Eliminate redundant TestFile in functional tests

src/funcTest/groovy/com/github/jengelman/gradle/plugins/shadow/PublishingSpec.groovy

@@ -60,14 +60,14 @@ class PublishingSpec extends PluginSpecification {
         run('publish')
 
         then:
-        File publishedFile = publishingRepo.rootDir.file('shadow/maven-all/1.0/maven-all-1.0.jar').canonicalFile
+        File publishedFile = publishingRepo.rootDir.resolve('shadow/maven-all/1.0/maven-all-1.0.jar').canonicalFile
         assert publishedFile.exists()
 
         and:
         contains(publishedFile, ['a.properties', 'a2.properties'])
 
         and:
-        File pom = publishingRepo.rootDir.file('shadow/maven-all/1.0/maven-all-1.0.pom').canonicalFile
+        File pom = publishingRepo.rootDir.resolve('shadow/maven-all/1.0/maven-all-1.0.pom').canonicalFile
         assert pom.exists()
 
         def contents = new XmlSlurper().parse(pom)
@@ -128,7 +128,7 @@ class PublishingSpec extends PluginSpecification {
         run('publish')
 
         then:
-        File publishedFile = publishingRepo.rootDir.file('shadow/maven-all/1.0/maven-all-1.0-my-classifier.my-ext').canonicalFile
+        File publishedFile = publishingRepo.rootDir.resolve('shadow/maven-all/1.0/maven-all-1.0-my-classifier.my-ext').canonicalFile
         assert publishedFile.exists()
     }
 
@@ -209,14 +209,14 @@ class PublishingSpec extends PluginSpecification {
         run('publish')
 
         then:
-        File publishedFile = publishingRepo.rootDir.file('shadow/maven-all/1.0/maven-all-1.0.jar').canonicalFile
+        File publishedFile = publishingRepo.rootDir.resolve('shadow/maven-all/1.0/maven-all-1.0.jar').canonicalFile
         assert publishedFile.exists()
 
         and:
         contains(publishedFile, ['a.properties', 'a2.properties'])
 
         and:
-        File pom = publishingRepo.rootDir.file('shadow/maven-all/1.0/maven-all-1.0.pom').canonicalFile
+        File pom = publishingRepo.rootDir.resolve('shadow/maven-all/1.0/maven-all-1.0.pom').canonicalFile
         assert pom.exists()
 
         def contents = new XmlSlurper().parse(pom)
@@ -273,17 +273,17 @@ class PublishingSpec extends PluginSpecification {
         run('publish')
 
         then:
-        File mainJar = publishingRepo.rootDir.file('com/acme/maven/1.0/maven-1.0.jar').canonicalFile
-        File shadowJar = publishingRepo.rootDir.file('com/acme/maven/1.0/maven-1.0-all.jar').canonicalFile
+        File mainJar = publishingRepo.rootDir.resolve('com/acme/maven/1.0/maven-1.0.jar').canonicalFile
+        File shadowJar = publishingRepo.rootDir.resolve('com/acme/maven/1.0/maven-1.0-all.jar').canonicalFile
         assert mainJar.exists()
         assert shadowJar.exists()
 
         and:
         contains(shadowJar, ['a.properties', 'a2.properties'])
 
         and: "publishes both a POM file and a Gradle metadata file"
-        File pom = publishingRepo.rootDir.file('com/acme/maven/1.0/maven-1.0.pom').canonicalFile
-        File gmm = publishingRepo.rootDir.file('com/acme/maven/1.0/maven-1.0.module').canonicalFile
+        File pom = publishingRepo.rootDir.resolve('com/acme/maven/1.0/maven-1.0.pom').canonicalFile
+        File gmm = publishingRepo.rootDir.resolve('com/acme/maven/1.0/maven-1.0.module').canonicalFile
         pom.exists()
         gmm.exists()
 
