move to state parameter and index level rather than prefix

This also includes a small change to force output of mappings even if empty
New zig correctly detects that without any field, we end up trying to use
a constant that does not exist (this is in the generated code)

codegen/src/main.zig

@@ -68,10 +68,9 @@ fn generateServices(allocator: *std.mem.Allocator, comptime _: []const u8, file:
     defer allocator.free(json);
     const model = try smithy.parse(allocator, json);
     defer model.deinit();
-    const ShapeInfo = @TypeOf(model.shapes[0]); // assume we have at least one shape
-    var shapes = std.StringHashMap(ShapeInfo).init(allocator);
+    var shapes = std.StringHashMap(smithy.ShapeInfo).init(allocator);
     defer shapes.deinit();
-    var services = std.ArrayList(ShapeInfo).init(allocator);
+    var services = std.ArrayList(smithy.ShapeInfo).init(allocator);
     defer services.deinit();
     for (model.shapes) |shape| {
         try shapes.put(shape.id, shape);
@@ -131,7 +130,7 @@ fn generateServices(allocator: *std.mem.Allocator, comptime _: []const u8, file:
 
         // Operations
         for (service.shape.service.operations) |op|
-            try generateOperation(allocator, shapes.get(op).?, shapes, writer, constant_name);
+            try generateOperation(allocator, shapes.get(op).?, shapes, writer);
     }
     return constant_names.toOwnedSlice();
 }
@@ -155,67 +154,115 @@ fn constantName(allocator: *std.mem.Allocator, id: []const u8) ![]const u8 {
     // Not a special case - just snake it
     return try snake.fromPascalCase(allocator, id);
 }
-fn generateOperation(allocator: *std.mem.Allocator, operation: smithy.ShapeInfo, shapes: anytype, writer: anytype, service: []const u8) !void {
+
+const GenerationState = struct {
+    type_stack: *std.ArrayList(*const smithy.ShapeInfo),
+    map_fields: *std.StringArrayHashMap(std.ArrayList([]const u8)),
+    allocator: *std.mem.Allocator,
+    indent_level: u64,
+    all_required: bool,
+};
+
+fn outputIndent(state: GenerationState, writer: anytype) !void {
+    const n_chars = 4 * state.indent_level;
+    try writer.writeByteNTimes(' ', n_chars);
+}
+fn generateOperation(allocator: *std.mem.Allocator, operation: smithy.ShapeInfo, shapes: std.StringHashMap(smithy.ShapeInfo), writer: anytype) !void {
     const snake_case_name = try snake.fromPascalCase(allocator, operation.name);
     defer allocator.free(snake_case_name);
 
-    const prefix = "    ";
     var type_stack = std.ArrayList(*const smithy.ShapeInfo).init(allocator);
     defer type_stack.deinit();
+    var map_fields = std.StringArrayHashMap(std.ArrayList([]const u8)).init(allocator);
+    defer {
+        for (map_fields.values()) |v|
+            v.deinit();
+        map_fields.deinit();
+    }
+    const state = GenerationState{
+        .type_stack = &type_stack,
+        .map_fields = &map_fields,
+        .allocator = allocator,
+        .indent_level = 1,
+        .all_required = false,
+    };
+    var child_state = state;
+    child_state.indent_level += 1;
     // indent should start at 4 spaces here
     const operation_name = avoidReserved(snake_case_name);
     try writer.print("pub const {s}: struct ", .{operation_name});
     _ = try writer.write("{\n");
     for (operation.shape.operation.traits) |trait| {
         if (trait == .http) {
+            try outputIndent(state, writer);
             _ = try writer.write("pub const http_config = .{\n");
+            try outputIndent(child_state, writer);
             try writer.print(".method = \"{s}\",\n", .{trait.http.method});
+            try outputIndent(child_state, writer);
             try writer.print(".uri = \"{s}\",\n", .{trait.http.uri});
+            try outputIndent(child_state, writer);
             try writer.print(".success_code = {d},\n", .{trait.http.code});
+            try outputIndent(state, writer);
             _ = try writer.write("};\n\n");
         }
     }
 
