support rest_xml with non-string payloads (e.g. S3 create bucket)

src/aws.zig

@@ -236,6 +236,8 @@ pub fn Request(comptime request_action: anytype) type {
                 }
             }
             aws_request.body = buffer.items;
+            var rest_xml_body: ?[]const u8 = null;
+            defer if (rest_xml_body) |b| options.client.allocator.free(b);
             if (Self.service_meta.aws_protocol == .rest_xml) {
                 if (std.mem.eql(u8, "PUT", aws_request.method) or std.mem.eql(u8, "POST", aws_request.method)) {
                     if (@hasDecl(ActionRequest, "http_payload")) {
@@ -255,8 +257,37 @@ pub fn Request(comptime request_action: anytype) type {
                             body_assigned = true;
                         }
 
-                        if (!body_assigned)
-                            return error.XmlSerializationNotImplemented;
+                        if (!body_assigned) {
+                            const sm = ActionRequest.metaInfo().service_metadata;
+                            if (!std.mem.eql(u8, sm.endpoint_prefix, "s3"))
+                                // Because the attributes below are most likely only
+                                // applicable to s3, we are better off to fail
+                                // early. This portion of the code base should
+                                // only be executed for s3 as no other known
+                                // service uses this protocol
+                                return error.NotImplemented;
+
+                            const attrs = try std.fmt.allocPrint(
+                                options.client.allocator,
+                                "xmlns=\"http://{s}.amazonaws.com/doc/{s}/\"",
+                                .{ sm.endpoint_prefix, sm.version },
+                            );
+                            defer options.client.allocator.free(attrs); // once serialized, the value should be copied over
+
+                            // Need to serialize this
+                            rest_xml_body = try xml_serializer.stringifyAlloc(
+                                options.client.allocator,
+                                payload,
+                                .{
+                                    .whitespace = .indent_2,
+                                    .root_name = request.fieldNameFor(ActionRequest.http_payload),
+                                    .root_attributes = attrs,
+                                    .emit_null_optional_fields = false,
+                                    .include_declaration = false,
+                                },
+                            );
+                            aws_request.body = rest_xml_body.?;
+                        }
                     } else {
                         return error.NotImplemented;
                     }
@@ -2305,7 +2336,10 @@ test "rest_xml_with_input_s3: S3 create bucket" {
         \\</CreateBucketConfiguration>
     , test_harness.request_options.request_body);
     // Response expectations
-    try std.testing.expectEqualStrings("9PEYBAZ9J7TPRX43", call.response_metadata.request_id);
+    try std.testing.expectEqualStrings(
+        "9PEYBAZ9J7TPRX43, host_id: u7lzgW0tIyRP15vSUsVOXxJ37OfVCO8lZmLIVuqeq5EE4tNp9qebb5fy+/kendlZpR4YQE+y4Xg=",
+        call.response_metadata.request_id,
+    );
 }
 test "rest_xml_no_input: S3 list buckets" {
     const allocator = std.testing.allocator;

src/xml_serializer.zig

@@ -20,6 +20,9 @@ pub const StringifyOptions = struct {
     /// Root element name to use when serializing a value that doesn't have a natural name
     root_name: ?[]const u8 = "root",
 
+    /// Root attributes (e.g. xmlns="...") that will be added to the root element node only
+    root_attributes: []const u8 = "",
+
     /// Function to determine the element name for an array item based on the element
     /// name of the array containing the elements. See arrayElementPluralToSingluarTransformation
     /// and arrayElementNoopTransformation functions for examples
@@ -58,7 +61,10 @@ pub fn stringify(
 
     // Start serialization with the root element
     const root_name = options.root_name;
-    try serializeValue(value, root_name, options, writer.any(), 0);
+    if (@typeInfo(@TypeOf(value)) != .optional or value == null)
+        try serializeValue(value, root_name, options, writer.any(), 0)
+    else
+        try serializeValue(value.?, root_name, options, writer.any(), 0);
 }
 
 /// Serializes a value to XML and returns an allocated string
@@ -84,18 +90,21 @@ fn serializeValue(
 ) !void {
     const T = @TypeOf(value);
 
+    // const output_indent = !(!options.emit_null_optional_fields and @typeInfo(@TypeOf(value)) == .optional and value == null);
+    const output_indent = options.emit_null_optional_fields or @typeInfo(@TypeOf(value)) != .optional or value != null;
+
+    if (output_indent and element_name != null)
         try writeIndent(writer, depth, options.whitespace);
 
