[IMP] compiler: add support for the .translate suffix

doc/reference/props.md

@@ -140,6 +140,28 @@ class SomeComponent extends Component {
 The `.bind` suffix also implies `.alike`, so these props will not cause additional
 renderings.
 
+## Translatable props
+
+When you need to pass a user-facing string to a subcomponent, you likely want it
+to be translated. Unfortunately, because props are arbitrary expressions, it wouldn't
+be practical for Owl to find out which parts of the expression are strings and translate
+them, and it also makes it difficult for tooling to extract these strings to generate
+terms to translate. While you can work around this issue by doing the translation in
+JavaScript, or by using `t-set` with a body (the body of `t-set` is translated),
+and passing the variable as a prop, this is a sufficiently common use case that Owl
+provides a suffix for this purpose: `.translate`.
+
+```xml
+<t t-name="ParentComponent">
+    <Child someProp.translate="some message"/>
+</t>
+```
+
+Note that the content of this attribute is _NOT_ treated as a JavaScript expression:
+it is treated as a string, as if it was an attribute on an HTML element, and translated
+before being passed to the component. If you need to interpolate some data into the
+string, you will still have to do this in JavaScript.
+
 ## Dynamic Props
 
 The `t-props` directive can be used to specify totally dynamic props:

doc/reference/slots.md

@@ -201,16 +201,17 @@ use this `Notebook` component:
 
 ```xml
 <Notebook>
-  <t t-set-slot="page1" title="'Page 1'">
+  <t t-set-slot="page1" title.translate="Page 1">
     <div>this is in the page 1</div>
   </t>
-  <t t-set-slot="page2" title="'Page 2'" hidden="somevalue">
+  <t t-set-slot="page2" title.translate="Page 2" hidden="somevalue">
     <div>this is in the page 2</div>
   </t>
 </Notebook>
 ```
 
-Slot params works like normal props, so one can use the `.bind` suffix to
+Slot params works like normal props, so one can use suffixes like `.translate`
+when a prop is a user facing string and should be translated, or `.bind` to
 bind a function if needed.
 
 ## Slot scopes

src/compiler/code_generator.ts

@@ -1136,7 +1136,11 @@ export class CodeGenerator {
    * "onClick.bind"    "onClick"        "onClick: bind(ctx, ctx['onClick'])"
    */
   formatProp(name: string, value: string): string {
-    value = this.captureExpression(value);
+    if (name.endsWith(".translate")) {
+      value = toStringExpression(this.translateFn(value));
+    } else {
+      value = this.captureExpression(value);
+    }
     if (name.includes(".")) {
       let [_name, suffix] = name.split(".");
       name = _name;
@@ -1145,6 +1149,7 @@ export class CodeGenerator {
           value = `(${value}).bind(this)`;
           break;
         case "alike":
+        case "translate":
           break;
         default:
           throw new OwlError("Invalid prop suffix");

tests/components/__snapshots__/props.test.ts.snap

@@ -66,6 +66,29 @@ exports[`.alike suffix in a simple case 2`] = `
 }"
 `;
 
+exports[`.translate props are translated 1`] = `
+"function anonymous(app, bdom, helpers
+) {
+  let { text, createBlock, list, multi, html, toggler, comment } = bdom;
+  const comp1 = app.createComponent(\`Child\`, true, false, false, []);
+
+  return function template(ctx, node, key = \\"\\") {
+    return comp1({message: \`translated message\`}, key + \`__1\`, node, this, null);
+  }
+}"
+`;
+
+exports[`.translate props are translated 2`] = `
+"function anonymous(app, bdom, helpers
+) {
+  let { text, createBlock, list, multi, html, toggler, comment } = bdom;
+
+  return function template(ctx, node, key = \\"\\") {
+    return text(ctx['props'].message);
+  }
+}"
+`;
+
 exports[`basics accept ES6-like syntax for props (with getters) 1`] = `
 "function anonymous(app, bdom, helpers
 ) {
@@ -412,6 +435,29 @@ exports[`can bind function prop with bind suffix 2`] = `
 }"
 `;
 
+exports[`can use .translate suffix 1`] = `
+"function anonymous(app, bdom, helpers
+) {
+  let { text, createBlock, list, multi, html, toggler, comment } = bdom;
+  const comp1 = app.createComponent(\`Child\`, true, false, false, []);
+
+  return function template(ctx, node, key = \\"\\") {
+    return comp1({message: \`some message\`}, key + \`__1\`, node, this, null);
+  }
+}"
+`;
+
+exports[`can use .translate suffix 2`] = `
+"function anonymous(app, bdom, helpers
+) {
+  let { text, createBlock, list, multi, html, toggler, comment } = bdom;
+
+  return function template(ctx, node, key = \\"\\") {
+    return text(ctx['props'].message);
+  }
+}"
+`;
+
 exports[`do not crash when binding anonymous function prop with bind suffix 1`] = `
 "function anonymous(app, bdom, helpers
 ) {

