feat(runtime-core): support app.config.globalProperties

per https://github.com/vuejs/rfcs/pull/117/

packages/runtime-core/src/apiCreateApp.ts

@@ -50,6 +50,7 @@ export interface AppConfig {
   devtools: boolean
   performance: boolean
   optionMergeStrategies: Record<string, OptionMergeFunction>
+  globalProperties: Record<string, any>
   isCustomElement: (tag: string) => boolean
   errorHandler?: (
     err: unknown,
@@ -86,6 +87,7 @@ export function createAppContext(): AppContext {
       isNativeTag: NO,
       devtools: true,
       performance: false,
+      globalProperties: {},
       optionMergeStrategies: {},
       isCustomElement: NO,
       errorHandler: undefined,

packages/runtime-core/src/componentProxy.ts

@@ -77,7 +77,15 @@ const enum AccessTypes {
 
 export const PublicInstanceProxyHandlers: ProxyHandler<any> = {
   get(target: ComponentInternalInstance, key: string) {
-    const { renderContext, data, propsProxy, accessCache, type, sink } = target
+    const {
+      renderContext,
+      data,
+      propsProxy,
+      accessCache,
+      type,
+      sink,
+      appContext
+    } = target
 
     // data / props / renderContext
     // This getter gets called for every property access on the render context
@@ -118,19 +126,24 @@ export const PublicInstanceProxyHandlers: ProxyHandler<any> = {
 
     // public $xxx properties & user-attached properties (sink)
     const publicGetter = publicPropertiesMap[key]
-    let cssModule
+    let cssModule, globalProperties
     if (publicGetter) {
       if (__DEV__ && key === '$attrs') {
         markAttrsAccessed()
       }
       return publicGetter(target)
+    } else if (hasOwn(sink, key)) {
+      return sink[key]
     } else if (
       (cssModule = type.__cssModules) &&
       (cssModule = cssModule[key])
     ) {
       return cssModule
-    } else if (hasOwn(sink, key)) {
-      return sink[key]
+    } else if (
+      ((globalProperties = appContext.config.globalProperties),
+      hasOwn(globalProperties, key))
+    ) {
+      return globalProperties[key]
     } else if (__DEV__ && currentRenderingInstance) {
       warn(
         `Property ${JSON.stringify(key)} was accessed during render ` +