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Can create a crash by returning an invalid fuzzer from andThen #160

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jwoudenberg opened this issue May 24, 2017 · 4 comments · May be fixed by #183
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Can create a crash by returning an invalid fuzzer from andThen #160

jwoudenberg opened this issue May 24, 2017 · 4 comments · May be fixed by #183
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bug fuzzers

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@jwoudenberg
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This fuzzer will run into a Debug.crash:

myFuzz : Fuzzer Int
myFuzz =
    int |> andThen (\_ -> frequency [])

Error message reads:

    This test failed because it threw an exception: "Error: Ran into a `Debug.crash` in module `Fuzz.Internal` on line 63
    The message provided by the code author is:

        This shouldn't happen: Fuzz.Internal.unpackGenVal"

Looking at the code I don't think there's a ton we can do about this, but I wanted to report anyway. andThen, by its nature, ensures we only know whether a fuzzer is valid after running it which conflicts with the idea of fuzzer validness itself.
@jwoudenberg jwoudenberg mentioned this issue May 24, 2017
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jwoudenberg commented May 24, 2017 •
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Found another crashing fuzzer in this category. This one is unrelated to andThen and seems fixable.

myFuzz : Fuzzer Int
myFuzz =
    frequency
        [ ( 1, frequency [] )
        ]

@mgold mgold self-assigned this May 25, 2017
@jwoudenberg jwoudenberg mentioned this issue May 28, 2017
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@mgold mgold added fuzzers and removed fuzzers labels Jun 7, 2017
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mgold commented Jul 9, 2017

Is this fixed by #183?

@jwoudenberg
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@mgold Yes!

@jwoudenberg jwoudenberg linked a pull request Jul 9, 2017 that will close this issue
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@rtfeldman rtfeldman mentioned this issue Aug 12, 2018
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mgold commented Aug 14, 2018

Current behavior:

↓ Example
✗ #160

    This test failed because it threw an exception: "Error: Ran into a `Debug.crash` in module `Fuzz.Internal`
    
    This was caused by the `case` expression between lines 54 and 59.
    One of the branches ended with a crash and the following value got through:
    
        Nothing
    
    The message provided by the code author is:
    
        Returning an invalid fuzzer from `andThen` is currently unsupported"

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Removing Fuzz.andThen
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