The quiet ignoring of deprecated GMT 4 options

[PaulWessel]

Major options in GMT have changed over time . This annoys long-time users so we only make such changes when we must, and we have let the "old ways" be allowed for quite some time now (GMT 5 was released in 2013). There seems to be several types of compatibilities:

1. Some modules used one option letter (say -A) for a feature and now uses another letter (say -B) for the same feature. Examples might be -W for histogram width in pshistogram which now is -Tinc since this allows us to have a much more flexible setup for bins. If the user specifies the old -W we do figure out what to do, but we do not give a deprecated message.
2. In other modules, such as psrose, the old -C was replaced by -E, and if we find -C we print "Option -C for mode-vector(s) is deprecated; use -E instead.". However, it is only printed if the compatibility level is 5.
3. For some common options from the past we quietly accept them. Here is the code:

		case 'Z':
			if (!gmt_M_compat_check (GMT, 4)) error++;
			break;
		case 'E':
			if (gmt_M_compat_check (GMT, 4))
				error += GMT->common.p.active == false;
			else
				error++;
			break;
		case 'm': if (!gmt_M_compat_check (GMT, 4)) error++; break;
		case 'S': if (!gmt_M_compat_check (GMT, 4)) error++; break;
		case 'F': if (!gmt_M_compat_check (GMT, 4)) error++; break;

So those with long memory will remember that -F used to set pixel grid registration (currently -r), -S used to set 2-d spline boundary conditions (currently -n), -Z set 3-D z-level (now in -p), -E set perspective view (-p), -m told GMT 4 to expect a multi-segment file (now automatic). With the GMT_COMPATIBILITY = 4 stuck as is forever, no message at all may be given (e.g., #3455). I have to do this to get an error:

gmt blockmedian -R-2/2/-2/2 -I1 -S t.txt --GMT_COMPATIBILITY=5
blockmedian [ERROR]: Unrecognized option -S

Note that the check here is crazy since blockmedian never had a -S but it gets caught up in the common option parsing. I also seem to remember that we pushed the GMT_MSG_COMPAT verbose warning down the list so as not to annoy people. Yes, adding -Vc to the blockmedian call gives no error, so that part is broken I guess.

We need to make some changes. Here is a list of possibilities:

1. In GMT modern mode, we should absolutely, positively not honor old deprecated options. What a nightmare, but there is no code that takes this into account presently.
2. When do we increase the default setting on GMT_COMPATIBILITY? 2025? Surely, with 6.1 coming out 7 years after GMT 5, maybe inch it up to at least 5? If people are still running ancient GMT 4 script they expect to work then they do need to get with the program and make changes or just install GMT 4 for those tasks.
3. GMT 4-ever: Leave as is but go back and add annoying compatibility messages when these things happen, don't quietly let bad shit go down.

Feedback please, @GenericMappingTools/core.

[anbj]

As the NTPsec folks put it,

We have deliberately jettisoned support for ancient legacy hardware and operating systems in order to ship code that is security-hardened, simpler, drastically less bulky, easier to understand, and easier to maintain.

Maybe, at one point, is it necessary to force people into entering the new millennium.

[PaulWessel]

Yes, perhaps we can get some ear plugs to avoid listening to the screaming and kicking.

[seisman]

Compatibility with old syntax makes the codes bigger and more difficult to read and maintain, especially for new developers/contributors.

I think we can improve the deprecation warnings like:

Option -C is deprecated. Use -E instead. The old syntax will be deprecated in GMT 6.X.0. 

Before releasing GMT 6.X.0, we then can remove the old backward compatibility codes.

[stale]

This issue has been automatically marked as stale because it has not had activity in the last 90 days. It will be closed if no further activity occurs within 7 days. Thank you for your contributions.

[stale]

This issue has been automatically marked as stale because it has not had activity in the last 90 days. It will be closed if no further activity occurs within 7 days. Thank you for your contributions.