0": {
+				get: () => () => "shared singleton v1.0.0",
+				loaded: true
+			},
+			"2.0.0": {
+				get: () => () => "shared singleton v2.0.0"
+			}
+		}
+	};
+	{
+		const result = await import("singletonWithoutVersion");
+		expect(result.default).toBe("shared singleton v1.0.0");
+	}
+});

test/configCases/sharing/consume-module/webpack.config.js

@@ -54,6 +54,10 @@ module.exports = {
 					requiredVersion: "1.1.0",
 					singleton: true,
 					strictVersion: false
+				},
+				singletonWithoutVersion: {
+					requiredVersion: false,
+					singleton: true
 				}
 			}
 		})