Avoid NPE on outputFile checking

Should not occur as parameter outputFile is defined as required

src/it/read-project/pom.xml

@@ -4,7 +4,7 @@
   <modelVersion>4.0.0</modelVersion>
 
   <groupId>org.codehaus.mojo.properties.it</groupId>
-  <artifactId>write-project</artifactId>
+  <artifactId>read-project</artifactId>
   <version>0.0.1-SNAPSHOT</version>
 
   <build>

src/it/settings.xml

@@ -47,7 +47,14 @@ under the License.
           </snapshots>
         </pluginRepository>
       </pluginRepositories>
+
+      <properties>
+        <!-- properties for IT write-active-profile -->
+        <settings-properties-test1>value1</settings-properties-test1>
+        <settings-properties-test2>value2</settings-properties-test2>
+      </properties>
     </profile>
+
   </profiles>
   <activeProfiles>
     <activeProfile>it-repo</activeProfile>

src/it/write-active-profile/invoker.properties

@@ -0,0 +1 @@
+invoker.goals = clean generate-resources

src/it/write-active-profile/pom.xml

@@ -0,0 +1,44 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<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>org.codehaus.mojo.properties.it</groupId>
+  <artifactId>write-active-profilet</artifactId>
+  <version>0.0.1-SNAPSHOT</version>
+
+  <build>
+    <plugins>
+      <plugin>
+        <groupId>org.codehaus.mojo</groupId>
+        <artifactId>properties-maven-plugin</artifactId>
+        <version>@project.version@</version>
+        <executions>
+          <execution>
+            <phase>generate-resources</phase>
+            <goals>
+              <goal>write-active-profile-properties</goal>
+            </goals>
+            <configuration>
+              <outputFile>${project.build.outputDirectory}/project.properties</outputFile>
+            </configuration>
+          </execution>
+        </executions>
+      </plugin>
+    </plugins>
+  </build>
+
+  <profiles>
+    <profile>
+      <id>test-profile</id>
+      <activation>
+        <activeByDefault>true</activeByDefault>
+      </activation>
+      <properties>
+        <project-properties-test1>value21</project-properties-test1>
+        <project-properties-test2>value22</project-properties-test2>
+      </properties>
+    </profile>
+  </profiles>
+
+</project>

src/it/write-active-profile/verify.groovy

@@ -0,0 +1,18 @@
+import java.nio.file.Files
+
+File prop = new File(basedir, 'target/classes/project.properties')
+assert prop.exists()
+
+def properties = new Properties()
+try (InputStream input = Files.newInputStream(prop.toPath())) {
+    properties.load(input)
+}
+
+def expected = [
+        'project-properties-test1' : 'value21',
+        'project-properties-test2' : 'value22',
+        'settings-properties-test1': 'value1',
+        'settings-properties-test2': 'value2'
+]
+
+assert properties.equals(expected)

src/main/java/org/codehaus/mojo/properties/AbstractWritePropertiesMojo.java

@@ -73,6 +73,10 @@ protected void writeProperties(Properties properties) throws MojoExecutionExcept
      * @throws MojoExecutionException {@link MojoExecutionException}
      */
     protected void validateOutputFile() throws MojoExecutionException {
+        if (outputFile == null) {
+            throw new MojoExecutionException("outputFile parameter is missing");
+        }
+
         if (outputFile.isDirectory()) {
             throw new MojoExecutionException("outputFile must be a file and not a directory");
         }

src/main/java/org/codehaus/mojo/properties/WriteActiveProfileProperties.java

@@ -53,12 +53,12 @@ protected WriteActiveProfileProperties(List<PropertiesManager> propertiesManager
     @Override
     public void execute() throws MojoExecutionException {
         validateOutputFile();
-        List<Profile> list = getProject().getActiveProfiles();
-        if (getLog().isInfoEnabled()) {
-            getLog().debug(list.size() + " profile(s) active");
-        }
+
+        List<Profile> profiles = getProject().getActiveProfiles();
+        getLog().debug("Active profile: " + profiles);
+
         Properties properties = new Properties();
-        for (Profile profile : list) {
+        for (Profile profile : profiles) {
             if (profile.getProperties() != null) {
                 properties.putAll(profile.getProperties());
             }