Improved error when proj_create doesn't recognize definition

[frewsxcv]

#include <proj.h>
#include <stdio.h>

int main() {
    PJ* pj_point = proj_create(0, "a b c d e f g h i j");
    if (pj_point) {
        printf("proj_create succeeded\n");
    } else {
        int errno = proj_context_errno(0);
        const char* error_string = proj_errno_string(errno);
        printf("%s\n", error_string);
    }
    return 0;
}

If PROJ doesn't recognize the definition provided to proj_create, the error that gets returned is generic error of unknown origin which makes it hard for users finding out what went wrong

[frewsxcv]

One other thing to add is the proj_create documentation recommends retrieving the errno if the call fails:

If creation of the transformation object fails, the function returns 0 and the PROJ error number is updated. The error number can be read with proj_errno() or proj_context_errno().

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[frewsxcv]

Does anyone know where the relevant code is? I might have capacity to make this change

[direvus]

Hi @frewsxcv, running your sample code I get:

proj_create: unrecognized format / unknown name
Unknown error (code 4096)

Maybe this has been improved since you raised the issue?

I think "proj_create: unrecognized format" is clear enough to point users in the right direction. Is there anything about it you'd want to change?

[frewsxcv]

Thanks for the update!

[frewsxcv]

Hi @frewsxcv, running your sample code I get:

proj_create: unrecognized format / unknown name
Unknown error (code 4096)

Maybe this has been improved since you raised the issue?

I think "proj_create: unrecognized format" is clear enough to point users in the right direction. Is there anything about it you'd want to change?

The proj_create: unrecognized format is getting logged by the logger, from what I understand. Unknown error (code 4096) is the actual string that gets returned, which is what would get displayed to the user, which isn't so helpful.

[direvus]

OK @frewsxcv, thanks, I think I understand the problem better now.

I think this works better if we have proj_create set the error code to INVALID_OP_WRONG_SYNTAX ("Invalid PROJ string syntax") when the underlying function throws a ParsingException. Does that work for you?

With this change, running your test program outputs as follows:

proj_create: unrecognized format / unknown name
Invalid PROJ string syntax

[frewsxcv]

@direvus Yep, that's perfect. Thanks!