fix: merge multiple class attributes into single attribute

- codegen.zig: collect class values and output as single merged attribute
- template.zig: respect quoted flag to prevent data lookup for static class values
- Added tests for multiple class merging scenarios

src/codegen.zig

@@ -354,19 +354,31 @@ pub const Compiler = struct {
     }
 
     fn visitAttributes(self: *Compiler, tag: *Node) CompilerError!void {
+        // Collect class values to merge them into a single attribute
+        var class_values = std.ArrayListUnmanaged([]const u8){};
+        defer class_values.deinit(self.allocator);
+
+        // First pass: collect class values and output non-class attributes
         for (tag.attrs.items) |attr| {
             if (attr.val) |val| {
-                // Skip empty class/style attributes
-                if (mem.eql(u8, attr.name, "class") or mem.eql(u8, attr.name, "style")) {
-                    // Skip if value is empty, null, or undefined
-                    if (val.len == 0 or
-                        mem.eql(u8, val, "''") or
-                        mem.eql(u8, val, "\"\"") or
-                        mem.eql(u8, val, "null") or
-                        mem.eql(u8, val, "undefined"))
-                    {
-                        continue;
+                // Check if value should be skipped (empty, null, undefined)
+                const should_skip = val.len == 0 or
+                    mem.eql(u8, val, "''") or
+                    mem.eql(u8, val, "\"\"") or
+                    mem.eql(u8, val, "null") or
+                    mem.eql(u8, val, "undefined");
+
+                if (mem.eql(u8, attr.name, "class")) {
+                    // Collect class values to merge later
+                    if (!should_skip) {
+                        try class_values.append(self.allocator, val);
                     }
+                    continue;
+                }
+
+                // Skip empty style attributes
+                if (mem.eql(u8, attr.name, "style") and should_skip) {
+                    continue;
                 }
 
                 // Check for boolean attributes in terse mode
@@ -398,6 +410,19 @@ pub const Compiler = struct {
                 try self.write(attr.name);
             }
         }
+
+        // Output merged class attribute if any classes were collected
+        if (class_values.items.len > 0) {
+            try self.writeChar(' ');
+            try self.write("class=\"");
+            for (class_values.items, 0..) |class_val, i| {
+                if (i > 0) {
+                    try self.writeChar(' ');
+                }
+                try self.write(class_val);
+            }
+            try self.writeChar('"');
+        }
     }
 
     fn visitText(self: *Compiler, text: *Node) CompilerError!void {

src/template.zig

@@ -288,7 +288,11 @@ fn renderTag(allocator: Allocator, output: *std.ArrayListUnmanaged(u8), tag: *No
             substituteArgValue(attr.val, bindings)
         else
             attr.val;
-        const attr_val = try evaluateAttrValue(allocator, final_val, data);
+        // Static/quoted values (e.g., from .class shorthand) should not be looked up in data
+        const attr_val = if (attr.quoted)
+            runtime.AttrValue{ .string = final_val orelse "" }
+        else
+            try evaluateAttrValue(allocator, final_val, data);
 
         // Collect class attributes for merging
         if (std.mem.eql(u8, attr.name, "class")) {
@@ -685,7 +689,11 @@ fn renderTagWithItem(allocator: Allocator, output: *std.ArrayListUnmanaged(u8),
 
     // Render attributes directly to output buffer (avoids intermediate allocations)
     for (tag.attrs.items) |attr| {
-        const attr_val = try evaluateAttrValue(allocator, attr.val, data);
+        // Static/quoted values (e.g., from .class shorthand) should not be looked up in data
+        const attr_val = if (attr.quoted)
+            runtime.AttrValue{ .string = attr.val orelse "" }
+        else
+            try evaluateAttrValue(allocator, attr.val, data);
 
         // Collect class attributes for merging
         if (std.mem.eql(u8, attr.name, "class")) {

src/tests/general_test.zig

@@ -202,6 +202,18 @@ test "Implicit div with ID" {
     try expectOutput("#content", .{}, "<div id=\"content\"></div>");
 }
 
+test "Multiple classes merged into single attribute" {
+    try expectOutput("div.foo.bar.baz", .{}, "<div class=\"foo bar baz\"></div>");
+}
+
+test "Multiple classes with text" {
+    try expectOutput(".a.b hello", .{}, "<div class=\"a b\">hello</div>");
+}
+
+test "Class attribute merged with shorthand classes" {
+    try expectOutput("div(class=\"foo\").bar.baz", .{}, "<div class=\"foo bar baz\"></div>");
+}
+
 // ─────────────────────────────────────────────────────────────────────────────
 // Test Case 10: &attributes spread operator
 // TODO: &attributes spread with JS object literal not yet implemented