Run witness checksums in task and only when compiling.

buildSrc/src/main/groovy/org/whispersystems/witness/WitnessPlugin.groovy

@@ -15,16 +15,31 @@ class WitnessPluginExtension {
 class WitnessPlugin implements Plugin<Project> {
 
     static String calculateSha256(file) {
-        MessageDigest md = MessageDigest.getInstance("SHA-256");
+        MessageDigest md = MessageDigest.getInstance('SHA-256')
         file.eachByte 4096, { bytes, size ->
-            md.update(bytes, 0, size);
+            md.update(bytes, 0, size)
         }
-        return md.digest().collect {String.format "%02x", it}.join();
+        return md.digest().collect { String.format '%02x', it }.join()
     }
 
     void apply(Project project) {
-        project.extensions.create("dependencyVerification", WitnessPluginExtension)
+        project.extensions.create('dependencyVerification', WitnessPluginExtension)
+
         project.afterEvaluate {
+            project.tasks
+                    .findAll { it.name =~ /compile/ }
+                    .each {
+                        it.dependsOn('verifyChecksums')
+                    }
+        }
+
+        project.task('verifyChecksums') {
+            group = 'Gradle Witness'
+            description = 'Verify the contents of dependencyVerification block in witness-verifications.gradle file(s) match the checksums of dependencies.'
+
+            doLast {
+                def allArtifacts = allArtifacts(project)
+
                 project.dependencyVerification.verify.each {
                     assertion ->
                         List parts = assertion[0].tokenize(':')
@@ -32,25 +47,30 @@ class WitnessPlugin implements Plugin<Project> {
                         String name = parts.get(1)
                         String hash = assertion[1]
 
-                    def artifacts = allArtifacts(project).findAll {
-                        return it.name.equals(name) && it.moduleVersion.id.group.equals(group)
+                        def artifacts = allArtifacts.findAll {
+                            it.moduleVersion.id.group == group && it.name == name
                         }
 
                         artifacts.forEach { dependency ->
-                        println "Verifying " + group + ":" + name
+                            println "Verifying $group:$name"
 
                             if (dependency == null) {
-                            throw new InvalidUserDataException("No dependency for integrity assertion found: " + group + ":" + name)
+                                throw new InvalidUserDataException("No dependency for integrity assertion found: $group:$name")
                             }
 
-                        if (!hash.equals(calculateSha256(dependency.file))) {
-                            throw new InvalidUserDataException("Checksum failed for " + assertion)
+                            if (hash != calculateSha256(dependency.file)) {
+                                throw new InvalidUserDataException("Checksum failed for $assertion")
+                            }
                         }
                 }
             }
         }
 
-        project.task('calculateChecksums').doLast {
+        project.task('calculateChecksums') {
+            group = 'Gradle Witness'
+            description = 'Recalculate checksums of dependencies and update the witness-verifications.gradle file(s).'
+
+            doLast {
                 def stringBuilder = new StringBuilder()
 
                 stringBuilder.append '// Auto-generated, use ./gradlew calculateChecksums to regenerate\n\n'
@@ -67,10 +87,11 @@ class WitnessPlugin implements Plugin<Project> {
                             dep -> stringBuilder.append "\n        $dep,\n"
                         }
 
-            stringBuilder.append "    ]\n"
-            stringBuilder.append "}\n"
+                stringBuilder.append '    ]\n'
+                stringBuilder.append '}\n'
 
-            project.file("witness-verifications.gradle").write(stringBuilder.toString())
+                project.file('witness-verifications.gradle').write(stringBuilder.toString())
+            }
         }
     }