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Linter checks for the switch(rand(L, H)) pattern#302

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SpaceManiac merged 4 commits intoSpaceManiac:masterfrom
pali6:switch-rand-range-checks
Feb 8, 2022
Merged

Linter checks for the switch(rand(L, H)) pattern#302
SpaceManiac merged 4 commits intoSpaceManiac:masterfrom
pali6:switch-rand-range-checks

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@pali6 pali6 commented Feb 7, 2022 •
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A pattern such as

switch(rand(1, 3))
  if(1)
    foo()
  if(2)
    bar()
  if(3)
    baz()

is not uncommon in SS13 code. Sadly, it is also not uncommon for people to add new cases to a longer switch of this form and forget to change the rand arguments at the top. This PR adds a linter warning for when the rand range is not fully covered by the cases and for when a case lies completely outside of the rand range.

This currently generates 7 warnings on tgstation master. Sadly, it is (at least to me) not quite clear if the omissions of a part of the rand range are intentional there or not. However, I believe that even if they are intentional it is worth adding the missing part of the range as a case with empty body explicitly to make the intent clear to future developers.

As a less related (but perhaps more important) addition this PR now also adds a warning for switch branches of the form if(X || Y) which is pretty much always a mistake and should instead be if(X, Y). This lint generates 5 warnings on current tg code, seemingly all being actual mistakes.

@pali6
added checks for the switch(rand(_,_)) pattern
0a00a0c 
if the range is not fully covered by cases a warning is thrown
if a case is outside of the rand range a warning is thrown
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pali6 commented Feb 7, 2022 •
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Warnings emitted on tgstation master for reference:

code/modules/mob/mob_helpers.dm, line 103, column 3:
warning: Switch branches on rand() with range 1 to 20 but no case branch triggers for 2

code/modules/mob/mob_helpers.dm, line 142, column 3:
warning: Switch branches on rand() with range 1 to 15 but no case branch triggers for 6

code/datums/brain_damage/severe.dm, line 182, column 2:
warning: Switch branches on rand() with range 1 to 6 but no case branch triggers for 6

code/datums/components/singularity.dm, line 300, column 3:
warning: Elements in a switch-case branch separated by ||, this is likely in error and should be replaced by a comma

code/datums/components/singularity.dm, line 303, column 2:
warning: Elements in a switch-case branch separated by ||, this is likely in error and should be replaced by a comma

code/modules/surgery/advanced/lobotomy.dm, line 54, column 2:
warning: Switch branches on rand() with range 1 to 4 but no case branch triggers for 4

code/modules/hydroponics/hydroponics_chemreact.dm, line 15, column 2:
warning: Switch branches on rand() with range 0 to 100 but no case branch triggers for 0

code/game/machinery/requests_console.dm, line 319, column 3:
warning: Elements in a switch-case branch separated by ||, this is likely in error and should be replaced by a comma

code/modules/vending/_vending.dm, line 500, column 4:
warning: Switch branches on rand() with range 1 to 100 but no case branch triggers for 26

code/modules/power/singularity/singularity.dm, line 341, column 3:
warning: Elements in a switch-case branch separated by ||, this is likely in error and should be replaced by a comma

code/modules/power/singularity/singularity.dm, line 344, column 2:
warning: Elements in a switch-case branch separated by ||, this is likely in error and should be replaced by a comma

code/modules/ruins/lavalandruin_code/elephantgraveyard.dm, line 137, column 2:
warning: Switch branches on rand() with range 1 to 8 but no case branch triggers for 8

sohpeach
sohpeach reviewed Feb 7, 2022
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SpaceManiac
SpaceManiac approved these changes Feb 8, 2022
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Extremely good, thank you

@SpaceManiac SpaceManiac merged commit 0a121f6 into SpaceManiac:master Feb 8, 2022
@pali6 pali6 deleted the switch-rand-range-checks branch February 8, 2022 01:11
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KIBORG04 commented Feb 9, 2022 •
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Can you make it possible to disable warning warning Switch branches to rand() with a range from 1 to 6, but without branch triggers for 6 in configuration ? It is not always possible to solve this by inserting the missing IFs. Example:

/proc/some_func()
    for(var/i in 1 to 10)
        switch(rand(1, 20)
            if(1 to 2)
                ..code..
            if(3 to 15)
                ..code..
            if(16 to 20)
                ???
        do_post_switch()

If I replace ??? to break than get the wrong result, to continiue the same, to return the same. And there are no other options.

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SpaceManiac commented Feb 10, 2022

I recommend leaving it blank with an explanatory comment:

switch(rand(1, 20))
    if(1 to 9)
        bad_effect()
    if(10)
        // Neutral roll, do nothing.
    if(11 to 20)
        good_effect()

This also works fine with else in the final position, but for some reason not on the final if, but you can use a lone semicolon in that case:

switch(rand(1, 20))
    if(1 to 17)
        get_hurt()
    if(18 to 20)
        ; // Defense succeeded, no damage.

@KIBORG04 KIBORG04 mentioned this pull request Feb 10, 2022
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@pali6 pali6 mentioned this pull request Feb 10, 2022
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@pali6 @KIBORG04 @SpaceManiac @sohpeach