Fix missing function names in console.log and Bun.inspect (#6612)

* Fix missing function names in Bun.inspect

* Fix failing tests

* Handle @@toStringTag

* Update bindings.cpp

* Revert breaking changes to snapshots until a minor version

* Fix test

---------

Co-authored-by: Jarred Sumner <709451+Jarred-Sumner@users.noreply.github.com>

6 files changed, 94 insertions, 21 deletions

diff --git a/src/bun.js/bindings/bindings.cpp b/src/bun.js/bindings/bindings.cpp
index 117b848ef..58c5ae4d7 100644
--- a/src/bun.js/bindings/bindings.cpp
+++ b/src/bun.js/bindings/bindings.cpp
@@ -676,8 +676,8 @@ bool Bun__deepEquals(JSC__JSGlobalObject* globalObject, JSValue v1, JSValue v2,
                 if ((url2 == nullptr) != (url1 == nullptr)) {
                     return false;
                 }
-            } 
-            
+            }
+
             if (url2 && url1) {
                 // toEqual or toStrictEqual should return false when the URLs' href is not equal
                 // But you could have added additional properties onto the
@@ -3902,6 +3902,32 @@ void JSC__JSValue__getNameProperty(JSC__JSValue JSValue0, JSC__JSGlobalObject* a
     arg2->len = 0;
 }
 
+extern "C" void JSC__JSValue__getName(JSC__JSValue JSValue0, JSC__JSGlobalObject* globalObject, BunString* arg2)
+{
+    JSC::JSValue value = JSC::JSValue::decode(JSValue0);
+    if (!value.isObject()) {
+        *arg2 = BunStringEmpty;
+        return;
+    }
+    auto& vm = globalObject->vm();
+    auto scope = DECLARE_CATCH_SCOPE(globalObject->vm());
+    JSObject* object = value.getObject();
+    auto displayName = JSC::getCalculatedDisplayName(vm, object);
+
+    // JSC doesn't include @@toStringTag in calculated display name
+    if (displayName.isEmpty()) {
+        if (auto toStringTagValue = object->getIfPropertyExists(globalObject, vm.propertyNames->toStringTagSymbol)) {
+            if (toStringTagValue.isString()) {
+                displayName = toStringTagValue.toWTFString(globalObject);
+            }
+        }
+    }
+    if (scope.exception())
+        scope.clearException();
+
+    *arg2 = Bun::toStringRef(displayName);
+}
+
 JSC__JSValue JSC__JSValue__toError_(JSC__JSValue JSValue0)
 {
     JSC::JSValue value = JSC::JSValue::decode(JSValue0);
diff --git a/src/bun.js/bindings/bindings.zig b/src/bun.js/bindings/bindings.zig
index 98e91c1ca..3b6ab6af8 100644
--- a/src/bun.js/bindings/bindings.zig
+++ b/src/bun.js/bindings/bindings.zig
@@ -4096,9 +4096,10 @@ pub const JSValue = enum(JSValueReprInt) {
         cppFn("getNameProperty", .{ this, global, ret });
     }
 
-    pub fn getName(this: JSValue, global: *JSGlobalObject) ZigString {
-        var ret = ZigString.init("");
-        getNameProperty(this, global, &ret);
+    extern fn JSC__JSValue__getName(JSC.JSValue, *JSC.JSGlobalObject, *bun.String) void;
+    pub fn getName(this: JSValue, global: *JSGlobalObject) bun.String {
+        var ret = bun.String.empty;
+        JSC__JSValue__getName(this, global, &ret);
         return ret;
     }
 
diff --git a/src/bun.js/bindings/exports.zig b/src/bun.js/bindings/exports.zig
index 617530ec6..ec679f42d 100644
--- a/src/bun.js/bindings/exports.zig
+++ b/src/bun.js/bindings/exports.zig
@@ -1818,14 +1818,16 @@ pub const ZigConsoleClient = struct {
                             .ctx = this.writer,
                             .failed = false,
                         };
-                        var name_str = ZigString.init("");
 
-                        value.getNameProperty(globalThis, &name_str);
-                        if (name_str.len > 0 and !strings.eqlComptime(name_str.slice(), "Object")) {
+                        var name_str = value.getName(globalThis);
+                        defer name_str.deref();
+                        if (!name_str.isEmpty() and !name_str.eqlComptime("Object")) {
                             writer.print("{} ", .{name_str});
                         } else {
-                            value.getPrototype(globalThis).getNameProperty(globalThis, &name_str);
-                            if (name_str.len > 0 and !strings.eqlComptime(name_str.slice(), "Object")) {
+                            name_str.deref();
+                            name_str = value.getPrototype(globalThis).getName(globalThis);
+
+                            if (!name_str.isEmpty() and !name_str.eqlComptime("Object")) {
                                 writer.print("{} ", .{name_str});
                             }
                         }
@@ -2184,10 +2186,10 @@ pub const ZigConsoleClient = struct {
                     }
                 },
                 .Function => {
-                    var printable = ZigString.init(&name_buf);
-                    value.getNameProperty(this.globalThis, &printable);
+                    var printable = value.getName(this.globalThis);
+                    defer printable.deref();
 
