Make js.Bridge aware of string.String for input parameters

Avoids having to allocate small strings when going from v8 -> Zig. Also
added a discriminatory type, string.Global which uses the arena, rather than
the call_arena, if an allocation _is_ necessary. (This is similar to a feature
we had before, but was lost in zigdom). Strings from v8 that need to be
persisted, can be allocated directly v8 -> arena, rather than v8 -> call_arena
-> arena.

I think there are a lot of places where we should use string.String - where
strings are expected to be short (e.g. attribute names). But started with just
document.querySelector and querySelectorAll.

src/browser/js/Local.zig

@@ -18,6 +18,7 @@
 
 const std = @import("std");
 const log = @import("../../log.zig");
+const string = @import("../../string.zig");
 
 const js = @import("js.zig");
 const bridge = @import("bridge.zig");
@@ -619,6 +620,19 @@ fn jsValueToStruct(self: *const Local, comptime T: type, js_val: js.Value) !?T {
             };
             return try promise.persist();
         },
+        string.String => {
+            if (!js_val.isString()) {
+                return null;
+            }
+            return try self.valueToStringSSO(js_val, .{.allocator = self.ctx.call_arena});
+        },
+        string.Global => {
+            if (!js_val.isString()) {
+                return null;
+            }
+            // Use arena for persistent strings
+            return .{.str = try self.valueToStringSSO(js_val, .{ .allocator = self.ctx.arena }) };
+        },
         else => {
             if (!js_val.isObject()) {
                 return null;
@@ -927,6 +941,15 @@ fn probeJsValueToZig(self: *const Local, comptime T: type, js_val: js.Value) !Pr
             }
         },
         .@"struct" => {
+            // Handle string.String and string.Global specially
+            if (T == string.String or T == string.Global) {
+                if (js_val.isString()) {
+                    return .{ .ok = {} };
+                }
+                // Anything can be coerced to a string
+                return .{ .coerce = {} };
+            }
+
             // We don't want to duplicate the code for this, so we call
             // the actual conversion function.
             const value = (try self.jsValueToStruct(T, js_val)) orelse {
@@ -1118,6 +1141,46 @@ fn _jsStringToZig(self: *const Local, comptime null_terminate: bool, str: anytyp
     return buf;
 }
 
+// Convert JS string to string.String with SSO
+pub fn valueToStringSSO(self: *const Local, js_val: js.Value, opts: ToStringOpts) !string.String {
+    const string_handle = v8.v8__Value__ToString(js_val.handle, self.handle) orelse {
+        return error.JsException;
+    };
+    return self.jsStringToStringSSO(string_handle, opts);
+}
+
+pub fn jsStringToStringSSO(self: *const Local, str: anytype, opts: ToStringOpts) !string.String {
+    const handle = if (@TypeOf(str) == js.String) str.handle else str;
+    const len: usize = @intCast(v8.v8__String__Utf8Length(handle, self.isolate.handle));
+
+    if (len <= 12) {
+        var content: [12]u8 = @splat(0);
+        const n = v8.v8__String__WriteUtf8(handle, self.isolate.handle, &content, len, v8.NO_NULL_TERMINATION | v8.REPLACE_INVALID_UTF8);
+        if (comptime IS_DEBUG) {
+            std.debug.assert(n == len);
+        }
+        return .{ .len = @intCast(len), .payload = .{ .content = content } };
+    }
+
+    const allocator = opts.allocator orelse self.call_arena;
+    const buf = try allocator.alloc(u8, len);
+    const n = v8.v8__String__WriteUtf8(handle, self.isolate.handle, buf.ptr, buf.len, v8.NO_NULL_TERMINATION | v8.REPLACE_INVALID_UTF8);
+    if (comptime IS_DEBUG) {
+        std.debug.assert(n == len);
+    }
+
+    var prefix: [4]u8 = @splat(0);
+    @memcpy(&prefix, buf[0..4]);
+
+    return .{
+        .len = @intCast(len),
+        .payload = .{ .heap = .{
+            .prefix = prefix,
+            .ptr = buf.ptr,
+        } },
+    };
+}
+
 // == Promise Helpers ==
 pub fn rejectPromise(self: *const Local, value: anytype) !js.Promise {
     var resolver = js.PromiseResolver.init(self);

src/browser/webapi/Document.zig

@@ -282,12 +282,12 @@ pub fn getSelection(self: *Document) *Selection {
     return &self._selection;
 }
 
-pub fn querySelector(self: *Document, input: []const u8, page: *Page) !?*Element {
-    return Selector.querySelector(self.asNode(), input, page);
+pub fn querySelector(self: *Document, input: String, page: *Page) !?*Element {
+    return Selector.querySelector(self.asNode(), input.str(), page);
 }
 
