fix(compiler-dom): stringifyStatic should remove attribute bindings with null value (#3477)

fix #3475

packages/compiler-dom/__tests__/transforms/stringifyStatic.spec.ts

@@ -294,4 +294,26 @@ describe('stringify static html', () => {
       })
     })
   })
+
+  test('should remove attribute for `null`', () => {
+    const { ast } = compileWithStringify(
+      `<div>${repeat(
+        `<span :title="null"></span>`,
+        StringifyThresholds.ELEMENT_WITH_BINDING_COUNT
+      )}</div>`
+    )
+    expect(ast.hoists[0]).toMatchObject({
+      type: NodeTypes.JS_CALL_EXPRESSION,
+      callee: CREATE_STATIC,
+      arguments: [
+        JSON.stringify(
+          `${repeat(
+            `<span></span>`,
+            StringifyThresholds.ELEMENT_WITH_BINDING_COUNT
+          )}`
+        ),
+        '5'
+      ]
+    })
+  })
 })

packages/compiler-dom/src/transforms/stringifyStatic.ts

@@ -264,6 +264,7 @@ function stringifyElement(
     } else if (p.type === NodeTypes.DIRECTIVE && p.name === 'bind') {
       // constant v-bind, e.g. :foo="1"
       let evaluated = evaluateConstant(p.exp as SimpleExpressionNode)
+      if (evaluated != null) {
         const arg = p.arg && (p.arg as SimpleExpressionNode).content
         if (arg === 'class') {
           evaluated = normalizeClass(evaluated)
@@ -275,6 +276,7 @@ function stringifyElement(
         )}"`
       }
     }
+  }
   if (context.scopeId) {
     res += ` ${context.scopeId}`
   }