std: add json.stringify to encode arbitrary values to JSON
daurnimator
parent
c5ca0fe237
commit
5a20604820
266
lib/std/json.zig
266
lib/std/json.zig
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@ -1686,3 +1686,269 @@ test "string copy option" {
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}
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testing.expect(found_nocopy);
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}
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pub const StringifyOptions = struct {
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// TODO: indentation options?
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// TODO: make escaping '/' in strings optional?
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// TODO: allow picking if []u8 is string or array?
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};
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pub fn stringify(
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value: var,
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options: StringifyOptions,
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context: var,
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comptime Errors: type,
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comptime output: fn (@TypeOf(context), []const u8) Errors!void,
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) Errors!void {
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const T = @TypeOf(value);
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switch (@typeInfo(T)) {
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.Float, .ComptimeFloat => {
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return std.fmt.formatFloatScientific(value, std.fmt.FormatOptions{}, context, Errors, output);
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},
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.Int, .ComptimeInt => {
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return std.fmt.formatIntValue(value, "", std.fmt.FormatOptions{}, context, Errors, output);
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},
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.Bool => {
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return output(context, if (value) "true" else "false");
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},
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.Optional => {
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if (value) |payload| {
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return try stringify(payload, options, context, Errors, output);
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} else {
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return output(context, "null");
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}
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},
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.Enum => {
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if (comptime std.meta.trait.hasFn("jsonStringify")(T)) {
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return value.jsonStringify(options, context, Errors, output);
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}
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@compileError("Unable to stringify enum '" ++ @typeName(T) ++ "'");
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},
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.Union => {
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if (comptime std.meta.trait.hasFn("jsonStringify")(T)) {
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return value.jsonStringify(options, context, Errors, output);
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}
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const info = @typeInfo(T).Union;
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if (info.tag_type) |UnionTagType| {
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inline for (info.fields) |u_field| {
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if (@enumToInt(@as(UnionTagType, value)) == u_field.enum_field.?.value) {
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return try stringify(@field(value, u_field.name), options, context, Errors, output);
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}
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}
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} else {
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@compileError("Unable to stringify untagged union '" ++ @typeName(T) ++ "'");
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}
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},
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.Struct => |S| {
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if (comptime std.meta.trait.hasFn("jsonStringify")(T)) {
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return value.jsonStringify(options, context, Errors, output);
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}
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try output(context, "{");
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comptime var field_output = false;
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inline for (S.fields) |Field, field_i| {
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// don't include void fields
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if (Field.field_type == void) continue;
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if (!field_output) {
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field_output = true;
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} else {
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try output(context, ",");
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}
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try stringify(Field.name, options, context, Errors, output);
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try output(context, ":");
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try stringify(@field(value, Field.name), options, context, Errors, output);
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}
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try output(context, "}");
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return;
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},
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.Pointer => |ptr_info| switch (ptr_info.size) {
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.One => {
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// TODO: avoid loops?
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return try stringify(value.*, options, context, Errors, output);
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},
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// TODO: .Many when there is a sentinel (waiting for https://github.com/ziglang/zig/pull/3972)
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.Slice => {
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if (ptr_info.child == u8 and std.unicode.utf8ValidateSlice(value)) {
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try output(context, "\"");
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var i: usize = 0;
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while (i < value.len) : (i += 1) {
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switch (value[i]) {
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// normal ascii characters
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0x20...0x21, 0x23...0x2E, 0x30...0x5B, 0x5D...0x7F => try output(context, value[i .. i + 1]),
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// control characters with short escapes
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'\\' => try output(context, "\\\\"),
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'\"' => try output(context, "\\\""),
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'/' => try output(context, "\\/"),
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0x8 => try output(context, "\\b"),
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0xC => try output(context, "\\f"),
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'\n' => try output(context, "\\n"),
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'\r' => try output(context, "\\r"),
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'\t' => try output(context, "\\t"),
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else => {
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const ulen = std.unicode.utf8ByteSequenceLength(value[i]) catch unreachable;
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const codepoint = std.unicode.utf8Decode(value[i .. i + ulen]) catch unreachable;
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if (codepoint <= 0xFFFF) {
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// If the character is in the Basic Multilingual Plane (U+0000 through U+FFFF),
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// then it may be represented as a six-character sequence: a reverse solidus, followed
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// by the lowercase letter u, followed by four hexadecimal digits that encode the character's code point.
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try output(context, "\\u");
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try std.fmt.formatIntValue(codepoint, "x", std.fmt.FormatOptions{ .width = 4, .fill = '0' }, context, Errors, output);
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} else {
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// To escape an extended character that is not in the Basic Multilingual Plane,
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// the character is represented as a 12-character sequence, encoding the UTF-16 surrogate pair.
