False positives + query ideas for variables with leading underscores. #655

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1. xiemaisi commented on Dec 10, 2018

   

   xiemaisi

   on Dec 10, 2018

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   It's a convention (...)

   I'm sure you're right, but could we have a reference for that convention? I'd also like to point out that in the examples you give you should be able to just omit the _* variables altogether:

   const [a, , c, d, e, f] = something
2. s0 commented on Dec 10, 2018

   

   s0

   on Dec 10, 2018

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   I'm sure you're right, but could we have a reference for that convention?

   Here are a few of places:

   • Typescript compiler's behaviour for compiler flags --noUnusedParameters and --noUnusedLocals

     Parameters declaration with names starting with _ are exempt from the unused parameter checking. e.g.:

     function returnNull(_a) { // OK
         return null;
     }

     (If we decide it's not a widely-enough used convention for JS, we could potentially enable it for TS only)

   • ESLint documentation on no-unused-vars. Uses prefix underscores as an example for the argsIgnorePattern option:

     The argsIgnorePattern option specifies exceptions not to check for usage: arguments whose names match a regexp pattern. For example, variables whose names begin with an underscore.

   • Ruby's community coding conventions:

     Prefix with _ unused block parameters and local variables. It's also acceptable to use just _ (although it's a bit less descriptive). This convention is recognized by the Ruby interpreter and tools like RuboCop and will suppress their unused variable warnings.

   I'd also like to point out that in the examples you give you should be able to just omit the _* variables altogether

   Ah yes!
3. xiemaisi commented on Dec 11, 2018

   

   xiemaisi

   on Dec 11, 2018

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   OK, thanks, that looks fairly widely accepted.

   If we decide it's not a widely-enough used convention for JS, we could potentially enable it for TS only

   We could, but to be honest I doubt we'll lose any interesting results by enabling it for JS as well.

   👍React with 👍1Reacted by Sam Lanning
4. semmle-qlci

   closed this as completedin #656on Dec 12, 2018