[cfe-dev] PList output for clang Tidy

[Alexander Kornienko]

Hi Gåbor,

The problem with this approach is that it results in a significant code
duplication:
  * the whole error filtering logic will need to be duplicated for
the AnalyzerDiagnosticConsumer that handles plist output (note that
diagnostic filtering won't work for plist output of analyzer results in
your patch). And it seems that it will require making significantly more
changes to ento::PlistDiagnostics than just making it public and inheriting
from it.
  * plist-formatting the output of non-analyzer diagnostics to a certain
degree duplicates what is being done in PlistDiagnostics (and duplication
will likely increase as the output formats for these two kinds of
diagnostics are brought closer together).

As I've noted earlier, extending DiagnosticsEngine would be one possible
solution (probably not the easiest one, though). Maybe pulling out some
reusable parts will allow to reduce code duplication while basically having
the same design as you propose. I suspect however that the former approach
can result in a more maintainable code.

P.S. I would appreciate if you sent patches via Phabricator for a more
convenient review. Thanks!

-- Alex

On Fri, Mar 27, 2015 at 12:50 PM, Gábor Horváth <xazax.hun at gmail.com> wrote:

> Hi,
>
> I had some free time this week and I started to implement a prototype for
> clang tidy plist output (patches are attached to this mail). In this first
> attempt I tried to keep clang changes minimal. To achieve this, running
> clang tidy generates two separate plist output: one for the reports that
> are generated by the clang static analyzer and one for the reports
> generated by tidy checkers. I try to make these two kinds of plists as
> similar as possible. I did not add note and fixit information to the plists
> yet and the plists which contains reports from tidy checkers do not contain
> a file list. I choose this separate plist design because the
> PathDiagnosticConsumers and DiagnosticConsumers have different life times.
> Supporting one output would add too much extra complexity in my opinion
> (unless the clang diagnostic engine learns to handle path diagnostics).
>
> What is your opinion about the design? Should I continue the
> implementation or should I change the design?
>
> Regards,
> Gábor
>
>
>
> On 12 January 2015 at 16:10, Alexander Kornienko <alexfh at google.com>
> wrote:
>
>> Hi Gábor,
>>
>> On Mon, Jan 5, 2015 at 11:21 AM, Gábor Horváth <xazax.hun at gmail.com>
>> wrote:
>>
>>> On 5 January 2015 at 11:02, Manuel Klimek <klimek at google.com> wrote:
>>>
>>>> +chandler and daniel; I think that are all the chefs we need for this
>>>> particular porridge
>>>>
>>>> On Mon Jan 05 2015 at 10:05:02 AM Gábor Horváth <xazax.hun at gmail.com>
>>>> wrote:
>>>>
>>>>> Hello everyone,
>>>>>
>>>>> The Clang Static analyzer can output the diagnostics in plist format.
>>>>> It is a useful feature, because it is easy to parse that format with 3rd
>>>>> party tools, hence integrating clang tools with others.
>>>>>
>>>>> Unfortunately the plist reporting format is not supported by Clang
>>>>> Tidy. We would like to add plist support to it. This involves a lot of
>>>>> changes both to the format and the public API, so I want your opinion, how
>>>>> to do it.
>>>>>
>>>>> In my opinion we need to extend the plist format to:
>>>>> * Support notes that are not events
>>>>> * Support fixits
>>>>>
>>>>> What do you think, what would be the bast way to extend the format
>>>>> with those informations?
>>>>>
>>>>
>> Ted or Anna can say whether it's possible to extend the plist Static
>> Analyzer output format and what's the best way to do this. Also, as you
>> noted, most of PlistDiagnostics should be factored out and exposed in a
>> form of some API to be reusable. This can be done completely independent of
>> the ClangTidy part of the changes. Ted, Anna and Jordan should be the right
>> people to send relevant patches to.
>>
>>
>>> The plist reporting related functionality is not part of the Clang
>>>>> public API at the moment. The best would be, if the Static Analyzer and
>>>>> regular diagnostics could be reported to the same plist output file. To
>>>>> achieve this, the diagnostic consumer that outputs to the plist should
>>>>> support both PathDiagnostics and regular Diagnostics. It would be
>>>>> redundant to reimplement the whole functionality in Clang Tidy. To reduce
>>>>> the redundancy, we would like to refactor several plist related helper
>>>>> functions out from PlistDiagnostics and make it available in public
>>>>> headers. We would also like to make PlistDiagnostics class available
>>>>> so we can inherit from it. What do you think, what would be the best way to
>>>>> organize these changes?
>>>>>
>>>>
>>>> If I remember correctly, Chandler has long ago proposed to merge the
>>>> different diagnostic types we have into one central clang diagnostic type
>>>> that supports all our use cases.
>>>>
>>>
>> Chandler, do you have any thoughts on this?
>>
>>
>>> I personally would need to see a CL to judge whether it makes sense, but
>>>> generally, I think what you say sounds like it's the right direction (if
>>>> you agree with the sentence above: make clang's basic diagnostic system
>>>> powerful enough to support the analyzer's use cases, and then switch the
>>>> analyzer and clang-tidy to use it).
>>>>
>>>>
>>> In my proposal it would be possible to create a Diag Consumer that can
>>> consume both PathDiagnostics and regular Diagnostics. It would be possible,
>>> to make the same object to consume both Clang and Static Analyzer diags.
>>>
>>
>> The problem is not consuming messages from the Static Analyzer in a
>> different format (ClangTidy already subscribes to PathDiagnostics), but the
>> fact that ClangTidy uses Clang DiagnosticsEngine internally to handle
>> diagnostics from the Static Analyzer, from all checks, and from the
>> compiler. It means that to handle all information from PathDiagnostic we'd
>> need to either extend Clang's diagnostic subsystem or rewrite a significant
>> part of ClangTidy to introduce an alternative way to handle PathDiagnostics
>> inside ClangTidy. It seems to me that the former is a much superior
>> solution.
>>
>> In any case we'd also need to extend the ClangTidyError structure (used
>> to return ClangTidy results to clients) to accommodate additional
>> information from PathDiagnostic.
>>
>> It may not be as clean as merging the two kinds of diagnostics, but I
>>> suspect this approach is faster to implement. In the long term I do agree
>>> that, it would be desirable to use the same mechanisms for both Static
>>> Analyzer and Clang. But I am not sure that, I have enough time for a
>>> refactoring like that.
>>>
>>>
>>>>
>>>> I'd vote for renaming PList to something non-horrible in the process,
>>>> (I still have no idea what the "P" stands for), but that's bikeshedding.
>>>>
>>>
>>> I don't know if we could rename that. PList is not Clang specific, Apple
>>> uses this format in other projects as well.
>>>
>>
>>>
>>>>
>>>> Cheers,
>>>> /Manuel
>>>>
>>>>
>>>
>>> Thanks,
>>> Gábor
>>>
>>
>>
>> Regards,
>> Alex
>>
>
>
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