Little things.

api/src/main/groovy/com/jessebrault/ssg/html/PageToHtmlSpecProviders.groovy

@@ -5,9 +5,11 @@ import com.jessebrault.ssg.provider.CollectionProvider
 import com.jessebrault.ssg.provider.CollectionProviders
 import com.jessebrault.ssg.task.TaskSpec
 import com.jessebrault.ssg.util.ExtensionUtil
+import groovy.transform.NullCheck
 
 import java.util.function.Function
 
+@NullCheck
 final class PageToHtmlSpecProviders {
 
     static CollectionProvider<PageToHtmlSpec> from(CollectionProvider<Page> pagesProvider) {

api/src/main/groovy/com/jessebrault/ssg/page/PagesProviders.groovy

@@ -3,12 +3,14 @@ package com.jessebrault.ssg.page
 import com.jessebrault.ssg.provider.CollectionProvider
 import com.jessebrault.ssg.provider.CollectionProviders
 import com.jessebrault.ssg.util.ExtensionUtil
+import groovy.transform.NullCheck
 import org.slf4j.Logger
 import org.slf4j.LoggerFactory
 
 import java.util.function.BiPredicate
 import java.util.function.Predicate
 
+@NullCheck
 final class PagesProviders {
 
     private static final Logger logger = LoggerFactory.getLogger(PagesProviders)
@@ -17,7 +19,11 @@ final class PagesProviders {
         from(pagesDirectory, pageTypes) { file, path -> true }
     }
 
-    static CollectionProvider<Page> from(File pagesDirectory, Collection<PageType> pageTypes, BiPredicate<File, String> filter) {
+    static CollectionProvider<Page> from(
+            File pagesDirectory,
+            Collection<PageType> pageTypes,
+            BiPredicate<File, String> filter
+    ) {
         CollectionProviders.fromDirectory(pagesDirectory) { file, relativePath ->
             if (filter.test(file, relativePath)) {
                 def extension = ExtensionUtil.getExtension(relativePath)

api/src/main/groovy/com/jessebrault/ssg/task/TaskFactorySpec.groovy

@@ -45,4 +45,9 @@ final class TaskFactorySpec<T extends TaskFactory> {
         concat(this, other)
     }
 
+    @Override
+    String toString() {
+        "TaskFactorySpec(name: ${ this.name })"
+    }
+
 }

cli/src/main/groovy/com/jessebrault/ssg/AbstractBuildCommand.groovy

@@ -69,7 +69,12 @@ abstract class AbstractBuildCommand extends AbstractSubCommand {
                 buildScriptBinding,
                 diagnostics.&addAll
         )) {
-            diagnostics.each { logger.warn(it) }
+            diagnostics.each {
+                logger.error(it.message)
+                if (it.exception != null) {
+                    it.exception.printStackTrace()
+                }
+            }
             logger.traceExit(1)
         } else {
             logger.traceExit(0)