core-api: switch component data to use a global store

.changeset/rich-socks-move.md

@@ -0,0 +1,6 @@
+---
+'@backstage/core-api': patch
+'@backstage/core': patch
+---
+
+Internal refactor of how component data is access to avoid polluting components and make it possible to bridge across versions.

packages/core-api/src/extensions/componentData.test.tsx

@@ -59,4 +59,63 @@ describe('elementData', () => {
       'Attempted to attach duplicate data "my-data" to component "MyComponent"',
     );
   });
+
+  describe('works across versions', () => {
+    function getDataSymbol() {
+      const Component = () => null;
+      attachComponentData(Component, 'my-data', {});
+      const [symbol] = Object.getOwnPropertySymbols(Component);
+      return symbol;
+    }
+
+    it('should should be able to get data from older versions', () => {
+      const symbol = getDataSymbol();
+
+      const data = { foo: 'bar' };
+      const Component = () => null;
+      attachComponentData(Component, 'my-data', data);
+
+      const element = <Component />;
+      expect((element as any).type[symbol].map.get('my-data')).toBe(data);
+    });
+
+    it('should should be able to attach data for older versions', () => {
+      const symbol = getDataSymbol();
+
+      const data = { foo: 'bar' };
+      const Component = () => null;
+      (Component as any)[symbol] = {
+        map: new Map([['my-data', data]]),
+      };
+
+      const element = <Component />;
+      expect(getComponentData(element, 'my-data')).toBe(data);
+    });
+
+    it('should be able to get data from newer versions', () => {
+      const data = { foo: 'bar' };
+      const Component = () => null;
+      attachComponentData(Component, 'my-data', data);
+
+      const element = <Component />;
+      const container = (global as any)[
+        '__@backstage/component-data-store__'
+      ].store.get(element.type);
+      expect(container.map.get('my-data')).toBe(data);
+    });
+
+    it('should should be able to attach data for newer versions', () => {
+      const data = { foo: 'bar' };
+      const Component = () => null;
+      (global as any)['__@backstage/component-data-store__'].store.set(
+        Component,
+        {
+          map: new Map([['my-data', data]]),
+        },
+      );
+
+      const element = <Component />;
+      expect(getComponentData(element, 'my-data')).toBe(data);
+    });
+  });
 });

packages/core-api/src/extensions/componentData.tsx

@@ -15,21 +15,40 @@
  */
 
 import { ComponentType, ReactNode } from 'react';
+import { globalObject } from '../lib/globalObject';
 
+// TODO(Rugvip): Access via symbol is deprecated, remove once on 0.3.x
 const DATA_KEY = Symbol('backstage-component-data');
 
-type DataContainer = {
-  map: Map<string, unknown>;
-};
-
 type ComponentWithData<P> = ComponentType<P> & {
   [DATA_KEY]?: DataContainer;
 };
 
-type ReactNodeWithData = ReactNode & {
-  type?: { [DATA_KEY]?: DataContainer };
+type DataContainer = {
+  map: Map<string, unknown>;
 };
 
+type MaybeComponentNode = ReactNode & {
+  type?: ComponentType<any> & { [DATA_KEY]?: DataContainer };
+};
+
+const GLOBAL_KEY = '__@backstage/component-data-store__';
+
+// The store is bridged across versions using the global object
+function getStore() {
+  let storeObj = globalObject[GLOBAL_KEY] as
+    | { store: WeakMap<ComponentType<any>, DataContainer> }
+    | undefined;
+  if (!storeObj) {
+    const store = new WeakMap<ComponentType<any>, DataContainer>();
+    storeObj = { store };
+    globalObject[GLOBAL_KEY] = storeObj;
+  }
+  return storeObj.store;
+}
+
+const store = getStore();
+
 export function attachComponentData<P>(
   component: ComponentType<P>,
   type: string,
@@ -37,9 +56,11 @@ export function attachComponentData<P>(
 ) {
   const dataComponent = component as ComponentWithData<P>;
 
-  let container = dataComponent[DATA_KEY];
+  let container = store.get(component) || dataComponent[DATA_KEY];
   if (!container) {
-    container = dataComponent[DATA_KEY] = { map: new Map() };
+    container = { map: new Map() };
+    store.set(component, container);
+    dataComponent[DATA_KEY] = container;
   }
 
   if (container.map.has(type)) {
@@ -60,7 +81,12 @@ export function getComponentData<T>(
     return undefined;
   }
 
-  const container = (node as ReactNodeWithData).type?.[DATA_KEY];
+  const component = (node as MaybeComponentNode).type;
+  if (!component) {
+    return undefined;
+  }
+
+  const container = store.get(component) || component[DATA_KEY];
   if (!container) {
     return undefined;
   }

packages/core-api/src/lib/globalObject.ts

@@ -0,0 +1,29 @@
+/*
+ * Copyright 2021 Spotify AB
+ *
+ * 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.
+ */
+
+// https://github.com/zloirock/core-js/issues/86#issuecomment-115759028
+function getGlobal() {
+  if (typeof window !== 'undefined' && window.Math === Math) {
+    return window;
+  }
+  if (typeof self !== 'undefined' && self.Math === Math) {
+    return self;
+  }
+  // eslint-disable-next-line no-new-func
+  return Function('return this')();
+}
+
+export const globalObject = getGlobal();