f31980c18f
* Removing unused/broken daml.bzl rules, adding Scala codegen rule Scala codegen rule: dar_to_scala follows the same approach as dar_to_java with a few differences: - dar_to_scala supports multiple dars as an input - dar_to_scala does not try to compile the generated scala (separation of responsibilities) * Using dar_to_scala to compile quickstart-scala example * Fixing formatting * Add dependency to examples-quickstart-scala-bin So if example does not compile, it can't be published. * Fixing the path to the jar executable * Changing scala codegen rule to rely on zipper instead of jar JDK's jar creates srcjar with timestamped files, zipper doesn't timestamp files. This means we can create reproducible/deterministic/ cacheable srcjars * Addressing code review comments, wrong var name |
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| BUILD.bazel | ||
| codegen.bzl | ||
| README.md | ||
Developer's guide to DAML Scala code generator
For the User's guide to the Scala code generator see:
docs/daml-scala-code-gen-user-guide.rst
Introduction
The DAML Scala code generator produces wrapper classes that correspond to DAML contract templates and DAML user defined types (records/variants that are the right hand side of a DAML type synonym). They are intended to be used by application developers and they provide the same level of type safety as the DAML langauge itself.
Working with Scala macros
The code makes heavy use of Scala macros and quasiquotes.
More information on Scala macros can be found here
There is some great documentation on quasiquotes here In particular, this page is a great reference
You may also find this guide on the Scala Reflection API useful as macros/quasiquotes make use of it. See here
The reference documentation for the Reflection API is available here
I have also found it very useful to use the Scala console to see the abstract syntax tree (AST) structure
showRaw is your friend
You can use the Reflection API's showRaw function to see which
constructors are used in a quasiquoted expression/statement/definition.
From an SBT console open a Scala console with:
> console
Then:
scala> val universe: scala.reflect.runtime.universe.type = scala.reflect.runtime.universe
universe: reflect.runtime.universe.type = scala.reflect.runtime.JavaUniverse@712e80d8
scala> import universe._
import universe._
Then (for example):
scala> showRaw(q"obj.method")
res2: String = Select(Ident(TermName("obj")), TermName("method"))
Use Ctrl-D to get back to SBT console
Understanding the code
The best way to understand the structure of the generated code is to
read DamlContractTemplate.scala and DamlUserDefinedType.scala. The
Scala macros are quite readable and both classes have informative comments.