From 5ba3a2722374e3fc6b1afd447e92ca4dcfdb9d6f Mon Sep 17 00:00:00 2001
From: fagossa <fagossa@gmail.com>
Date: Wed, 24 Jul 2019 15:55:14 +0200
Subject: [PATCH] Fix #8474

This commit does the following :
* List the available constructors while creating a module, when no available constructor is found
* Add a new unit test
* Add a new utility function in ConstructorUtils
---
 .../scala/play/api/inject/ModulesSpec.scala   | 22 +++++++++++++++++++
 .../play/libs/reflect/ConstructorUtils.java   | 18 +++++++++++++++
 .../main/scala/play/api/inject/Module.scala   |  5 ++++-
 3 files changed, 44 insertions(+), 1 deletion(-)

diff --git a/core/play-guice/src/test/scala/play/api/inject/ModulesSpec.scala b/core/play-guice/src/test/scala/play/api/inject/ModulesSpec.scala
index f83b3e2b4e2..6eead1274ed 100644
--- a/core/play-guice/src/test/scala/play/api/inject/ModulesSpec.scala
+++ b/core/play-guice/src/test/scala/play/api/inject/ModulesSpec.scala
@@ -10,6 +10,7 @@ import org.specs2.matcher.BeEqualTypedValueCheck
 import org.specs2.mutable.Specification
 import play.api.Configuration
 import play.api.Environment
+import play.api.PlayException
 import play.{ Environment => JavaEnvironment }
 
 class ModulesSpec extends Specification {
@@ -63,6 +64,22 @@ class ModulesSpec extends Specification {
       }
     }
 
+    "list current constructor parameters when any match" in {
+      val env = Environment.simple()
+      val conf = Configuration(
+        "play.modules.enabled" -> Seq(
+          classOf[InvalidConfigModule].getName
+        )
+      )
+
+      Modules.locate(env, conf) must throwA[PlayException].like {
+        case e =>
+          val firstConstructorParameters  = "(com.typesafe.config.Config, java.lang.String, long)"
+          val secondConstructorParameters = "(com.typesafe.config.Config, java.lang.String)"
+          e.getMessage must contain(s"$firstConstructorParameters, $secondConstructorParameters")
+      }
+    }
+
   }
 
 }
@@ -78,3 +95,8 @@ class ScalaGuiceModule(val environment: Environment, val configuration: Configur
 class JavaGuiceConfigModule(val environment: JavaEnvironment, val config: Config) extends AbstractModule {
   override def configure(): Unit = ()
 }
+
+class InvalidConfigModule(val config: Config, val ignored: String) extends AbstractModule {
+  def this(config: Config, ignored: String, useless: Long) = this(config, ignored)
+  override def configure(): Unit = ()
+}
diff --git a/core/play/src/main/java/play/libs/reflect/ConstructorUtils.java b/core/play/src/main/java/play/libs/reflect/ConstructorUtils.java
index ffd21bb2284..928779b33a9 100644
--- a/core/play/src/main/java/play/libs/reflect/ConstructorUtils.java
+++ b/core/play/src/main/java/play/libs/reflect/ConstructorUtils.java
@@ -18,6 +18,7 @@
 
 import java.lang.reflect.Constructor;
 import java.lang.reflect.Modifier;
+import java.util.Arrays;
 
 /** Imported from apache.commons.lang3 3.6 */
 public class ConstructorUtils {
@@ -115,6 +116,23 @@ public static <T> Constructor<T> getMatchingAccessibleConstructor(
     return result;
   }
 
+  /**
+   * Finds the class names of all accessible constructors.
+   *
+   * @param <T> the constructor type
+   * @return the constructors parameters, empty array if no matching accessible constructor found
+   */
+  public static <T> String[][] getConstructorParameters(final Class<T> type) {
+    Constructor[] allConstructors = type.getDeclaredConstructors();
+    return Arrays.stream(allConstructors)
+        .map(
+            cons ->
+                Arrays.stream(cons.getParameterTypes())
+                    .map(Class::getCanonicalName)
+                    .toArray(String[]::new))
+        .toArray(String[][]::new);
+  }
+
   /**
    * Learn whether the specified class is generally accessible, i.e. is declared in an entirely
    * {@code public} manner.
diff --git a/core/play/src/main/scala/play/api/inject/Module.scala b/core/play/src/main/scala/play/api/inject/Module.scala
index 1324d8c94a7..7b88306e266 100644
--- a/core/play/src/main/scala/play/api/inject/Module.scala
+++ b/core/play/src/main/scala/play/api/inject/Module.scala
@@ -171,7 +171,10 @@ object Modules {
           tryConstruct()
         }
         .getOrElse {
-          throw new PlayException("No valid constructors", "Module [" + className + "] cannot be instantiated.")
+          val parameters: Array[Array[String]] = ConstructorUtils.getConstructorParameters(moduleClass)
+          throw new PlayException(s"""No valid public constructors for ${moduleClass.getCanonicalName}. Expected one of:
+            ${parameters.map(_.mkString("(", ", ", ")")).mkString(", ")}
+            """.stripMargin, "Module [" + className + "] cannot be instantiated.")
         }
     } catch {
       case e: PlayException       => throw e