Correctly determine the version of the underlying javac tool (#357)

Ignore and deprecate CompilerConfiguration values as they are unreliable (and don't
represent the used javac version)

Make test execution more resilient by interpolating settings.xml
correctly and make sure commons-lang 2.0 is resolved prior to unit
testing

This closes #356

plexus-compiler-api/src/main/java/org/codehaus/plexus/compiler/CompilerConfiguration.java

@@ -500,10 +500,20 @@ public void setOptimize(boolean optimize) {
         this.optimize = optimize;
     }
 
+    /**
+     * @deprecated Don't use any longer because this is just the configured version which does not necessarily match the version
+     * of the actually executed compiler binary
+     */
+    @Deprecated
     public String getCompilerVersion() {
         return compilerVersion;
     }
 
+    /**
+     * @deprecated Don't use any longer because this is just the configured version which does not necessarily match the version
+     * of the actually executed compiler binary
+     */
+    @Deprecated
     public void setCompilerVersion(String compilerVersion) {
         this.compilerVersion = compilerVersion;
     }

plexus-compiler-test/pom.xml

@@ -50,7 +50,7 @@
     </dependency>
     <dependency>
       <groupId>org.apache.maven</groupId>
-      <artifactId>maven-settings</artifactId>
+      <artifactId>maven-settings-builder</artifactId>
       <version>${mavenVersion}</version>
     </dependency>
     <dependency>

plexus-compiler-test/src/main/java/org/codehaus/plexus/compiler/AbstractCompilerTest.java

@@ -41,11 +41,13 @@
 import org.apache.maven.artifact.repository.DefaultArtifactRepository;
 import org.apache.maven.artifact.repository.layout.ArtifactRepositoryLayout;
 import org.apache.maven.artifact.versioning.VersionRange;
+import org.apache.maven.properties.internal.SystemProperties;
 import org.apache.maven.settings.Settings;
-import org.apache.maven.settings.io.xpp3.SettingsXpp3Reader;
+import org.apache.maven.settings.building.DefaultSettingsBuilderFactory;
+import org.apache.maven.settings.building.DefaultSettingsBuildingRequest;
+import org.apache.maven.settings.building.SettingsBuildingRequest;
 import org.codehaus.plexus.testing.PlexusTest;
 import org.codehaus.plexus.util.FileUtils;
-import org.codehaus.plexus.util.ReaderFactory;
 import org.codehaus.plexus.util.StringUtils;
 import org.hamcrest.io.FileMatchers;
 import org.junit.jupiter.api.BeforeEach;
@@ -83,7 +85,13 @@ final void setUpLocalRepo() throws Exception {
         if (localRepo == null) {
             File settingsFile = new File(System.getProperty("user.home"), ".m2/settings.xml");
             if (settingsFile.exists()) {
-                Settings settings = new SettingsXpp3Reader().read(ReaderFactory.newXmlReader(settingsFile));
+                SettingsBuildingRequest request = new DefaultSettingsBuildingRequest();
+                request.setUserSettingsFile(settingsFile);
+                request.setSystemProperties(SystemProperties.getSystemProperties());
+                Settings settings = new DefaultSettingsBuilderFactory()
+                        .newInstance()
+                        .build(request)
+                        .getEffectiveSettings();
                 localRepo = settings.getLocalRepository();
             }
         }
@@ -116,7 +124,7 @@ protected List<String> getClasspath() throws Exception {
         File file = getLocalArtifactPath("commons-lang", "commons-lang", "2.0", "jar");
 
         assertThat(
-                "test prerequisite: commons-lang library must be available in local repository, expected ",
+                "test prerequisite: commons-lang library must be available in local repository at " + file,
                 file,
                 FileMatchers.aReadableFile());