| 1 | const std = @import("std"); |
| 2 | const string = []const u8; |
| 3 | const extras = @import("./lib.zig"); |
| 4 | const expectSimilarType = extras.expectSimilarType; |
| 5 | |
| 6 | /// Creates a new version of struct T where all fields are optional. |
| 7 | /// Name inspried by https://www.typescriptlang.org/docs/handbook/utility-types.html#partialtype. |
| 8 | pub fn Partial(comptime T: type) type { |
| 9 | const fields = std.meta.fields(T); |
| 10 | var names: [fields.len][]const u8 = undefined; |
| 11 | var types: [fields.len]type = undefined; |
| 12 | var attrs: [fields.len]std.builtin.Type.StructField.Attributes = undefined; |
| 13 | for (fields, 0..) |item, i| { |
| 14 | names[i] = item.name; |
| 15 | types[i] = ?item.type; |
| 16 | attrs[i] = .{ .default_value_ptr = &@as(?item.type, null) }; |
| 17 | } |
| 18 | return @Struct(.auto, null, &names, &types, &attrs); |
| 19 | } |
| 20 | |
| 21 | test { |
| 22 | try expectSimilarType( |
| 23 | Partial(struct { |
| 24 | a: u32, |
| 25 | b: u8, |
| 26 | c: u16, |
| 27 | }), |
| 28 | struct { |
| 29 | a: ?u32, |
| 30 | b: ?u8, |
| 31 | c: ?u16, |
| 32 | }, |
| 33 | ); |
| 34 | } |
| 35 | |
| 36 | test { |
| 37 | try expectSimilarType( |
| 38 | Partial(struct { |
| 39 | a: ?u8, |
| 40 | }), |
| 41 | struct { |
| 42 | a: ??u8, |
| 43 | }, |
| 44 | ); |
| 45 | } |