Tslint: Confused by the configuration document

[EFanZh]

According to the configuration document:

rules?: { [name: string]: RuleSetting }: A map of rule names to their configuration settings.

• These rules are applied to .ts and .tsx files.
• Each rule is associated with an object containing:
• options?: any: An array of values that are specific to a rule.
• severity?: "default" | "error" | "warning" | "off": Severity level. Level "error" will cause exit code 2.
• A boolean value may be specified instead of the above object, and is equivalent to setting no options with default severity.
• Any rules specified in this block will override those configured in any base configuration being extended.
• Check out the full rules list here.

To my understanding, the document says a rule should be associated with an object like this:

{
    "options": ["option1", "option2", "option3"],
    "serverity": "some value"
}

Or a boolean:

true

Or another boolean:

false

Is my understanding correct? If so, does specifying true has the same meaning as specifying false?

The document says the value of "options" is an array, for a rule like no-empty whose type is a string, should I enclose the string with an array?

Also, I saw many rule examples specifying an array with a leading true:

"indent": [true, "spaces", 4]

"interface-name": [true, "never-prefix"]

"max-classes-per-file": [true, 5, "exclude-class-expressions"]

I couldn‘t find anything about this in the document. What does the leading true mean?

[cyrilgandon]

After reading the function that parses those rules (https://github.com/palantir/tslint/blob/master/src/configuration.ts#L392), I assume that:

• The new correct way to pass options is with { "options": ["option1", "option2", "option3"], "severity": "some value" }
• The documentation is outdated, because "indent": [true, "spaces", 4] is considered legacy (see the comment // old style: array)
• "indent": [true, "spaces", 4] is strictly equivalent to "indent": { "options": ["spaces", 4] }

For boolean:

if (typeof ruleConfigValue === "boolean") {
        // old style: boolean
        ruleArguments = [];
        ruleSeverity = ruleConfigValue ? defaultRuleSeverity : "off";
    }

So:

• "indent": true is strictly equivalent to "indent": { "options": []}
• "indent": false is strictly equivalent to "indent": { "options": [], "severity": "off"}

[EFanZh]

Thanks for clearing that up. Maybe the documentation should be updated to address this. It is really confusing for new users.