deprecate *PUBLIC*API* metrics

* `PUBLIC_API`, `PUBLIC_UNDOCUMENTED_API` and `PUBLIC_DOCUMENTED_API_DENSITY`
  were depricated since SQ 6.2 (https://jira.sonarsource.com/browse/SONAR-8328)
  but existed as custom sonar-cxx metrics

* the minimal supported SQ version now is 6.7

* moreover, it looks like there is a general problem in displaying
  custom metrics (see SonarOpenCommunity#1509)

* that means that nobody a) expects that the SQ plugin implements the
  deprectad metrics and b) nobody misses them (because they are just not
  visualized)

* the squid check `UndocumentedApiCheck` is not affected
  (it doesn't rely on the stored metric, but visits the AST
  by itself) but `CxxPublicApiVisitorTest` had to be rewritten

* BTW public API measurements belong to the obligatory AST Visitors
  and introduce the time overhead of ~6% (measured with SonarOpenCommunity#1507,
  6% means, that if there is no sensors activated at all
  the importing of C++ project will still cause a calculation
  of a bunch of metrics; summary overhead of this calculation
  considered as 100%)

cxx-sensors/src/main/java/org/sonar/cxx/sensors/squid/CxxSquidSensor.java

@@ -256,24 +256,6 @@ private void saveMeasures(InputFile inputFile, SourceFile squidFile, SensorConte
       .withValue(squidFile.getInt(CxxMetric.COMPLEXITY)).save();
     context.<Integer>newMeasure().forMetric(CoreMetrics.COMMENT_LINES).on(inputFile)
       .withValue(squidFile.getInt(CxxMetric.COMMENT_LINES)).save();
-    context.<Integer>newMeasure().forMetric(CoreMetrics.PUBLIC_API).on(inputFile)
-      .withValue(squidFile.getInt(CxxMetric.PUBLIC_API)).save();
-    context.<Integer>newMeasure().forMetric(CoreMetrics.PUBLIC_UNDOCUMENTED_API).on(inputFile)
-      .withValue(squidFile.getInt(CxxMetric.PUBLIC_UNDOCUMENTED_API)).save();
-
-    // Configuration properties for SQ 6.2++
-    // see https://jira.sonarsource.com/browse/SONAR-8328
-    if (!language.getMetricsCache().isEmpty()) {
-      int publicApi = squidFile.getInt(CxxMetric.PUBLIC_API);
-      int publicUndocumentedApi = squidFile.getInt(CxxMetric.PUBLIC_UNDOCUMENTED_API);
-      double densityOfPublicDocumentedApi = (publicApi > publicUndocumentedApi) ? ((publicApi - publicUndocumentedApi) / (double) publicApi * 100.0) : 0.0;
-      context.<Integer>newMeasure().forMetric(language.getMetric(CxxMetrics.PUBLIC_API_KEY))
-        .on(inputFile).withValue(publicApi).save();
-      context.<Integer>newMeasure().forMetric(language.getMetric(CxxMetrics.PUBLIC_UNDOCUMENTED_API_KEY)).on(inputFile)
-        .withValue(publicUndocumentedApi).save();
-      context.<Double>newMeasure().forMetric(language.getMetric(CxxMetrics.PUBLIC_DOCUMENTED_API_DENSITY_KEY))
-        .on(inputFile).withValue(densityOfPublicDocumentedApi).save();
-    }
 
     for(SquidSensor sensor: squidSensors) {
       sensor.publishMeasureForFile(inputFile, squidFile, context);

cxx-sensors/src/main/java/org/sonar/cxx/sensors/utils/CxxMetrics.java

@@ -45,12 +45,6 @@ public class CxxMetrics implements Metrics {
   private final CxxLanguage language;
   private final String domain;
 
-  // Introduce own documentation metrics, after they has been removed from SQ core
-  // see https://jira.sonarsource.com/browse/SONAR-8328
-  public static final String PUBLIC_API_KEY = "public_api";
-  public static final String PUBLIC_UNDOCUMENTED_API_KEY = "public_undocumented_api";
-  public static final String PUBLIC_DOCUMENTED_API_DENSITY_KEY = "public_documented_api_density";
-
   /**
    * CxxMetrics
    *
@@ -61,36 +55,6 @@ public CxxMetrics(CxxLanguage language) {
     this.language = language;
     this.domain = language.getKey().toUpperCase(Locale.ENGLISH);
 
