[Kotlin Java8] Support closures

The implementation of t he `ConstantPoolTypeIntrospector` did not fully
support closures.

Using a closure without  scoped variables would result
in a null pointer exception.  E.g:

```java
Given("^A statement with a body expression$") { assertTrue(true) }
```

 This is resolved check if the member reference method equals the magic
 constant "INSTANCE" and return no type arguments.

Related issues:
 - #1123
 - #1126

 This fixes #1123

History.md

@@ -1,5 +1,6 @@
 ## [2.0.0-SNAPSHOT](https://github.com/cucumber/cucumber-jvm/compare/v1.2.5...master) (In Git)
 
+* [Java8, Kotlin Java8] Support java 8 method references ([#1140](https://github.com/cucumber/cucumber-jvm/pull/1140) M.P. Korstanje) 
 * [Core] Show explicit error message when field name missed in table header ([#1014](https://github.com/cucumber/cucumber-jvm/pull/1014) Mykola Gurov) 
 * [Examples] Properly quit selenium in webbit examples ([#1146](https://github.com/cucumber/cucumber-jvm/pull/1146) Alberto Scotto)
 * [JUnit] Use AssumptionFailed to mark scenarios/steps as skipped ([#1142](https://github.com/cucumber/cucumber-jvm/pull/1142) Björn Rasmusson)

java8/src/main/java/cucumber/runtime/java8/ConstantPoolTypeIntrospector.java

@@ -35,6 +35,11 @@ public Type[] getGenericTypes(Class<? extends StepdefBody> clazz, Class<? extend
         final String[] member = getMemberReference(constantPool);
         final int parameterCount = interfac3.getTypeParameters().length;
 
+        // Kotlin lambda expression without arguments or closure variables
+        if (member[REFERENCE_METHOD].equals("INSTANCE")) {
+            return handleKotlinInstance();
+        }
+
         final jdk.internal.org.objectweb.asm.Type[] argumentTypes = jdk.internal.org.objectweb.asm.Type.getArgumentTypes(member[REFERENCE_ARGUMENT_TYPES]);
 
         // If we are one parameter short, this is a
@@ -75,6 +80,10 @@ private static Type[] handleLambda(jdk.internal.org.objectweb.asm.Type[] argumen
         return typeArguments;
     }
 
+    private static Type[] handleKotlinInstance() {
+        return new Type[0];
+    }
+
     private static String[] getMemberReference(ConstantPool constantPool) {
         int size = constantPool.getSize();
 

kotlin-java8/README.md

@@ -0,0 +1,6 @@
+Java 8 Bindings for Kotlin
+==========================
+
+This module only runs tests.
+
+You can use `cucumber-java` or `cucumber-java8` directly in Kotlin.

kotlin-java8/pom.xml

@@ -0,0 +1,93 @@
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+
+    <parent>
+        <groupId>io.cucumber</groupId>
+        <artifactId>cucumber-jvm</artifactId>
+        <relativePath>../pom.xml</relativePath>
+        <version>2.0.0-SNAPSHOT</version>
+    </parent>
+
+    <artifactId>cucumber-kotlin-java8</artifactId>
+    <packaging>jar</packaging>
+    <name>Cucumber-JVM: Kotlin Java8</name>
+
+    <properties>
+        <kotlin.version>1.1.2-2</kotlin.version>
+    </properties>
+
+    <dependencies>
+        <dependency>
+            <groupId>io.cucumber</groupId>
+            <artifactId>cucumber-java8</artifactId>
+        </dependency>
+        <dependency>
+            <groupId>io.cucumber</groupId>
+            <artifactId>cucumber-junit</artifactId>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>junit</groupId>
+            <artifactId>junit</artifactId>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>net.sourceforge.cobertura</groupId>
+            <artifactId>cobertura</artifactId>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.jetbrains.kotlin</groupId>
+            <artifactId>kotlin-stdlib</artifactId>
+            <version>${kotlin.version}</version>
+            <scope>test</scope>
+        </dependency>
+    </dependencies>
+
+    <build>
+        <sourceDirectory>${project.basedir}/src/main/kotlin</sourceDirectory>
+        <testSourceDirectory>${project.basedir}/src/test/kotlin</testSourceDirectory>
+        <plugins>
+            <plugin>
+                <artifactId>kotlin-maven-plugin</artifactId>
+                <groupId>org.jetbrains.kotlin</groupId>
+                <version>${kotlin.version}</version>
+                <executions>
+                    <execution>
+                        <id>compile</id>
+                        <goals>
+                            <goal>compile</goal>
+                        </goals>
+                    </execution>
+                    <execution>
+                        <id>test-compile</id>
+                        <goals>
+                            <goal>test-compile</goal>
+                        </goals>
+                    </execution>
+                </executions>
+            </plugin>
+            <plugin>
+                <artifactId>maven-jar-plugin</artifactId>
+                <configuration>
+                    <skip>true</skip>
+                </configuration>
+            </plugin>
+            <plugin>
+                <artifactId>maven-install-plugin</artifactId>
+                <configuration>
+                    <skip>true</skip>
+                </configuration>
+            </plugin>
+            <plugin>
+                <artifactId>maven-deploy-plugin</artifactId>
+                <configuration>
+                    <skip>true</skip>
+                </configuration>
+            </plugin>
+        </plugins>
+    </build>
+
+</project>

