[FIX] compiler, components: allow empty slot

Before this commit, a t-set-slot that has no content was not even compiled, and thus not passed
to the component for which it has was defined

After this commit, we allow a t-set-slot to have no content (because it can have slot props)

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

@@ -1444,6 +1444,71 @@ exports[`slots simple default slot, variation 2`] = `
 }"
 `;
 
+exports[`slots simple named and empty slot -- 2 1`] = `
+"function anonymous(bdom, helpers
+) {
+  let { text, createBlock, list, multi, html, toggler, component, comment } = bdom;
+  let { capture, markRaw } = helpers;
+  
+  return function template(ctx, node, key = \\"\\") {
+    const ctx1 = capture(ctx);
+    return component(\`Child\`, {slots: markRaw({'myEmptySlot': {myProp: 'myProp text'}})}, key + \`__1\`, node, ctx);
+  }
+}"
+`;
+
+exports[`slots simple named and empty slot -- 2 2`] = `
+"function anonymous(bdom, helpers
+) {
+  let { text, createBlock, list, multi, html, toggler, component, comment } = bdom;
+  let { callSlot } = helpers;
+  
+  let block1 = createBlock(\`<span><block-child-0/></span>\`);
+  
+  function defaultContent1(ctx, node, key = \\"\\") {
+    return text(\`default empty\`);
+  }
+  
+  return function template(ctx, node, key = \\"\\") {
+    const b3 = callSlot(ctx, node, key, 'myEmptySlot', false, null, defaultContent1);
+    return block1([], [b3]);
+  }
+}"
+`;
+
+exports[`slots simple named and empty slot 1`] = `
+"function anonymous(bdom, helpers
+) {
+  let { text, createBlock, list, multi, html, toggler, component, comment } = bdom;
+  let { capture, markRaw } = helpers;
+  
+  function slot1(ctx, node, key = \\"\\") {
+    return text(\`some text\`);
+  }
+  
+  return function template(ctx, node, key = \\"\\") {
+    const ctx1 = capture(ctx);
+    return component(\`Child\`, {slots: markRaw({'myEmptySlot': {}, 'default': {__render: slot1, __ctx: ctx1}})}, key + \`__1\`, node, ctx);
+  }
+}"
+`;
+
+exports[`slots simple named and empty slot 2`] = `
+"function anonymous(bdom, helpers
+) {
+  let { text, createBlock, list, multi, html, toggler, component, comment } = bdom;
+  let { callSlot } = helpers;
+  
+  let block1 = createBlock(\`<span><block-child-0/><block-child-1/></span>\`);
+  
+  return function template(ctx, node, key = \\"\\") {
+    const b2 = callSlot(ctx, node, key, 'default', false, null);
+    const b3 = callSlot(ctx, node, key, 'myEmptySlot', false, null);
+    return block1([], [b2, b3]);
+  }
+}"
+`;
+
 exports[`slots simple slot with slot scope 1`] = `
 "function anonymous(bdom, helpers
 ) {

tests/components/slots.test.ts

@@ -74,6 +74,43 @@ describe("slots", () => {
     expect(fixture.innerHTML).toBe("<span>other text</span>");
   });
 
+  test("simple named and empty slot", async () => {
+    class Child extends Component {
+      static template = xml`<span><t t-slot="default" /><t t-slot="myEmptySlot"/></span>`;
+
+      setup() {
+        expect(this.props.slots["myEmptySlot"]).toBeTruthy();
+      }
+    }
+
+    class Parent extends Component {
+      static template = xml`<Child>some text<t t-set-slot="myEmptySlot" /></Child>`;
+      static components = { Child };
+    }
+    await mount(Parent, fixture);
+
+    expect(fixture.innerHTML).toBe("<span>some text</span>");
+  });
+
+  test("simple named and empty slot -- 2", async () => {
+    class Child extends Component {
+      static template = xml`<span><t t-slot="myEmptySlot">default empty</t></span>`;
+
+      setup() {
+        expect(this.props.slots["myEmptySlot"]).toBeTruthy();
+        expect(this.props.slots["myEmptySlot"].myProp).toBe("myProp text");
+      }
+    }
+
+    class Parent extends Component {
+      static template = xml`<Child><t t-set-slot="myEmptySlot" myProp="'myProp text'" /></Child>`;
+      static components = { Child };
+    }
+    await mount(Parent, fixture);
+
+    expect(fixture.innerHTML).toBe("<span>default empty</span>");
+  });
+
   test("default slot with slot scope: shorthand syntax", async () => {
     let child: any;
     class Child extends Component {