[IMP] qweb: add option to allow duplicate templates

doc/qweb.md

@@ -95,12 +95,14 @@ It's API is quite simple:
   const qweb = new owl.QWeb(TEMPLATES);
   ```
 
-- **`addTemplate(name, xmlStr)`**: add a specific template.
+- **`addTemplate(name, xmlStr, allowDuplicate)`**: add a specific template.
 
   ```js
   qweb.addTemplate("mytemplate", "<div>hello</div>");
   ```
 
+  If the optional `allowDuplicate` is set to `true`, then `QWeb` will simply return whenever a template is added for a second time.  Otherwise, `QWeb` will crash.
+
 - **`addTemplates(xmlStr)`**: add a list of templates (identified by `t-name`
   attribute).
 

src/qweb_core.ts

@@ -173,7 +173,10 @@ export class QWeb extends EventBus {
    * Add a template to the internal template map.  Note that it is not
    * immediately compiled.
    */
-  addTemplate(name: string, xmlString: string) {
+  addTemplate(name: string, xmlString: string, allowDuplicate?: boolean) {
+    if (allowDuplicate && name in this.templates) {
+      return;
+    }
     const doc = parseXML(xmlString);
     if (!doc.firstChild) {
       throw new Error("Invalid template (should not be empty)");

tests/qweb.test.ts

@@ -25,13 +25,15 @@ describe("static templates", () => {
   });
 
   test("simple dynamic value", () => {
-    qweb.addTemplate("test", "<t><t t-esc=\"text\"/></t>");
-    expect(renderToString(qweb, "test", {text: "hello vdom"})).toBe("hello vdom");
+    qweb.addTemplate("test", '<t><t t-esc="text"/></t>');
+    expect(renderToString(qweb, "test", { text: "hello vdom" })).toBe(
+      "hello vdom"
+    );
   });
 
   test("simple string, with some dynamic value", () => {
-    qweb.addTemplate("test", "<t>hello <t t-esc=\"text\"/></t>");
-    expect(renderToString(qweb, "test", {text: "vdom"})).toBe("hello vdom");
+    qweb.addTemplate("test", '<t>hello <t t-esc="text"/></t>');
+    expect(renderToString(qweb, "test", { text: "vdom" })).toBe("hello vdom");
   });
 
   test("empty div", () => {
@@ -71,6 +73,9 @@ describe("error handling", () => {
 
   test("cannot add twice the same template", () => {
     qweb.addTemplate("test", `<t></t>`);
+    expect(() => qweb.addTemplate("test", "<div/>", true)).not.toThrow(
+      "already defined"
+    );
     expect(() => qweb.addTemplate("test", "<div/>")).toThrow("already defined");
   });