Saturday, November 5, 2016

If 6 turned out to be 9

You may have heard the smash hit "If 6 was 9" by Jimi Hendrix (if not there's a link below). In my JavaScript code I have statements like this:

if (6 == 9)
{ // ... then something

You might rightfully wonder why.  What is this guy up to? Has he gone off the edge, or even "jumped the shark"?

The reason I have code like that is that Visual Studio marks all unreachable code as errors, as red dots in the scroll-bar. While I think that's a great feature in an IDE which I'd rather have than not have, I don't quite agree that unreachable code rises to the level of error. It doesn't break things, the program still runs, correctly perhaps. It's good to know the dead code is there, so it can be removed  before going to production. But it's also good to know it was left there on some purpose, for the time being.

The reason I often don't remove unreachable code (right away) is that it it may be an example of good working code. Often it contains an earlier version of something I'm in the process of re-designing. I want to be able to easily switch back to it if needed, if only to see how in fact it did work, when it did. The unreachable code works, it just doesn't do what I want the program to do at the moment, maybe later. Maybe not. Maybe. You want to keep it around.

It might be NEW code which doesn't quite yet work because of the latest changes I have made, or need to make  elsewhere in the program under development.  I still want to be able to test and execute other parts of my program which do not depend on the as-yet-not-ready code.

I could comment it out.  But then I would need to uncomment  it when and if I want to run it. Problem with that is when uncommenting it is easy to uncomment too much, or too little. You can not be sure if what you uncommented ever worked actually.  So, I often like to keep unreachable code as is in my program, during development.

The problem with the IDE marking unreachable code as error is that such "errors"  become noise which can hide real errors, real show-stoppers.

I've discovered over time than one of the biggest time-wasters in development can be the continuous restarting of the debugger. If you KNOW there are errors which will cause it  to crash, perhaps an undeclared variable,  you should fix those errors before restarting the debugger.

You would like the IDE to notify you of any such possible "show-stoppers" before trying to start the show.

And yes it does, for many of such errors. The problem becomes if  you already have 3 "errors"  in your error-list, 3 red-dots in the scroll-bar caused by unreachable code. It then becomes hard to notice when a 4th red dot appears, because of some real error - which you should fix before wasting time on  debugger restart. Only to crash because of an undeclared variable,  fix  that, rinse and repeat. The hour of coding time is soon up, my friend.

To clearly mark unreachable code as INTENTIONALLY unreachable,  I put it inside:  

if (6 == 9)
{ // ... then something

Voila! That segment no longer shows as an error in Visual Studio. BTW:  Had I used 'false'  as the condition the IDE would be "smart"  enough to recognize it as unreachable code  and would report it as error. But Jimi saves the day.

When I see this segment of code later it reminds me of the Jimi Hendrix  song, and makes it clear that this, at least, is not my coding error but something I put there deliberately, for a good reason.

Check it out:

© 2016 Panu Viljamaa. All rights reserved

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