fix(runtime-core): should preserve props casing when component has no declared props

close #583

packages/runtime-core/__tests__/rendererAttrsFallthrough.spec.ts

@@ -32,7 +32,8 @@ describe('attribute fallthrough', () => {
             id: 'test',
             class: 'c' + count.value,
             style: { color: count.value ? 'red' : 'green' },
-            onClick: inc
+            onClick: inc,
+            'data-id': 1
           })
       }
     }
@@ -66,6 +67,7 @@ describe('attribute fallthrough', () => {
     expect(node.getAttribute('class')).toBe('c2 c0')
     expect(node.style.color).toBe('green')
     expect(node.style.fontWeight).toBe('bold')
+    expect(node.dataset.id).toBe('1')
     node.dispatchEvent(new CustomEvent('click'))
     expect(click).toHaveBeenCalled()
 

packages/runtime-core/src/componentProps.ts

@@ -127,13 +127,17 @@ export function resolveProps(
       if (key === 'key' || key === 'ref') continue
       // prop option names are camelized during normalization, so to support
       // kebab -> camel conversion here we need to camelize the key.
-      const camelKey = camelize(key)
-      if (hasDeclaredProps && !hasOwn(options, camelKey)) {
-        // Any non-declared props are put into a separate `attrs` object
-        // for spreading. Make sure to preserve original key casing
-        ;(attrs || (attrs = {}))[key] = rawProps[key]
+      if (hasDeclaredProps) {
+        const camelKey = camelize(key)
+        if (hasOwn(options, camelKey)) {
+          setProp(camelKey, rawProps[key])
+        } else {
+          // Any non-declared props are put into a separate `attrs` object
+          // for spreading. Make sure to preserve original key casing
+          ;(attrs || (attrs = {}))[key] = rawProps[key]
+        }
       } else {
-        setProp(camelKey, rawProps[key])
+        setProp(key, rawProps[key])
       }
     }
   }