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我正尝试使用Circe创建一个隐式编码器。然而,这个编码器将使用注释创建,因此我使用了Scalameta。这是我的代码。然而,编译器抱怨在quasiquotes中有一个覆盖语句。使用scala meta和quasiquotes定义隐式编码器
class HalResource extends StaticAnnotation {
inline def apply(defn: Any): Any = meta {
val q"..$mods class $tName (..$params) extends $template {..$stats}" = defn
q"object $tName {${createApply(tName)}}"
}
private def createApply(className: Type.Name): Defn.Def = {
q"""
import _root_.io.circe.Json
import _root_.io.circe.syntax._
import _root_.io.circe.Encoder
implicit def encoder = Encoder[$className] {
override def apply(a: $className): Json = {
val (simpleFields: Seq[Term.Param], nonSimpleFields: Seq[Term.Param]) =
params.partition(field => field.decltpe.fold(false) {
case _: Type.Name => true
case _ => false
})
val embedded: Seq[(String, Json)] = nonSimpleFields.map(field => field.name.syntax -> field.name.value.asJson)
val simpleJsonFields: Seq[(String, Json)] = simpleFields.map(field => field.name.syntax -> field.name.value.asJson)
val baseSeq: Seq[(String, Json)] = Seq(
"_links" -> Json.obj(
"href" -> Json.obj(
"self" -> Json.fromString("self_reference")
)
),
"_embedded" -> Json.fromFields(embedded),
) ++ simpleJsonFields
val result: Seq[(String, Json)] = baseSeq ++ simpleJsonFields
Json.fromFields(result)
}
}
"""
}
}
构建文件如下:
import sbt.Keys.{scalaVersion, scalacOptions}
val circeVersion = "0.8.0"
lazy val circeDependencies = Seq(
"io.circe" %% "circe-core",
"io.circe" %% "circe-generic",
"io.circe" %% "circe-parser"
).map(_ % circeVersion)
lazy val commonSettings = Seq(
name := "Annotation",
version := "1.0",
scalaVersion := "2.12.2",
scalacOptions ++= Seq("-unchecked", "-deprecation", "-feature"),
resolvers += Resolver.sonatypeRepo("releases")
)
lazy val macroAnnotationSettings = Seq(
addCompilerPlugin("org.scalameta" % "paradise" % "3.0.0-M9" cross CrossVersion.full),
scalacOptions += "-Xplugin-require:macroparadise",
scalacOptions in (Compile, console) ~= (_ filterNot (_ contains "paradise"))
)
lazy val projectThatDefinesMacroAnnotations = project.in(file("annotation-definition"))
.settings(commonSettings)
.settings(
name := "HalResource",
libraryDependencies += "org.scalameta" %% "scalameta" % "1.8.0" % Provided,
macroAnnotationSettings)
lazy val annotation = project.in(file("."))
.settings(commonSettings)
.settings(macroAnnotationSettings)
.settings(
libraryDependencies ++= circeDependencies
).dependsOn(projectThatDefinesMacroAnnotations)
因此,我仍然得到: 宏注释不能扩展(对于最常见的原因是,你需要启用宏观天堂插件;另一种可能性是,您尝试在定义它的同一编译运行中使用宏注释)
谢谢@AlexeyRomanov,这是一个愚蠢的错误。但是,当我尝试在case类上使用该注释时,我仍然遇到问题,出现以下错误:[error] /Users/ibenardetelevis/Personal/annotation/src/main/scala/Mdsol.scala:25:宏注释可能(最常见的原因是您需要启用宏观天堂插件;另一种可能性是您尝试在定义它的同一编译运行中使用宏注释) ' – igalbenardete
通过路径判断,Mdsol .scala'在同一个项目中。如果是这样,这正是错误消息中描述的第二个原因。如果你只是想测试它,将Mdsol移动到src/test/scala中,如果你在其他地方需要它,将你的项目分成两个模块。 –
为防万一您也有理由1,请参阅http://scalameta.org/tutorial/#Setupbuild。 –