Raise a diagnostic for unnecessary IGNORE statements

libs/natlint/src/main/java/org/amshove/natlint/analyzers/UnnecessaryIgnoreAnalyzer.java

@@ -0,0 +1,48 @@
+package org.amshove.natlint.analyzers;
+
+import org.amshove.natlint.api.AbstractAnalyzer;
+import org.amshove.natlint.api.DiagnosticDescription;
+import org.amshove.natlint.api.IAnalyzeContext;
+import org.amshove.natlint.api.ILinterContext;
+import org.amshove.natparse.DiagnosticSeverity;
+import org.amshove.natparse.NodeUtil;
+import org.amshove.natparse.ReadOnlyList;
+import org.amshove.natparse.natural.IIgnoreNode;
+import org.amshove.natparse.natural.IStatementListNode;
+import org.amshove.natparse.natural.ISyntaxNode;
+
+public class UnnecessaryIgnoreAnalyzer extends AbstractAnalyzer
+{
+	public static final DiagnosticDescription UNNECESSARY_IGNORE = DiagnosticDescription.create(
+		"NL025",
+		"IGNORE is unnecessary",
+		DiagnosticSeverity.INFO
+	);
+
+	@Override
+	public ReadOnlyList<DiagnosticDescription> getDiagnosticDescriptions()
+	{
+		return ReadOnlyList.of(UNNECESSARY_IGNORE);
+	}
+
+	@Override
+	public void initialize(ILinterContext context)
+	{
+		context.registerNodeAnalyzer(IIgnoreNode.class, this::analyzeIgnore);
+	}
+
+	private void analyzeIgnore(ISyntaxNode node, IAnalyzeContext context)
+	{
+		var ignore = (IIgnoreNode) node;
+
+		if (!(NodeUtil.findFirstParentOfType(ignore, IStatementListNode.class)instanceof IStatementListNode parent))
+		{
+			return;
+		}
+
+		if (parent.statements().size() > 1)
+		{
+			context.report(UNNECESSARY_IGNORE.createDiagnostic(ignore));
+		}
+	}
+}

libs/natlint/src/test/java/org/amshove/natlint/analyzers/UnnecessaryIgnoreAnalyzerShould.java

@@ -0,0 +1,83 @@
+package org.amshove.natlint.analyzers;
+
+import org.amshove.natlint.linter.AbstractAnalyzerTest;
+import org.junit.jupiter.api.Test;
+
+class UnnecessaryIgnoreAnalyzerShould extends AbstractAnalyzerTest
+{
+	protected UnnecessaryIgnoreAnalyzerShould()
+	{
+		super(new UnnecessaryIgnoreAnalyzer());
+	}
+
+	@Test
+	void reportADiagnosticIfIgnoreIsUnnecessaryInIfs()
+	{
+		testDiagnostics(
+			"""
+			DEFINE DATA LOCAL
+			END-DEFINE
+			IF TRUE
+			  WRITE 'Hi'
+			  IGNORE
+			END-IF
+			END
+			""",
+			expectDiagnostic(4, UnnecessaryIgnoreAnalyzer.UNNECESSARY_IGNORE)
+		);
+	}
+
+	@Test
+	void reportNoDiagnosticIfIgnoreIsNeccessaryInIfs()
+	{
+		testDiagnostics(
+			"""
+				DEFINE DATA LOCAL
+				END-DEFINE
+				IF TRUE
+				  IGNORE
+				END-IF
+				END
+				""",
+			expectNoDiagnosticOfType(UnnecessaryIgnoreAnalyzer.UNNECESSARY_IGNORE)
+		);
+	}
+
+	@Test
+	void reportADiagnosticIfIgnoreIsTheOnlyStatementInAModule()
+	{
+		testDiagnostics(
+			"""
+				DEFINE DATA LOCAL
+				END-DEFINE
+				IGNORE
+				END
+				""",
+			expectDiagnostic(2, UnnecessaryIgnoreAnalyzer.UNNECESSARY_IGNORE)
+		);
+	}
+
+	@Test
+	void reportNoDiagnosticIfIgnoreIsNeccessaryInDecideBlcosk()
+	{
+		testDiagnostics(
+			"""
+				DEFINE DATA LOCAL
+				1 #VAR (N1)
+				END-DEFINE
+				DECIDE ON FIRST VALUE OF #VAR
+				  VALUE 1
+				    IGNORE
+				  VALUE 2
+				    IGNORE
+				  NONE VALUE
+				    IGNORE
+				  ANY VALUE
+				    IGNORE
+				END-DECIDE
+				END
+				""",
+			expectNoDiagnosticOfType(UnnecessaryIgnoreAnalyzer.UNNECESSARY_IGNORE)
+		);
+	}
+}

tools/ruletranslator/src/main/resources/rules/NL025

@@ -0,0 +1,6 @@
+name: IGNORE is unnecessary
+priority: MINOR
+tags: pitfall,confusing
+type: CODE_SMELL
+description:
+If an ``IGNORE`` is not the only statement in a block, it is unnecessary and can be removed.