Use scalameta for codegen #205
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I find this easier to work with than the existing printer, which is basically doing fancy string concatenation, because scalameta gives us a nice AST with which to model the code. It also provides quasiquotes, which are very convenient, and it indents the code correctly for us. (Unfortunately we end up losing a lot of the type information when we do a catamorphism, and we have to add it back in using casting. I haven't found a nice way around this. Open to suggestions.) If people are happy with this approach, I suggest we remove `higherkindness.skeuomorph.mu.print` and update the Mu sbt plugin to use the new scalameta-based codegen. In future we could also migrate the OpenAPI codegen to scalameta.
| val codegen: higherkindness.skeuomorph.mu.Protocol[Mu[MuF]] => String = { | ||
| p: higherkindness.skeuomorph.mu.Protocol[Mu[MuF]] => | ||
| val tree = higherkindness.skeuomorph.mu.codegen.protocol(p, streamCtor) | ||
| //println(tree.structure) |
| streamCtor: (Type, Type) => Type.Apply | ||
| )(implicit T: Basis[MuF, T]): Pkg = { | ||
| val packageName = protocol.pkg.getOrElse("proto") | ||
| val packageTerm = packageName.parse[Term].get.as[Term.Ref] |
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I'm not familiar with the scalameta API but is the get safe?
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Nope! Need to have a think about error handling. Maybe the whole thing should return an Either. That would also mean we could make the casts slightly more palatable by making them return an Either instead of throwing an exception.
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Done. Everything now returns Either[String, ?].
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| val expected = expectation(ct, useIdiom) | ||
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| (actual.clean must beEqualTo(expected.clean)) :| s""" |
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Rather than stripping whitespaces and doing string comparison, we can parse the expected output into a scalameta tree and compare trees instead.
Everything now returns an Either[String, ?]
This is to check that the `knownCoproductTypes` optimization is being applied correctly. Also removed the test for printing a protocol, as I'm about to deprecate that feature.
This is so it will be executed even if you call `codegen.schema` directly instead of calling it via `codegen.protocol`.
cb372
changed the title
Forgot it was also used to import things like the names of serialization types, compression types, etc. It's easier, cleaner and less error-prone to import the package once than remember to fully qualify everything in that package.
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I'm pretty happy with this now. I've requested a review from @pepegar as he wrote the original printer. @juanpedromoreno Do you want to have a look too? |
docs/docs/docs/index.md
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| val avroSchema: Schema = new Schema.Parser().parse(definition) | ||
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| val toMuSchema: Schema => Mu[MuF] = | ||
| scheme.hylo(transformAvro[Mu[MuF]].algebra, fromAvro) | ||
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| val printSchemaAsScala: Mu[MuF] => String = | ||
| muprint.schema.print _ | ||
| codegen.schema(_).right.get.syntax |
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I know this is an example, but, does it make sense if we show something like this? (taking into account that Either is right-biased):
codegen.schema(_).map(_.syntax)
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@pepegar I'm going to merge this, but feel free to review later if you have time. I'm happy to make another PR to address any comments. |
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Sure thing, sorry @cb372 , I reviewed today mornign but didn't submit the approved! Great job :) |
I find this easier to work with than the existing printer, which is basically doing fancy string concatenation, because scalameta gives us a nice AST with which to model the code. It also provides quasiquotes, which are very convenient, and it indents the code correctly for us.
(Unfortunately we end up losing a lot of the type information when we do a catamorphism, and we have to add it back in using casting. I haven't found a nice way around this. Open to suggestions.)
The codegen takes a stream type constructor as an argument, allowing the sbt plugin to choose between FS2 and Monix for streaming more cleanly than it does currently. It also includes an
import higherkindess.mu.rpc.protocol._statement so we don't have to add the import in the sbt plugin.If people are happy with the scalameta approach, I suggest we remove
higherkindness.skeuomorph.mu.printand update the Mu sbt plugin to use the new scalameta-based codegen. In future we could also migrate the OpenAPI codegen to scalameta. In this PR I've kepthigherkindness.skeuomorph.mu.printbut added a@deprecatedannotation.