What is the difference between `extends` and `rulesDirectory` in TSLint

Question

The TSLint.json config file (https://github.com/palantir/tslint) supports extends and a rulesDirectory array like so

{
  "extends": [
    "tslint-microsoft-contrib",
    "tslint-config-security"
  ],
  "rulesDirectory": [
    "node_modules/tslint-eslint-rules/dist/rules",
    "node_modules/tslint-microsoft-contrib",
    "node_modules/tslint-config-security"
  ]
}

The docs seem slightly open to interpretation for new users unfamiliar to the tool.

I would appreciate if anyone could clarify a few points on the behaviour of extends and rulesDirectory in relation to use in the VS Code editor and tslinting in general.

1. Does extends only provide a default configuration (if provided by package)?

2. and is this therefore different to rulesDirectory?

   • Does rulesDirectory only provide rules for you to specifically opt-in(and is required if specifying rules in the root tslint.json)?

   • Should I still specify the tslint packages in both extends and rulesDirectory?

3. Assuming extends provides defaults from another tslint config file, would I be able to specify the rulesDirectory and add a rule to override a specific flag?

Concerned because only some of the rules show up in IntelliSense autocompletion and just a few behaviours that I would appreciate more clarity for.

Answer 1

What is the difference between extends and rulesDirectory in TSLint

They are very different.

• extends allows you to apply an existing tslint config and then extend it
• rulesDirectory simply allows you to add directories for custom rules.