[IMP] qweb: allow multiclasses in t-att-class object form

the low level method htmlelement.classList.add does not accept multiple
classes in one string, which is why, in owl, the expression

`<div t-att-class="{'a b c': value}" />`

did not work as one might expect. It is however very convenient in real
life templates, so this commit improve owl by adding support for this
feature.

closes #813

tests/qweb/__snapshots__/qweb.test.ts.snap

@@ -7,7 +7,7 @@ exports[`attributes class and t-att-class should combine together 1`] = `
     let utils = this.constructor.utils;
     let scope = Object.create(context);
     let h = this.h;
-    let _1 = utils.toObj(scope['value']);
+    let _1 = utils.toClassObj(scope['value']);
     Object.assign(_1, {'hello':true})
     let c3 = [], p3 = {key:3,class:_1};
     let vn3 = h('div', p3, c3);
@@ -74,7 +74,7 @@ exports[`attributes dynamic class attribute 1`] = `
     let utils = this.constructor.utils;
     let scope = Object.create(context);
     let h = this.h;
-    let _1 = utils.toObj(scope['c']);
+    let _1 = utils.toClassObj(scope['c']);
     let c2 = [], p2 = {key:2,class:_1};
     let vn2 = h('div', p2, c2);
     return vn2;
@@ -88,7 +88,7 @@ exports[`attributes dynamic empty class attribute 1`] = `
     let utils = this.constructor.utils;
     let scope = Object.create(context);
     let h = this.h;
-    let _1 = utils.toObj(scope['c']);
+    let _1 = utils.toClassObj(scope['c']);
     let c2 = [], p2 = {key:2,class:_1};
     let vn2 = h('div', p2, c2);
     return vn2;
@@ -195,7 +195,7 @@ exports[`attributes from object variables set previously 1`] = `
     let c1 = [], p1 = {key:1};
     let vn1 = h('div', p1, c1);
     scope.o = {a:'b'};
-    let _2 = utils.toObj(scope.o.a);
+    let _2 = utils.toClassObj(scope.o.a);
     let c3 = [], p3 = {key:3,class:_2};
     let vn3 = h('span', p3, c3);
     c1.push(vn3);
@@ -213,7 +213,7 @@ exports[`attributes from variables set previously 1`] = `
     let c1 = [], p1 = {key:1};
     let vn1 = h('div', p1, c1);
     scope.abc = 'def';
-    let _2 = utils.toObj(scope.abc);
+    let _2 = utils.toClassObj(scope.abc);
     let c3 = [], p3 = {key:3,class:_2};
     let vn3 = h('span', p3, c3);
     c1.push(vn3);
@@ -288,7 +288,7 @@ exports[`attributes t-att-class and class should combine together 1`] = `
     let scope = Object.create(context);
     let h = this.h;
     let _2 = {'hello':true};
-    Object.assign(_2, utils.toObj(scope['value']))
+    Object.assign(_2, utils.toClassObj(scope['value']))
     let c3 = [], p3 = {key:3,class:_2};
     let vn3 = h('div', p3, c3);
     return vn3;
@@ -303,7 +303,7 @@ exports[`attributes t-att-class with object 1`] = `
     let scope = Object.create(context);
     let h = this.h;
     let _2 = {'static':true};
-    Object.assign(_2, utils.toObj({a:scope['b'],c:scope['d'],e:scope['f']}))
+    Object.assign(_2, utils.toClassObj({a:scope['b'],c:scope['d'],e:scope['f']}))
     let c3 = [], p3 = {key:3,class:_2};
     let vn3 = h('div', p3, c3);
     return vn3;

tests/qweb/__snapshots__/qweb_t_att.test.ts.snap

@@ -0,0 +1,29 @@
+// Jest Snapshot v1, https://goo.gl/fbAQLP
+
+exports[`qweb t-att t-att-class with multiple classes 1`] = `
+"function anonymous(context, extra
+) {
+    // Template name: \\"test\\"
+    let utils = this.constructor.utils;
+    let scope = Object.create(context);
+    let h = this.h;
+    let _1 = utils.toClassObj({'a b c':scope['value']});
+    let c2 = [], p2 = {key:2,class:_1};
+    let vn2 = h('div', p2, c2);
+    return vn2;
+}"
+`;
+
+exports[`qweb t-att t-att-class with multiple classes 2`] = `
+"function anonymous(context, extra
+) {
+    // Template name: \\"test\\"
+    let utils = this.constructor.utils;
+    let scope = Object.create(context);
+    let h = this.h;
+    let _3 = utils.toClassObj({['a b c']:scope['value']});
+    let c4 = [], p4 = {key:4,class:_3};
+    let vn4 = h('div', p4, c4);
+    return vn4;
+}"
+`;

tests/qweb/qweb_t_att.test.ts

@@ -0,0 +1,27 @@
+import { QWeb } from "../../src/qweb/index";
+import { renderToString } from "../helpers";
+
+//------------------------------------------------------------------------------
+// Setup and helpers
+//------------------------------------------------------------------------------
+
+function render(template, context = {}) {
+  const qweb = new QWeb();
+  qweb.addTemplate("test", template);
+  return renderToString(qweb, "test", context);
+}
+
+//------------------------------------------------------------------------------
+// Tests
+//------------------------------------------------------------------------------
+
+describe("qweb t-att", () => {
+  test("t-att-class with multiple classes", () => {
+    expect(render(`<div t-att-class="{'a b c': value}" />`, { value: true })).toBe(
+      '<div class="a b c"></div>'
+    );
+    expect(render(`<div t-att-class="{['a b c']: value}" />`, { value: true })).toBe(
+      '<div class="a b c"></div>'
+    );
+  });
+});