Work around apparent bug in Gradle 6.1 DirectoryProperty#file

src/integrationTest/groovy/com/getkeepsafe/dexcount/IntegrationSpec.groovy

@@ -40,6 +40,28 @@ class IntegrationSpec extends Specification {
         "3.4.0"         | "6.5.1"       || 7435       | 926        | 3847
     }
 
+    @Unroll
+    def "completes successfully using AGP #agpVersion and Gradle #gradleVersion"() {
+        given: "an integration test project"
+        def project = projectDir(agpVersion, gradleVersion)
+
+        when:
+        def result = GradleRunner.create()
+            .withGradleVersion(gradleVersion)
+            .withProjectDir(project)
+            .withArguments(":app:countDebugDexMethods", "--stacktrace")
+            .build()
+
+        then:
+        result.task(":app:countDebugDexMethods").outcome == TaskOutcome.SUCCESS
+
+        // These version combinations were known to fail at some point.
+        // This spec serves to guard against regression.
+        where:
+        agpVersion | gradleVersion | reportedIn
+        "4.0.0"    | "6.1.1"       | "https://github.com/KeepSafe/dexcount-gradle-plugin/issues/410"
+    }
+
     @Unroll
     def "counting AARs using AGP #agpVersion and Gradle #gradleVersion"() {
         given: "an integration test project"

src/main/java/com/getkeepsafe/dexcount/plugin/AbstractLegacyTaskApplicator.java

@@ -143,7 +143,7 @@ protected void createTask(
         String treePath = path.replace("outputs", "intermediates") + "/tree.compact.gz";
 
         TaskProvider<LegacyGeneratePackageTreeTask> gen = getProject().getTasks().register(treeTaskName, LegacyGeneratePackageTreeTask.class, t -> {
-            t.setDescription("Generates dex method count for ${variant.name}.");
+            t.setDescription("Generates dex method count for " + variant.getName() + ".");
             t.setGroup("Reporting");
 
             t.getConfigProperty().set(getExt());

src/main/java/com/getkeepsafe/dexcount/treegen/workers/BaseWorker.java

@@ -54,14 +54,14 @@ public interface Params extends WorkParameters {
         Property<PrintOptions> getPrintOptions();
     }
 
+    private File outputDirectory = null;
+
     @Override
     public void execute() {
         try {
             PackageTree packageTree = generatePackageTree();
 
-            File outputDir = getParameters().getOutputDirectory().get().getAsFile();
-            FileUtils.deleteDirectory(outputDir);
-            FileUtils.forceMkdir(outputDir);
+            ensureCleanOutputDirectory();
 
             writeIntermediateThriftFile(packageTree);
             writeSummaryFile(packageTree);
@@ -72,6 +72,11 @@ public void execute() {
         }
     }
 
+    private void ensureCleanOutputDirectory() throws IOException {
+        FileUtils.deleteDirectory(getOutputDirectory());
+        FileUtils.forceMkdir(getOutputDirectory());
+    }
+
     private void writeIntermediateThriftFile(PackageTree packageTree) throws IOException {
         TreeGenOutput thrift = new TreeGenOutput.Builder()
             .tree(PackageTree.toThrift(packageTree))
@@ -92,7 +97,7 @@ private void writeIntermediateThriftFile(PackageTree packageTree) throws IOExcep
     }
 
     private void writeSummaryFile(PackageTree packageTree) throws IOException {
-        File summaryFile = getParameters().getOutputDirectory().file("summary.csv").get().getAsFile();
+        File summaryFile = new File(getOutputDirectory(), "summary.csv");
         FileUtils.forceMkdirParent(summaryFile);
 
         String headers = "methods,fields,classes";
@@ -109,7 +114,7 @@ private void writeSummaryFile(PackageTree packageTree) throws IOException {
     }
 
     private void writeChartFiles(PackageTree packageTree) throws IOException {
-        File chartDirectory = getParameters().getOutputDirectory().dir("chart").get().getAsFile();
+        File chartDirectory = new File(getOutputDirectory(), "chart");
         FileUtils.forceMkdir(chartDirectory);
 
         PrintOptions options = getParameters().getPrintOptions().get()
@@ -140,13 +145,20 @@ private void writeChartFiles(PackageTree packageTree) throws IOException {
     private void writeFullTree(PackageTree packageTree) throws IOException {
         PrintOptions options = getParameters().getPrintOptions().get();
         String fullCountFileName = getParameters().getOutputFileName().get() + options.getOutputFormat().getExtension();
-        File fullCountFile = getParameters().getOutputDirectory().file(fullCountFileName).get().getAsFile();
+        File fullCountFile = new File(getOutputDirectory(), fullCountFileName);
 
         try (BufferedWriter bw = Files.newBufferedWriter(fullCountFile.toPath())) {
             packageTree.print(bw, options.getOutputFormat(), options);
         }
     }
 
+    private File getOutputDirectory() {
+        if (outputDirectory == null) {
+            outputDirectory = getParameters().getOutputDirectory().get().getAsFile();
+        }
+        return outputDirectory;
+    }
+
     protected abstract PackageTree generatePackageTree() throws IOException;
 
     protected abstract String getInputRepresentation();