create a test that fails to demonstrate issue #75

plugin/src/it/basic-using-docker-directory/Dockerfile

@@ -0,0 +1,8 @@
+FROM scratch
+MAINTAINER David Flemström <dflemstr@spotify.com>
+
+ENV BASE /opt/base
+
+COPY target/docker/lib $BASE/lib
+
+ADD src/main/docker/foo.txt $BASE/

plugin/src/it/basic-using-docker-directory/pom.xml

@@ -0,0 +1,82 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!--
+  -/-/-
+  Dockerfile Maven Plugin
+  %%
+  Copyright (C) 2015 - 2016 Spotify AB
+  %%
+  Licensed under the Apache License, Version 2.0 (the "License");
+  you may not use this file except in compliance with the License.
+  You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+  Unless required by applicable law or agreed to in writing, software
+  distributed under the License is distributed on an "AS IS" BASIS,
+  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+  See the License for the specific language governing permissions and
+  limitations under the License.
+  -\-\-
+  -->
+
+<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+
+    <groupId>com.spotify.it</groupId>
+    <artifactId>basic</artifactId>
+    <version>1.0-SNAPSHOT</version>
+
+    <description>A simple IT verifying the basic use case.</description>
+
+    <properties>
+        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
+    </properties>
+
+    <dependencies>
+        <!-- an arbitrary dependency we can make this test copy to the target/docker/ directory --> 
+        <dependency>
+            <groupId>commons-lang</groupId>
+            <artifactId>commons-lang</artifactId>
+            <version>2.4</version>
+        </dependency>
+
+    </dependencies>
+
+    <build>
+        <plugins>
+
+            <!-- Copy Maven dependencies into target/lib/ -->
+            <plugin>
+              <artifactId>maven-dependency-plugin</artifactId>
+              <executions>
+                <execution>
+                  <phase>initialize</phase>
+                  <goals>
+                    <goal>copy-dependencies</goal>
+                  </goals>
+                  <configuration>
+                    <overWriteReleases>false</overWriteReleases>
+                    <includeScope>runtime</includeScope>
+                    <outputDirectory>${project.build.directory}/docker/lib</outputDirectory>
+                  </configuration>
+                </execution>
+              </executions>
+            </plugin>
+
+            <plugin>
+                <groupId>@project.groupId@</groupId>
+                <artifactId>@project.artifactId@</artifactId>
+                <version>@project.version@</version>
+                <executions>
+                    <execution>
+                        <id>default</id>
+                        <goals>
+                            <goal>build</goal>
+                        </goals>
+                    </execution>
+                </executions>
+            </plugin>
+        </plugins>
+    </build>
+</project>

plugin/src/it/basic-using-docker-directory/src/main/docker/foo.txt

@@ -0,0 +1 @@
+# a text file to copy over

plugin/src/it/basic-using-docker-directory/src/main/java/com/foo/Foo.java

@@ -0,0 +1,8 @@
+package com.foo;
+
+
+public class Foo {
+    public static void main(String[] args) {
+        // don't do anything.
+    }
+}

plugin/src/it/basic-using-docker-directory/verify.groovy

@@ -0,0 +1,21 @@
+/*
+ * -/-/-
+ * Dockerfile Maven Plugin
+ * %%
+ * Copyright (C) 2015 - 2016 Spotify AB
+ * %%
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ * 
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ * 
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ * -\-\-
+ */
+File imageIdFile = new File(basedir, "target/docker/image-id")
+assert imageIdFile.isFile()

plugin/src/main/java/com/spotify/plugin/dockerfile/AbstractDockerMojo.java

@@ -293,10 +293,19 @@ private void writeTestMetadata() throws MojoExecutionException {
       for (String name : dockerInfoDirectory.list()) {
         final File sourceFile = new File(dockerInfoDirectory, name);
         final File targetFile = new File(testMetadataDir, name);
-        try {
-          Files.copy(sourceFile, targetFile);
-        } catch (IOException e) {
-          throw new MojoExecutionException("Could not copy files", e);
+        if (sourceFile.isDirectory()) {
+          getLog().warn("A directory was found inside the docker info directory at "
+              + dockerInfoDirectory.getAbsolutePath()
+              + " - this usually indicates that you have used this directory for something other"
+              + " than this plugin. "
+              + "For proper functionality, please configure the `dockerfile.dockerInfoDirectory`"
+              + " property to something that is only used by this plugin.");
+        } else {
+          try {
+            Files.copy(sourceFile, targetFile);
+          } catch (IOException e) {
+            throw new MojoExecutionException("Could not copy files", e);
+          }
         }
       }
     }