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我正嘗試使用Circe創建一個隱式編碼器。然而,這個編碼器將使用註釋創建,因此我使用了Scalameta。這是我的代碼。然而,編譯器抱怨在quasiquotes中有一個覆蓋語句。使用scala meta和quasiquotes定義隱式編碼器
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)
}
}
"""
}
}
構建文件如下:
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: 宏註釋不能擴展(對於最常見的原因是,你需要啓用宏觀天堂插件;另一種可能性是,您嘗試在定義它的同一編譯運行中使用宏註釋)
謝謝@AlexeyRomanov,這是一個愚蠢的錯誤。但是,當我嘗試在case類上使用該註釋時,我仍然遇到問題,出現以下錯誤:[error] /Users/ibenardetelevis/Personal/annotation/src/main/scala/Mdsol.scala:25:宏註釋可能(最常見的原因是您需要啓用宏觀天堂插件;另一種可能性是您嘗試在定義它的同一編譯運行中使用宏註釋) ' – igalbenardete
通過路徑判斷,Mdsol .scala'在同一個項目中。如果是這樣,這正是錯誤消息中描述的第二個原因。如果你只是想測試它,將Mdsol移動到src/test/scala中,如果你在其他地方需要它,將你的項目分成兩個模塊。 –
爲防萬一您也有理由1,請參閱http://scalameta.org/tutorial/#Setupbuild。 –