tests/components/__snapshots__/slots.test.ts.snap

@@ -1,5 +1,30 @@
 // Jest Snapshot v1, https://goo.gl/fbAQLP
 
+exports[`slots .translate slot props are translated 1`] = `
+"function anonymous(app, bdom, helpers
+) {
+  let { text, createBlock, list, multi, html, toggler, comment } = bdom;
+  let { capture, markRaw } = helpers;
+  const comp1 = app.createComponent(\`Child\`, true, true, false, []);
+
+  return function template(ctx, node, key = \\"\\") {
+    const ctx1 = capture(ctx);
+    return comp1({slots: markRaw({'default': {message: \`translated message\`}})}, key + \`__1\`, node, this, null);
+  }
+}"
+`;
+
+exports[`slots .translate slot props are translated 2`] = `
+"function anonymous(app, bdom, helpers
+) {
+  let { text, createBlock, list, multi, html, toggler, comment } = bdom;
+
+  return function template(ctx, node, key = \\"\\") {
+    return text(ctx['props'].slots.default.message);
+  }
+}"
+`;
+
 exports[`slots can define a default content 1`] = `
 "function anonymous(app, bdom, helpers
 ) {
@@ -201,6 +226,31 @@ exports[`slots can render only empty slot 1`] = `
 }"
 `;
 
+exports[`slots can use .translate suffix on slot props 1`] = `
+"function anonymous(app, bdom, helpers
+) {
+  let { text, createBlock, list, multi, html, toggler, comment } = bdom;
+  let { capture, markRaw } = helpers;
+  const comp1 = app.createComponent(\`Child\`, true, true, false, []);
+
+  return function template(ctx, node, key = \\"\\") {
+    const ctx1 = capture(ctx);
+    return comp1({slots: markRaw({'default': {message: \`some message\`}})}, key + \`__1\`, node, this, null);
+  }
+}"
+`;
+
+exports[`slots can use .translate suffix on slot props 2`] = `
+"function anonymous(app, bdom, helpers
+) {
+  let { text, createBlock, list, multi, html, toggler, comment } = bdom;
+
+  return function template(ctx, node, key = \\"\\") {
+    return text(ctx['props'].slots.default.message);
+  }
+}"
+`;
+
 exports[`slots can use component in default-content of t-slot 1`] = `
 "function anonymous(app, bdom, helpers
 ) {

tests/components/props.test.ts

@@ -299,6 +299,34 @@ test("bound functions are considered 'alike'", async () => {
   expect(fixture.innerHTML).toBe("3child");
 });
 
+test("can use .translate suffix", async () => {
+  class Child extends Component {
+    static template = xml`<t t-esc="props.message"/>`;
+  }
+
+  class Parent extends Component {
+    static template = xml`<Child message.translate="some message"/>`;
+    static components = { Child };
+  }
+
+  await mount(Parent, fixture);
+  expect(fixture.innerHTML).toBe("some message");
+});
+
+test(".translate props are translated", async () => {
+  class Child extends Component {
+    static template = xml`<t t-esc="props.message"/>`;
+  }
+
+  class Parent extends Component {
+    static template = xml`<Child message.translate="some message"/>`;
+    static components = { Child };
+  }
+
+  await mount(Parent, fixture, { translateFn: () => "translated message" });
+  expect(fixture.innerHTML).toBe("translated message");
+});
+
 test("throw if prop uses an unknown suffix", async () => {
   class Child extends Component {
     static template = xml`<t t-esc="props.val"/>`;

tests/components/slots.test.ts

@@ -179,6 +179,34 @@ describe("slots", () => {
     expect(fixture.innerHTML).toBe("<span>default empty</span>");
   });
 
+  test("can use .translate suffix on slot props", async () => {
+    class Child extends Component {
+      static template = xml`<t t-esc="props.slots.default.message"/>`;
+    }
+
+    class Parent extends Component {
+      static template = xml`<Child><t t-set-slot="default" message.translate="some message"/></Child>`;
+      static components = { Child };
+    }
+
+    await mount(Parent, fixture);
+    expect(fixture.innerHTML).toBe("some message");
+  });
+
+  test(".translate slot props are translated", async () => {
+    class Child extends Component {
+      static template = xml`<t t-esc="props.slots.default.message"/>`;
+    }
+
+    class Parent extends Component {
+      static template = xml`<Child><t t-set-slot="default" message.translate="some message"/></Child>`;
+      static components = { Child };
+    }
+
+    await mount(Parent, fixture, { translateFn: () => "translated message" });
+    expect(fixture.innerHTML).toBe("translated message");
+  });
+
   test("default slot with slot scope: shorthand syntax", async () => {
     let child: any;
     class Child extends Component {