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std.json: support field aliases #10193

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std.json: support field aliases #10193

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94ebda6
std.json: support field aliases
travisstaloch Nov 21, 2021
ec6c3ee
std.json: move field_aliases to struct decl
travisstaloch Nov 22, 2021
3136da2
std.json: make field_alias a `?[*:0]const u8`
travisstaloch Nov 22, 2021
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63 changes: 61 additions & 2 deletions lib/std/json.zig
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Original file line number Diff line number Diff line change
Expand Up @@ -1555,6 +1555,54 @@ test "skipValue" {
}
}

test "field aliases" {
const S = struct {
value: u8,
a: u8,
z: u8,
pub const __field_aliases = .{
.value = "__value",
.a = "__a",
.z = "__z",
};
};
const text =
\\{"__value": 42, "__a": 43, "__z": 44}
;

const s = try parse(S, &TokenStream.init(text), .{});
try testing.expectEqual(@as(u8, 42), s.value);
try testing.expectEqual(@as(u8, 43), s.a);
try testing.expectEqual(@as(u8, 44), s.z);
}

test "field alias escapes" {
const text =
\\{"__f\u006fo": 42}
;

{
// match field, mismatched alias
const S = struct {
foo: u8,
pub const __field_aliases = .{ .foo = "__bar" };
};
try testing.expectError(
error.UnknownField,
parse(S, &TokenStream.init(text), .{}),
);
}
{
// match field, match alias
const S = struct {
foo: u8,
pub const __field_aliases = .{ .foo = "__foo" };
};
const s = try parse(S, &TokenStream.init(text), .{});
try testing.expectEqual(@as(u8, 42), s.foo);
}
}

fn ParseInternalError(comptime T: type) type {
// `inferred_types` is used to avoid infinite recursion for recursive type definitions.
const inferred_types = [_]type{};
Expand Down Expand Up @@ -1730,6 +1778,10 @@ fn parseInternal(
}
}

// support for field_aliases
const FieldAliases = std.enums.EnumFieldStruct(T, ?[*:0]const u8, @as(?[*:0]const u8, null));
const field_aliases: FieldAliases = if (@hasDecl(T, "__field_aliases")) T.__field_aliases else .{};

while (true) {
switch ((try tokens.next()) orelse return error.UnexpectedEndOfJson) {
.ObjectEnd => break,
Expand All @@ -1739,8 +1791,15 @@ fn parseInternal(
child_options.allow_trailing_data = true;
var found = false;
inline for (structInfo.fields) |field, i| {
// TODO: using switches here segfault the compiler (#2727?)
if ((stringToken.escapes == .None and mem.eql(u8, field.name, key_source_slice)) or (stringToken.escapes == .Some and (field.name.len == stringToken.decodedLength() and encodesTo(field.name, key_source_slice)))) {
const field_name = comptime if (@field(field_aliases, field.name)) |alias|
mem.span(alias)
else
field.name;

if ((stringToken.escapes == .None and mem.eql(u8, field_name, key_source_slice)) or
(stringToken.escapes == .Some and ((field_name.len == stringToken.decodedLength() and encodesTo(field_name, key_source_slice)))))
{
// TODO: using switches here segfault the compiler (#2727?)
// if (switch (stringToken.escapes) {
// .None => mem.eql(u8, field.name, key_source_slice),
// .Some => (field.name.len == stringToken.decodedLength() and encodesTo(field.name, key_source_slice)),
Expand Down