+    try outputIndent(state, writer);
     try writer.print("action_name: []const u8 = \"{s}\",\n", .{operation.name});
+    try outputIndent(state, writer);
     _ = try writer.write("Request: type = ");
     if (operation.shape.operation.input) |member| {
-        try generateTypeFor(allocator, member, shapes, writer, prefix, false, &type_stack, false);
+        try generateTypeFor(member, shapes, writer, state, false);
         _ = try writer.write("\n");
-        try generateMetadataFunction(service, operation_name, prefix, writer);
+        try generateMetadataFunction(operation_name, state, writer);
     } else {
         _ = try writer.write("struct {\n");
-        try generateMetadataFunction(service, operation_name, prefix, writer);
+        try generateMetadataFunction(operation_name, state, writer);
     }
     _ = try writer.write(",\n");
+    try outputIndent(state, writer);
     _ = try writer.write("Response: type = ");
     if (operation.shape.operation.output) |member| {
-        try generateTypeFor(allocator, member, shapes, writer, "    ", false, &type_stack, true);
+        try generateTypeFor(member, shapes, writer, state, true);
     } else _ = try writer.write("struct {}"); // we want to maintain consistency with other ops
     _ = try writer.write(",\n");
 
     if (operation.shape.operation.errors) |errors| {
+        try outputIndent(state, writer);
         _ = try writer.write("ServiceError: type = error{\n");
         for (errors) |err| {
             const err_name = getErrorName(shapes.get(err).?.name); // need to remove "exception"
+            try outputIndent(child_state, writer);
             try writer.print("{s},\n", .{err_name});
         }
+        try outputIndent(state, writer);
         _ = try writer.write("},\n");
     }
     _ = try writer.write("} = .{};\n");
 }
 