-    Metric<?> metric = new Metric.Builder(getKey(PUBLIC_API_KEY, language), "Public API", Metric.ValueType.INT)
-      .setDescription("Public API")
-      .setDirection(Metric.DIRECTION_WORST)
-      .setQualitative(Boolean.FALSE)
-      .setDomain(this.domain)
-      .create();
-    saveMetric(PUBLIC_API_KEY, metric);
-
-    metric = new Metric.Builder(getKey(PUBLIC_DOCUMENTED_API_DENSITY_KEY, language), "Public Documented API (%)", Metric.ValueType.PERCENT)
-      .setDescription("Public documented classes and functions balanced by ncloc")
-      .setDirection(Metric.DIRECTION_BETTER)
-      .setQualitative(Boolean.TRUE)
-      .setDomain(this.domain)
-      .setWorstValue(0.0)
-      .setBestValue(100.0)
-      .setOptimizedBestValue(true)
-      .create();
-    saveMetric(PUBLIC_DOCUMENTED_API_DENSITY_KEY, metric);
-
-    metric = new Metric.Builder(getKey(PUBLIC_UNDOCUMENTED_API_KEY, language), "Public Undocumented API", Metric.ValueType.INT)
-      .setDescription("Public undocumented classes, functions and variables")
-      .setDirection(Metric.DIRECTION_WORST)
-      .setQualitative(Boolean.TRUE)
-      .setDomain(this.domain)
-      .setBestValue(0.0)
-      .setDirection(Metric.DIRECTION_WORST)
-      .setOptimizedBestValue(true)
-      .create();
-    saveMetric(PUBLIC_UNDOCUMENTED_API_KEY, metric);
-
     saveMetric(CxxCompilerSensor.KEY, buildReportMetric(CxxCompilerSensor.KEY, "Compiler issues"));
     saveMetric(CxxCppCheckSensor.KEY, buildReportMetric(CxxCppCheckSensor.KEY, "CppCheck issues"));
     saveMetric(CxxOtherSensor.KEY, buildReportMetric(CxxOtherSensor.KEY, "Other tools issues"));

cxx-sensors/src/test/java/org/sonar/cxx/sensors/utils/CxxMetricsTest.java

@@ -83,18 +83,7 @@ public void setUp() {
   @Test
   public void getMetricsTest() {
     List<?> list = metrics.getMetrics();
-    assertThat(list.size()).isEqualTo(14);
+    assertThat(list.size()).isEqualTo(11);
   }
 
-  @Test
-  public void getMetricTest() {
-    Metric<?> metric = language.getMetric(CxxMetrics.PUBLIC_API_KEY);
-    assertThat(metric).isNotNull();
-
-    metric = language.getMetric(CxxMetrics.PUBLIC_UNDOCUMENTED_API_KEY);
-    assertThat(metric).isNotNull();
-
-    metric = language.getMetric(CxxMetrics.PUBLIC_DOCUMENTED_API_DENSITY_KEY);
-    assertThat(metric).isNotNull();
-  }
 }

cxx-squid/src/main/java/org/sonar/cxx/CxxAstScanner.java

@@ -39,7 +39,6 @@
 import org.sonar.cxx.visitors.CxxLinesOfCodeInFunctionBodyVisitor;
 import org.sonar.cxx.visitors.CxxLinesOfCodeVisitor;
 import org.sonar.cxx.visitors.CxxParseErrorLoggerVisitor;
-import org.sonar.cxx.visitors.CxxPublicApiVisitor;
 import org.sonar.squidbridge.AstScanner;
 import org.sonar.squidbridge.CommentAnalyser;
 import org.sonar.squidbridge.SourceCodeBuilderCallback;
@@ -201,9 +200,6 @@ public SourceCode createSourceCode(SourceCode parentSourceCode, AstNode astNode)
     builder.withSquidAstVisitor(new LinesVisitor<>(CxxMetric.LINES));
     builder.withSquidAstVisitor(new CxxLinesOfCodeVisitor<>(CxxMetric.LINES_OF_CODE));
     builder.withSquidAstVisitor(new CxxLinesOfCodeInFunctionBodyVisitor<>());
-    builder.withSquidAstVisitor(new CxxPublicApiVisitor<>(CxxMetric.PUBLIC_API,
-      CxxMetric.PUBLIC_UNDOCUMENTED_API)
-      .withHeaderFileSuffixes(conf.getHeaderFileSuffixes()));
 
     builder.withSquidAstVisitor(CommentsVisitor.<Grammar>builder().withCommentMetric(CxxMetric.COMMENT_LINES)
       .withNoSonar(true)

cxx-squid/src/main/java/org/sonar/cxx/api/CxxMetric.java

@@ -33,9 +33,7 @@ public enum CxxMetric implements MetricDef {
   CLASSES,
   COMPLEXITY,
   COGNITIVE_COMPLEXITY,
-  COMMENT_LINES,
-  PUBLIC_API,
-  PUBLIC_UNDOCUMENTED_API;
+  COMMENT_LINES;
 
   @Override
   public String getName() {

cxx-squid/src/test/java/org/sonar/cxx/api/CxxMetricTest.java

@@ -27,7 +27,7 @@ public class CxxMetricTest {
   @Test
   public void test() {
     SoftAssertions softly = new SoftAssertions();
-    softly.assertThat(CxxMetric.values()).hasSize(12);
+    softly.assertThat(CxxMetric.values()).hasSize(10);
 
     for (CxxMetric metric : CxxMetric.values()) {
       softly.assertThat(metric.getName()).isEqualTo(metric.name());