wip: ref v-for compat

packages/compiler-core/src/compat/compatConfig.ts

@@ -20,6 +20,7 @@ export const enum CompilerDeprecationTypes {
   COMPILER_V_BIND_OBJECT_ORDER = 'COMPILER_V_BIND_OBJECT_ORDER',
   COMPILER_V_ON_NATIVE = 'COMPILER_V_ON_NATIVE',
   COMPILER_V_IF_V_FOR_PRECEDENCE = 'COMPILER_V_IF_V_FOR_PRECEDENCE',
+  COMPILER_V_FOR_REF = 'COMPILER_V_FOR_REF',
   COMPILER_NATIVE_TEMPLATE = 'COMPILER_NATIVE_TEMPLATE',
   COMPILER_INLINE_TEMPLATE = 'COMPILER_INLINE_TEMPLATE',
   COMPILER_FILTERS = 'COMPILER_FILTER'
@@ -78,6 +79,13 @@ const deprecationData: Record<CompilerDeprecationTypes, DeprecationData> = {
     link: `https://v3.vuejs.org/guide/migration/v-if-v-for.html`
   },
 
+  [CompilerDeprecationTypes.COMPILER_V_FOR_REF]: {
+    message:
+      `Ref usage on v-for no longer creates array ref values in Vue 3. ` +
+      `Consider using function refs or refactor to avoid ref usage altogether.`,
+    link: `https://v3.vuejs.org/guide/migration/array-refs.html`
+  },
+
   [CompilerDeprecationTypes.COMPILER_NATIVE_TEMPLATE]: {
     message:
       `<template> with no special directives will render as a native template ` +

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

@@ -590,6 +590,25 @@ export function buildProps(
         runtimeDirectives.push(prop)
       }
     }
+
+    if (
+      __COMPAT__ &&
+      prop.type === NodeTypes.ATTRIBUTE &&
+      prop.name === 'ref' &&
+      context.scopes.vFor > 0 &&
+      checkCompatEnabled(
+        CompilerDeprecationTypes.COMPILER_V_FOR_REF,
+        context,
+        prop.loc
+      )
+    ) {
+      properties.push(
+        createObjectProperty(
+          createSimpleExpression('refInFor', true),
+          createSimpleExpression('true', false)
+        )
+      )
+    }
   }
 
   let propsExpression: PropsExpression | undefined = undefined