Cannot define a readonly global with mutable fields

[hramrach]

Reading the documentation I see no option to declare a global readonly (so that it cannot be replaced) but making all its fields mutable.

Understandably this is not a great interface but it's a fact of life that a runtime provides its data to lua code in this fashion.

[alerque]

I don't think it is currently possible to lint for that, nor will I likely have time or interest in figuring it out. If you can figure out a clean way to implement it I'd consider a PR contributing a new config.

[arichard4]

If there are a fixed set of fields that you'd expect to be mutable, you can explicitly mark them out as being mutable on a global read-only like so:

.luacheckrc

stds.mutable_readonly = {
	read_globals={
		x = {
			fields = {
				example_field_name = {
					read_only = false,

				}
			}
		}
	}
}
std = "min+mutable_readonly"

test.lua

x = 3
x.example_field_name = 1

luacheck test.lua
test.lua:1:1: setting read-only global variable x

(If the fields can be tables, you'll also want to add "other_fields = true")

This seems to only work for globals/read_globals defined in a std, not if you define them directly in the config file. I don't know why, and this isn't clearly documented; I found this by playing around with the luacheckrc file a bit. ¯\ (ツ) /¯

[hramrach]

Yes, there is a fixed set of fields that are mutable: all possible fields.

[alerque]

That isn't what "fixed set" means. Is there a master list of all possible top level keys?

[hramrach]

It's basically access to something like the Unix environment - C strings indexed by C strings.

[ale5000-git]

There is also the opposite problem, how make the global mutable but all its field readonly?
When I extend the string library, example:

function string:findsomething()
end

and then I have some global string:

string1
string2

even objects with string fields:
my_object.string3

Then the string itself should be mutable but the function findsomething (or the functions) not.

Note: This is just an example but pose the case I have 100 functions and 100 strings, then I have to manually specify 10000 cases to make the base object read-write but fields read-only?

[ale5000-git]

Why not something like this?

globals = {
	string1 = {
		read_only = false,
		read_only_fields = true,
		fields = {
			findsomething = {}
		},
	},
}