allow parameterless components to be used. fixes #124

zalando · Jan 17, 2019 · 4a93c0e · 4a93c0e
1 parent 1001284
commit 4a93c0e
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Showing 3 changed files with 72 additions and 6 deletions.
diff --git a/macros/src/main/scala/org/zalando/grafter/macros/ReaderMacro.scala b/macros/src/main/scala/org/zalando/grafter/macros/ReaderMacro.scala
@@ -49,11 +49,11 @@ object ReaderMacro {
 
             // if there are no case class parameters we need to create a fake
             // "unit" parameter to avoid clashes with the "transitiveReader" implicit created by the @readers
-            // annotation. In return the @returns annotation provides an implicit Reader[A, Unit]
+            // annotation. In return the @readers annotation provides an implicit Reader[A, Unit]
             if (caseclassParameters.isEmpty)
               outputs(c)(classTree, className, companionTree) {
                 q"""
-                 implicit def reader[$genericTypeName, $tp](implicit unitReader: cats.data.Reader[$genericTypeName, Unit], ..$implicitReaderParameters): cats.data.Reader[$genericTypeName, $className[${tp.name}]] = {
+                 implicit def reader[$genericTypeName, $tp](implicit unitReader: cats.data.Reader[$genericTypeName, org.zalando.grafter.macros.GrafterUnit], ..$implicitReaderParameters): cats.data.Reader[$genericTypeName, $className[${tp.name}]] = {
                    cats.data.Reader { r =>
                      // to avoid unused value warning
                      if (true) unitReader else unitReader
@@ -75,6 +75,20 @@ object ReaderMacro {
             }
 
           case Nil =>
+            if (caseclassParameters.isEmpty)
+              outputs(c)(classTree, className, companionTree) {
+                q"""
+
+                 implicit def reader[$genericTypeName](implicit unitReader: cats.data.Reader[$genericTypeName, org.zalando.grafter.macros.GrafterUnit], ..$implicitReaderParameters): cats.data.Reader[$genericTypeName, $className] = {
+                   cats.data.Reader { r =>
+                     // to avoid unused value warning
+                     if (true) unitReader else unitReader
+                     new ${TypeName(klassName)}
+                   }
+                 }
+               """
+              }
+            else
             outputs(c)(classTree, className, companionTree) {
               q"""
          implicit def reader[$genericTypeName](implicit ..$readerImplicitParameters): cats.data.Reader[$genericTypeName, $className] = {
@@ -99,6 +113,14 @@ object ReaderMacro {
 
 }
 
+case class GrafterUnit()
+
+object GrafterUnit {
+  implicit def unitReader[A]: cats.data.Reader[A, org.zalando.grafter.macros.GrafterUnit] =
+    cats.data.Reader(_ => org.zalando.grafter.macros.GrafterUnit())
+
+}
+
 class reader extends StaticAnnotation {
   def macroTransform(annottees: Any*): Any = macro ReaderMacro.impl
 }
diff --git a/macros/src/main/scala/org/zalando/grafter/macros/ReadersMacro.scala b/macros/src/main/scala/org/zalando/grafter/macros/ReadersMacro.scala
@@ -59,10 +59,6 @@ object ReadersMacro {
               q"""
                 ..$implicitReaders
                 ..$implicitTransitiveReaders
-
-                implicit def unitReader: cats.data.Reader[$className, Unit] =
-                  cats.data.Reader(_ => ())
-
                 ..$readerIdentity
               """
             }

diff --git a/tests/src/test/scala/org/zalando/grafter/ParameterlessComponentSpec.scala b/tests/src/test/scala/org/zalando/grafter/ParameterlessComponentSpec.scala
@@ -0,0 +1,48 @@
+package org.zalando.grafter.macros
+
+
+/**
+ *  This is a compilation test to check that a component without parameters
+ *  can still be injected. see #124
+ */
+object ParameterlessComponentSpec {
+  @readers
+  case class ApplicationConfiguration(httpConfig: HttpConfig, additionalConfig: AdditionalConfig)
+
+  /**
+   * For a nested configuration you need to annotate the nested elements with the @readers annotation
+   * as well
+   */
+  @readers
+  case class HttpConfig(cfg1: HttpSubConfig1, cfg2: HttpSubConfig2)
+
+  case class HttpSubConfig1(port: Int)
+  case class HttpSubConfig2(host: String)
+  case class AdditionalConfig(config3: String)
+
+  @reader
+  case class HttpClient(config: HttpSubConfig2)
+
+
+  @reader
+  case class SomeService(client: HttpClient)
+
+  @reader
+  case class SomeServiceWithoutParameters()
+
+  @reader
+  case class WebApplication(someService: SomeService, emptyService: SomeServiceWithoutParameters)
+
+
+  object MyApp extends App {
+
+    val config = ApplicationConfiguration(
+        HttpConfig(HttpSubConfig1(80),  HttpSubConfig2("bla")),
+        AdditionalConfig("3")
+    )
+
+    val app = WebApplication.reader[ApplicationConfiguration].apply(config)
+
+  }
+}
+