Suggestion: Use typescript to parse JSON config file

[ajafff]

TypeScript@2.5 uses its own parser to parse tsconfig.json files. We could use ts.readConfigFile or ts.parseConfigFileTextToJson for tslint.json files as well.
This API allows comments and trailing commas (and even tolerates single quotes, but returns an error for each single quoted string). It can also be used for better error reporting as it contains way more details than exceptions thrown by JSON.parse.

Before v2.5 the function only accepts comments, but that's probably OK as a fallback because that's also what the current implementation of tslint does.

Related: #1721

[ajafff]

An update on this: ts.parseConfigFileTextToJson does not support negative numbers. Currently TSLint core rules don't expect negative numbers, but it could break configurations with custom rules.

I'll open an issue in the typescript repo to ask if this is intended.

[ajafff]

microsoft/TypeScript#19552 landed in TypeScript. The fix will be released with version 2.7.0
That means we cannot use it until we drop support for all typescript versions older than 2.7.0

[JoshuaKGoldberg]

#1071 is also open for moving to cosmiconfig. Do you have any thoughts or preferences here @ajafff?

[JoshuaKGoldberg]

💀 It's time! 💀

TSLint is being deprecated and no longer accepting pull requests for major new changes or features. See #4534. 😱

If you'd like to see this change implemented, you have two choices:

• Recommended: Check if this is available in ESLint + typescript-eslint ✅
• Not Recommended: Fork TSLint locally 🤷‍♂️

👋 It was a pleasure open sourcing with you!

If you believe this message was posted here in error, please comment so we can re-open the issue!

[JoshuaKGoldberg]

🤖 Beep boop! 👉 TSLint is deprecated 👈 (#4534) and you should switch to typescript-eslint! 🤖

🔒 This issue is being locked to prevent further unnecessary discussions. Thank you! 👋