Fix memory leak in response.clone(), further reduce memory usage of Request & Response (#3902)

* Atomize respsone.url & response.statusText

* Fix warning

* Atomize Request & Response URLs when possible

* Fix memory leak in response.clone()

bun/bench/snippets on  jarred/atomize
❯ mem bun --smol request-response-clone.mjs
cpu: Apple M1 Max
runtime: bun 0.7.2 (arm64-darwin)

benchmark             time (avg)             (min … max)       p75       p99      p995
-------------------------------------------------------- -----------------------------
req.clone().url     77.3 ns/iter  (40.35 ns … 222.64 ns)  91.53 ns 128.11 ns 172.78 ns
resp.clone().url  162.43 ns/iter    (116 ns … 337.77 ns)  177.4 ns 232.38 ns 262.65 ns

Peak memory usage: 60 MB

bun/bench/snippets on  jarred/atomize
❯ mem bun-0.7.1 --smol request-response-clone.mjs
cpu: Apple M1 Max
runtime: bun 0.7.1 (arm64-darwin)

benchmark             time (avg)             (min … max)       p75       p99      p995
-------------------------------------------------------- -----------------------------
req.clone().url   115.85 ns/iter  (80.35 ns … 247.39 ns) 128.19 ns 181.93 ns 207.23 ns
resp.clone().url  252.32 ns/iter  (202.6 ns … 351.07 ns) 266.56 ns 325.88 ns 334.73 ns

Peak memory usage: 1179 MB

* Update tests

* Update js_ast.zig

* Update test

---------

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

3 files changed, 36 insertions, 24 deletions

diff --git a/src/bun.js/api/filesystem_router.zig b/src/bun.js/api/filesystem_router.zig
index 216f66b7f..edb666040 100644
--- a/src/bun.js/api/filesystem_router.zig
+++ b/src/bun.js/api/filesystem_router.zig
@@ -75,6 +75,8 @@ const DeprecatedGlobalRouter = struct {
         };
 
         var path_: ?ZigString.Slice = null;
+        var req_url_slice: ZigString.Slice = .{};
+        defer req_url_slice.deinit();
         var pathname: string = "";
         defer {
             if (path_) |path| {
@@ -88,7 +90,8 @@ const DeprecatedGlobalRouter = struct {
             var url = URL.parse(path_.?.slice());
             pathname = url.pathname;
         } else if (arg.as(Request)) |req| {
-            var url = URL.parse(req.url);
+            req_url_slice = req.url.toUTF8(bun.default_allocator);
+            var url = URL.parse(req_url_slice.slice());
             pathname = url.pathname;
         }
 
@@ -389,11 +392,11 @@ pub const FileSystemRouter = struct {
             if (argument.isCell()) {
                 if (argument.as(JSC.WebCore.Request)) |req| {
                     req.ensureURL() catch unreachable;
-                    break :brk ZigString.Slice.fromUTF8NeverFree(req.url).clone(globalThis.allocator()) catch unreachable;
+                    break :brk req.url.toUTF8(globalThis.allocator());
                 }
 
                 if (argument.as(JSC.WebCore.Response)) |resp| {
-                    break :brk ZigString.Slice.fromUTF8NeverFree(resp.url).clone(globalThis.allocator()) catch unreachable;
+                    break :brk resp.url.toUTF8(globalThis.allocator());
                 }
             }
 
diff --git a/src/bun.js/api/html_rewriter.zig b/src/bun.js/api/html_rewriter.zig
index 92e9790c6..f754e3e23 100644
--- a/src/bun.js/api/html_rewriter.zig
+++ b/src/bun.js/api/html_rewriter.zig
@@ -454,8 +454,8 @@ pub const HTMLRewriter = struct {
                 result.body.init.headers = headers.cloneThis(global);
             }
 
-            result.url = bun.default_allocator.dupe(u8, original.url) catch unreachable;
-            result.status_text = bun.default_allocator.dupe(u8, original.status_text) catch unreachable;
+            result.url = original.url.clone();
+            result.status_text = original.status_text.clone();
 
             var input = original.body.value.useAsAnyBlob();
             sink.input = input;
diff --git a/src/bun.js/api/server.zig b/src/bun.js/api/server.zig
index 801745aee..10afa4ac1 100644
--- a/src/bun.js/api/server.zig
+++ b/src/bun.js/api/server.zig
@@ -1069,7 +1069,7 @@ fn NewRequestContext(comptime ssl_enabled: bool, comptime debug_mode: bool, comp
         byte_stream: ?*JSC.WebCore.ByteStream = null,
 
         /// Used in errors
-        pathname: []const u8 = "",
+        pathname: bun.String = bun.String.empty,
 