-    // const write_outer_element =
-    //     @typeInfo(T) != .optional or
-    //     options.emit_strings_as_arrays == false or
-    //     (@typeInfo(T) == .optional and element_name != null) or
-    //     (options.emit_strings_as_arrays and (@typeInfo(T) != .array or @typeInfo(T).array.child != u8));
     // Start element tag
     if (@typeInfo(T) != .optional and @typeInfo(T) != .array) {
         if (element_name) |n| {
             try writer.writeAll("<");
             try writer.writeAll(n);
+            if (depth == 0 and options.root_attributes.len > 0) {
+                try writer.writeByte(' ');
+                try writer.writeAll(options.root_attributes);
+            }
             try writer.writeAll(">");
         }
     }
@@ -197,8 +206,9 @@ fn serializeValue(
                     else
                         field.name; // TODO: field mapping
 
+                const field_value = @field(value, field.name);
                 try serializeValue(
-                    @field(value, field.name),
+                    field_value,
                     field_name,
                     options,
                     writer,
@@ -206,9 +216,13 @@ fn serializeValue(
                 );
 
                 if (options.whitespace != .minified) {
+                    if (!options.emit_null_optional_fields and @typeInfo(@TypeOf(field_value)) == .optional and field_value == null) {
+                        // Skip writing anything
+                    } else {
                         try writer.writeByte('\n');
                     }
                 }
+            }
 
             try writeIndent(writer, depth, options.whitespace);
         },
@@ -661,3 +675,119 @@ test "structs with custom field names" {
         , result);
     }
 }
+
+test "structs with optional values" {
+    const testing = std.testing;
+    const allocator = testing.allocator;
+
+    const Person = struct {
+        first_name: []const u8,
+        middle_name: ?[]const u8 = null,
+        last_name: []const u8,
+    };
+
+    const person = Person{
+        .first_name = "John",
+        .last_name = "Doe",
+    };
+
+    {
+        const result = try stringifyAlloc(
+            allocator,
+            person,
+            .{
+                .whitespace = .indent_2,
+                .emit_null_optional_fields = false,
+                .root_attributes = "xmlns=\"http://example.com/blah/xxxx/\"",
+            },
+        );
+        defer allocator.free(result);
+        try testing.expectEqualStrings(
+            \\<?xml version="1.0" encoding="UTF-8"?>
+            \\<root xmlns="http://example.com/blah/xxxx/">
+            \\  <first_name>John</first_name>
+            \\  <last_name>Doe</last_name>
+            \\</root>
+        , result);
+    }
+}
+
+test "optional structs with value" {
+    const testing = std.testing;
+    const allocator = testing.allocator;
+
+    const Person = struct {
+        first_name: []const u8,
+        middle_name: ?[]const u8 = null,
+        last_name: []const u8,
+    };
+
+    const person: ?Person = Person{
+        .first_name = "John",
+        .last_name = "Doe",
+    };
+
+    {
+        const result = try stringifyAlloc(
+            allocator,
+            person,
+            .{
+                .whitespace = .indent_2,
+                .emit_null_optional_fields = false,
+                .root_attributes = "xmlns=\"http://example.com/blah/xxxx/\"",
+            },
+        );
+        defer allocator.free(result);
+        try testing.expectEqualStrings(
+            \\<?xml version="1.0" encoding="UTF-8"?>
+            \\<root xmlns="http://example.com/blah/xxxx/">
+            \\  <first_name>John</first_name>
+            \\  <last_name>Doe</last_name>
+            \\</root>
+        , result);
+    }
+}
+
+test "nested optional structs with value" {
+    const testing = std.testing;
+    const allocator = testing.allocator;
+
+    const Name = struct {
+        first_name: []const u8,
+        middle_name: ?[]const u8 = null,
+        last_name: []const u8,
+    };
+
+    const Person = struct {
+        name: ?Name,
+    };
+
+    const person: ?Person = Person{
+        .name = .{
+            .first_name = "John",
+            .last_name = "Doe",
+        },
+    };
+
+    {
+        const result = try stringifyAlloc(
+            allocator,
+            person,
+            .{
+                .whitespace = .indent_2,
+                .emit_null_optional_fields = false,
+                .root_attributes = "xmlns=\"http://example.com/blah/xxxx/\"",
+            },
+        );
+        defer allocator.free(result);
+        try testing.expectEqualStrings(
+            \\<?xml version="1.0" encoding="UTF-8"?>
+            \\<root xmlns="http://example.com/blah/xxxx/">
+            \\  <name>
+            \\    <first_name>John</first_name>
+            \\    <last_name>Doe</last_name>
+            \\  </name>
+            \\</root>
+        , result);
+    }
+}