Tslint: Add severity of errors

[lachvoj]

Please add severity of errors into rules to distinguish if it's functionality issue or just code readability issue.

[Lexicality]

I support this - I would very much like to be able to fail the build due to class-name violations, but not comment-format.
It'd be great if you could do it in the same way as ESLint where you can specify off, warning or error when activating a rule in the config.

[readme42]

:+1: this would be great!

[jkillian]

:+1: I like this idea as well

[pgatilov]

:+1: please!

[jkillian]

Related to #629 perhaps. Rules could have a default severity that could be overriden in tslint.json

[JoshuaKGoldberg]

+1, this would be great

Would it be feasible to add a "warnings"option to tslint.jsons?

Edit: alternately, it would be cool to expand the tslint.json format to allow for more complex settings:

{
    "defaults": {
        "severity": "error"
    },
    "rules": {
        "radix": true,
        "semicolon": {
            "rule": "always",
            "severity": "warning"
        }
    }
}

...in the future, if some sort of options like auto-fixing were to be added, they could go in there too?

[jkillian]

I'm thinking about implementing this soon, I like the idea of each rule taking an object as configuration. (This is also very nice code-wise, since rules only accept a boolean or array right now, we can implement this feature with no backwards-compat breakage.)

I like a format similar to what's specified above:

"rules": {
  "align": {
    "mode": "off",
    "options": ["parameters", "arguments"]
  }
}

"mode": could be either "off", "warn", "error", or "on". If "on", the default level of warning would be used.

Open questions:

• Should we stick with the ESLint way of things and also allow 0, 1, 2, and 3 instead of "off", "warn", "error", "on", etc?
• Do we want an "on" option at all?
• I like the name "mode" because it's easy to type, but should we pick a different name?

I also like how this proposal makes it easy to add in additional options for things like auto-fixing, as mentioned above.

This would probable be implemented in two steps:

1. Adding in the code to handle object configurations for rules.
2. Writing the code to make different modes act differently (exit status, etc)

[Lexicality]

I'm _fairly_ sure the number severities in ESLint are backwards compatibility only. Unless you use the same rule format (eg an array rather than an object) there's not much point I would say.
Perhaps "level" instead of mode?

[jkillian]

Realized #629 is a better issue to discuss rule configuration schema issues, so moved some comments over there!

[adidahiya]

shipped in 5.0

[ErikCupal]

@adidahiya Sorry if I missed something, but how to turn all errors back to warnings in version 5.0? I tried this so far..

{
    "defaults": {
        "severity": "warning"
    },
    ...
}

[adidahiya]

@ErikCupal "defaultSeverity": "warning". see https://palantir.github.io/tslint/usage/configuration/

[nchen63]

defaultSeverity only applies to rules in the current file and doesn't affect rules in the recommended config. Right now we don't have a way to reset the inherited severity levels besides overriding the severity one by one.

[adidahiya]

@nchen63 ah, I didn't realize that. I think it would be more intuitive for defaultSeverity to be a global setting that applies to all rules that have been loaded -- it should override any base configurations

[emilio-martinez]

@adidahiya I agree. I've faced this issue myself where a bunch of rules are throwing an error instead of a warning for "defaultSeverity": "warning", i.e., I thought that was meant to be global. Is there a place where that specific issue is being tracked? (since this is closed, I mean)

[adidahiya]

@emilio-martinez yes, #2569 (linked right above your comment)

[emilio-martinez]

@adidahiya cool. Thank you!