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const high = @intCast(u16, (codepoint - 0x10000) >> 10) + 0xD800;
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const low = @intCast(u16, codepoint & 0x3FF) + 0xDC00;
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try output(context, "\\u");
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try std.fmt.formatIntValue(high, "x", std.fmt.FormatOptions{ .width = 4, .fill = '0' }, context, Errors, output);
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try output(context, "\\u");
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try std.fmt.formatIntValue(low, "x", std.fmt.FormatOptions{ .width = 4, .fill = '0' }, context, Errors, output);
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}
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i += ulen - 1;
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},
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}
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}
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try output(context, "\"");
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return;
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}
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try output(context, "[");
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for (value) |x, i| {
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if (i != 0) {
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try output(context, ",");
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}
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try stringify(x, options, context, Errors, output);
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}
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try output(context, "]");
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return;
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},
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else => @compileError("Unable to stringify type '" ++ @typeName(T) ++ "'"),
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},
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.Array => |info| {
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return try stringify(value[0..], options, context, Errors, output);
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},
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else => @compileError("Unable to stringify type '" ++ @typeName(T) ++ "'"),
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}
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unreachable;
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}
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fn teststringify(expected: []const u8, value: var) !void {
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const TestStringifyContext = struct {
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expected_remaining: []const u8,
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fn testStringifyWrite(context: *@This(), bytes: []const u8) !void {
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if (context.expected_remaining.len < bytes.len) {
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std.debug.warn(
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\\====== expected this output: =========
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\\{}
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\\======== instead found this: =========
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\\{}
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\\======================================
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, .{
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context.expected_remaining,
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bytes,
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});
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return error.TooMuchData;
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}
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if (!mem.eql(u8, context.expected_remaining[0..bytes.len], bytes)) {
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std.debug.warn(
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\\====== expected this output: =========
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\\{}
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\\======== instead found this: =========
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\\{}
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\\======================================
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, .{
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context.expected_remaining[0..bytes.len],
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bytes,
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});
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return error.DifferentData;
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}
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context.expected_remaining = context.expected_remaining[bytes.len..];
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}
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};
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var buf: [100]u8 = undefined;
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var context = TestStringifyContext{ .expected_remaining = expected };
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try stringify(value, StringifyOptions{}, &context, error{
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TooMuchData,
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DifferentData,
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}, TestStringifyContext.testStringifyWrite);
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if (context.expected_remaining.len > 0) return error.NotEnoughData;
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}
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test "stringify basic types" {
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try teststringify("false", false);
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try teststringify("true", true);
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try teststringify("null", @as(?u8, null));
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try teststringify("null", @as(?*u32, null));
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try teststringify("42", 42);
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try teststringify("4.2e+01", 42.0);
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try teststringify("42", @as(u8, 42));
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try teststringify("42", @as(u128, 42));
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try teststringify("4.2e+01", @as(f32, 42));
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try teststringify("4.2e+01", @as(f64, 42));
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}
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test "stringify string" {
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try teststringify("\"hello\"", "hello");
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try teststringify("\"with\\nescapes\\r\"", "with\nescapes\r");
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try teststringify("\"with unicode\\u0001\"", "with unicode\u{1}");
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try teststringify("\"with unicode\\u0080\"", "with unicode\u{80}");
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try teststringify("\"with unicode\\u00ff\"", "with unicode\u{FF}");
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try teststringify("\"with unicode\\u0100\"", "with unicode\u{100}");
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try teststringify("\"with unicode\\u0800\"", "with unicode\u{800}");
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try teststringify("\"with unicode\\u8000\"", "with unicode\u{8000}");
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try teststringify("\"with unicode\\ud799\"", "with unicode\u{D799}");
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try teststringify("\"with unicode\\ud800\\udc00\"", "with unicode\u{10000}");
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try teststringify("\"with unicode\\udbff\\udfff\"", "with unicode\u{10FFFF}");
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}
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test "stringify tagged unions" {
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try teststringify("42", union(enum) {
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Foo: u32,
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Bar: bool,
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}{ .Foo = 42 });
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}
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test "stringify struct" {
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try teststringify("{\"foo\":42}", struct {
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foo: u32,
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}{ .foo = 42 });
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}
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test "stringify struct with void field" {
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try teststringify("{\"foo\":42}", struct {
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foo: u32,
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bar: void = {},
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}{ .foo = 42 });
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}
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test "stringify array of structs" {
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const MyStruct = struct {
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foo: u32,
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};
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try teststringify("[{\"foo\":42},{\"foo\":100},{\"foo\":1000}]", [_]MyStruct{
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MyStruct{ .foo = 42 },
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MyStruct{ .foo = 100 },
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MyStruct{ .foo = 1000 },
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});
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}
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test "stringify struct with custom stringifier" {
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try teststringify("[\"something special\",42]", struct {
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foo: u32,
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const Self = @This();
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pub fn jsonStringify(
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value: Self,
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options: StringifyOptions,
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context: var,
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comptime Errors: type,
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comptime output: fn (@TypeOf(context), []const u8) Errors!void,
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) !void {
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try output(context, "[\"something special\",");
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try stringify(42, options, context, Errors, output);
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try output(context, "]");
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}
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}{ .foo = 42 });
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}
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