fix(compiler-core): make v-once work with v-if/else-if/else (#2182)

Partial fix for #2035

packages/compiler-core/src/ast.ts

@@ -236,7 +236,7 @@ export interface CompoundExpressionNode extends Node {
 export interface IfNode extends Node {
   type: NodeTypes.IF
   branches: IfBranchNode[]
-  codegenNode?: IfConditionalExpression
+  codegenNode?: IfConditionalExpression | CacheExpression // <div v-if v-once>
 }
 
 export interface IfBranchNode extends Node {

packages/compiler-core/src/transforms/vIf.ts

@@ -20,7 +20,8 @@ import {
   IfNode,
   createVNodeCall,
   AttributeNode,
-  locStub
+  locStub,
+  CacheExpression
 } from '../ast'
 import { createCompilerError, ErrorCodes } from '../errors'
 import { processExpression } from './transformExpression'
@@ -62,13 +63,7 @@ export const transformIf = createStructuralDirectiveTransform(
           ) as IfConditionalExpression
         } else {
           // attach this branch's codegen node to the v-if root.
-          let parentCondition = ifNode.codegenNode!
-          while (
-            parentCondition.alternate.type ===
-            NodeTypes.JS_CONDITIONAL_EXPRESSION
-          ) {
-            parentCondition = parentCondition.alternate
-          }
+          const parentCondition = getParentCondition(ifNode.codegenNode!)
           parentCondition.alternate = createCodegenNodeForBranch(
             branch,
             key + ifNode.branches.length - 1,
@@ -293,3 +288,19 @@ function isSameKey(
   }
   return true
 }
+
+function getParentCondition(
+  node: IfConditionalExpression | CacheExpression
+): IfConditionalExpression {
+  while (true) {
+    if (node.type === NodeTypes.JS_CONDITIONAL_EXPRESSION) {
+      if (node.alternate.type === NodeTypes.JS_CONDITIONAL_EXPRESSION) {
+        node = node.alternate
+      } else {
+        return node
+      }
+    } else if (node.type === NodeTypes.JS_CACHE_EXPRESSION) {
+      node = node.value as IfConditionalExpression
+    }
+  }
+}