Report row and line number when generating errors, instead of an absolute position

[CarterLi]

Is your feature request related to a problem? Please describe.

Currently yyjson reports

Error: failed to parse JSON config file `config.jsonc` at pos 513: unexpected character

Describe the solution you'd like

Error: failed to parse JSON config file `config.jsonc` at line X, row Y: unexpected character

Describe alternatives you've considered

Error: failed to parse JSON config file `config.jsonc` at pos X,Y: unexpected character

Additional context

I use yyjson for parsing config files. It would be easier to find where the problem is if users can get its line and row number.

[ibireme]

I think it would be better to add a new helper function.

[TkTech]

A new api that returns detailed parser/ error information as structured data instead of an error message would be fantastic - it would let me make the python yyjson wrapper truly drop-in to replace the standard library. Right now, I can't properly populate the JSONDecoderError exception because of the lack of pos. A similar issue in simdjson has been open for years.

[ibireme]

I've come up with a new API, let's see if it meets the needs? @CarterLi @TkTech

/**
 Locate the line and column number for a byte position in a string.
 This can be used to get better description for error position.
 
 @param str The input string.
 @param len The byte length of the input string.
 @param pos The byte position within the input string.
 @param line A pointer to receive the line number, starting from 1.
 @param col  A pointer to receive the column number, starting from 1.
 @param chr  A pointer to receive the character index, starting from 0.
 @return true on success, false if `str` is NULL or `pos` is out of bounds.
 @note Line/column/character are calculated based on Unicode characters for
    compatibility with text editors. For multi-byte UTF-8 characters,
    the returned value may not directly correspond to the byte position.
 */
yyjson_api bool yyjson_locate_pos(const char *str, size_t len, size_t pos,
                                  size_t *line, size_t *col, size_t *chr);

[TkTech]

I believe this checks all the boxes 👍 . I'm in Korea until the 15th and will test it in py_yyjson shortly after I return.

[CarterLi]

I think it's good enough for position locating. I'm waiting for a new release then.

Another question: we are reporting unexpected character, which is a general error and may not be very helpful. Can we report what charactor yyjson expects?

For example: fastfetch-cli/fastfetch#866 (comment)

Can we report a comma is expected?

[ibireme]

Can we report a comma is expected?

Error messages like these could be easily improved, please create a new issue and I will address it soon.

[CarterLi]

I found it a little bit hard to use with yyjson_read_file, since you don't have the json string but have to load the file content manually

[ibireme]

I found it a little bit hard to use with yyjson_read_file, since you don't have the json string but have to load the file content manually

The yyjson_read_file function reads the file into a string, which gets modified during parsing, so this string can only be used once and can't be used for row and column locating. It seems more appropriate to add a yyjson_locate_pos_file function to read the file again.

[CarterLi]

The yyjson_read_file function reads the file into a string, which gets modified during parsing, so this string can only be used once and can't be used for row and column locating

Got it.

It seems more appropriate to add a yyjson_locate_pos_file function to read the file again.

Seems not necessary IMO. yyjson_locate_pos should be ok.

[ibireme]

Seems not necessary IMO. yyjson_locate_pos should be ok.

Okay, then I won't reopen it.