[cfe-dev] [PATCH] Fixit for incorrect includes

[Aaron Ballman]

On Tue, Jul 17, 2012 at 1:39 PM, David Blaikie <dblaikie at gmail.com> wrote:
> On Tue, Jul 17, 2012 at 11:35 AM, Aaron Ballman <aaron at aaronballman.com> wrote:
>> On Tue, Jul 17, 2012 at 1:10 PM, David Blaikie <dblaikie at gmail.com> wrote:
>>> On Tue, Jul 17, 2012 at 11:01 AM, Aaron Ballman <aaron at aaronballman.com> wrote:
>>>> On Tue, Jul 17, 2012 at 12:55 PM, David Blaikie <dblaikie at gmail.com> wrote:
>>>>> On Tue, Jul 17, 2012 at 10:48 AM, Aaron Ballman <aaron at aaronballman.com> wrote:
>>>>>> On Tue, Jul 17, 2012 at 12:10 PM, David Blaikie <dblaikie at gmail.com> wrote:
>>>>>>> On Tue, Jul 17, 2012 at 9:14 AM, Aaron Ballman <aaron at aaronballman.com> wrote:
>>>>>>>> This patch creates a fixit for include directives where the file could
>>>>>>>> not be found when using angle brackets, but can be found when using
>>>>>>>> quotes.  The converse is not needed since quoted includes will search
>>>>>>>> angle bracket locations by default.
>>>>>>>>
>>>>>>>> Eg)
>>>>>>>> #include <header.h>  // can be found via #include "header.h" instead
>>>>>>>>
>>>>>>>> Thoughts?
>>>>>>>
>>>>>>> Seems like a neat idea to me - but I'm not an authoritative sign-off.
>>>>>>>
>>>>>>> You used NULL as null constants for 2 of the conditional operators,
>>>>>>> then 0 for the third - that seems inconsistent. You might want to
>>>>>>> check what the prevailing style is in this file & stick to that
>>>>>>> (generally in LLVM, '0' seems to be winning as the authoritative null
>>>>>>> pointer constant, I believe).
>>>>>>
>>>>>> Easy enough to rectify (I'll standardize on 0) -- this was a copy from
>>>>>> above, so I'll fix up there as well.
>>>>>>
>>>>>>> Did you consider adding this case to the existing fixit testing files?
>>>>>>> They're already a grab-bag of things that can be fixed (this helps
>>>>>>> keep the test suite fast by not adding more separate test file
>>>>>>> executions) & this seems like it'd be at home there.
>>>>>>
>>>>>> I thought about it, but it strikes me as different enough to warrant
>>>>>> its own test case.  Specifically, the fixit behavior is kind of
>>>>>> tricky.  Because the fixit writes out a separate file, but in a
>>>>>> different directory, I have to be a bit sneaky otherwise the header
>>>>>> file isn't available.  This is because the temp file goes to the
>>>>>> Output directory, but the header file remains in the FixIt directory.
>>>>>> To work around this, I copy the testcase to a temp file, modify the
>>>>>> testcase file directly with the fixit,
>>>>>
>>>>> Why can't you modify the temp file directly instead? (& you'd have to
>>>>> copy the header over too, I suppose - you can identify the temp
>>>>> directory with %T which means you can copy to fixed name files if
>>>>> that's important (as it would be for the header name): %T/foo.cpp or
>>>>> whatever)
>>>>
>>>> You learn something new every day!  I didn't realize you could use %T
>>>> for the temp directory.  Now the testcase looks like:
>>>>
>>>> // RUN: %clang_cc1 -fsyntax-only -verify %s
>>>> // RUN: cp %s %t
>>>> // RUN: cp %S/fixit-include.h %T
>>>> // RUN: not %clang_cc1 -fsyntax-only -fixit %t
>>>> // RUN: %clang_cc1 -Wall -pedantic %t
>>>>
>>>> Which is cleaner (to me).  Thanks!
>>>>
>>>>> & yeah, arguable whether the existing fixit cases should be burdened
>>>>> with this mucking about - I don't mind too strongly either way.
>>>>
>>>> Since include errors are fatal,
>>>
>>> This actually raises a good question/point: when Clang encounters
>>> fatal errors it basically stops, right? (it doesn't produce more
>>> diagnostics) That's incorrect if we've provided a fixit and recovered
>>> from the error - when fixits are provided we should recover as if the
>>> code were written that way. With your change as it stands we
>>> "successfully" apply fixits for this code:
>>>
>>> #include <non_existent.h>
>>> int main(float) {
>>> }
>>>
>>> because we didn't provide the error about main. What we should get is
>>> the error about main and no fixit application because we encountered
>>> an unfixable error.
>>
>> I'm not actually recovering with my patch -- I'm still early returning
>> out of HandleIncludeDirective.
>
> Yep, that's probably incorrect. If Clang issues a fixit, it
> should/must recover as if the user wrote the code the way the fixit
> suggests.
>
>> So if this is possible to "fixit",
>> does that mean this really shouldn't be a fatal error in this case?
>
> I believe so, yes.

That seems like a larger change than I was hoping for.  What are the
consequences of this?  Do we want to have a fatal and non-fatal
variant of the error (fatal for when no fixit is available)?

~Aaron