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Macro implicits don't work outside package

See original GitHub issue

Issue Description

Hey. Check this out: https://github.com/japgolly/upickle/commit/9a976af73ed46eeb7364829e457a973719ed9a7b

Eg2 compiles but Eg1 doesn’t.

[error] upickle/jvm/shared/test/scala/upickle/blah/blah.scala:7: uPickle does not know how to read [upickle.elsewhere.YYY]s; define an implicit Reader[upickle.elsewhere.YYY] to teach it how
[error]   def blah(j: String): YYY = read[YYY](j)
[error]                                       ^
[warn] one warning found
[error] one error found
[error] upickle/js/shared/test/scala/upickle/blah/blah.scala:7: uPickle does not know how to read [upickle.elsewhere.YYY]s; define an implicit Reader[upickle.elsewhere.YYY] to teach it how
[error]   def blah(j: String): YYY = read[YYY](j)
[error]                                       ^
[warn] one warning found
[error] one error found

Issue Analytics

State:
Created 8 years ago
Comments:17 (13 by maintainers)

Top GitHub Comments

1reaction

l15k4commented, Feb 24, 2016

I knew that this issue made it so risky to choose upickle for a project and yet I did it again and here I am, chasing this issue for 3 hours… Even though my code is entirely within a single package and I know about a few other tricks that usually solved it like proper ordering and avoiding nested classes… And still god damn :

The referenced trait [[Aggregation]] does not have any sub-classes. This may happen due to a limitation of scalac (SI-7046) given that the trait is not in the same package. If this is the case, the hierarchy may be defined using integer constants.

The incremental compiler in Intellij is the biggest trap because it works works works until you do sbt clean and find it doesn’t work god knows why after 2 hours of development…

Anyway, rules of thumb :

keep all components of model (trait, case classes) and serialization invocation within a single package
don’t use nested classes
keep AST ordering of components in your scala files, ie. if some case class inherits from a sealed trait, have this trait declared above the case class, etc. etc. etc.
???

Btw the @japgolly’s trick with “implicit realization close to data source” doesn’t work for me…

0reactions

lihaoyicommented, Dec 19, 2017

Moot with 0.5.1