#33 "source code style rule definition"

- now there are also class members of type Optional<?> (instead of wrapping them on-the-fly in the getter)
- had to add OptionalTypeAdapter because Gson does not!!! support Optional<?> in 2022 (see google/gson#1102)

README.md

@@ -225,3 +225,7 @@ Unresolvable methods (no coverage information available):
 1. usage of immutable data structures only
     1. for collections defensive copies and `Collections.unmodifiableXzy(...)` in constructor
     1. other fields or elements in collections have to be immutable
+1. usage of `Optional<?>` (was actually designed for method return types only, but is the only JDK built-in way to indicate a nullable value (all `@Nullable` annotations are from third-party libraries))
+    1. never pass or return `null`, use `Optional<?>` instead (this eliminates the need for `null` checks everywhere)
+    1. but prefer method overloading or usage of a builder over `Optional<?>` method parameters
+    1. even use `Optional<?>` for class fields (avoids unnecessary `Optional.ofNullable(...)` calls in getter of immutable objects)

test-gap-analysis-maven-plugin/src/main/java/com/scheible/testgapanalysis/maven/OptionalTypeAdapter.java

@@ -0,0 +1,31 @@
+package com.scheible.testgapanalysis.maven;
+
+import com.google.gson.JsonDeserializationContext;
+import com.google.gson.JsonDeserializer;
+import com.google.gson.JsonElement;
+import com.google.gson.JsonParseException;
+import com.google.gson.JsonSerializationContext;
+import com.google.gson.JsonSerializer;
+import java.lang.reflect.Type;
+import java.util.Optional;
+
+/**
+ * Unfortunately Gson has no built-in support for Optional.
+ *
+ * @author sj
+ */
+class OptionalTypeAdapter implements JsonDeserializer<Optional<?>>, JsonSerializer<Optional<?>> {
+
+	OptionalTypeAdapter() {
+	}
+
+	@Override
+	public Optional<?> deserialize(final JsonElement element, final Type type, final JsonDeserializationContext context) throws JsonParseException {
+		throw new UnsupportedOperationException("Not supported yet.");
+	}
+
+	@Override
+	public JsonElement serialize(final Optional<?> value, final Type type, final JsonSerializationContext context) {
+		return context.serialize(value.orElse(null));
+	}
+}

test-gap-analysis-maven-plugin/src/main/java/com/scheible/testgapanalysis/maven/TestGapAnalysisMojo.java

@@ -105,7 +105,8 @@ private void logReport(final TestGapReport report) {
 
 	private void writeJsonReport(final TestGapReport report) throws MojoExecutionException {
 		final File reportFile = new File(buildDir, "test-gap-report.json");
-		final Gson gson = new GsonBuilder().disableHtmlEscaping().setPrettyPrinting().create();
+		final Gson gson = new GsonBuilder().disableHtmlEscaping().setPrettyPrinting()
+				.registerTypeAdapter(Optional.class, new OptionalTypeAdapter()).create();
 
 		try {
 			Files.write(reportFile.toPath(), gson.toJson(report).getBytes());
@@ -114,3 +115,4 @@ private void writeJsonReport(final TestGapReport report) throws MojoExecutionExc
 		}
 	}
 }
+

test-gap-analysis/src/main/java/com/scheible/testgapanalysis/analysis/testgap/TestGapReport.java

@@ -58,8 +58,8 @@ public static class TestGapMethod {
 		private final int sourceLine;
 		private final int sourceColumn;
 
-		private final String coveredMethodName;
-		private final Integer coveredMethodLine;
+		private final Optional<String> coveredMethodName;
+		private final Optional<Integer> coveredMethodLine;
 
 		private TestGapMethod(final String topLevelTypeFqn, final String description, final int sourceLine,
 				final int sourceColumn, final String coveredMethodName, final Integer coveredMethodLine) {
@@ -68,8 +68,8 @@ private TestGapMethod(final String topLevelTypeFqn, final String description, fi
 			this.sourceLine = sourceLine;
 			this.sourceColumn = sourceColumn;
 