-fn generateMetadataFunction(_: []const u8, operation_name: []const u8, comptime prefix: []const u8, writer: anytype) !void {
+fn generateMetadataFunction(operation_name: []const u8, state: GenerationState, writer: anytype) !void {
     // TODO: Shove these lines in here, and also the else portion
     // pub fn metaInfo(self: @This()) struct { service: @TypeOf(sts), action: @TypeOf(sts.get_caller_identity) } {
     //     return .{ .service = sts, .action = sts.get_caller_identity };
     // }
     // We want to add a short "get my parents" function into the response
-    try writer.print("{s}    ", .{prefix});
+    var child_state = state;
+    child_state.indent_level += 1;
+    try outputIndent(child_state, writer);
     _ = try writer.write("pub fn metaInfo() struct { ");
     try writer.print("service_metadata: @TypeOf(service_metadata), action: @TypeOf({s})", .{operation_name});
-    _ = try writer.write(" } {\n" ++ prefix ++ "        return .{ .service_metadata = service_metadata, ");
+    _ = try writer.write(" } {\n");
+    child_state.indent_level += 1;
+    try outputIndent(child_state, writer);
+    _ = try writer.write("return .{ .service_metadata = service_metadata, ");
     try writer.print(".action = {s}", .{operation_name});
-    _ = try writer.write(" };\n" ++ prefix ++ "    }\n" ++ prefix ++ "}");
+    _ = try writer.write(" };\n");
+    child_state.indent_level -= 1;
+    try outputIndent(child_state, writer);
+    _ = try writer.write("}\n");
+    try outputIndent(state, writer);
+    try writer.writeByte('}');
 }
 fn getErrorName(err_name: []const u8) []const u8 {
     if (endsWith("Exception", err_name))
@@ -231,7 +278,7 @@ fn endsWith(item: []const u8, str: []const u8) bool {
     return std.mem.eql(u8, item, str[str.len - item.len ..]);
 }
 /// return type is anyerror!void as this is a recursive function, so the compiler cannot properly infer error types
-fn generateTypeFor(allocator: *std.mem.Allocator, shape_id: []const u8, shapes: anytype, writer: anytype, prefix: []const u8, all_required: bool, type_stack: anytype, end_structure: bool) anyerror!void {
+fn generateTypeFor(shape_id: []const u8, shapes: std.StringHashMap(smithy.ShapeInfo), writer: anytype, state: GenerationState, end_structure: bool) anyerror!void {
     if (shapes.get(shape_id) == null) {
         std.debug.print("Shape ID not found. This is most likely a bug. Shape ID: {s}\n", .{shape_id});
         return error.InvalidType;
@@ -242,7 +289,7 @@ fn generateTypeFor(allocator: *std.mem.Allocator, shape_id: []const u8, shapes:
     const shape = shape_info.shape;
     // Check for ourselves up the stack
     var self_occurences: u8 = 0;
-    for (type_stack.items) |i| {
+    for (state.type_stack.items) |i| {
         // NOTE: shapes.get isn't providing a consistent pointer - is it allocating each time?
         // we will therefore need to compare ids
         if (std.mem.eql(u8, i.*.id, shape_info.id))
@@ -264,60 +311,69 @@ fn generateTypeFor(allocator: *std.mem.Allocator, shape_id: []const u8, shapes:
         // type to properly reference. Realistically, AWS or the service
         // must be blocking deep recursion somewhere or this would be a great
         // DOS attack
-        try generateSimpleTypeFor("nothing", "[]const u8", writer, all_required);
+        try generateSimpleTypeFor("nothing", "[]const u8", writer);
         std.log.warn("Type cycle detected, limiting depth. Type: {s}", .{shape_id});
         // std.log.info("  Type stack:\n", .{});
         // for (type_stack.items) |i|
         //     std.log.info("  {s}", .{i.*.id});
         return;
     }
-    try type_stack.append(&shape_info);
+    try state.type_stack.append(&shape_info);
     switch (shape) {
         .structure => {
-            try generateComplexTypeFor(allocator, shape.structure.members, "struct", shapes, writer, prefix, all_required, type_stack);
+            try generateComplexTypeFor(shape_id, shape.structure.members, "struct", shapes, writer, state);
             if (end_structure) {
                 // epilog
-                try writer.print("{s}", .{prefix});
+                try outputIndent(state, writer);
                 _ = try writer.write("}");
             }
         },
         .uniontype => {
-            try generateComplexTypeFor(allocator, shape.uniontype.members, "union", shapes, writer, prefix, all_required, type_stack);
+            try generateComplexTypeFor(shape_id, shape.uniontype.members, "union", shapes, writer, state);
             // epilog
-            try writer.print("{s}", .{prefix});
+            try outputIndent(state, writer);
             _ = try writer.write("}");
         },
-        .string => |s| try generateSimpleTypeFor(s, "[]const u8", writer, all_required),
-        .integer => |s| try generateSimpleTypeFor(s, "i64", writer, all_required),
+        .string => |s| try generateSimpleTypeFor(s, "[]const u8", writer),
+        .integer => |s| try generateSimpleTypeFor(s, "i64", writer),
         .list => {
             _ = try writer.write("[]");
-            try generateTypeFor(allocator, shape.list.member_target, shapes, writer, prefix, all_required, type_stack, true);
+            try generateTypeFor(shape.list.member_target, shapes, writer, state, true);
         },
         .set => {
             _ = try writer.write("[]");
-            try generateTypeFor(allocator, shape.set.member_target, shapes, writer, prefix, all_required, type_stack, true);
+            try generateTypeFor(shape.set.member_target, shapes, writer, state, true);
         },
-        .timestamp => |s| try generateSimpleTypeFor(s, "i64", writer, all_required),
-        .blob => |s| try generateSimpleTypeFor(s, "[]const u8", writer, all_required),
-        .boolean => |s| try generateSimpleTypeFor(s, "bool", writer, all_required),
-        .double => |s| try generateSimpleTypeFor(s, "f64", writer, all_required),
-        .float => |s| try generateSimpleTypeFor(s, "f32", writer, all_required),
-        .long => |s| try generateSimpleTypeFor(s, "i64", writer, all_required),
+        .timestamp => |s| try generateSimpleTypeFor(s, "i64", writer),
+        .blob => |s| try generateSimpleTypeFor(s, "[]const u8", writer),
+        .boolean => |s| try generateSimpleTypeFor(s, "bool", writer),
+        .double => |s| try generateSimpleTypeFor(s, "f64", writer),
+        .float => |s| try generateSimpleTypeFor(s, "f32", writer),
+        .long => |s| try generateSimpleTypeFor(s, "i64", writer),
         .map => {
+            // TODO: We need this:
+            //
+            // pub fn jsonStringifyField(self: @This(), comptime field_name: []const u8, options: anytype, out_stream: anytype) !bool {
+            //     if (std.mem.eql(u8, "tags", field_name))
+            //         return try serializeMap(self.tags, self.jsonFieldNameFor("tags"), options, out_stream);
+            //     return false;
+            // }
             _ = try writer.write("[]struct {\n");
-            const new_prefix = try std.fmt.allocPrint(allocator, "    {s}", .{prefix});
-            defer allocator.free(new_prefix);
-            try writer.print("{s}    key: ", .{prefix});
-            if (!all_required) try writeOptional(shape.map.traits, writer, null);
-            try generateTypeFor(allocator, shape.map.key, shapes, writer, prefix, all_required, type_stack, true);
-            if (!all_required) try writeOptional(shape.map.traits, writer, " = null");
+            var child_state = state;
+            child_state.indent_level += 1;
+            try outputIndent(child_state, writer);
+            _ = try writer.write("key: ");
+            try writeOptional(shape.map.traits, writer, null);
+            try generateTypeFor(shape.map.key, shapes, writer, state, true);
+            try writeOptional(shape.map.traits, writer, " = null");
             _ = try writer.write(",\n");
-            try writer.print("{s}    value: ", .{prefix});
-            if (!all_required) try writeOptional(shape.map.traits, writer, null);
-            try generateTypeFor(allocator, shape.map.key, shapes, writer, prefix, all_required, type_stack, true);
-            if (!all_required) try writeOptional(shape.map.traits, writer, " = null");
+            try outputIndent(child_state, writer);
+            _ = try writer.write("value: ");
+            try writeOptional(shape.map.traits, writer, null);
+            try generateTypeFor(shape.map.key, shapes, writer, state, true);
+            try writeOptional(shape.map.traits, writer, " = null");
             _ = try writer.write(",\n");
-            _ = try writer.write(prefix);
+            try outputIndent(state, writer);
             _ = try writer.write("}");
         },
         else => {
@@ -326,25 +382,19 @@ fn generateTypeFor(allocator: *std.mem.Allocator, shape_id: []const u8, shapes:
             // return error{UnimplementedShapeType}.UnimplementedShapeType;
         },
     }
-    _ = type_stack.pop();
+    _ = state.type_stack.pop();
 }
 
