test runner: don't crash pretty-printing a Map or Set whose size property is not a number

src/runtime/test_runner/pretty_format.rs

@@ -1718,7 +1718,7 @@ impl<'a> Formatter<'a> {
                     let length_value = value
                         .get(self.global_this, "size")?
                         .unwrap_or_else(|| JSValue::js_number_from_int32(0));
-                    let length = length_value.to_int32();
+                    let length = length_value.coerce_to_i32(self.global_this)?;
 
                     let prev_quote_strings = self.quote_strings;
                     self.quote_strings = true;
@@ -1762,7 +1762,7 @@ impl<'a> Formatter<'a> {
                     let length_value = value
                         .get(self.global_this, "size")?
                         .unwrap_or_else(|| JSValue::js_number_from_int32(0));
-                    let length = length_value.to_int32();
+                    let length = length_value.coerce_to_i32(self.global_this)?;
 
                     let prev_quote_strings = self.quote_strings;
                     self.quote_strings = true;

test/js/bun/test/expect-map-set-size-crash.test.ts

@@ -0,0 +1,67 @@
+import { expect, test } from "bun:test";
+import { bunEnv, bunExe, normalizeBunSnapshot } from "harness";
+
+test("failing matcher on a Map or Set whose size is not a number still reports the mismatch", async () => {
+  await using proc = Bun.spawn({
+    cmd: [
+      bunExe(),
+      "-e",
+      `const { expect } = require("bun:test");
+const weakSet = new WeakSet();
+weakSet.size = {};
+const weakMap = new WeakMap();
+weakMap.size = "abc";
+const set = new Set([1, 2]);
+Object.defineProperty(set, "size", { value: {} });
+const map = new Map([[1, 2]]);
+Object.defineProperty(map, "size", { value: null });
+const selfSized = new WeakMap();
+selfSized.size = selfSized;
+for (const value of [weakSet, weakMap, set, map, { nested: selfSized }]) {
+  try {
+    expect(value).toEqual(1);
+  } catch (e) {
+    console.log(e.message);
+  }
+}`,
+    ],
+    env: bunEnv,
+    stderr: "pipe",
+  });
+
+  const [stdout, stderr, exitCode] = await Promise.all([proc.stdout.text(), proc.stderr.text(), proc.exited]);
+
+  expect(stderr).toBe("");
+  expect(normalizeBunSnapshot(stdout)).toMatchInlineSnapshot(`
+    "expect(received).toEqual(expected)
+
+    Expected: 1
+    Received: WeakSet {}
+
+    expect(received).toEqual(expected)
+
+    Expected: 1
+    Received: WeakMap {}
+
+    expect(received).toEqual(expected)
+
+    Expected: 1
+    Received: Set {}
+
+    expect(received).toEqual(expected)
+
+    Expected: 1
+    Received: Map {}
+
+    expect(received).toEqual(expected)
+
+    - 1
+    + {
+    +   "nested": WeakMap {},
+    + }
+
+    - Expected  - 1
+    + Received  + 3"
+  `);
+  expect(exitCode).toBe(0);
+});