Re-run the license task on the project configurations/dependencies ch…

…anges (#213)

The idea is simple - as the license task depends on the Gradle build script itself
let's mark the build script as the task input.

A slight drawback of this approach is that the license task will re-run after every
build script change, i.e. it will be UP-TO-DATE less often. But changing the build
script should not happen that often compared to the code changes and Gradle would
need to re-configure the project anyway during the next build so re-running the license
task should be acceptable.

An alternative approach could be to declare *all* project properties that affect
the task outcome as inputs to the task.

Closes #212.

gradle-license-plugin/src/main/kotlin/com/jaredsburrows/license/LicenseReportTask.kt

@@ -16,6 +16,7 @@ import org.gradle.api.artifacts.ResolvedArtifact
 import org.gradle.api.artifacts.ResolvedDependency
 import org.gradle.api.artifacts.dsl.DependencyHandler
 import org.gradle.api.tasks.Input
+import org.gradle.api.tasks.InputFile
 import org.gradle.api.tasks.Optional
 import org.gradle.api.tasks.TaskAction
 import java.io.File
@@ -30,6 +31,10 @@ internal open class LicenseReportTask : BaseLicenseReportTask() { // tasks can't
 
   @Input var assetDirs = emptyList<File>()
   @Optional @Input var variantName: String? = null
+  // This input is used by the task indirectly via some project properties (such as "configurations" and "dependencies")
+  // that affect the task's outcome. When the mentioned project properties change the task should re-run the next time
+  // it is requested and should *not* be marked as UP-TO-DATE.
+  @InputFile var buildFile: File? = null
 
   private val projects = mutableListOf<Model>()
   private var pomConfiguration = "poms"

gradle-license-plugin/src/main/kotlin/com/jaredsburrows/license/projectAndroid.kt

@@ -96,6 +96,7 @@ private fun Project.configureVariant(
         .srcDirs
         .toList()
       it.variantName = variant.name
+      it.buildFile = buildFile
     }
   }
 }

gradle-license-plugin/src/main/kotlin/com/jaredsburrows/license/projectJava.kt

@@ -18,5 +18,7 @@ internal fun Project.isJavaProject(): Boolean {
  * All of these plugins will apply the JavaPlugin(relies on JavaBasePlugin) or JavaPlatformPlugin.
  */
 internal fun Project.configureJavaProject() {
-  tasks.register("licenseReport", LicenseReportTask::class.java)
+  tasks.register("licenseReport", LicenseReportTask::class.java) {
+    it.buildFile = buildFile
+  }
 }

gradle-license-plugin/src/test/groovy/com/jaredsburrows/license/LicensePluginAndroidSpec.groovy

@@ -234,6 +234,81 @@ final class LicensePluginAndroidSpec extends Specification {
     taskName << ['licenseDebugReport', 'licenseReleaseReport']
   }
 
+  @Unroll def 'not UP-TO-DATE when dependencies change'() {
+    given:
+    def originalBuildFile = """
+      buildscript {
+        dependencies {
+          classpath files($classpathString)
+        }
+      }
+
+      repositories {
+        maven {
+          url '${mavenRepoUrl}'
+        }
+      }
+
+      apply plugin: 'com.android.application'
+      apply plugin: 'com.jaredsburrows.license'
+
+      android {
+        compileSdkVersion $compileSdkVersion
+
+        defaultConfig {
+          applicationId 'com.example'
+        }
+      }
+
+      dependencies {
+        implementation 'com.android.support:appcompat-v7:26.1.0'
+      }
+      """
+    def modifiedBuildFile = """
+      buildscript {
+        dependencies {
+          classpath files($classpathString)
+        }
+      }
+
+      repositories {
+        maven {
+          url '${mavenRepoUrl}'
+        }
+      }
+
+      apply plugin: 'com.android.application'
+      apply plugin: 'com.jaredsburrows.license'
+
+      android {
+        compileSdkVersion $compileSdkVersion
+
+        defaultConfig {
+          applicationId 'com.example'
+        }
+      }
+
+      dependencies {
+        implementation 'com.android.support:appcompat-v7:26.1.0'
+        // This is a new dependency
+        implementation 'com.android.support:design:26.1.0'
+      }
+      """
+
+    when:
+    buildFile << originalBuildFile
+    def result1 = gradleWithCommand(testProjectDir.root, "${taskName}", '-s')
+    buildFile << modifiedBuildFile
+    def result2 = gradleWithCommand(testProjectDir.root, "${taskName}", '-s')
+
+    then:
+    result1.task(":${taskName}").outcome == SUCCESS
+    result2.task(":${taskName}").outcome == SUCCESS
+
+    where:
+    taskName << ['licenseDebugReport', 'licenseReleaseReport']
+  }
+
   @Unroll def '#taskName with buildTypes'() {
     given:
     buildFile <<