DustMite, a D test case minimization tool

[KennyTM~]

On May 21, 11 06:01, Vladimir Panteleev wrote:
> Inspired by Tigris Delta and the "Want to help DMD bugfixing? Write a
> simple utility" thread from digitalmars.D.learn. I hope the DMD
> development team will find this useful.
>
> Advantages over Tigris delta:
>
> * Easy to use (takes only two arguments, no need to fiddle with levels)
> * Readable output (comments and indentation are preserved)
> * Native support for multiple files (accepts a path to an entire
> directory for input)
> * Written for D
> * Written in D
> * Not written in Perl
> * Can recognize constructs such as try/catch, function invariants
> (in/out/body)
> * Only 440 lines of source code
>
> If you've never used delta: this is a tool which attempts to shrink
> files by deleting fragments iteratively, as long as the file satisfies a
> user-specified condition (for example, a specific error message when
> passed through the compiler).
>
> Usage:
>
> 1. Formulate a condition command, which should exit with a status code
> of 0 when DustMite is on the right track, and anything else otherwise.
> Example: dmd test.d 2>&1 | grep -qF "Assertion failed"
> 2. Place all the files that dustmite is to minimize in a new directory.
> 3. If you'd like to test your condition command, don't forget to clean
> up temporary files afterwards.
> 4. Run: dustmite path/to/directory test-command
> 5. After a while, dustmite will finish working and create
> path/to/directory.reduced
>
> I've tested it with a self-induced "bug" in std.datetime, it seems to
> work great. If you find that it breaks on something, let me know.
>
> https://github.com/CyberShadow/DustMite
>

Nice tool! I tried to use it to reduce bug 6044, but encountered 2 problems:

1. DustMite will load _all_ files, including the _binary_ ones, which
    is seldom in valid UTF-8 encoding, and that causes a UtfException to
    be thrown from 'save.dump' because 'e.header' contains those invalid
    character. (BTW, Andrei, is it really necessary to include the whole
    invalid string in the exception?!)

2. For 6044, DustMite has overdone. It has reduced to an obviously
    invalid program

       void main() {
           alias Maybe A;
       // ok
           A.Impl!int u;       // error
       }

    but I guess it can't be avoided, since its error message is exactly
    the same as the correct one I reported.