allow static and dynamic attributes to combine in qweb

web/static/tests/core/__snapshots__/qweb_vdom.test.ts.snap

@@ -156,6 +156,19 @@ exports[`attributes static attributes with dashes 1`] = `
 }"
 `;
 
+exports[`attributes t-att-class and class should combine together 1`] = `
+"function anonymous(context,extra
+) {
+    let h = this.h;
+    let _1 = 'hello';
+    let _3 = context['value'];
+    let _2 = 'hello' + (_3 ? ' ' + _3 : '');
+    let c4 = [], p4 = {key:4,attrs:{class: _1,class: _2}};
+    let vn4 = h('div', p4, c4);
+    return vn4;
+}"
+`;
+
 exports[`attributes tuple literal 1`] = `
 "function anonymous(context,extra
 ) {

web/static/tests/core/qweb_vdom.test.ts

@@ -420,6 +420,12 @@ describe("attributes", () => {
     const expected = `<div foo="&lt;foo" bar="&lt;bar&gt;" baz="&lt;&quot;&lt;baz&gt;&quot;&gt;" qux="&lt;&gt;"></div>`;
     expect(result).toBe(expected);
   });
+
+  test("t-att-class and class should combine together", () => {
+    qweb.addTemplate("test", `<div class="hello" t-att-class="value"/>`);
+    const result = renderToString(qweb, "test", { value: "world" });
+    expect(result).toBe(`<div class="hello world"></div>`);
+  });
 });
 
 describe("t-call (template calling", () => {