wip: attr coersion compat

packages/runtime-dom/src/modules/attrs.ts

@@ -15,6 +15,10 @@ export function patchAttr(
       el.setAttributeNS(xlinkNS, key, value)
     }
   } else {
+    if (__COMPAT__ && compatCoerceAttr(el, key, value)) {
+      return
+    }
+
     // note we are only checking boolean attributes that don't have a
     // corresponding dom prop of the same name here.
     const isBoolean = isSpecialBooleanAttr(key)
@@ -25,3 +29,46 @@ export function patchAttr(
     }
   }
 }
+
+// 2.x compat
+import { makeMap, NOOP } from '@vue/shared'
+import { compatUtils, DeprecationTypes } from '@vue/runtime-core'
+
+const isEnumeratedAttr = __COMPAT__
+  ? /*#__PURE__*/ makeMap('contenteditable,draggable,spellcheck')
+  : NOOP
+
+export function compatCoerceAttr(
+  el: Element,
+  key: string,
+  value: unknown
+): boolean {
+  if (isEnumeratedAttr(key)) {
+    const v2CocercedValue =
+      value === null
+        ? 'false'
+        : typeof value !== 'boolean' && value !== undefined
+          ? 'true'
+          : null
+    if (
+      v2CocercedValue &&
+      compatUtils.softAssertCompatEnabled(
+        DeprecationTypes.ATTR_ENUMERATED_COERSION,
+        key,
+        value,
+        v2CocercedValue
+      )
+    ) {
+      el.setAttribute(key, v2CocercedValue)
+      return true
+    }
+  } else if (
+    value === false &&
+    !isSpecialBooleanAttr(key) &&
+    compatUtils.softAssertCompatEnabled(DeprecationTypes.ATTR_FALSE_VALUE, key)
+  ) {
+    el.removeAttribute(key)
+    return true
+  }
+  return false
+}