Report usage of preview API only when the project compliance is at latest #3943 (#3947)

* Report warning about preview API being used instead of error when target platform is not latest. Keep everything else same.

#3947

Author: jarthana

org.eclipse.jdt.core.compiler.batch/src/org/eclipse/jdt/internal/compiler/problem/ProblemReporter.java

@@ -9560,33 +9560,31 @@ public void previewAPIUsed(Scope scope, int sourceStart, int sourceEnd, IBinaryA
 			}
 		} else
 			if (CharOperation.equals(valuePair.getName(), ConstantPool.REFLECTIVE)) {
-			if (valuePair.getValue() instanceof BooleanConstant bool)
-				isReflective = bool.booleanValue();
+				if (valuePair.getValue() instanceof BooleanConstant bool)
+					isReflective = bool.booleanValue();
 		}
 	}
 
-
-	String[] arguments = { featureName };
 	int problemId = -1;
 	int severity = -1;
 	if (!this.options.enablePreviewFeatures) {
-		problemId = IProblem.PreviewAPIDisabled;
-		severity = isReflective ? ProblemSeverities.Warning : ProblemSeverities.Error;
+		if (this.options.complianceLevel < ClassFileConstants.getLatestJDKLevel()) {
+			problemId = IProblem.PreviewAPIUsed;
+			severity = ProblemSeverities.Warning;
+		} else {
+			problemId = IProblem.PreviewAPIDisabled;
+			severity = isReflective ? ProblemSeverities.Warning : ProblemSeverities.Error;
+		}
 	} else {
 		this.referenceContext.compilationResult().usesPreview = true;
 		if (this.options.isAnyEnabled(IrritantSet.PREVIEW)) {
 			severity = ProblemSeverities.Warning;
 			problemId = IProblem.PreviewAPIUsed;
 		}
 	}
-	if (problemId != -1 && severity != -1)
-		this.handle(
-				problemId,
-				arguments,
-				arguments,
-				severity,
-				sourceStart,
-				sourceEnd);
+	if (problemId == -1 || severity == -1) return;
+	String[] arguments = { featureName };
+	this.handle(problemId, arguments, arguments, severity, sourceStart, sourceEnd);
 }
 //Returns true if the problem is handled and reported (only errors considered and not warnings)
 private boolean validateRestrictedKeywords(char[] name, int start, int end, boolean reportSyntaxError) {

org.eclipse.jdt.core.tests.compiler/src/org/eclipse/jdt/core/tests/compiler/regression/PreviewFlagTest.java

