[FIX] blockdom: toString method in multi could crash

src/blockdom/multi.ts

@@ -127,7 +127,7 @@ export class VMulti {
   }
 
   toString(): string {
-    return this.children.map((c) => c!.toString()).join("");
+    return this.children.map((c) => (c ? c!.toString() : "")).join("");
   }
 }
 

tests/blockdom/multi.test.ts

@@ -77,6 +77,11 @@ describe("multi blocks", () => {
     expect(fixture.innerHTML).toBe("ab");
   });
 
+  test("multi vnode can be used as text", () => {
+    mount(text(multi([text("a"), undefined]) as any), fixture);
+    expect(fixture.innerHTML).toBe("a");
+  });
+
   test("multi inside a block", async () => {
     const block = createBlock("<div><block-child-0/></div>");
     const tree = block([], [multi([text("foo"), text("bar")])]);

tests/compiler/__snapshots__/t_set.test.ts.snap

@@ -87,6 +87,31 @@ exports[`t-set set from attribute lookup 1`] = `
 }"
 `;
 
+exports[`t-set set from body literal (with t-if/t-else 1`] = `
+"function anonymous(bdom, helpers
+) {
+  let { text, createBlock, list, multi, html, toggler, component, comment } = bdom;
+  let { isBoundary, withDefault, LazyValue } = helpers;
+  
+  function value1(ctx, node, key = \\"\\") {
+    let b2,b3;
+    if (ctx['condition']) {
+      b2 = text(\`true\`);
+    } else {
+      b3 = text(\`false\`);
+    }
+    return multi([b2, b3]);
+  }
+  
+  return function template(ctx, node, key = \\"\\") {
+    ctx = Object.create(ctx);
+    ctx[isBoundary] = 1
+    ctx[\`value\`] = new LazyValue(value1, ctx, node);
+    return text(ctx['value']);
+  }
+}"
+`;
+
 exports[`t-set set from body literal 1`] = `
 "function anonymous(bdom, helpers
 ) {

tests/compiler/t_set.test.ts

@@ -38,6 +38,19 @@ describe("t-set", () => {
     expect(renderToString(template)).toBe("ok");
   });
 
+  test("set from body literal (with t-if/t-else", () => {
+    const template = `
+      <t>
+        <t t-set="value">
+          <t t-if="condition">true</t>
+          <t t-else="">false</t>
+        </t>
+        <t t-esc="value"/>
+      </t>`;
+    expect(renderToString(template, { condition: true })).toBe("true");
+    expect(renderToString(template, { condition: false })).toBe("false");
+  });
+
   test("set from attribute lookup", () => {
     const template = `<div><t t-set="stuff" t-value="value"/><t t-esc="stuff"/></div>`;
     expect(renderToString(template, { value: "ok" })).toBe("<div>ok</div>");