refactor: fix implementation of SFC :slotted id handling

fix #2892

packages/runtime-core/src/componentRenderContext.ts

@@ -0,0 +1,57 @@
+import { ComponentInternalInstance } from './component'
+import { isRenderingCompiledSlot } from './helpers/renderSlot'
+import { closeBlock, openBlock } from './vnode'
+
+/**
+ * mark the current rendering instance for asset resolution (e.g.
+ * resolveComponent, resolveDirective) during render
+ */
+export let currentRenderingInstance: ComponentInternalInstance | null = null
+export let currentScopeId: string | null = null
+
+export function setCurrentRenderingInstance(
+  instance: ComponentInternalInstance | null
+) {
+  currentRenderingInstance = instance
+  currentScopeId = (instance && instance.type.__scopeId) || null
+}
+
+/**
+ * Set scope id when creating hoisted vnodes.
+ * @private compiler helper
+ */
+export function setScopeId(id: string | null) {
+  currentScopeId = id
+}
+
+/**
+ * Wrap a slot function to memoize current rendering instance
+ * @private compiler helper
+ */
+export function withCtx(
+  fn: Function,
+  ctx: ComponentInternalInstance | null = currentRenderingInstance
+) {
+  if (!ctx) return fn
+  const renderFnWithContext = (...args: any[]) => {
+    // If a user calls a compiled slot inside a template expression (#1745), it
+    // can mess up block tracking, so by default we need to push a null block to
+    // avoid that. This isn't necessary if rendering a compiled `<slot>`.
+    if (!isRenderingCompiledSlot) {
+      openBlock(true /* null block that disables tracking */)
+    }
+    const prevInstance = currentRenderingInstance
+    setCurrentRenderingInstance(ctx)
+    const res = fn(...args)
+    setCurrentRenderingInstance(prevInstance)
+    if (!isRenderingCompiledSlot) {
+      closeBlock()
+    }
+    return res
+  }
+  // mark this as a compiled slot function.
+  // this is used in vnode.ts -> normalizeChildren() to set the slot
+  // rendering flag.
+  renderFnWithContext._c = true
+  return renderFnWithContext
+}