[IMP] qweb: add warning if t-key is missing in some cases

closes #71

tests/__snapshots__/qweb.test.ts.snap

@@ -534,6 +534,37 @@ exports[`foreach iterate, position 1`] = `
 }"
 `;
 
+exports[`foreach warn if no key in some case 1`] = `
+"function anonymous(context,extra
+) {
+    context = Object.create(context);
+    var h = this.utils.h;
+    var c1 = [], p1 = {key:1};
+    var vn1 = h('div', p1, c1);
+    var _2 = [1, 2];
+    if (!_2) { throw new Error('QWeb error: Invalid loop expression')}
+    if (typeof _2 === 'number') { _2 = Array.from(Array(_2).keys())}
+    var _3 = _2 instanceof Array ? _2 : Object.keys(_2);
+    var _4 = _2 instanceof Array ? _2 : Object.values(_2);
+    for (let i = 0; i < _3.length; i++) {
+        context.item_first = i === 0;
+        context.item_last = i === _3.length - 1;
+        context.item_parity = i % 2 === 0 ? 'even' : 'odd';
+        context.item_index = i;
+        context.item = _3[i];
+        context.item_value = _4[i];
+        var c5 = [], p5 = {key:5};
+        var vn5 = h('span', p5, c5);
+        c1.push(vn5);
+        var _6 = context['item'];
+        if (_6 || _6 === 0) {
+            c5.push({text: _6});
+        }
+    }
+    return vn1;
+}"
+`;
+
 exports[`loading templates can initialize qweb with a string 1`] = `
 "function anonymous(context,extra
 ) {
@@ -1367,7 +1398,7 @@ exports[`t-ref refs in a loop 1`] = `
         context.item_index = i;
         context.item = _3[i];
         context.item_value = _4[i];
-        var c5 = [], p5 = {key:5};
+        var c5 = [], p5 = {key:context['item']};
         var vn5 = h('div', p5, c5);
         c1.push(vn5);
         const ref6 = context['item']

tests/component.test.ts

@@ -819,7 +819,7 @@ describe("composition", () => {
     class ParentWidget extends Widget {
       inlineTemplate = `
         <div>
-          <t t-foreach="state.list" t-ref="'child'" t-widget="Widget"/>
+          <t t-foreach="state.list" t-as="elem" t-ref="'child'" t-key="elem" t-widget="Widget"/>
         </div>`;
       widgets = { Widget };
       state = { list: <any>[] };
@@ -1029,7 +1029,7 @@ describe("composition", () => {
       inlineTemplate = `
         <div>
           <t t-foreach="state.numbers" t-as="number">
-            <t t-widget="ChildWidget" t-props="{n: number}"/>
+            <t t-widget="ChildWidget" t-key="number" t-props="{n: number}"/>
           </t>
         </div>`;
       state = {

tests/qweb.test.ts

@@ -726,10 +726,29 @@ describe("foreach", () => {
   test("throws error if invalid loop expression", () => {
     qweb.addTemplate(
       "test",
-      `<div><t t-foreach="abc" t-as="item"><span/></t></div>`
+      `<div><t t-foreach="abc" t-as="item"><span t-key="item_index"/></t></div>`
     );
     expect(() => qweb.render("test")).toThrow("Invalid loop expression");
   });
+
+  test("warn if no key in some case", () => {
+    const consoleWarn = console.warn;
+    console.warn = jest.fn();
+
+    qweb.addTemplate(
+      "test",
+      `
+      <div>
+        <t t-foreach="[1, 2]" t-as="item">
+          <span><t t-esc="item"/></span>
+        </t>
+    </div>`
+    );
+    renderToString(qweb, "test");
+    expect(console.warn).toHaveBeenCalledTimes(1);
+    console.warn = consoleWarn;
+  });
+
 });
 
 describe("misc", () => {
@@ -966,7 +985,7 @@ describe("t-ref", () => {
     qweb.addTemplate("test", `
       <div>
         <t t-foreach="items" t-as="item">
-          <div t-ref="item"><t t-esc="item"/></div>
+          <div t-ref="item" t-key="item"><t t-esc="item"/></div>
         </t>
       </div>`);
     let refs: any = {};