[FIX] runtime: correctly throw an error for duplicate object keys

Currently when checking for duplicate keys, we insert the value of the
key as is in a set then check for unicity against those. When the key is
an object, we check for duplicates based on object identity, whereas the
keys are used by owl as strings, and so using objects can cause
duplicate key errors that do not throw correctly but crash in the owl
internals.

This commit fixes that by making the duplicate checking code serialize
the key to string before insertion and when comparing against existing
keys.

src/compiler/code_generator.ts

@@ -877,9 +877,9 @@ export class CodeGenerator {
       // Throw error on duplicate keys in dev mode
       this.helpers.add("OwlError");
       this.addLine(
-        `if (keys${block.id}.has(key${this.target.loopLevel})) { throw new OwlError(\`Got duplicate key in t-foreach: \${key${this.target.loopLevel}}\`)}`
+        `if (keys${block.id}.has(String(key${this.target.loopLevel}))) { throw new OwlError(\`Got duplicate key in t-foreach: \${key${this.target.loopLevel}}\`)}`
       );
-      this.addLine(`keys${block.id}.add(key${this.target.loopLevel});`);
+      this.addLine(`keys${block.id}.add(String(key${this.target.loopLevel}));`);
     }
     let id: string;
     if (ast.memo) {

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

@@ -53,8 +53,8 @@ exports[`list of components crash on duplicate key in dev mode 1`] = `
     for (let i1 = 0; i1 < l_block1; i1++) {
       ctx[\`item\`] = v_block1[i1];
       const key1 = 'child';
-      if (keys1.has(key1)) { throw new OwlError(\`Got duplicate key in t-foreach: \${key1}\`)}
-      keys1.add(key1);
+      if (keys1.has(String(key1))) { throw new OwlError(\`Got duplicate key in t-foreach: \${key1}\`)}
+      keys1.add(String(key1));
       const props1 = {};
       helpers.validateProps(\`Child\`, props1, this);
       c_block1[i1] = withKey(comp1(props1, key + \`__1__\${key1}\`, node, this, null), key1);
@@ -75,6 +75,42 @@ exports[`list of components crash on duplicate key in dev mode 2`] = `
 }"
 `;
 
+exports[`list of components crash when using object as keys that serialize to the same string 1`] = `
+"function anonymous(app, bdom, helpers
+) {
+  let { text, createBlock, list, multi, html, toggler, comment } = bdom;
+  let { prepareList, OwlError, withKey } = helpers;
+  const comp1 = app.createComponent(\`Child\`, true, false, false, true);
+  
+  return function template(ctx, node, key = \\"\\") {
+    ctx = Object.create(ctx);
+    const [k_block1, v_block1, l_block1, c_block1] = prepareList([{},{}]);;
+    const keys1 = new Set();
+    for (let i1 = 0; i1 < l_block1; i1++) {
+      ctx[\`item\`] = v_block1[i1];
+      const key1 = ctx['item'];
+      if (keys1.has(String(key1))) { throw new OwlError(\`Got duplicate key in t-foreach: \${key1}\`)}
+      keys1.add(String(key1));
+      const props1 = {};
+      helpers.validateProps(\`Child\`, props1, this);
+      c_block1[i1] = withKey(comp1(props1, key + \`__1__\${key1}\`, node, this, null), key1);
+    }
+    return list(c_block1);
+  }
+}"
+`;
+
+exports[`list of components crash when using object as keys that serialize to the same string 2`] = `
+"function anonymous(app, bdom, helpers
+) {
+  let { text, createBlock, list, multi, html, toggler, comment } = bdom;
+  
+  return function template(ctx, node, key = \\"\\") {
+    return text(\`\`);
+  }
+}"
+`;
+
 exports[`list of components list of sub components inside other nodes 1`] = `
 "function anonymous(app, bdom, helpers
 ) {

tests/components/t_foreach.test.ts

@@ -331,4 +331,32 @@ describe("list of components", () => {
     console.info = consoleInfo;
     expect(mockConsoleWarn).toBeCalledTimes(1);
   });
+
+  test("crash when using object as keys that serialize to the same string", async () => {
+    const consoleInfo = console.info;
+    console.info = jest.fn();
+    class Child extends Component {
+      static template = xml``;
+    }
+
+    class Parent extends Component {
+      static template = xml`
+        <t t-foreach="[{}, {}]" t-as="item" t-key="item">
+          <Child/>
+        </t>
+      `;
+      static components = { Child };
+    }
+
+    const app = new App(Parent, { test: true });
+    const mountProm = expect(app.mount(fixture)).rejects.toThrow(
+      "Got duplicate key in t-foreach: [object Object]"
+    );
+    await expect(nextAppError(app)).resolves.toThrow(
+      "Got duplicate key in t-foreach: [object Object]"
+    );
+    await mountProm;
+    console.info = consoleInfo;
+    expect(mockConsoleWarn).toBeCalledTimes(1);
+  });
 });