@@ -28,7 +28,7 @@ public class PreviewFlagTest extends AbstractRegressionTest9 {
 	static {
 //		TESTS_NUMBERS = new int [] { 1 };
 //		TESTS_RANGE = new int[] { 1, -1 };
-//		TESTS_NAMES = new String[] { "testIssue3614_001" };
+//		TESTS_NAMES = new String[] { "testIssue3943_001" };
 //		TESTS_NAMES = new String[] { "testIssue3614_001" };
 	}
 	private String extraLibPath;
@@ -151,15 +151,21 @@ public static void main(String[] args) {
 							ScopedValue<Integer> si = ScopedValue.newInstance();
 							System.out.println(si == null ? "hello" : "world");
 						}
+						public int foo() {}
 					}
 					"""
 			},
-			"----------\n" +
-			"1. ERROR in X.java (at line 3)\n" +
-			"	ScopedValue<Integer> si = ScopedValue.newInstance();\n" +
-			"	                          ^^^^^^^^^^^\n" +
-			"This API is part of the preview feature 'Scoped Values' which is disabled by default. Use --enable-preview to enable\n" +
-			"----------\n",
+				"----------\n" +
+				"1. ERROR in X.java (at line 3)\n" +
+				"	ScopedValue<Integer> si = ScopedValue.newInstance();\n" +
+				"	                          ^^^^^^^^^^^\n" +
+				"This API is part of the preview feature 'Scoped Values' which is disabled by default. Use --enable-preview to enable\n" +
+				"----------\n" +
+				"2. ERROR in X.java (at line 6)\n" +
+				"	public int foo() {}\n" +
+				"	           ^^^^^\n" +
+				"This method must return a result of type int\n" +
+				"----------\n",
 			null,
 			true,
 			options);
@@ -181,12 +187,12 @@ public static void main(String... args) {}
 				"""
 			};
 		runner.expectedCompilerLog =
-			"----------\n" +
-			"1. WARNING in X.java (at line 4)\n" +
-			"	return tree.isModule();\n" +
-			"	       ^^^^^^^^^^^^^^^\n" +
-			"This API is part of the preview feature 'Module Import Declarations' which is disabled by default. Use --enable-preview to enable\n" +
-			"----------\n";
+				"----------\n" +
+				"1. WARNING in X.java (at line 4)\n" +
+				"	return tree.isModule();\n" +
+				"	       ^^^^^^^^^^^^^^^\n" +
+				"This API is part of the preview feature 'Module Import Declarations' which is disabled by default. Use --enable-preview to enable\n" +
+				"----------\n";
 		runner.runConformTest();
 	}
 	public void testIssue3614_003_enabled() throws Exception {
@@ -218,4 +224,74 @@ public void main(String... args) {
 		runner.expectedOutputString = "42";
 		runner.runConformTest();
 	}
+	public void testIssue3943_001() throws IOException, ClassFormatException {
+		Map<String, String> options = getCompilerOptions();
+		String str = options.get(CompilerOptions.OPTION_Compliance);
+		options.put(CompilerOptions.OPTION_Compliance, CompilerOptions.VERSION_23);
+		options.put(CompilerOptions.OPTION_Source, CompilerOptions.VERSION_23);
+		options.put(CompilerOptions.OPTION_TargetPlatform, CompilerOptions.VERSION_23);
+		options.put(CompilerOptions.OPTION_EnablePreviews, CompilerOptions.DISABLED);
+		runNegativeTest(new String[] {
+				"X.java",
+				"""
+				public class X {
+					public static void main(String[] args) {
+						ScopedValue<Integer> si = ScopedValue.newInstance();
+						System.out.println(si == null ? "hello" : "world");
+					}
+					public int foo() {}
+				}
+				"""},
+				"----------\n" +
+				"1. WARNING in X.java (at line 3)\n" +
+				"	ScopedValue<Integer> si = ScopedValue.newInstance();\n" +
+				"	                          ^^^^^^^^^^^\n" +
+				"You are using an API that is part of the preview feature \'Scoped Values\' and may be removed in future\n" +
+				"----------\n" +
+				"2. ERROR in X.java (at line 6)\n" +
+				"	public int foo() {}\n" +
+				"	           ^^^^^\n" +
+				"This method must return a result of type int\n" +
+				"----------\n",
+			null,
+			true,
+			options);
+		options.put(CompilerOptions.OPTION_Compliance, str);
+		options.put(CompilerOptions.OPTION_Source, str);
+		options.put(CompilerOptions.OPTION_TargetPlatform, str);
+		options.put(CompilerOptions.OPTION_EnablePreviews, CompilerOptions.ENABLED);
+	}
+	public void testIssue3943_002() throws IOException, ClassFormatException {
+		Map<String, String> options = getCompilerOptions();
+		String str = options.get(CompilerOptions.OPTION_Compliance);
+		options.put(CompilerOptions.OPTION_Compliance, CompilerOptions.VERSION_23);
+		options.put(CompilerOptions.OPTION_Source, CompilerOptions.VERSION_23);
+		options.put(CompilerOptions.OPTION_TargetPlatform, CompilerOptions.VERSION_23);
+		options.put(CompilerOptions.OPTION_EnablePreviews, CompilerOptions.DISABLED);
+		runNegativeTest(new String[] {
+				"X.java",
+				"""
+				public class X {
+					@SuppressWarnings("preview")
+					public static void main(String[] args) {
+						ScopedValue<Integer> si = ScopedValue.newInstance();
+						System.out.println(si == null ? "hello" : "world");
+					}
+					public int foo() {}
+				}
+				"""},
+				"----------\n" +
+				"1. ERROR in X.java (at line 7)\n" +
+				"	public int foo() {}\n" +
+				"	           ^^^^^\n" +
+				"This method must return a result of type int\n" +
+				"----------\n",
+			null,
+			true,
+			options);
+		options.put(CompilerOptions.OPTION_Compliance, str);
+		options.put(CompilerOptions.OPTION_Source, str);
+		options.put(CompilerOptions.OPTION_TargetPlatform, str);
+		options.put(CompilerOptions.OPTION_EnablePreviews, CompilerOptions.ENABLED);
+	}
 }