-// fn generateSimpleTypeFor(shape: anytype, type_name: []const u8, writer: anytype, _: bool) !void {
-fn generateSimpleTypeFor(_: anytype, type_name: []const u8, writer: anytype, all_required: bool) !void {
-    // current compiler checks unused variables, but can't handle multiple unused
-    // function parameters. We don't want to change the signature in case we need to work with
-    // these in the future, so this stupid code is only here to trick the compiler
-    if (all_required or !all_required)
+fn generateSimpleTypeFor(_: anytype, type_name: []const u8, writer: anytype) !void {
     _ = try writer.write(type_name); // This had required stuff but the problem was elsewhere. Better to leave as function just in case
 }
-
-fn generateComplexTypeFor(allocator: *std.mem.Allocator, members: []smithy.TypeMember, type_type_name: []const u8, shapes: anytype, writer: anytype, prefix: []const u8, all_required: bool, type_stack: anytype) anyerror!void {
+fn generateComplexTypeFor(shape_id: []const u8, members: []smithy.TypeMember, type_type_name: []const u8, shapes: std.StringHashMap(smithy.ShapeInfo), writer: anytype, state: GenerationState) anyerror!void {
+    _ = shape_id;
     const Mapping = struct { snake: []const u8, json: []const u8 };
-    var json_field_name_mappings = try std.ArrayList(Mapping).initCapacity(allocator, members.len);
+    var json_field_name_mappings = try std.ArrayList(Mapping).initCapacity(state.allocator, members.len);
     defer {
-        for (json_field_name_mappings.items) |mapping| {
-            allocator.free(mapping.snake);
-        }
+        for (json_field_name_mappings.items) |mapping|
+            state.allocator.free(mapping.snake);
         json_field_name_mappings.deinit();
     }
     // There is an httpQueryParams trait as well, but nobody is using it. API GW
@@ -353,28 +403,26 @@ fn generateComplexTypeFor(allocator: *std.mem.Allocator, members: []smithy.TypeM
     // Same with httpPayload
     //
     // httpLabel is interesting - right now we just assume anything can be used - do we need to track this?
-    var http_query_mappings = try std.ArrayList(Mapping).initCapacity(allocator, members.len);
+    var http_query_mappings = try std.ArrayList(Mapping).initCapacity(state.allocator, members.len);
     defer {
-        for (http_query_mappings.items) |mapping| {
-            allocator.free(mapping.snake);
-        }
+        for (http_query_mappings.items) |mapping|
+            state.allocator.free(mapping.snake);
         http_query_mappings.deinit();
     }
-    var http_header_mappings = try std.ArrayList(Mapping).initCapacity(allocator, members.len);
+    var http_header_mappings = try std.ArrayList(Mapping).initCapacity(state.allocator, members.len);
     defer {
-        for (http_header_mappings.items) |mapping| {
-            allocator.free(mapping.snake);
-        }
+        for (http_header_mappings.items) |mapping|
+            state.allocator.free(mapping.snake);
         http_header_mappings.deinit();
     }
     // prolog. We'll rely on caller to get the spacing correct here
     _ = try writer.write(type_type_name);
     _ = try writer.write(" {\n");
+    var child_state = state;
+    child_state.indent_level += 1;
     for (members) |member| {
-        const new_prefix = try std.fmt.allocPrint(allocator, "    {s}", .{prefix});
-        defer allocator.free(new_prefix);
         // This is our mapping
-        const snake_case_member = try snake.fromPascalCase(allocator, member.name);
+        const snake_case_member = try snake.fromPascalCase(state.allocator, member.name);
         // So it looks like some services have duplicate names?! Check out "httpMethod"
         // in API Gateway. Not sure what we're supposed to do there. Checking the go
         // sdk, they move this particular duplicate to 'http_method' - not sure yet
@@ -384,20 +432,21 @@ fn generateComplexTypeFor(allocator: *std.mem.Allocator, members: []smithy.TypeM
             switch (trait) {
                 .json_name => {
                     found_name_trait = true;
-                    json_field_name_mappings.appendAssumeCapacity(.{ .snake = try allocator.dupe(u8, snake_case_member), .json = trait.json_name });
+                    json_field_name_mappings.appendAssumeCapacity(.{ .snake = try state.allocator.dupe(u8, snake_case_member), .json = trait.json_name });
                 },
-                .http_query => http_query_mappings.appendAssumeCapacity(.{ .snake = try allocator.dupe(u8, snake_case_member), .json = trait.http_query }),
-                .http_header => http_header_mappings.appendAssumeCapacity(.{ .snake = try allocator.dupe(u8, snake_case_member), .json = trait.http_header }),
+                .http_query => http_query_mappings.appendAssumeCapacity(.{ .snake = try state.allocator.dupe(u8, snake_case_member), .json = trait.http_query }),
+                .http_header => http_header_mappings.appendAssumeCapacity(.{ .snake = try state.allocator.dupe(u8, snake_case_member), .json = trait.http_header }),
                 else => {},
             }
         }
         if (!found_name_trait)
-            json_field_name_mappings.appendAssumeCapacity(.{ .snake = try allocator.dupe(u8, snake_case_member), .json = member.name });
-        defer allocator.free(snake_case_member);
-        try writer.print("{s}    {s}: ", .{ prefix, avoidReserved(snake_case_member) });
-        if (!all_required) try writeOptional(member.traits, writer, null);
-        try generateTypeFor(allocator, member.target, shapes, writer, new_prefix, all_required, type_stack, true);
-        if (!all_required and !std.mem.eql(u8, "union", type_type_name))
+            json_field_name_mappings.appendAssumeCapacity(.{ .snake = try state.allocator.dupe(u8, snake_case_member), .json = member.name });
+        defer state.allocator.free(snake_case_member);
+        try outputIndent(child_state, writer);
+        try writer.print("{s}: ", .{avoidReserved(snake_case_member)});
+        try writeOptional(member.traits, writer, null);
+        try generateTypeFor(member.target, shapes, writer, child_state, true);
+        if (!std.mem.eql(u8, "union", type_type_name))
             try writeOptional(member.traits, writer, " = null");
         _ = try writer.write(",\n");
     }
@@ -409,12 +458,10 @@ fn generateComplexTypeFor(allocator: *std.mem.Allocator, members: []smithy.TypeM
     //     .marker = "Marker",
     //     .max_items = "MaxItems",
     // };
-    var constprefix = try std.fmt.allocPrint(allocator, "{s}    ", .{prefix});
-    defer allocator.free(constprefix);
     if (http_query_mappings.items.len > 0) _ = try writer.write("\n");
-    try writeMappings(constprefix, "pub ", "http_query", http_query_mappings, writer);
+    try writeMappings(child_state, "pub ", "http_query", http_query_mappings, false, writer);
     if (http_query_mappings.items.len > 0 and http_header_mappings.items.len > 0) _ = try writer.write("\n");
-    try writeMappings(constprefix, "pub ", "http_header", http_header_mappings, writer);
+    try writeMappings(child_state, "pub ", "http_header", http_header_mappings, false, writer);
 
