fix: respect type order when boolean casting multi-typed props

fix #7485

src/core/util/props.js

@@ -27,12 +27,18 @@ export function validateProp (
   const prop = propOptions[key]
   const absent = !hasOwn(propsData, key)
   let value = propsData[key]
-  // handle boolean props
-  if (isType(Boolean, prop.type)) {
+  // boolean casting
+  const booleanIndex = getTypeIndex(Boolean, prop.type)
+  if (booleanIndex > -1) {
     if (absent && !hasOwn(prop, 'default')) {
       value = false
-    } else if (!isType(String, prop.type) && (value === '' || value === hyphenate(key))) {
-      value = true
+    } else if (value === '' || value === hyphenate(key)) {
+      // only cast empty string / same name to boolean if
+      // boolean has higher priority
+      const stringIndex = getTypeIndex(String, prop.type)
+      if (stringIndex < 0 || booleanIndex < stringIndex) {
+        value = true
+      }
     }
   }
   // check default value
@@ -179,15 +185,18 @@ function getType (fn) {
   return match ? match[1] : ''
 }
 
-function isType (type, fn) {
-  if (!Array.isArray(fn)) {
-    return getType(fn) === getType(type)
+function isSameType (a, b) {
+  return getType(a) === getType(b)
+}
+
+function getTypeIndex (type, expectedTypes): number {
+  if (!Array.isArray(expectedTypes)) {
+    return isSameType(expectedTypes, type) ? 0 : -1
   }
-  for (let i = 0, len = fn.length; i < len; i++) {
-    if (getType(fn[i]) === getType(type)) {
-      return true
+  for (let i = 0, len = expectedTypes.length; i < len; i++) {
+    if (isSameType(expectedTypes[i], type)) {
+      return i
     }
   }
-  /* istanbul ignore next */
-  return false
+  return -1
 }

test/unit/features/options/props.spec.js

@@ -512,4 +512,21 @@ describe('Options props', () => {
       expect(`"${attr}" is a reserved attribute`).toHaveBeenWarned()
     })
   })
+
+  it('should consider order when casting [Boolean, String] multi-type props', () => {
+    const vm = new Vue({
+      template: '<test ref="test" booleanOrString stringOrBoolean />',
+      components: {
+        test: {
+          template: '<div></div>',
+          props: {
+            booleanOrString: [Boolean, String],
+            stringOrBoolean: [String, Boolean]
+          }
+        }
+      }
+    }).$mount()
+    expect(vm.$refs.test.$props.booleanOrString).toBe(true)
+    expect(vm.$refs.test.$props.stringOrBoolean).toBe('')
+  })
 })