-                    if (printable.len == 0) {
+                    if (printable.isEmpty()) {
                         writer.print(comptime Output.prettyFmt("<cyan>[Function]<r>", enable_ansi_colors), .{});
                     } else {
                         writer.print(comptime Output.prettyFmt("<cyan>[Function: {}]<r>", enable_ansi_colors), .{printable});
@@ -2890,8 +2892,8 @@ pub const ZigConsoleClient = struct {
                         }
 
                         var display_name = value.getName(this.globalThis);
-                        if (display_name.len == 0) {
-                            display_name = ZigString.init("Object");
+                        if (display_name.isEmpty()) {
+                            display_name = String.static("Object");
                         }
                         writer.print(comptime Output.prettyFmt("<r><cyan>[{} ...]<r>", enable_ansi_colors), .{
                             display_name,
diff --git a/test/bundler/esbuild/default.test.ts b/test/bundler/esbuild/default.test.ts
index ac820848a..575c82258 100644
--- a/test/bundler/esbuild/default.test.ts
+++ b/test/bundler/esbuild/default.test.ts
@@ -1280,7 +1280,7 @@ describe("bundler", () => {
       `,
     },
     run: {
-      stdout: "[Function] undefined undefined",
+      stdout: "[Function: fs] undefined undefined",
     },
     target: "browser",
   });
diff --git a/test/bundler/esbuild/splitting.test.ts b/test/bundler/esbuild/splitting.test.ts
index 427bd3d51..b9105e727 100644
--- a/test/bundler/esbuild/splitting.test.ts
+++ b/test/bundler/esbuild/splitting.test.ts
@@ -359,6 +359,7 @@ describe("bundler", () => {
     },
     entryPoints: ["/a.js", "/b.js", "/c.js"],
     splitting: true,
+    target: "bun",
     runtimeFiles: {
       "/test.js": /* js */ `
         import './out/c.js';
@@ -372,9 +373,9 @@ describe("bundler", () => {
       `,
     },
     run: [
-      { file: "/out/a.js", stdout: "side effects! [Function]\nsetValue 123" },
-      { file: "/out/b.js", stdout: "side effects! [Function]\nb" },
-      { file: "/test.js", stdout: "side effects! [Function]\nsetValue 123\nobserver 123\nb" },
+      { file: "/out/a.js", stdout: "side effects! [Function: getValue]\nsetValue 123" },
+      { file: "/out/b.js", stdout: "side effects! [Function: getValue]\nb" },
+      { file: "/test.js", stdout: "side effects! [Function: getValue]\nsetValue 123\nobserver 123\nb" },
     ],
   });
   itBundled("splitting/CrossChunkAssignmentDependenciesRecursive", {
@@ -513,8 +514,8 @@ describe("bundler", () => {
     splitting: true,
     minifyIdentifiers: true,
     run: [
-      { file: "/out/a.js", stdout: "[Function]" },
-      { file: "/out/b.js", stdout: "[Function]" },
+      { file: "/out/a.js", stdout: "[Function: f]" },
+      { file: "/out/b.js", stdout: "[Function: f]" },
     ],
   });
   itBundled("splitting/HybridESMAndCJSESBuildIssue617", {
diff --git a/test/js/bun/util/inspect.test.js b/test/js/bun/util/inspect.test.js
index c2cfe11bf..c0ccc877a 100644
--- a/test/js/bun/util/inspect.test.js
+++ b/test/js/bun/util/inspect.test.js
@@ -362,3 +362,46 @@ it("new Date(..)", () => {
 it("Bun.inspect.custom exists", () => {
   expect(Bun.inspect.custom).toBe(util.inspect.custom);
 });
+
+describe("Functions with names", () => {
+  const closures = [
+    () => function f() {},
+    () => {
+      var f = function () {};
+      return f;
+    },
+    () => {
+      const f = function () {};
+      // workaround transpiler inlining losing the display name
+      // TODO: preserve the name on functions being inlined
+      f.length;
+      return f;
+    },
+    () => {
+      let f = function () {};
+      // workaround transpiler inlining losing the display name
+      // TODO: preserve the name on functions being inlined
+      f.length;
+      return f;
+    },
+    () => {
+      var f = function f() {};
+      return f;
+    },
+    () => {
+      var foo = function f() {};
+      return foo;
+    },
+    () => {
+      function f() {}
+      var foo = f;
+      return foo;
+    },
+  ];
+
+  for (let closure of closures) {
+    it(JSON.stringify(closure.toString()), () => {
+      expect(Bun.inspect(closure())).toBe("[Function: f]");
+    });
+  }
+});