Implementing #709: Remove snapshot idempotency

src/main/java/org/codehaus/mojo/versions/SetMojo.java

@@ -65,6 +65,8 @@
 import org.codehaus.plexus.components.interactivity.PrompterException;
 import org.codehaus.plexus.util.StringUtils;
 
+import static org.codehaus.plexus.util.StringUtils.isEmpty;
+
 /**
  * Sets the current project's version and based on that change propagates that change onto any child modules as
  * necessary.
@@ -298,8 +300,13 @@ public void execute() throws MojoExecutionException, MojoFailureException
             getLog().info( "SNAPSHOT found.  BEFORE " + version + "  --> AFTER: " + newVersion );
         }
 
-        if ( StringUtils.isEmpty( newVersion ) )
+        if ( isEmpty( newVersion ) )
         {
+            if ( removeSnapshot )
+            {
+                getLog().info( "removeSnapshot enabled whilst the version is not a snapshot: nothing to do." );
+                return;
+            }
             if ( settings.isInteractiveMode() )
             {
                 try
@@ -319,12 +326,6 @@ public void execute() throws MojoExecutionException, MojoFailureException
                                                       + "or run in interactive mode" );
             }
         }
-        if ( StringUtils.isEmpty( newVersion ) )
-        {
-            throw new MojoExecutionException( "You must specify the new version, either by using the newVersion "
-                                                  + "property (that is -DnewVersion=... on the command line) "
-                                                  + "or run in interactive mode" );
-        }
 
         if ( !"onchange".equals( updateBuildOutputTimestampPolicy ) && !"always".equals(
             updateBuildOutputTimestampPolicy ) && !"never".equals( updateBuildOutputTimestampPolicy ) )
@@ -614,7 +615,7 @@ private void updateBuildOutputTimestamp( ModifiedPomXMLEventReader pom, Model mo
     {
         String buildOutputTimestamp = model.getProperties().getProperty( "project.build.outputTimestamp" );
 
-        if ( buildOutputTimestamp == null || StringUtils.isEmpty( buildOutputTimestamp ) )
+        if ( buildOutputTimestamp == null || isEmpty( buildOutputTimestamp ) )
         {
             // no Reproducible Builds output timestamp defined
             return;

src/test/java/org/codehaus/mojo/versions/SetMojoTest.java

@@ -1,7 +1,13 @@
 package org.codehaus.mojo.versions;
 
 import java.io.File;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.nio.file.Paths;
+import java.util.Arrays;
+import java.util.Objects;
 
+import org.apache.maven.execution.MavenExecutionRequest;
 import org.apache.maven.model.Model;
 import org.apache.maven.plugin.MojoExecutionException;
 import org.apache.maven.plugin.MojoFailureException;
@@ -11,6 +17,7 @@
 import org.junit.Rule;
 import org.junit.Test;
 
+import static java.nio.file.StandardCopyOption.REPLACE_EXISTING;
 import static org.hamcrest.MatcherAssert.assertThat;
 import static org.hamcrest.Matchers.containsString;
 import static org.hamcrest.Matchers.is;
@@ -106,4 +113,38 @@ public void testVersionlessDependency() throws Exception
                 new File( "target/test-classes/org/codehaus/mojo/set/versionless-01" ), "set" );
         myMojo.execute();
     }
+
+    @Test
+    public void testRemoveSnapshotIdempotency()
+            throws Exception
+    {
+        Path pomDir = Files.createTempDirectory( "set-" );
+        try
+        {
+            Files.copy( Paths.get( "src/test/resources/org/codehaus/mojo/set/remove-snapshot/pom.xml" ),
+                    Paths.get( pomDir.toString(),  "pom.xml" ), REPLACE_EXISTING );
+
+            SetMojo firstRun = (SetMojo) mojoRule.lookupConfiguredMojo( pomDir.toFile(), "set" );
+            firstRun.execute();
+            assertThat( String.join( "", Files.readAllLines( Paths.get( pomDir.toString(), "pom.xml" ) ) ),
+                    containsString( "<version>1.0</version>" ) );
+
+            // no exception should be thrown, the file should stay with version "1.0"
+            SetMojo secondRun = (SetMojo) mojoRule.lookupConfiguredMojo( pomDir.toFile(), "set" );
+            MavenExecutionRequest request =
+                    (MavenExecutionRequest) getVariableValueFromObject( secondRun.settings, "request" );
+            setVariableValueToObject( request, "interactiveMode", false );
+            secondRun.execute();
+            assertThat( String.join( "", Files.readAllLines( Paths.get( pomDir.toString(), "pom.xml" ) ) ),
+                    containsString( "<version>1.0</version>" ) );
+        }
+        finally
+        {
+            if ( pomDir != null && pomDir.toFile().exists() )
+            {
+                Arrays.stream( Objects.requireNonNull( pomDir.toFile().listFiles() ) ).forEach( File::delete );
+                pomDir.toFile().delete();
+            }
+        }
+    }
 }

src/test/resources/org/codehaus/mojo/set/remove-snapshot/pom.xml

@@ -0,0 +1,23 @@
+<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>default-group</groupId>
+    <artifactId>default-artifact</artifactId>
+    <version>1.0-SNAPSHOT</version>
+
+    <build>
+        <plugins>
+            <plugin>
+                <groupId>org.codehaus.mojo</groupId>
+                <artifactId>versions-maven-plugin</artifactId>
+                <goals>
+                    <goal>set</goal>
+                </goals>
+                <configuration>
+                    <removeSnapshot>true</removeSnapshot>
+                    <generateBackupPoms>false</generateBackupPoms>
+                </configuration>
+            </plugin>
+        </plugins>
+    </build>
+</project>