SONARJAVA-6196 S1451 should provide a default template for headers

java-checks-test-sources/default/src/main/java/checks/FileHeaderCheck/Class4.java

@@ -0,0 +1,7 @@
+
+package checks.FileHeaderCheck;
+
+public class Class4 {
+}
+// Compliant
+

java-checks-test-sources/default/src/main/java/checks/FileHeaderCheck/Class5.java

@@ -0,0 +1,5 @@
+package checks.FileHeaderCheck;
+
+public class Class5 {
+}
+// Compliant

java-checks-test-sources/default/src/main/java/checks/FileHeaderCheck/Class6.java

@@ -0,0 +1,11 @@
+/*
+ * <Your-Product-Name>
+ * Copyright (c) <Year-From>-<Year-To> <Your-Company-Name>
+ *
+ * Please configure this header in your SonarCloud/SonarQube quality profile.
+ */
+package checks.FileHeaderCheck;
+
+public class Class6 {
+}
+// Compliant (default header)

java-checks-test-sources/default/src/main/java/checks/FileHeaderCheck/Regex5.java

@@ -0,0 +1,6 @@
+
+package checks.FileHeaderCheck;
+
+public class Regex5 {
+}
+// Compliant

java-checks-test-sources/default/src/main/java/checks/FileHeaderCheck/Regex6.java

@@ -0,0 +1,5 @@
+package checks.FileHeaderCheck;
+
+public class Regex6 {
+}
+// Compliant

java-checks/src/main/java/org/sonar/java/checks/FileHeaderCheck.java

@@ -31,7 +31,14 @@
 @Rule(key = "S1451")
 public class FileHeaderCheck extends IssuableSubscriptionVisitor {
 
-  private static final String DEFAULT_HEADER_FORMAT = "";
+  private static final String DEFAULT_HEADER_FORMAT = """
+    /*
+     * <Your-Product-Name>
+     * Copyright (c) <Year-From>-<Year-To> <Your-Company-Name>
+     *
+     * Please configure this header in your SonarCloud/SonarQube quality profile.
+     */
+    """;
   private static final String MESSAGE = "Add or update the header of this file.";
 
   @RuleProperty(
@@ -58,23 +65,28 @@ public List<Tree.Kind> nodesToVisit() {
   @Override
   public void setContext(JavaFileScannerContext context) {
     super.context = context;
-    if (isRegularExpression) {
-      if (searchPattern == null) {
-        try {
-          searchPattern = Pattern.compile(getHeaderFormat(), Pattern.DOTALL);
-        } catch (IllegalArgumentException e) {
-          throw new IllegalArgumentException("[" + getClass().getSimpleName() + "] Unable to compile the regular expression: " + headerFormat, e);
+    if (headerFormat.isEmpty()) {
+      expectedLines = new String[] {};
+      isRegularExpression = false;
+    } else {
+      if (isRegularExpression) {
+        if (searchPattern == null) {
+          try {
+            searchPattern = Pattern.compile(getHeaderFormat(), Pattern.DOTALL);
+          } catch (IllegalArgumentException e) {
+            throw new IllegalArgumentException("[" + getClass().getSimpleName() + "] Unable to compile the regular expression: " + headerFormat, e);
+          }
         }
+      } else {
+        expectedLines = headerFormat.split("(?:\r)?\n|\r");
       }
-    } else {
-      expectedLines = headerFormat.split("(?:\r)?\n|\r");
     }
     visitFile();
   }
 
   private String getHeaderFormat() {
     String format = headerFormat;
-    if(format.charAt(0) != '^') {
+    if (format.charAt(0) != '^') {
       format = "^" + format;
     }
     return format;
@@ -114,7 +126,6 @@ private static boolean matches(String[] expectedLines, List<String> lines) {
     } else {
       result = false;
     }
-
     return result;
   }
 

java-checks/src/test/java/org/sonar/java/checks/FileHeaderCheckTest.java

@@ -98,6 +98,26 @@ void test() {
       .onFile(mainCodeSourcesPath("checks/FileHeaderCheck/Class3.java"))
       .withCheck(check)
       .verifyNoIssues();
+
+    check = new FileHeaderCheck();
+    check.headerFormat = "";
+    CheckVerifier.newVerifier()
+      .onFile(mainCodeSourcesPath("checks/FileHeaderCheck/Class4.java"))
+      .withCheck(check)
+      .verifyNoIssues();
+
+    check = new FileHeaderCheck();
+    check.headerFormat = "";
+    CheckVerifier.newVerifier()
+      .onFile(mainCodeSourcesPath("checks/FileHeaderCheck/Class5.java"))
+      .withCheck(check)
+      .verifyNoIssues();
+
+    check = new FileHeaderCheck();
+    CheckVerifier.newVerifier()
+      .onFile(mainCodeSourcesPath("checks/FileHeaderCheck/Class6.java"))
+      .withCheck(check)
+      .verifyNoIssues();
   }
 
   @Test
@@ -139,6 +159,22 @@ void regex() {
       .onFile(mainCodeSourcesPath("checks/FileHeaderCheck/Regex4.java"))
       .withCheck(check)
       .verifyIssues();
+
+    check = new FileHeaderCheck();
+    check.headerFormat = "";
+    check.isRegularExpression = true;
+    CheckVerifier.newVerifier()
+      .onFile(mainCodeSourcesPath("checks/FileHeaderCheck/Regex5.java"))
+      .withCheck(check)
+      .verifyNoIssues();
+
+    check = new FileHeaderCheck();
+    check.headerFormat = "";
+    check.isRegularExpression = true;
+    CheckVerifier.newVerifier()
+      .onFile(mainCodeSourcesPath("checks/FileHeaderCheck/Regex6.java"))
+      .withCheck(check)
+      .verifyNoIssues();
   }
 
   @Test