Rule wishlist

[evaera]

This issue will track any rules we'd like to offer for typescript-eslint.

Some of these might already exist as base rules, like no-null-keyword

• Don't allow null
• Don't allow void expression
• Don't allow with statement
• Don't allow debugger statement
• Don't allow == or !=
• Don't allow block labels
• Don't allow regular expressions
• Don't allow accessing function/class prototype or indexing any other value from a function
• Don't allow yielding outside of async funtions
• Don't allow reserved Lua keywords
• Don't allow non-modules (e.g. don't allow global execution mode; must have one import/export)
• Don't use this outside of an object or class
• Server/client API access
• Don't allow exports in non-ModuleScripts
• ModuleScripts must export
• Don't allow dynamic import() statement
• Don't allow use of values typed as any
• Show invalid identifier names (with odd characters like $) as errors
• Don't allow rest operator for destructuring

[Validark]

• Don't allow LuaTuples in conditionals without indexing
  • Also, band-aid protect against string.find/match being checked naively (just because I think it is a common and obvious mistake).
    • It is also on my to-do list to add a few more string methods to roblox-ts so string.find doesn't need to be used in TS for every case. Add string.includes/string.indexOf methods roblox-ts#598
  • The equivalent error in the roblox-ts compiler can be removed. I think the compiler should only stop you from writing invalid code, and eslint should help you write better code (as well as clue you in when your program would make rbxtsc error)
• Don't allow for..in loops (there is a rule for disallowing for..in array loops we can steal code from)
• Ban the delete operator Support delete statement roblox-ts#547
• Ban getters/setters Disallow Getters/Setters roblox-ts#457
• Disallow arguments (built-in namespace in functions) Disallow fake arguments (in functions) roblox-ts#513
• Ban awaiting a never-promise (there is probably a rule for this) Warn developers if awaiting a non-promise roblox-ts#632 related: TS.await should work with non-promises roblox-ts#110
• Automatically fix Vector3/CFrame numeric operators to function calls bearing in mind Vector3.unm is missing roblox-ts#113
  • Auto-convert unary minus to .mul(-1)
• Don't allow spreading non-objects Protect against spreading non-objects roblox-ts#562
• Don't allow new methods (static or otherwise, unless Roblox gets first-class functions) Disallow new instance method in classes roblox-ts#536
• Warn developers they should NaN-check from RemoteEvents/RemoteFunctions Warn developers they should NaN-check from RemoteEvents/RemoteFunctions roblox-ts#600
• Don't allow implicitly casting booleans to numbers where applicable
• Enforce that metamethods are not defined as methods, but member functions Enforce that metamethods are defined as non-methods roblox-ts#466
• Ban destructuring methods from built-in TS namespaces like Object We should disallow destructuring from Object roblox-ts#425 or Roblox Instances Ban footgun of destructuring a method from an object roblox-ts#465 or strings Object literal destructuring should disallow built-in methods roblox-ts#318
• Ban indexing of non-existing Symbol.iterators We should disallow indexing Symbol.iterator from IterableFunctions roblox-ts#462
• Ban using methods which intersect with roblox-ts built-in ones Compiler should error on methods on a unioned Array/Non-Array roblox-ts#420
• Ban using fake namespaces without calling a method Disallow using Object other than calling one of its methods roblox-ts#366
• Don't allow spreading or iterating over unioned array | set | map
• Disallow indexing of unioned array | object We should disallow indexing union types of Object/Array roblox-ts#426
• Suggest changing arr.insert() at position 0 to arr.unshift(), arr.remove() at last position as arr.pop(), etc
• Disallow comma expressions with a good explanation for why Compiler errors are not verbose enough roblox-ts#637
• ? Automatically fix Instance.new or UDim2.new to new Instance and new UDim2, etc
• ? Automatically change : method call tokens to . (depends on what the AST does with the token)
• ? Imports should be in scope @rbxts/
• ? Give a good hint when accessing arbitrary indexes of Instances, e.g. part.InstanceName.InstanceName
• ? Indexing a nullable type tells you to use an if statement (future, ?.)
• Force LuaTuple destructuring in variable assignments, e.g. const a = FindPartOnRay() should be const [a] = . Also should work in for loops like gmatch loops.
• Disallow Object.keys,Object.values,Object.entries,Object.assign, and all other applicable functions which can be used to iterate through the members of Instances, since Instances can't be iterated through at run-time.
• No in operator on instances, no rest or spread destructuring instances
• Players.GetChildren should be Players.GetPlayers()

Throwing it out there:

• ? Disallow LuaTuples being used in user-defined ways. Only allow LuaTuples for built-ins.
• ? Suggest Object catastrophes be switched to Maps. (index signatures are hard)
• ? Warn when a number is defined too precisely, e.g. 0.00000000000000000000001
• ? Discuss disallowing import = require() statements ?

To be determined:

• Unary plus operator?

[osyrisrblx]

Future Rules

• Warn to use ?? when using || on a number/string.