[IMP] qweb: add support for t-tag directive

Very useful in some cases, when one needs to define a generic component.

closes #721

doc/reference/qweb_templating_language.md

@@ -13,6 +13,7 @@
   - [Setting Variables](#setting-variables)
   - [Conditionals](#conditionals)
   - [Dynamic Attributes](#dynamic-attributes)
+  - [Dynamic Tag Names](#dynamic-tag-names)
   - [Loops](#loops)
   - [Rendering Sub Templates](#rendering-sub-templates)
   - [Dynamic Sub Templates](#dynamic-sub-templates)
@@ -76,6 +77,7 @@ needs. Here is a list of all Owl specific directives:
 | `t-transition`           | [Defining an animation](animations.md#css-transitions)                          |
 | `t-slot`                 | [Rendering a slot](slots.md)                                                    |
 | `t-model`                | [Form input bindings](component.md#form-input-bindings)                         |
+| `t-tag`                  | [Rendering nodes with dynamic tag name](#dynamic-tag-names)                     |
 
 ## Reference
 
@@ -324,6 +326,22 @@ values) or a pair `[key, value]`. For example:
 <div t-att="['a', 'b']"/> <!-- <div a="b"></div> -->
 ```
 
+### Dynamic tag names
+
+When writing generic components or templates, the specific concrete tag for an
+HTML element is not known yet. In those situations, the `t-tag` directive is
+useful. It simply evaluates dynamically an expression to use as a tag name. The
+template:
+
+```xml
+<t t-tag="tag">
+    <span>content</span>
+</t>
+```
+
+will be rendered as `<div><span>content</span></div>` if the `tag` context key
+is set to `div`.
+
 ### Loops
 
 QWeb has an iteration directive `t-foreach` which take an expression returning the

src/qweb/qweb.ts

@@ -203,6 +203,7 @@ export class QWeb extends EventBus {
     att: 1,
     attf: 1,
     translation: 1,
+    tag: 1,
   };
   static DIRECTIVES: Directive[] = [];
 
@@ -614,7 +615,7 @@ export class QWeb extends EventBus {
       }
     }
 
-    if (node.nodeName !== "t") {
+    if (node.nodeName !== "t" || node.hasAttribute("t-tag")) {
       let nodeID = this._compileGenericNode(node, ctx, withHandlers);
       ctx = ctx.withParent(nodeID);
       let nodeHooks = {};
@@ -841,7 +842,14 @@ export class QWeb extends EventBus {
       ctx.addLine(`}`);
       ctx.closeIf();
     }
-    ctx.addLine(`let vn${nodeID} = h('${node.nodeName}', p${nodeID}, c${nodeID});`);
+    let nodeName = `'${node.nodeName}'`;
+    if ((<Element>node).hasAttribute("t-tag")) {
+      const tagExpr = (<Element>node).getAttribute("t-tag");
+      (<Element>node).removeAttribute("t-tag");
+      nodeName = `tag${ctx.generateID()}`;
+      ctx.addLine(`let ${nodeName} = ${ctx.formatExpression(tagExpr)};`);
+    }
+    ctx.addLine(`let vn${nodeID} = h(${nodeName}, p${nodeID}, c${nodeID});`);
     if (ctx.parentNode) {
       ctx.addLine(`c${ctx.parentNode}.push(vn${nodeID});`);
     } else if (ctx.loopNumber || ctx.hasKey0) {

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

@@ -0,0 +1,71 @@
+// Jest Snapshot v1, https://goo.gl/fbAQLP
+
+exports[`qweb t-tag simple usecases 1`] = `
+"function anonymous(context, extra
+) {
+    // Template name: \\"test\\"
+    let scope = Object.create(context);
+    let result;
+    let h = this.h;
+    let c1 = [], p1 = {key:1};
+    let tag2 = 'div';
+    let vn1 = h(tag2, p1, c1);
+    result = vn1;
+    return result;
+}"
+`;
+
+exports[`qweb t-tag simple usecases 2`] = `
+"function anonymous(context, extra
+) {
+    // Template name: \\"test\\"
+    let scope = Object.create(context);
+    let result;
+    let h = this.h;
+    let c3 = [], p3 = {key:3};
+    let tag4 = scope['tag'];
+    let vn3 = h(tag4, p3, c3);
+    result = vn3;
+    c3.push({text: \`text\`});
+    return result;
+}"
+`;
+
+exports[`qweb t-tag with multiple attributes 1`] = `
+"function anonymous(context, extra
+) {
+    // Template name: \\"test\\"
+    let scope = Object.create(context);
+    let result;
+    let h = this.h;
+    let _2 = {'blueberry':true};
+    let _3 = 'raspberry';
+    let c4 = [], p4 = {key:4,attrs:{taste: _3},class:_2};
+    let tag5 = scope['tag'];
+    let vn4 = h(tag5, p4, c4);
+    result = vn4;
+    c4.push({text: \`gooseberry\`});
+    return result;
+}"
+`;
+
+exports[`qweb t-tag with multiple child nodes 1`] = `
+"function anonymous(context, extra
+) {
+    // Template name: \\"test\\"
+    let scope = Object.create(context);
+    let result;
+    let h = this.h;
+    let c1 = [], p1 = {key:1};
+    let tag2 = scope['tag'];
+    let vn1 = h(tag2, p1, c1);
+    result = vn1;
+    c1.push({text: \` pear \`});
+    let c3 = [], p3 = {key:3};
+    let vn3 = h('span', p3, c3);
+    c1.push(vn3);
+    c3.push({text: \`apple\`});
+    c1.push({text: \` strawberry \`});
+    return result;
+}"
+`;

tests/qweb/qweb_t_tag.test.ts

@@ -0,0 +1,42 @@
+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-tag", () => {
+  test("simple usecases", () => {
+    expect(render(`<t t-tag="'div'"></t>`)).toBe("<div></div>");
+    expect(render(`<t t-tag="tag">text</t>`, { tag: "span" })).toBe("<span>text</span>");
+  });
+
+  test("with multiple child nodes", () => {
+    const template = `
+            <t t-tag="tag">
+                pear
+                <span>apple</span>
+                strawberry
+            </t>`;
+    expect(render(template, { tag: "div" })).toBe(
+      "<div> pear <span>apple</span> strawberry </div>"
+    );
+  });
+
+  test("with multiple attributes", () => {
+    const template = `
+            <t t-tag="tag" class="blueberry" taste="raspberry">gooseberry</t>`;
+    const expected = `<div taste=\"raspberry\" class=\"blueberry\">gooseberry</div>`;
+    expect(render(template, { tag: "div" })).toBe(expected);
+  });
+});