@@ -328,13 +328,13 @@ class PublishingSpec extends PluginSpecification {
 
         and: "verify shadow publication"
         assertions {
-            shadowJar = publishingRepo.rootDir.file('com/acme/maven-all/1.0/maven-all-1.0-all.jar').canonicalFile
+            shadowJar = publishingRepo.rootDir.resolve('com/acme/maven-all/1.0/maven-all-1.0-all.jar').canonicalFile
             assert shadowJar.exists()
             contains(shadowJar, ['a.properties', 'a2.properties'])
         }
 
         assertions {
-            pom = publishingRepo.rootDir.file('com/acme/maven-all/1.0/maven-all-1.0.pom').canonicalFile
+            pom = publishingRepo.rootDir.resolve('com/acme/maven-all/1.0/maven-all-1.0.pom').canonicalFile
             assert pom.exists()
             pomContents = new XmlSlurper().parse(pom)
             assert pomContents.dependencies[0].dependency.size() == 1
@@ -351,7 +351,7 @@ class PublishingSpec extends PluginSpecification {
         }
 
         assertions {
-            gmm = publishingRepo.rootDir.file('com/acme/maven-all/1.0/maven-all-1.0.module').canonicalFile
+            gmm = publishingRepo.rootDir.resolve('com/acme/maven-all/1.0/maven-all-1.0.module').canonicalFile
             assert gmm.exists()
             gmmContents = new JsonSlurper().parse(gmm)
             assert gmmContents.variants.size() == 1

src/funcTest/groovy/com/github/jengelman/gradle/plugins/shadow/util/AppendableMavenFileRepository.groovy

@@ -8,7 +8,7 @@ class AppendableMavenFileRepository extends MavenFileRepository {
 
     @Override
     AppendableMavenFileModule module(String groupId, String artifactId, Object version = '1.0') {
-        def artifactDir = rootDir.file("${groupId.replace('.', '/')}/$artifactId/$version")
+        def artifactDir = rootDir.resolve("${groupId.replace('.', '/')}/$artifactId/$version")
         return new AppendableMavenFileModule(artifactDir, groupId, artifactId, version as String)
     }
 

src/funcTest/groovy/com/github/jengelman/gradle/plugins/shadow/util/FileExtensions.groovy

@@ -0,0 +1,26 @@
+package com.github.jengelman.gradle.plugins.shadow.util
+
+/**
+ * TODO: this is used as extensions for Groovy, could be replaced after migrated to Kotlin.
+ *  Registered in resources/META-INF/services/org.codehaus.groovy.runtime.ExtensionModule.
+ */
+final class FileExtensions {
+    static final File resolve(File file, String relativePath) {
+        try {
+            return new File(file, relativePath)
+        } catch (RuntimeException e) {
+            throw new RuntimeException(String.format("Could not locate file '%s' relative to '%s'.", Arrays.toString(relativePath), file), e)
+        }
+    }
+
+    static final File createDir(File file) {
+        if (file.mkdirs()) {
+            return file
+        }
+        if (file.isDirectory()) {
+            return file
+        }
+        throw new AssertionError("Problems creating dir: " + file
+            + ". Diagnostics: exists=" + file.exists() + ", isFile=" + file.isFile() + ", isDirectory=" + file.isDirectory())
+    }
+}

src/funcTest/groovy/com/github/jengelman/gradle/plugins/shadow/util/PluginSpecification.groovy

@@ -1,6 +1,5 @@
 package com.github.jengelman.gradle.plugins.shadow.util
 
-import com.github.jengelman.gradle.plugins.shadow.util.file.TestFile
 import org.codehaus.plexus.util.IOUtil
 import org.gradle.testkit.runner.BuildResult
 import org.gradle.testkit.runner.GradleRunner
@@ -121,7 +120,7 @@ abstract class PluginSpecification extends Specification {
     }
 
     AppendableMavenFileRepository repo(String path = 'maven-repo') {
-        new AppendableMavenFileRepository(new TestFile(dir.toFile(), path))
+        new AppendableMavenFileRepository(dir.resolve(path).toFile())
     }
 
     void assertJarFileContentsEqual(File f, String path, String contents) {