Invoking code generated by an annotation processor

Wed Feb 10 20:59:44 UTC 2016

Thanks Jon for your fast answer. It's quite disappointing but it's better
to know it early.
It's sad to see how much effort we have put in our annotation processor,
that it's a good idea but fails because of some general java ecosystem
issue.

Though, talking of the issue with team mates, it became more clear. Let me
try to rephrase them more accurately than in my first mail.

It seems to me that the design of javac could be improved to accommodate
these 2 scenarios :

   1. in case of a parse error (for instance a missing ; a bad brace, etc.)
   , javac should stop everything and report the actual problem, without
   getting any further into the analysis and not report any linkage problem
   (because javac would know that annotation processors ain't gonna run and
   that can create false positive about missing linkages. All other parse
   errors should be reported.). It seems to me this would be a healthy "fail
   early" design.
   2. in case of a linkage error (for instance having a non existing import
   / calling a non existing method, etc.) then we should run the annotation
   processors on the partial AST. This mechanism is already in place to
   accomodate code generation.
   Then the linkage problems should be resolved and take into account the
   generated code, and only the remaining problems should show up. This is
   where javac actually fails because it reports all problems, including those
   that can be resolved by the code that is actually generated. Javac reports
   problem from a previous internal stage, it doesn't match the latest state
   it could reach internally where only 1 problem could not be resolved, the
   one that was not related to invoking generated code, it reports all
   linkages problem exactly like if no code was generated and no annotation
   processor had run.

Really, there is no way for javac to support those 2 scenarios ? I got the
strong feeling that it should but I understand my knowledge of javac has
huge holes. I have been surprised by the complexity of the compiler's code.

Thx again for your answer, it's been tremendously appreciated; there are
just a handful people would could have been able to answer my question I am
very happy someone actually did take the time to do it.

Stephane

2016-02-10 11:41 GMT-08:00 Jonathan Gibbons <jonathan.gibbons at oracle.com>:

>
>
> On 02/10/2016 09:09 AM, Stéphane NICOLAS wrote:
>
> I am facing a problem with Javac : I got a sweet annotation processor that
> generates a DSL and I invoke the generated code from my main code.
>
> Everything works fine except when there is an error in my main code : if I
> got a compile error in the main code, not related to the generated code,
> like a missing comma (parsing problem), or calling an inexisting method
> (linkage problem), then all calls to the annotation processor are marked as
> errors by the compiler.
>
> Ideally I am just looking for a way to get rid of those error messages,
> and keep only the original one that fails to compile.
>
> AFAIK, javac should support this scenario but it doesn't support it in a
> very convenient way and I don't understand exactly why..
>
> After reafing the javac code, open jdk 7 & 8, I realized that :
>
> Annotation processors are not called if there is any error to compile the
> code. As the annotation processor are not triggered, the calls to generated
> code get mark as an error.
>
> However, I could, by playing with shouldStopPolicy (+if error and if no
> error) trigger the annotation processor and generate the code. But still, I
> would receive in this case the errors related to calling the generated
> code. Like if the generated code was not taken into account, like if I was
> receiving errors from a previous compilation steps.
>
> I understand that javac parses the code, if it fails there, I will receive
> only an error about the actual problem. And this is great. I just want this
> error to show up, not any other, and it works fine. (Though I am wondering
> if this is always true even I clean my build & generated files before
> compiling)
>
> If there is a linkage problem in my original code, like calling an
> non-existent method, javac will relax the error and trigger the annotation
> processors and try to let them generate the code to see if the generated
> code that satisfies the linkage problem. But then, though there is a state
> in which javac will successfully satisfy all linkage related to generated
> code but not the other linkage error, I get all calls to generated code
> marked as errors. This is my problem. It looks like this internal state of
> the compiler is never accessible and errors returned do not match this
> state but more probably a previous internal state in which all linkage
> errors are aggregated and returned.
>
> I think there is a solution to achieve what I want but I couldn't find
> one. And the situation is bad : it may actually cancel the development of
> the annotation processor lib I am developing. Just because the errors are
> flooding the actual problem in the code.
>
> Would you have some time to advise me, and help me to make the lib work as
> expected.
> My goal is just to get only errors that are not related to calling
> generated code if they are not those who fail the compilation. I don't want
> to see my errors polluted by those calls if they are not responsible for
> breaking the compilation.
>
> Stephane
>
>
> Stephane,
>
> In general, there is no convenient solution for you here, because there is
> no way for javac to predict what unresolved symbols may or may not be
> generated by the annotation processor that has yet to be run.  And in
> general, it is not desirable to run annotation processors if the input
> source code has significant errors, such as syntax errors.
>
> -- Jon
>
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