Update config-luaurc.md

Update proposal to fix known issues

rfcs/config-luaurc.md

@@ -20,8 +20,10 @@ applied. When multiple files are used, the file closer to the .lua file override
 .luaurc is a JSON file that can also contain comments and trailing commas. The file can have the following keys:
 
 - `"mode"`: type checking mode, can be one of "nocheck", "nonstrict", "strict"
-- `"language"`: legacy specification of type checking mode, contains `"mode"` key - e.g. `{ "language": { "mode": "strict" } }`. Supported for backwards compatibility with existing .robloxrc files.
-- `"lint"`: linting settings; points to an object that contains keys corresponding to the names of linting rules (see https://luau-lang.org/lint) or `"*"` that means "all rules"; the values must be one of "disabled", "enabled", "fatal".
+- `"lint"`: lints to enable; points to an array of string literals that correspond to the names of linting rules (see https://luau-lang.org/lint), or `"*"` that means "all rules"
+- `"nolint"`: lints to disable; points to an array of string literals or `"*"`
+- `"lintErrors"`: a boolean that controls whether lint issues are reported as errors or warnings (off by default)
+- `"typeErrors"`: a boolean that controls whether type issues are reported as errors or warnings (on by default)
 - `"globals"`: extra global values; points to an array of strings where each string names a global that the type checker and linter must assume is valid and of type `any`
 
 Example of a valid .luaurc file:
@@ -29,28 +31,34 @@ Example of a valid .luaurc file:
 ```json5
 {
 	"mode": "nonstrict",
-	"lint": {
-		"*": "fatal",
-		"LocalUnused": "disabled",
-	},
+	"lint": "*",
+	"nolint": ["LocalUnused"],
+	"lintErrors": true,
 	"globals": ["expect"] // TestEZ
 }
 ```
 
+In addition to the JSON file, for consistency this proposal suggests allowing to *enable* lints on a per-file basis with `--!lint` hot comment, just like you can disable them with `--!nolint`.
+
+Note that in absence of a configuration file, we will use default settings: mode will be set to nonstrict, a set of lint warnings is going to be enabled by default (this proposal doesn't detail that set - that will be subject to a different proposal), type checking issues are going to be treated as errors, lint issues are going to be treated as warnings.
+
+## Design -- compatibility
+
+Today we support .robloxrc files; this proposal will keep parsing legacy specification of configuration for compatibility:
+
+- Top-level `"language"` key can refer to an object that has `"mode"` key that also defines language mode
+- Top-level `"lint"` key can refer to an object that has lint names as keys and `"disabled"`/`"enabled"`/`"fatal"` as values.
+
+These keys are only going to be supported for compatibility and only when the file name is .robloxrc (which is only going to be parsed by internal Roblox command line tools but this proposal mentions it for completeness).
+
 ## Drawbacks
 
 The introduction of configuration files means that it's now impossible to type check or lint sources in isolation, which complicates the code setup.
 
 File-based JSON configuration may or may not map cleanly to environments that don't support files, such as Roblox Studio.
 
-Support for two ways to specify the mode, "mode" and "language"/"mode", complicates specification a bit.
-
 Using JSON5 instead of vanilla JSON limits the interoperability.
 
-Making the default set of linting passes fatal requires enumerating them one by one, as "*": "fatal" means "enable all linting passes and make them fatal" (unlike -Werror).
-
-Making the type checking issues visible but non-fatal is impossible.
-
 ## Alternatives
 
 It's possible to consider forcing users to specify the source settings via `--!` comments exclusively. This is problematic as it may require excessive amounts of annotation though, which this proposal aims to simplify.