-			this.coveredMethodName = coveredMethodName;
-			this.coveredMethodLine = coveredMethodLine;
+			this.coveredMethodName = Optional.ofNullable(coveredMethodName);
+			this.coveredMethodLine = Optional.ofNullable(coveredMethodLine);
 		}
 
 		public TestGapMethod(final String topLevelTypeFqn, final String description, final int sourceLine,
@@ -100,17 +100,17 @@ public int getSourceColumn() {
 		}
 
 		public Optional<String> getCoveredMethodName() {
-			return Optional.ofNullable(coveredMethodName);
+			return coveredMethodName;
 		}
 
 		public Optional<Integer> getCoveredMethodLine() {
-			return Optional.ofNullable(coveredMethodLine);
+			return coveredMethodLine;
 		}
 
 		@Override
 		public String toString() {
-			final String coverageInfo = coveredMethodName != null && coveredMethodLine != null
-					? String.format(" resolved to '%s' with line %d", coveredMethodName, coveredMethodLine)
+			final String coverageInfo = coveredMethodName.isPresent() && coveredMethodLine.isPresent()
+					? String.format(" resolved to '%s' with line %d", coveredMethodName.get(), coveredMethodLine.get())
 					: "";
 			return String.format("%s%s at %d:%d%s", topLevelTypeFqn, description, sourceLine, sourceColumn,
 					coverageInfo);
@@ -144,7 +144,7 @@ public String toString() {
 	private final String workDir;
 
 	private final String oldCommitHash;
-	private final String newCommitHash;
+	private final Optional<String> newCommitHash;
 	private final Boolean compareWithWorkingCopyChanges;
 
 	private final Set<String> jaCoCoReportFiles;
@@ -176,7 +176,7 @@ public static WorkDirStep builder() {
 		this.workDir = builder.workDir;
 
 		this.oldCommitHash = builder.oldCommitHash;
-		this.newCommitHash = builder.newCommitHash.orElse(null);
+		this.newCommitHash = builder.newCommitHash;
 		compareWithWorkingCopyChanges = builder.newCommitHash.isPresent() ? null : Boolean.TRUE;
 
 		this.jaCoCoReportFiles = Collections.unmodifiableSet(new HashSet<>(builder.jaCoCoReportFiles));
@@ -210,7 +210,7 @@ public String getOldCommitHash() {
 	}
 
 	public Optional<String> getNewCommitHash() {
-		return Optional.ofNullable(newCommitHash);
+		return newCommitHash;
 	}
 
 	public Boolean getCompareWithWorkingCopyChanges() {

test-gap-analysis/src/main/java/com/scheible/testgapanalysis/parser/ParsedMethod.java

@@ -39,7 +39,7 @@ public enum MethodType {
 	private final int argumentCount;
 	private final List<String> argumentTypes;
 	private final Map<String, String> typeParameters;
-	private final String outerDeclaringType;
+	private final Optional<String> outerDeclaringType;
 
 	public static MethodTypeStep builder() {
 		return new BuilderImpl();
@@ -65,7 +65,7 @@ public static MethodTypeStep builder() {
 		argumentCount = argumentTypes.size();
 		this.typeParameters = Collections
 				.unmodifiableMap(builder.typeParameters != null ? new HashMap<>(builder.typeParameters) : emptyMap());
-		this.outerDeclaringType = builder.outerDeclaringType.orElse(null);
+		this.outerDeclaringType = builder.outerDeclaringType;
 	}
 
 	public MethodType getMethodType() {
@@ -175,7 +175,7 @@ public Map<String, String> getTypeParameters() {
 	}
 
 	public Optional<String> getOuterDeclaringType() {
-		return Optional.of(outerDeclaringType);
+		return outerDeclaringType;
 	}
 
 	public String getDescription() {
@@ -238,6 +238,6 @@ public String toString() {
 				+ ", empty=" + empty + (!argumentTypes.isEmpty() ? ", parameterTypes=" + argumentTypes : "")
 				+ ", argumentCount=" + argumentCount
 				+ (!typeParameters.isEmpty() ? ", typeParameters=" + typeParameters : "")
-				+ (outerDeclaringType != null ? ", outerDeclaringType=" + outerDeclaringType : "") + "]";
+				+ (outerDeclaringType.isPresent() ? ", outerDeclaringType=" + outerDeclaringType.get() : "") + "]";
 	}
 }