fix: expect().resolves and expect().rejects now return promises

Previously, matchers under `expect().resolves` and `expect().rejects`
would return `undefined` instead of a promise. This caused issues when
trying to chain or await matcher results.

This fix adds a helper function `returnMatcherValue()` that checks if
async flags (.resolves/.rejects) are set and returns a resolved promise
instead of undefined. All matchers now use this helper.

Fixes #23420

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <[email protected]>

Author: Claude Bot

src/bun.js/test/expect.zig

@@ -848,7 +848,7 @@ pub const Expect = struct {
         if (existing_value) |saved_value| {
             if (strings.eqlLong(pretty_value.slice(), saved_value, true)) {
                 Jest.runner.?.snapshots.passed += 1;
-                return .js_undefined;
+                return this.returnMatcherValue(globalThis);
             }
 
             Jest.runner.?.snapshots.failed += 1;
@@ -863,7 +863,7 @@ pub const Expect = struct {
             return globalThis.throwPretty(fmt, .{diff_format});
         }
 
-        return .js_undefined;
+        return this.returnMatcherValue(globalThis);
     }
 
     pub fn getStaticNot(globalThis: *JSGlobalObject, _: JSValue, _: JSValue) bun.JSError!JSValue {
@@ -1231,6 +1231,16 @@ pub const Expect = struct {
         vm.autoGarbageCollect();
     }
 
+    /// Helper function for matchers to return the correct value based on whether
+    /// .resolves or .rejects was used. When async flags are set, returns a resolved promise.
+    /// Otherwise returns undefined.
+    pub inline fn returnMatcherValue(this: *const Expect, globalThis: *JSGlobalObject) JSValue {
+        if (this.flags.promise != .none) {
+            return JSPromise.resolvedPromiseValue(globalThis, .js_undefined);
+        }
+        return .js_undefined;
+    }
+
     pub fn doUnreachable(globalThis: *JSGlobalObject, callframe: *CallFrame) bun.JSError!JSValue {
         const arg = callframe.arguments_old(1).ptr[0];
 
@@ -2246,6 +2256,7 @@ const strings = bun.strings;
 const jsc = bun.jsc;
 const CallFrame = jsc.CallFrame;
 const JSGlobalObject = jsc.JSGlobalObject;
+const JSPromise = jsc.JSPromise;
 const JSValue = jsc.JSValue;
 const VirtualMachine = jsc.VirtualMachine;
 const ZigString = jsc.ZigString;

src/bun.js/test/expect/toBe.zig

@@ -22,7 +22,7 @@ pub fn toBe(
     var pass = try right.isSameValue(left, globalThis);
 
     if (not) pass = !pass;
-    if (pass) return .js_undefined;
+    if (pass) return this.returnMatcherValue(globalThis);
 
     // handle failure
     var formatter = jsc.ConsoleObject.Formatter{ .globalThis = globalThis, .quote_strings = true };

src/bun.js/test/expect/toBeArray.zig

@@ -9,7 +9,7 @@ pub fn toBeArray(this: *Expect, globalThis: *JSGlobalObject, callFrame: *CallFra
     const not = this.flags.not;
     const pass = value.jsType().isArray() != not;
 
-    if (pass) return .js_undefined;
+    if (pass) return this.returnMatcherValue(globalThis);
 
     var formatter = jsc.ConsoleObject.Formatter{ .globalThis = globalThis, .quote_strings = true };
     defer formatter.deinit();

src/bun.js/test/expect/toBeArrayOfSize.zig

@@ -24,7 +24,7 @@ pub fn toBeArrayOfSize(this: *Expect, globalThis: *JSGlobalObject, callFrame: *C
     var pass = value.jsType().isArray() and @as(i32, @intCast(try value.getLength(globalThis))) == size.toInt32();
 
     if (not) pass = !pass;
-    if (pass) return .js_undefined;
+    if (pass) return this.returnMatcherValue(globalThis);
 
     var formatter = jsc.ConsoleObject.Formatter{ .globalThis = globalThis, .quote_strings = true };
     defer formatter.deinit();

src/bun.js/test/expect/toBeBoolean.zig

@@ -9,7 +9,7 @@ pub fn toBeBoolean(this: *Expect, globalThis: *JSGlobalObject, callFrame: *CallF
     const not = this.flags.not;
     const pass = value.isBoolean() != not;
 
-    if (pass) return .js_undefined;
+    if (pass) return this.returnMatcherValue(globalThis);
 
     var formatter = jsc.ConsoleObject.Formatter{ .globalThis = globalThis, .quote_strings = true };
     defer formatter.deinit();

src/bun.js/test/expect/toBeCloseTo.zig

@@ -43,7 +43,7 @@ pub fn toBeCloseTo(this: *Expect, globalThis: *JSGlobalObject, callFrame: *CallF
     }
 
     if (std.math.isPositiveInf(expected) and std.math.isPositiveInf(received)) {
-        return .js_undefined;
+        return this.returnMatcherValue(globalThis);
     }
 
     const expected_diff = bun.pow(10, -precision) / 2;
@@ -53,7 +53,7 @@ pub fn toBeCloseTo(this: *Expect, globalThis: *JSGlobalObject, callFrame: *CallF
     const not = this.flags.not;
     if (not) pass = !pass;
 
-    if (pass) return .js_undefined;
+    if (pass) return this.returnMatcherValue(globalThis);
 
     var formatter = jsc.ConsoleObject.Formatter{ .globalThis = globalThis, .quote_strings = true };
     defer formatter.deinit();

src/bun.js/test/expect/toBeDate.zig

@@ -9,7 +9,7 @@ pub fn toBeDate(this: *Expect, globalThis: *JSGlobalObject, callFrame: *CallFram
     const not = this.flags.not;
     const pass = value.isDate() != not;
 
-    if (pass) return .js_undefined;
+    if (pass) return this.returnMatcherValue(globalThis);
 
     var formatter = jsc.ConsoleObject.Formatter{ .globalThis = globalThis, .quote_strings = true };
     defer formatter.deinit();

src/bun.js/test/expect/toBeDefined.zig

@@ -9,7 +9,7 @@ pub fn toBeDefined(this: *Expect, globalThis: *JSGlobalObject, callFrame: *CallF
     const not = this.flags.not;
     var pass = !value.isUndefined();
     if (not) pass = !pass;
-    if (pass) return .js_undefined;
+    if (pass) return this.returnMatcherValue(globalThis);
 
     // handle failure
     var formatter = jsc.ConsoleObject.Formatter{ .globalThis = globalThis, .quote_strings = true };

src/bun.js/test/expect/toBeEmpty.zig

@@ -61,7 +61,7 @@ pub fn toBeEmpty(this: *Expect, globalThis: *JSGlobalObject, callFrame: *CallFra
     }
 
     if (not) pass = !pass;
-    if (pass) return .js_undefined;
+    if (pass) return this.returnMatcherValue(globalThis);
 
     if (not) {
         const signature = comptime getSignature("toBeEmpty", "", true);

src/bun.js/test/expect/toBeEmptyObject.zig

@@ -10,7 +10,7 @@ pub fn toBeEmptyObject(this: *Expect, globalThis: *JSGlobalObject, callFrame: *C
     var pass = try value.isObjectEmpty(globalThis);
 
     if (not) pass = !pass;
-    if (pass) return thisValue;
+    if (pass) return this.returnMatcherValue(globalThis);
 
     var formatter = jsc.ConsoleObject.Formatter{ .globalThis = globalThis, .quote_strings = true };
     defer formatter.deinit();