     // Add in json mappings. The function looks like this:
     //
@@ -426,23 +473,39 @@ fn generateComplexTypeFor(allocator: *std.mem.Allocator, members: []smithy.TypeM
     //     return @field(mappings, field_name);
     // }
     //
-    var fieldnameprefix = try std.fmt.allocPrint(allocator, "{s}        ", .{prefix});
-    defer allocator.free(fieldnameprefix);
-    try writer.print("\n{s}    pub fn jsonFieldNameFor(_: @This(), comptime field_name: []const u8) []const u8 ", .{prefix});
+    try writer.writeByte('\n');
+    try outputIndent(child_state, writer);
+    _ = try writer.write("pub fn jsonFieldNameFor(_: @This(), comptime field_name: []const u8) []const u8 ");
     _ = try writer.write("{\n");
-    try writeMappings(fieldnameprefix, "", "mappings", json_field_name_mappings, writer);
-    try writer.print("{s}        return @field(mappings, field_name);\n{s}", .{ prefix, prefix });
+    var grandchild_state = child_state;
+    grandchild_state.indent_level += 1;
+    // We need to force output here becaseu we're referencing the field in the return statement below
+    try writeMappings(grandchild_state, "", "mappings", json_field_name_mappings, true, writer);
+    try outputIndent(grandchild_state, writer);
+    _ = try writer.write("return @field(mappings, field_name);\n");
+    try outputIndent(child_state, writer);
     _ = try writer.write("}\n");
+
+    // TODO: Deal with the jsonStringifyField stuff
 }
 