         /// Used either for temporary blob data or fallback
         /// When the response body is a temporary value
@@ -1550,10 +1550,9 @@ fn NewRequestContext(comptime ssl_enabled: bool, comptime debug_mode: bool, comp
                 stream.unpipe();
             }
 
-            if (this.pathname.len > 0) {
-                ctxLog("finalizeWithoutDeinit: this.pathname.len > 0 null", .{});
-                this.allocator.free(bun.constStrToU8(this.pathname));
-                this.pathname = "";
+            if (!this.pathname.isEmpty()) {
+                this.pathname.deref();
+                this.pathname = bun.String.empty;
             }
 
             // if we are waiting for the body yet and the request was not aborted we can safely clear the onData callback
@@ -2235,7 +2234,7 @@ fn NewRequestContext(comptime ssl_enabled: bool, comptime debug_mode: bool, comp
                 request_object.uws_request = req;
 
                 request_object.ensureURL() catch {
-                    request_object.url = "";
+                    request_object.url = bun.String.empty;
                 };
 
                 // we have to clone the request headers here since they will soon belong to a different request
@@ -2244,7 +2243,7 @@ fn NewRequestContext(comptime ssl_enabled: bool, comptime debug_mode: bool, comp
                 }
 
                 if (comptime debug_mode) {
-                    ctx.pathname = bun.default_allocator.dupe(u8, request_object.url) catch unreachable;
+                    ctx.pathname = request_object.url.clone();
                 }
 
                 // This object dies after the stack frame is popped
@@ -2596,15 +2595,28 @@ fn NewRequestContext(comptime ssl_enabled: bool, comptime debug_mode: bool, comp
             runErrorHandlerWithStatusCode(this, value, 500);
         }
 
-        fn ensurePathname(this: *RequestContext) []const u8 {
-            if (this.pathname.len > 0)
-                return this.pathname;
+        const PathnameFormatter = struct {
+            ctx: *RequestContext,
+
+            pub fn format(formatter: @This(), comptime fmt: []const u8, opts: std.fmt.FormatOptions, writer: anytype) !void {
+                var this = formatter.ctx;
+
+                if (!this.pathname.isEmpty()) {
+                    try this.pathname.format(fmt, opts, writer);
+                    return;
+                }
 
-            if (!this.flags.has_abort_handler) {
-                return this.req.url();
+                if (!this.flags.has_abort_handler) {
+                    try writer.writeAll(this.req.url());
+                    return;
+                }
+
+                try writer.writeAll("/");
             }
+        };
 
-            return "/";
+        fn ensurePathname(this: *RequestContext) PathnameFormatter {
+            return .{ .ctx = this };
         }
 
         pub inline fn shouldCloseConnection(this: *const RequestContext) bool {
@@ -2625,7 +2637,7 @@ fn NewRequestContext(comptime ssl_enabled: bool, comptime debug_mode: bool, comp
                     vm.log,
                     error.ExceptionOcurred,
                     exception_list.toOwnedSlice() catch @panic("TODO"),
-                    "<r><red>{s}<r> - <b>{s}<r> failed",
+                    "<r><red>{s}<r> - <b>{}<r> failed",
                     .{ @as(string, @tagName(this.method)), this.ensurePathname() },
                 );
             } else {
@@ -4900,8 +4912,7 @@ pub fn NewServer(comptime ssl_enabled_: bool, comptime debug_mode_: bool) type {
                 }
 
                 existing_request = Request{
-                    .url = url.href,
-                    .url_was_allocated = true,
+                    .url = bun.String.create(url.href),
                     .headers = headers,
                     .body = JSC.WebCore.InitRequestBodyValue(body) catch unreachable,
                     .method = method,
@@ -4943,7 +4954,7 @@ pub fn NewServer(comptime ssl_enabled_: bool, comptime debug_mode_: bool) type {
             }
 
             if (response_value.as(JSC.WebCore.Response)) |resp| {
-                resp.url = this.allocator.dupe(u8, existing_request.url) catch unreachable;
+                resp.url = existing_request.url.clone();
             }
             return JSC.JSPromise.resolvedPromiseValue(ctx, response_value).asObjectRef();
         }
@@ -5295,7 +5306,6 @@ pub fn NewServer(comptime ssl_enabled_: bool, comptime debug_mode_: bool) type {
             }
 
             request_object.* = .{
-                .url = "",
                 .method = ctx.method,
                 .uws_request = req,
                 .https = ssl_enabled,
@@ -5398,7 +5408,6 @@ pub fn NewServer(comptime ssl_enabled_: bool, comptime debug_mode_: bool) type {
             }
 
             request_object.* = .{
-                .url = "",
                 .method = ctx.method,
                 .uws_request = req,
                 .upgrader = ctx,