kotlin-java8/src/test/kotlin/cucumber/runtime/kotlin/test/LambdaStepdefs.kt

@@ -0,0 +1,55 @@
+package cucumber.runtime.kotlin.test;
+
+import cucumber.api.DataTable
+import cucumber.api.Scenario
+import cucumber.api.java8.En
+import org.junit.Assert.*
+
+var lastInstance : LambdaStepdefs? = null
+
+class LambdaStepdefs : En {
+
+    init {
+        Before { scenario: Scenario ->
+            assertNotSame(this, lastInstance)
+            lastInstance = this
+        }
+
+        Given("^this data table:$") { peopleTable: DataTable ->
+            val people = peopleTable.asList(Person::class.java)
+            assertEquals("Aslak", people[0].first)
+            assertEquals("Hellesøy", people[0].last)
+        }
+
+        val alreadyHadThisManyCukes = 1
+        Given("^I have (\\d+) cukes in my belly$") { n: Long ->
+            assertEquals(1, alreadyHadThisManyCukes)
+            assertEquals(42L, n)
+        }
+
+        val localState = "hello"
+        Then("^I really have (\\d+) cukes in my belly") { i: Int ->
+            assertEquals(42, i)
+            assertEquals("hello", localState)
+        }
+
+        Given("^A statement with a body expression$") { assertTrue(true) }
+
+        Given("^A statement with a simple match$", { -> assertTrue(true) })
+
+        val localInt = 1
+        Given("^A statement with a scoped argument$", { assertEquals(2, localInt + 1) })
+
+        Given("^I will give you (\\d+) and ([\\d\\.]+) and (\\w+) and (\\d+)$") { a: Int, b: Float, c: String, d: Int ->
+            assertEquals(1, a)
+            assertEquals(2.2f, b)
+            assertEquals("three", c)
+            assertEquals(4, d)
+        }
+    }
+
+    class Person {
+        internal var first: String? = null
+        internal var last: String? = null
+    }
+}

kotlin-java8/src/test/kotlin/cucumber/runtime/kotlin/test/RunCukesTest.kt

@@ -0,0 +1,8 @@
+package cucumber.runtime.kotlin.test
+
+import cucumber.api.junit.Cucumber
+import org.junit.runner.RunWith
+
+@RunWith(Cucumber::class)
+class RunCukesTest {
+}

kotlin-java8/src/test/resources/cucumber/runtime/kotlin/test/kotlin.feature

@@ -0,0 +1,25 @@
+Feature: Kotlin
+
+  Scenario: use the API with Java8 style
+    Given I have 42 cukes in my belly
+    Then I really have 42 cukes in my belly
+
+  Scenario: another scenario which should have isolated state
+    Given I have 42 cukes in my belly
+    And something that isn't defined
+
+  Scenario: Parameterless lambdas
+    Given A statement with a simple match
+    Given A statement with a scoped argument
+
+  Scenario: I can use body expressions
+    Given A statement with a body expression
+
+  Scenario: Multi-param lambdas
+    Given I will give you 1 and 2.2 and three and 4
+
+  Scenario: use a table
+    Given this data table:
+      | first  | last     |
+      | Aslak  | Hellesøy |
+      | Donald | Duck     |

pom.xml

@@ -192,6 +192,16 @@
                 <artifactId>android-examples</artifactId>
                 <version>${project.version}</version>
             </dependency>
+            <dependency>
+                <groupId>io.cucumber</groupId>
+                <artifactId>cucumber-java8</artifactId>
+                <version>${project.version}</version>
+            </dependency>
+            <dependency>
+                <groupId>io.cucumber</groupId>
+                <artifactId>cucumber-kotlin-java8</artifactId>
+                <version>${project.version}</version>
+            </dependency>
 
             <!-- Spring stuff -->
             <dependency>
@@ -581,6 +591,7 @@
             </activation>
             <modules>
                 <module>java8</module>
+                <module>kotlin-java8</module>
             </modules>
         </profile>