Move createExtensionDataContainer() to shared, internal location

Signed-off-by: Eric Peterson <ericpeterson@spotify.com>

packages/frontend-internal/src/wiring/createExtensionDataContainer.ts

@@ -0,0 +1,66 @@
+/*
+ * Copyright 2024 The Backstage Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import {
+  AnyExtensionDataRef,
+  ExtensionDataContainer,
+  ExtensionDataRef,
+  ExtensionDataValue,
+} from '@backstage/frontend-plugin-api';
+
+export function createExtensionDataContainer<UData extends AnyExtensionDataRef>(
+  values: Iterable<
+    UData extends ExtensionDataRef<infer IData, infer IId>
+      ? ExtensionDataValue<IData, IId>
+      : never
+  >,
+  declaredRefs?: ExtensionDataRef<any, any, any>[],
+): ExtensionDataContainer<UData> {
+  const container = new Map<string, ExtensionDataValue<any, any>>();
+  const verifyRefs =
+    declaredRefs && new Map(declaredRefs.map(ref => [ref.id, ref]));
+
+  for (const output of values) {
+    if (verifyRefs) {
+      if (!verifyRefs.delete(output.id)) {
+        throw new Error(
+          `extension data '${output.id}' was provided but not declared`,
+        );
+      }
+    }
+    container.set(output.id, output);
+  }
+
+  const remainingRefs =
+    verifyRefs &&
+    Array.from(verifyRefs.values()).filter(ref => !ref.config.optional);
+  if (remainingRefs && remainingRefs.length > 0) {
+    throw new Error(
+      `missing required extension data value(s) '${remainingRefs
+        .map(ref => ref.id)
+        .join(', ')}'`,
+    );
+  }
+
+  return {
+    get(ref) {
+      return container.get(ref.id)?.value;
+    },
+    [Symbol.iterator]() {
+      return container.values();
+    },
+  } as ExtensionDataContainer<UData>;
+}

packages/frontend-internal/src/wiring/index.ts

@@ -14,5 +14,6 @@
  * limitations under the License.
  */
 
+export { createExtensionDataContainer } from './createExtensionDataContainer';
 export { OpaqueExtensionDefinition } from './InternalExtensionDefinition';
 export { OpaqueFrontendPlugin } from './InternalFrontendPlugin';