Skip to content

std.json: Adds jsonParse to override parsing behavior #8791

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Closed
wants to merge 1 commit into from
Closed

std.json: Adds jsonParse to override parsing behavior #8791

Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
43 changes: 28 additions & 15 deletions lib/std/json.zig
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -1708,6 +1708,9 @@ fn parseInternal(comptime T: type, token: Token, tokens: *TokenStream, options:
}

pub fn parse(comptime T: type, tokens: *TokenStream, options: ParseOptions) !T {
if (comptime std.meta.trait.hasFn("jsonParse")(T)) {
Copy link
Contributor

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

This will only work at the top level: the internal recursion uses parseInternal.

Copy link
Contributor Author

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Whoops, for all examples I tried I somehow never had one where the root did not have jsonParse implemented. What's stopping us from simply keeping a boolean on TokenStream to know if we need the lookahead or not?

Copy link
Contributor Author

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

I have investigated, and the token parser indeed badly needs an overhaul. I couldn't find a simple enough way to get this properly done without a refactor, but I can't do that right now, so for the time being I will close this PR.

return T.jsonParse(tokens, options);
}
const token = (try tokens.next()) orelse return error.UnexpectedEndOfJson;
return parseInternal(T, token, tokens, options);
}
Expand Down Expand Up @@ -2014,12 +2017,12 @@ test "parse into struct with duplicate field" {
const ballast = try testing.allocator.alloc(u64, 1);
defer testing.allocator.free(ballast);

const options_first = ParseOptions{
const options_first = ParseOptions{
.allocator = testing.allocator,
.duplicate_field_behavior = .UseFirst
.duplicate_field_behavior = .UseFirst,
};

const options_last = ParseOptions{
const options_last = ParseOptions{
.allocator = testing.allocator,
.duplicate_field_behavior = .UseLast,
};
Expand All @@ -2043,6 +2046,25 @@ test "parse into struct with duplicate field" {
try testing.expectError(error.UnexpectedValue, parse(T3, &TokenStream.init(str), options_last));
}

test "parse struct with custom parser" {
const T = struct {
const Self = @This();
a: bool,
b: u64,

pub fn jsonParse(tokens: *TokenStream, options: ParseOptions) !Self {
return Self{
.a = true,
.b = try parse(u64, tokens, options),
};
}
};

const r = try parse(T, &TokenStream.init("42"), .{});
try testing.expect(r.a);
try testing.expectEqual(@as(u64, 42), r.b);
}

/// A non-stream JSON parser which constructs a tree of Value's.
pub const Parser = struct {
allocator: *Allocator,
Expand Down Expand Up @@ -2627,6 +2649,9 @@ pub fn stringify(
out_stream: anytype,
) @TypeOf(out_stream).Error!void {
const T = @TypeOf(value);
if (comptime std.meta.trait.hasFn("jsonStringify")(T)) {
return value.jsonStringify(options, out_stream);
}
switch (@typeInfo(T)) {
.Float, .ComptimeFloat => {
return std.fmt.formatFloatScientific(value, std.fmt.FormatOptions{}, out_stream);
Expand All @@ -2648,17 +2673,9 @@ pub fn stringify(
}
},
.Enum => {
if (comptime std.meta.trait.hasFn("jsonStringify")(T)) {
Copy link
Contributor

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

only enum/union/struct can have user traits; it makes more sense to keep them here?

Copy link
Contributor Author

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

This is exactly why I found it reasonable to move it outside: it stops this check from getting repeated in the code without altering behavior. Since I applied the same reasoning to jsonParse and jsonStringify is effectively its pair I thought it was a good idea to have the same logic applied to it.

return value.jsonStringify(options, out_stream);
}

@compileError("Unable to stringify enum '" ++ @typeName(T) ++ "'");
},
.Union => {
if (comptime std.meta.trait.hasFn("jsonStringify")(T)) {
return value.jsonStringify(options, out_stream);
}

const info = @typeInfo(T).Union;
if (info.tag_type) |UnionTagType| {
inline for (info.fields) |u_field| {
Expand All @@ -2671,10 +2688,6 @@ pub fn stringify(
}
},
.Struct => |S| {
if (comptime std.meta.trait.hasFn("jsonStringify")(T)) {
return value.jsonStringify(options, out_stream);
}

try out_stream.writeByte('{');
comptime var field_output = false;
var child_options = options;
Expand Down