Address PR #395 review feedback

- Split run-on sentence in AssertionError message
- Use HashMap import instead of fully qualified name
- Move Mojo variable declaration into try block (nested try-finally)
- Return defensive copy from getValidationTimeEvents() for encapsulation

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: cowwoc

src/main/java/org/apache/maven/buildcache/BuildCacheMojosExecutionStrategy.java

@@ -24,6 +24,7 @@
 
 import java.io.File;
 import java.nio.file.Path;
+import java.util.HashMap;
 import java.util.HashSet;
 import java.util.List;
 import java.util.Map;
@@ -182,7 +183,7 @@ public void execute(
                             || result.getValidationTimeEvents().isEmpty()) {
                         throw new AssertionError(
                                 "Validation-time properties not captured for project " + projectName
-                                        + ". This is a bug - validation-time capture should always succeed when saving to cache.");
+                                        + ". This is a bug. Validation-time capture should always succeed when saving to cache.");
                     }
                     LOGGER.debug("Using validation-time properties for cache storage (consistent lifecycle point)");
                     cacheController.save(result, mojoExecutions, result.getValidationTimeEvents());
@@ -468,7 +469,7 @@ private static String normalizedPath(Path path, Path baseDirPath) {
      */
     private Map<String, MojoExecutionEvent> captureValidationTimeProperties(
             MavenSession session, MavenProject project, List<MojoExecution> mojoExecutions) {
-        Map<String, MojoExecutionEvent> validationTimeEvents = new java.util.HashMap<>();
+        Map<String, MojoExecutionEvent> validationTimeEvents = new HashMap<>();
 
         for (MojoExecution mojoExecution : mojoExecutions) {
             // Skip mojos that don't execute or are in clean phase
@@ -477,19 +478,22 @@ private Map<String, MojoExecutionEvent> captureValidationTimeProperties(
                 continue;
             }
 
-            Mojo mojo = null;
             try {
                 mojoExecutionScope.enter();
                 mojoExecutionScope.seed(MavenProject.class, project);
                 mojoExecutionScope.seed(MojoExecution.class, mojoExecution);
 
-                mojo = mavenPluginManager.getConfiguredMojo(Mojo.class, session, mojoExecution);
-                MojoExecutionEvent event = new MojoExecutionEvent(session, project, mojoExecution, mojo);
-                validationTimeEvents.put(mojoExecutionKey(mojoExecution), event);
+                Mojo mojo = mavenPluginManager.getConfiguredMojo(Mojo.class, session, mojoExecution);
+                try {
+                    MojoExecutionEvent event = new MojoExecutionEvent(session, project, mojoExecution, mojo);
+                    validationTimeEvents.put(mojoExecutionKey(mojoExecution), event);
 
-                LOGGER.debug(
-                        "Captured validation-time properties for {}",
-                        mojoExecution.getMojoDescriptor().getFullGoalName());
+                    LOGGER.debug(
+                            "Captured validation-time properties for {}",
+                            mojoExecution.getMojoDescriptor().getFullGoalName());
+                } finally {
+                    mavenPluginManager.releaseMojo(mojo, mojoExecution);
+                }
 
             } catch (PluginConfigurationException | PluginContainerException e) {
                 LOGGER.warn(
@@ -502,9 +506,6 @@ private Map<String, MojoExecutionEvent> captureValidationTimeProperties(
                 } catch (MojoExecutionException e) {
                     LOGGER.debug("Error exiting mojo execution scope: {}", e.getMessage());
                 }
-                if (mojo != null) {
-                    mavenPluginManager.releaseMojo(mojo, mojoExecution);
-                }
             }
         }
 

src/main/java/org/apache/maven/buildcache/CacheResult.java

@@ -18,6 +18,7 @@
  */
 package org.apache.maven.buildcache;
 
+import java.util.HashMap;
 import java.util.Map;
 
 import org.apache.maven.buildcache.xml.Build;
@@ -150,6 +151,6 @@ public boolean isFinal() {
     }
 
     public Map<String, MojoExecutionEvent> getValidationTimeEvents() {
-        return validationTimeEvents;
+        return validationTimeEvents != null ? new HashMap<>(validationTimeEvents) : null;
     }
 }