feat(core): add staticClass merge from slot

src/compiler/codegen/index.js

@@ -457,7 +457,16 @@ function genSlot (el: ASTElement, state: CodegenState): string {
   const slotName = el.slotName || '"default"'
   const children = genChildren(el, state)
   let res = `_t(${slotName}${children ? `,${children}` : ''}`
-  const attrs = el.attrs && `{${el.attrs.map(a => `${camelize(a.name)}:${a.value}`).join(',')}}`
+  let attrs
+  if (el.attrs) {
+    attrs = `{${el.attrs.map(a => `${camelize(a.name)}:${a.value}`).join(',')}`
+  }
+  if (el.staticClass) {
+    attrs = attrs ? `${attrs},` : '{' + `class:${el.staticClass}`
+  }
+  if (attrs) {
+    attrs += '}'
+  }
   const bind = el.attrsMap['v-bind']
   if ((attrs || bind) && !children) {
     res += `,null`

src/core/instance/render-helpers/render-slot.js

@@ -37,6 +37,9 @@ export function renderSlot (
         )
       }
       slotNodes._rendered = true
+      if (props && props.class) {
+        slotNodes[0].data.staticClass += ` ${props.class}`
+      }
     }
     nodes = slotNodes || fallback
   }

test/unit/features/directives/class.spec.js

@@ -138,6 +138,29 @@ describe('Directive v-bind:class', () => {
     }).then(done)
   })
 
+  it('class merge from slot', done => {
+    const vm = new Vue({
+      template: `
+        <component1>
+          <div class="staticClass" slot="test">
+            some text
+          </div>
+        </component1>
+      `,
+      components: {
+        component1: {
+          template: `
+            <div>
+              <slot name="test" class="fromSlot"/>
+            </div>
+          `
+        }
+      }
+    }).$mount()
+    expect(vm.$el.children[0].className).toBe('staticClass fromSlot')
+    done()
+  })
+
   it('deep update', done => {
     const vm = new Vue({
       template: '<div :class="test"></div>',

test/unit/modules/compiler/codegen.spec.js

@@ -208,6 +208,13 @@ describe('codegen', () => {
     )
   })
 
+  it('generate slot with class', () => {
+    assertCodegen(
+      '<div><slot class="class1"></slot></div>',
+      `with(this){return _c('div',[_t("default",null,{class:"class1"})],2)}`
+    )
+  })
+
   it('generate class binding', () => {
     // static
     assertCodegen(