I've been doing some thinking on how I think it should be:

• Road - build whenever there's an available roadtype, but disable stations when no vehicles are available
• Ship - Same as road - canals and other water infrastructure should be able to be built, but not docks
• Train - Only if there are trains available (makes no sense to me to be able to build rails if you don't have any trains to put them on, so keep as is)
• Aircraft - Only if there are aircraft available (same as trains)

Yay/Nay?

I'm totally OK with your reasoning.

Aircraft: Should heliport building be available when there are not VTOL aircraft available? Regular airport building be available if there are no airplanes (but helicopters/blimps exist)?

That's part of the aircraft build window, not the main toolbar :)
But for consistency with road/railtypes, i guess heliports should be disabled if there are no helicopters available (though airports should be buildable if only helicopters are available, as they have hangars)

I don't understand why this is desirable, nor why it's labeled as a "Fix".

The current behaviour is a feature that someone deliberately added. It's helpful to avoid players mistakenly building infrastructure they can't use. That situation exists in many games with commonly-chosen settings, and the behaviour is consistent between all infrastructure type.

This change makes the behaviour inconsistent between infrastructure types, and opens up inexperienced or just distracted players to frustrating mistakes.

It's of use only in the case where:

1. No road/sea vehicles are available, which is fairly unusual.
2. Someone [for reasons unexplained, either here or in the linked report] wants to build useless infrastructure.
3. They haven't used the setting removed in this series, which allows exactly that behaviour as a non-default option.

(skim-reading the patch, it looks like the option might be non-functional for roadtypes? If so, that would be a real fix)

Why effectively flip the default behaviour, and then remove the option, in favour of a niche use-case rather than consistency and newbie-friendliness?

Roads are special, because you might want to influence the way towns grow, even if you don't have any road vehicles to build

As for VTOL, that's kinda the same as railtypes like monorail/maglev?

I am +/-0 on whether to make the change.

BUT

We ban building currently because it's fricking annoying to build a route then discover there are no vehicles available.

It's an easy mistake to make if the route building tools aren't disabled, and we have not found any other way to assist players to avoid the mistake.

We ban building currently because it's fricking annoying to build a route then discover there are no vehicles available.

It's an easy mistake to make if the route building tools aren't disabled, and we have not found any other way to assist players to avoid the mistake.

Idea on warnings players that while they can build the infrastructure, no vehicles are available: A warning bar that shows up above (or below) the build toolbar. I also like the idea of disabling the station and depot construction tools.

Edit: This can also be extended to ships, so companies can build water infrastructure at all times.

Idea on warnings players that while they can build the infrastructure, no vehicles are available: A warning bar that shows up above (or below) the build toolbar. I also like the idea of disabling the station and depot construction tools.

How about one of those red warning dialogs the first time you open the construction menu? It would leave more space to explain what's going on.

Please leave other languages to eints; could you remove that from this PR? Tnx :)

Divide the roadtype list into 2, with a horizontal separator?

• roads with vehicles available
• roads without vehicles available

??

I like the idea of a separated drop-down list, but I've no idea how we'd label the 2 lists

@TrueBrain Other language modifications, sure, but removals too? Leaving them in would cause compile warnings until the next eints run, which I'm not a particular fan of

We could count the number of vehicles available for each type? And show that in a badge after the name

e.g. "Trails (10 vehicles available)", "Yellow Brick Road (0 vehicles available)".

I'm not convinced by that at all, but it's an idea we can kick around a bit?

Or maybe change the color of the text of the road or rail type when the road/track type is available, but no vehicles are available for that type?

@TrueBrain Other language modifications, sure, but removals too? Leaving them in would cause compile warnings until the next eints run, which I'm not a particular fan of

Wrote it on IRC, but might as well here too :D

This is what we have been doing a lot lately (after frosch123 pointed out we shouldn't be doing it by hand), and it works fine. Sure, till eints runs you will get warnings, but you can run eints manually if you want to (like I did today). Either way, eints does its thing once a day, before the nightly, so worst case you are left with warnings for a whopping 24 hours :)
Removals especially shouldn't be done manually, as it is very hard for a reviewer to spot if you made a mistake, and if you by accident remove the wrong string from other languages, that does more harm. It really is better to leave it to a tool that is designed to take care of such jobs :)

So especially removals of other languages should be left to eints; not to humans :)

As example: #8426 <- only did the renaming, not the removals. This was done by eints here: 7b515fa

PS: manually runs can be done by devs here: https://github.com/OpenTTD/workflows/actions?query=workflow%3A%22Eints+to+Git%22

With #8521 I took a similar but different approach to this PR (in fact, I "stole" some commits :D).

I fully agree with the issue that just because max-road-vehicle is zero, it doesn't mean I shouldn't be able to build roads. And to say: then you have to change a setting, feels a bit weird to me.

So what I basically did is: always enable the toolbar buttons, but disable the build depot/station etc (similar as in last image here). Next, I changed the tooltip to, when hover over, show why they are disabled. I think that informs the player sufficiently what the situation is, while still allowing building roads and canals before you have vehicles available.