Support build.gradle.kts

Previously, determination of a Gradle repository was dependent on the
existence of a build.gradle file.  With the adoption of Kotlin in the Gradle
community, it now needs to inlcude build.gradle.kts.  This change updates the
buildpack to look for that file as well.

[resolves #3]

Signed-off-by: Ben Hale <bhale@pivotal.io>

README.md

@@ -6,7 +6,7 @@ This buildpack is designed to work in collaboration with other buildpacks.
 ## Detection
 The detection phase passes if
 
-* `<APPLICATION_ROOT>/build.gradle` exists
+* `<APPLICATION_ROOT>/build.gradle` or `<APPLICATION_ROOT>/build.gradle.kts` exists
   * Contributes `gradle` to the build plan
   * Contributes `jvm-application` to the build plan
   * Contributes `openjdk-jdk` to the build plan

buildsystem/gradle.go

@@ -42,12 +42,17 @@ func GradleBuildPlanContribution() buildplan.BuildPlan {
 
 // IsGradle returns whether this application is built using Gradle.
 func IsGradle(application application.Application) bool {
-	exists, err := helper.FileExists(filepath.Join(application.Root, "build.gradle"))
+	e1, err := helper.FileExists(filepath.Join(application.Root, "build.gradle"))
 	if err != nil {
 		return false
 	}
 
-	return exists
+	e2, err := helper.FileExists(filepath.Join(application.Root, "build.gradle.kts"))
+	if err != nil {
+		return false
+	}
+
+	return e1 || e2
 }
 
 // NewGradleBuildSystem creates a new Gradle BuildSystem instance. OK is true if build plan contains "gradle"

buildsystem/gradle_test.go

@@ -92,6 +92,12 @@ func TestGradle(t *testing.T) {
 
 				g.Expect(buildsystem.IsGradle(f.Build.Application)).To(BeTrue())
 			})
+
+			it("returns true if build.gradle.kts does exist", func() {
+				test.TouchFile(t, f.Build.Application.Root, "build.gradle.kts")
+
+				g.Expect(buildsystem.IsGradle(f.Build.Application)).To(BeTrue())
+			})
 		})
 
 		when("NewGradleBuildSystem", func() {

detect/main_test.go

@@ -47,6 +47,12 @@ func TestDetect(t *testing.T) {
 			g.Expect(d(f.Detect)).To(Equal(detect.PassStatusCode))
 		})
 
+		it("passes with build.gradle.kts", func() {
+			test.TouchFile(t, f.Detect.Application.Root, "build.gradle.kts")
+
+			g.Expect(d(f.Detect)).To(Equal(detect.PassStatusCode))
+		})
+
 		it("passes with pom.xml", func() {
 			test.TouchFile(t, f.Detect.Application.Root, "pom.xml")