std.io.Reader.readUntilDelimiter* functions lose last byte if it is past the max size

[Vexu]

Seems like this could be resolved by requiring space for the delimiter.

More tests are also needed.

[jmc-88]

Could you elaborate on "this could be resolved by requiring space for the delimiter"? I'm not sure I understand the proposal.

const std = @import("std");

test "9594" {
    const reader = std.io.fixedBufferStream("1234567\n").reader();

    var buf: [3 + 1]u8 = undefined; // I want to read at most 3 byte, + 1 for the delimiter
    try std.testing.expectError(error.StreamTooLong, reader.readUntilDelimiter(&buf, '\n')); // ← still eats the '5'?
    try std.testing.expectEqualStrings("567", try reader.readUntilDelimiter(&buf, '\n')); // ← reads "67\n" instead
}