-pub fn querySelectorAll(self: *Document, input: []const u8, page: *Page) !*Selector.List {
-    return Selector.querySelectorAll(self.asNode(), input, page);
+pub fn querySelectorAll(self: *Document, input: String, page: *Page) !*Selector.List {
+    return Selector.querySelectorAll(self.asNode(), input.str(), page);
 }
 
 pub fn getImplementation(_: *const Document) DOMImplementation {

src/cdp/Node.zig

@@ -344,7 +344,7 @@ test "cdp Node: Registry register" {
     var doc = page.window._document;
 
     {
-        const dom_node = (try doc.querySelector("#a1", page)).?.asNode();
+        const dom_node = (try doc.querySelector(testing.newString("#a1"), page)).?.asNode();
         const node = try registry.register(dom_node);
         const n1b = registry.lookup_by_id.get(1).?;
         const n1c = registry.lookup_by_node.get(node.dom).?;
@@ -356,7 +356,7 @@ test "cdp Node: Registry register" {
     }
 
     {
-        const dom_node = (try doc.querySelector("p", page)).?.asNode();
+        const dom_node = (try doc.querySelector(testing.newString("p"), page)).?.asNode();
         const node = try registry.register(dom_node);
         const n1b = registry.lookup_by_id.get(2).?;
         const n1c = registry.lookup_by_node.get(node.dom).?;
@@ -400,18 +400,18 @@ test "cdp Node: search list" {
         defer page._session.removePage();
         var doc = page.window._document;
 
-        const s1 = try search_list.create((try doc.querySelectorAll("a", page))._nodes);
+        const s1 = try search_list.create((try doc.querySelectorAll(testing.newString("a"), page))._nodes);
         try testing.expectEqual("1", s1.name);
         try testing.expectEqualSlices(u32, &.{ 1, 2 }, s1.node_ids);
 
         try testing.expectEqual(2, registry.lookup_by_id.count());
         try testing.expectEqual(2, registry.lookup_by_node.count());
 
-        const s2 = try search_list.create((try doc.querySelectorAll("#a1", page))._nodes);
+        const s2 = try search_list.create((try doc.querySelectorAll(testing.newString("#a1"), page))._nodes);
         try testing.expectEqual("2", s2.name);
         try testing.expectEqualSlices(u32, &.{1}, s2.node_ids);
 
-        const s3 = try search_list.create((try doc.querySelectorAll("#a2", page))._nodes);
+        const s3 = try search_list.create((try doc.querySelectorAll(testing.newString("#a2"), page))._nodes);
         try testing.expectEqual("3", s3.name);
         try testing.expectEqualSlices(u32, &.{2}, s3.node_ids);
 

src/cdp/testing.zig

@@ -33,6 +33,7 @@ pub const expectEqual = base.expectEqual;
 pub const expectError = base.expectError;
 pub const expectEqualSlices = base.expectEqualSlices;
 pub const pageTest = base.pageTest;
+pub const newString = base.newString;
 
 const Client = struct {
     allocator: Allocator,

src/http/Http.zig

@@ -271,17 +271,21 @@ pub const Header = struct {
 };
 
 pub const Headers = struct {
-    headers: *c.curl_slist,
+    headers: ?*c.curl_slist,
     cookies: ?[*c]const u8,
 
     pub fn init(user_agent: [:0]const u8) !Headers {
         const header_list = c.curl_slist_append(null, user_agent);
-        if (header_list == null) return error.OutOfMemory;
+        if (header_list == null) {
+            return error.OutOfMemory;
+        }
         return .{ .headers = header_list, .cookies = null };
     }
 
     pub fn deinit(self: *const Headers) void {
-        c.curl_slist_free_all(self.headers);
+        if (self.headers) |hdr| {
+            c.curl_slist_free_all(hdr);
+        }
     }
 
     pub fn add(self: *Headers, header: [*c]const u8) !void {

src/string.zig

@@ -188,6 +188,13 @@ pub const String = packed struct {
     }
 };
 
+// Discriminatory type that signals the bridge to use arena instead of call_arena
+// Use this for strings that need to persist beyond the current call
+// The caller can unwrap and store just the underlying .str field
+pub const Global = struct {
+    str: String,
+};
+
 fn asUint(comptime string: anytype) std.meta.Int(
     .unsigned,
     @bitSizeOf(@TypeOf(string.*)) - 8, // (- 8) to exclude sentinel 0

src/testing.zig

@@ -176,6 +176,11 @@ pub fn print(comptime fmt: []const u8, args: anytype) void {
     }
 }
 
+const String = @import("string.zig").String;
+pub fn newString(str: []const u8) String {
+    return String.init(arena_allocator, str, .{}) catch unreachable;
+}
+
 pub const Random = struct {
     var instance: ?std.Random.DefaultPrng = null;