fix(runtime-core): avoid manual slot invocation in template expressions interfering with block tracking

fix #1745

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

@@ -10,6 +10,8 @@ import {
 import { PatchFlags, SlotFlags } from '@vue/shared'
 import { warn } from '../warning'
 
+export let isRenderingTemplateSlot = false
+
 /**
  * Compiler runtime helper for rendering `<slot/>`
  * @private
@@ -33,15 +35,20 @@ export function renderSlot(
     slot = () => []
   }
 
-  return (
-    openBlock(),
-    createBlock(
-      Fragment,
-      { key: props.key },
-      slot ? slot(props) : fallback ? fallback() : [],
-      (slots as RawSlots)._ === SlotFlags.STABLE
-        ? PatchFlags.STABLE_FRAGMENT
-        : PatchFlags.BAIL
-    )
-  )
+  // a compiled slot disables block tracking by default to avoid manual
+  // invocation interfering with template-based block tracking, but in
+  // `renderSlot` we can be sure that it's template-based so we can force
+  // enable it.
+  isRenderingTemplateSlot = true
+  const rendered = (openBlock(),
+  createBlock(
+    Fragment,
+    { key: props.key },
+    slot ? slot(props) : fallback ? fallback() : [],
+    (slots as RawSlots)._ === SlotFlags.STABLE
+      ? PatchFlags.STABLE_FRAGMENT
+      : PatchFlags.BAIL
+  ))
+  isRenderingTemplateSlot = false
+  return rendered
 }

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

@@ -4,6 +4,7 @@ import {
   currentRenderingInstance
 } from '../componentRenderUtils'
 import { ComponentInternalInstance } from '../component'
+import { setBlockTracking } from '../vnode'
 
 /**
  * Wrap a slot function to memoize current rendering instance
@@ -15,10 +16,15 @@ export function withCtx(
 ) {
   if (!ctx) return fn
   return function renderFnWithContext() {
+    // By default, compiled slots disables block tracking since the user may
+    // call it inside a template expression (#1745). It should only track when
+    // it's called by a template `<slot>`.
+    setBlockTracking(-1)
     const owner = currentRenderingInstance
     setCurrentRenderingInstance(ctx)
     const res = fn.apply(null, arguments as any)
     setCurrentRenderingInstance(owner)
+    setBlockTracking(1)
     return res
   }
 }