wip: invert compiler compat behavior default during tests

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

@@ -102,7 +102,9 @@ export function checkCompatEnabled(
   loc: SourceLocation | null,
   ...args: any[]
 ): boolean {
-  const enabled = getCompatValue(key, context) !== false
+  const value = getCompatValue(key, context)
+  // during tests, only enable when value is explicitly true
+  const enabled = __TEST__ ? value === true : value !== false
   if (__DEV__ && enabled) {
     warnDeprecation(key, context, loc, ...args)
   }

packages/compiler-core/src/errors.ts

@@ -13,9 +13,9 @@ export function defaultOnError(error: CompilerError) {
   throw error
 }
 
-export function defaultOnWarn(msg: string | CompilerError) {
-  __DEV__ &&
-    console.warn(`[Vue warn]`, typeof msg === 'string' ? msg : msg.message)
+export function defaultOnWarn(msg: CompilerError) {
+  throw new Error('foo')
+  __DEV__ && console.warn(`[Vue warn]`, msg.message)
 }
 
 export function createCompilerError<T extends number>(