fix: ensure backwards compat for pre-compiled sfc components

fix #3493

packages/runtime-core/src/componentRenderContext.ts

@@ -32,10 +32,25 @@ export function setCurrentRenderingInstance(
  * Set scope id when creating hoisted vnodes.
  * @private compiler helper
  */
-export function setScopeId(id: string | null) {
+export function pushScopeId(id: string | null) {
   currentScopeId = id
 }
 
+/**
+ * Technically we no longer need this after 3.0.8 but we need to keep the same
+ * API for backwards compat w/ code generated by compilers.
+ * @private
+ */
+export function popScopeId() {
+  currentScopeId = null
+}
+
+/**
+ * Only for backwards compat
+ * @private
+ */
+export const withScopeId = (_id: string) => withCtx
+
 /**
  * Wrap a slot function to memoize current rendering instance
  * @private compiler helper

packages/runtime-core/src/helpers/renderSlot.ts

@@ -26,7 +26,7 @@ export function renderSlot(
   // this is not a user-facing function, so the fallback is always generated by
   // the compiler and guaranteed to be a function returning an array
   fallback?: () => VNodeArrayChildren,
-  hasSlotted?: boolean
+  noSlotted?: boolean
 ): VNode {
   let slot = slots[name]
 
@@ -54,7 +54,7 @@ export function renderSlot(
       ? PatchFlags.STABLE_FRAGMENT
       : PatchFlags.BAIL
   )
-  if (hasSlotted && rendered.scopeId) {
+  if (!noSlotted && rendered.scopeId) {
     rendered.slotScopeIds = [rendered.scopeId + '-s']
   }
   isRenderingCompiledSlot--

packages/runtime-core/src/index.ts

@@ -226,8 +226,13 @@ export { HMRRuntime } from './hmr'
 // user code should avoid relying on them.
 
 // For compiler generated code
-// should sync with '@vue/compiler-core/src/runtimeConstants.ts'
-export { withCtx, setScopeId } from './componentRenderContext'
+// should sync with '@vue/compiler-core/src/runtimeHelpers.ts'
+export {
+  withCtx,
+  pushScopeId,
+  popScopeId,
+  withScopeId
+} from './componentRenderContext'
 export { renderList } from './helpers/renderList'
 export { toHandlers } from './helpers/toHandlers'
 export { renderSlot } from './helpers/renderSlot'