htp: fix case of nested FormField if first formField usage is with single parameter

[jrudolph]

So far, in #2283 the case for tuples was fixed which also worked for nested formField directives in most of the cases but not when the first usage was with a single argument.

Refs #73.

[akka-ci]

Test FAILed.

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Test FAILed.

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Test PASSed.

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Test PASSed.

[johanandren]

Tried to review this and looked at the previous PR but I don't understand how it works, could you give a brief explanation @jrudolph ?

[jrudolph]

See the comments below.

There is also an alternative one line change (with cheats):

toStrictEntity(...).wrap { pdm().asInstanceOf[Directive[_]] }.asInstanceOf[pdm.Out]

but would we like that?

[jrudolph]

That's basically the fix. We want to be sure that the complete inner part of a formField directive is wrapped in a toStrictEntity directive.

The problem in the old version was, that we couldn't prove that pdm() actually is a directive, so we couldn't use wrap.

[jrudolph]

That's the old fix which fixed it for formField('a, 'b), i.e. if there are more than two form fields, than fold the directives starting with toStrictEntity on the outside.

It didn't fix it for the other cases of a single form field, though. One potential solution would be to add toStrictEntity to all the implicits for the single form field above, that would work but would mean that we would add toStrictEntity as many times as we have formFields which would add a bit of overhead.

[jrudolph]

Thinking about it, there's already existing overhead: for every given field, we run the complete unmarshalling which seems wasteful. So, that could be another area of improvement.

[jrudolph]

So, the typesafe fix is to add enough types here (and everywhere) to declare that the result of pdf() above actually is a Directive and not just anything.

That is we add the Directive type here and remove the Directive wrapping in all types below. Note that type Directive1[T] = Directive[Tuple1[T]] etc.

[johanandren]

Thanks for the explanation!

LGTM

[raboof]

Nice to be more explicit about those types anyway

there are some ⇒ utf8 characters that snuck in there

[raboof]

MiMa:

[error]  * method formFields(akka.http.scaladsl.server.directives.FormFieldDirectives#FieldMagnet)java.lang.Object in trait akka.http.scaladsl.server.directives.FormFieldDirectives does not have a correspondent in current version
[error]    filter with: ProblemFilters.exclude[DirectMissingMethodProblem]("akka.http.scaladsl.server.directives.FormFieldDirectives.formFields")
[error]  * method formField(akka.http.scaladsl.server.directives.FormFieldDirectives#FieldMagnet)java.lang.Object in trait akka.http.scaladsl.server.directives.FormFieldDirectives does not have a correspondent in current version
[error]    filter with: ProblemFilters.exclude[DirectMissingMethodProblem]("akka.http.scaladsl.server.directives.FormFieldDirectives.formField")
[error]  * method formFields(akka.http.scaladsl.server.directives.FormFieldDirectives#FieldMagnet)akka.http.scaladsl.server.Directive in trait akka.http.scaladsl.server.directives.FormFieldDirectives is present only in current version
[error]    filter with: ProblemFilters.exclude[ReversedMissingMethodProblem]("akka.http.scaladsl.server.directives.FormFieldDirectives.formFields")
[error]  * method formField(akka.http.scaladsl.server.directives.FormFieldDirectives#FieldMagnet)akka.http.scaladsl.server.Directive in trait akka.http.scaladsl.server.directives.FormFieldDirectives is present only in current version
[error]    filter with: ProblemFilters.exclude[ReversedMissingMethodProblem]

[raboof]

Hmm tricky.

Perhaps we should start planning dropping support for 2.11 (some time after Akka 2.6 is released?) and postponing this PR until then?

[akka-ci]

Test FAILed.

[jrudolph]

I think I fixed the incompatibility now. The idea was to keep the Out type member alongside the new U type member. This way the erased result type is still AnyRef. I added different alternative using @pre213 and @since213 so that we can drop the extra structure once 2.12 support is gone.

[akka-ci]

Test PASSed.

[akka-ci]

Test PASSed.