types: use readonly array / collection types for user input (#10045)

* types: use readonly arrays

* chore: check on interface properties

* chore: ReadonlyCollection

* chore: exclude EventEmitter methods

* chore: resolve false positive

Author: almeidx

packages/discord.js/.eslintrc.json

@@ -204,6 +204,9 @@
     {
       "files": ["typings/*.ts", "scripts/*.mjs"],
       "parser": "@typescript-eslint/parser",
+      "parserOptions": {
+        "project": "./tsconfig.json"
+      },
       "plugins": ["@typescript-eslint"],
       "rules": {
         "@typescript-eslint/naming-convention": [
@@ -216,6 +219,33 @@
               "match": true
             }
           }
+        ],
+        "no-restricted-syntax": [
+          2,
+          {
+            "selector": "MethodDefinition[key.name!=on][key.name!=once][key.name!=off] > TSEmptyBodyFunctionExpression > Identifier :not(TSTypeOperator[operator=readonly]) > TSArrayType",
+            "message": "Array parameters on methods must be readonly"
+          },
+          {
+            "selector": "MethodDefinition > TSEmptyBodyFunctionExpression > Identifier TSTypeReference > Identifier[name=Collection]",
+            "message": "Parameters of type Collection on methods must use ReadonlyCollection"
+          },
+          {
+            "selector": "TSDeclareFunction > Identifier :not(TSTypeOperator[operator=readonly]) > TSArrayType",
+            "message": "Array parameters on functions must be readonly"
+          },
+          {
+            "selector": "TSDeclareFunction Identifier TSTypeReference > Identifier[name=Collection]",
+            "message": "Parameters of type Collection on functions must use ReadonlyCollection"
+          },
+          {
+            "selector": "TSInterfaceDeclaration TSPropertySignature :not(TSTypeOperator[operator=readonly]) > TSArrayType",
+            "message": "Array properties on interfaces must be readonly"
+          },
+          {
+            "selector": "TSInterfaceDeclaration TSPropertySignature TSTypeReference > Identifier[name=Collection]",
+            "message": "Interface properties of type Collection must use ReadonlyCollection"
+          }
         ]
       }
     }