-fn writeMappings(prefix: []const u8, @"pub": []const u8, mapping_name: []const u8, mappings: anytype, writer: anytype) !void {
-    if (mappings.items.len == 0) return;
-    try writer.print("{s}{s}const {s} = .", .{ prefix, @"pub", mapping_name });
-    _ = try writer.write("{\n");
-    for (mappings.items) |mapping| {
-        try writer.print("{s}    .{s} = \"{s}\",\n", .{ prefix, avoidReserved(mapping.snake), mapping.json });
+fn writeMappings(state: GenerationState, @"pub": []const u8, mapping_name: []const u8, mappings: anytype, force_output: bool, writer: anytype) !void {
+    if (mappings.items.len == 0 and !force_output) return;
+    try outputIndent(state, writer);
+    if (mappings.items.len == 0) {
+        try writer.print("{s}const {s} = ", .{ @"pub", mapping_name });
+        _ = try writer.write(".{};\n");
+        return;
     }
-    _ = try writer.write(prefix);
+    try writer.print("{s}const {s} = .", .{ @"pub", mapping_name });
+    _ = try writer.write("{\n");
+    var child_state = state;
+    child_state.indent_level += 1;
+    for (mappings.items) |mapping| {
+        try outputIndent(child_state, writer);
+        try writer.print(".{s} = \"{s}\",\n", .{ avoidReserved(mapping.snake), mapping.json });
+    }
+    try outputIndent(state, writer);
     _ = try writer.write("};\n");
 }