Debug tslint error

[mxl]

Bug Report

• TSLint version: 5.2.0
• TypeScript version: 2.3.2

Currently if an error is thrown while applying tslint rule it's logged as warning and only error message is included in log. This complicates debugging such cases. For example see #2696 where tslint printing the following log line:

Warning: Cannot read property 'kind' of undefined

without any details like stacktrace.

I suggest to add debug or verbose option that will enable output of stacktrace.
If that's ok I can submit a PR.

I'm not alone http://stackoverflow.com/q/43577136/746347

[ajafff]

TypedRule used to throw an exception when tslint was not run with --project --type-check. That caused some trouble when using the same tslint.json in CLI and for example in vscode-tslint.
To fix this everything was wrapped in try-catch.

Reverting/changing that behavior was also on my agenda, because I think it causes more trouble than it's actually worth.

There are several options:

• Remove the try-catch, replace the throw in TypedRule#apply with showWarningOnce('...'); return [];
  • still outputs a warning when not type checking
  • bugs in rules will crash the process
    • you notice that something when wrong
    • you get the whole stack trace
    • otherwise editor plugins might just swallow the warning
    • easier debugging by pausing at the uncaught exception
• log the whole stack trace by default
• add an option --debug or --verbose as described above and ...
  • throw
  • log the whole stack trace

Thoughts? @nchen63 @adidahiya @andy-hanson

[andy-hanson]

👍 for printing the whole stack trace. It's pretty cryptic otherwise, since there's no indication that the message is being printed because of an exception.

[ajafff]

@andy-hanson printing the stack trace by default doesn't play well will the exception thrown in TypedRule. Instead of throwing there, it should just call showWarningOnce and return.