Issue #124: Implement recipe for NewlineAtEndOfFile

.gitattributes

@@ -0,0 +1,5 @@
+# Test resources that need specific eol
+src/test/resources/org/checkstyle/autofix/recipe/newlineatendoffile/** -text
+
+# Force LF line endings for diff test files
+*.diff text eol=lf

src/main/java/org/checkstyle/autofix/CheckstyleCheck.java

@@ -23,6 +23,7 @@
 public enum CheckstyleCheck {
     FINAL_LOCAL_VARIABLE("com.puppycrawl.tools.checkstyle.checks.coding.FinalLocalVariableCheck"),
     HEADER("com.puppycrawl.tools.checkstyle.checks.header.HeaderCheck"),
+    NEWLINE_AT_END_OF_FILE("com.puppycrawl.tools.checkstyle.checks.NewlineAtEndOfFileCheck"),
     UPPER_ELL("com.puppycrawl.tools.checkstyle.checks.UpperEllCheck"),
     HEX_LITERAL_CASE("com.puppycrawl.tools.checkstyle.checks.HexLiteralCaseCheck"),
     REDUNDANT_IMPORT("com.puppycrawl.tools.checkstyle.checks.imports.RedundantImportCheck");

src/main/java/org/checkstyle/autofix/CheckstyleRecipeRegistry.java

@@ -30,6 +30,7 @@
 import org.checkstyle.autofix.recipe.FinalLocalVariable;
 import org.checkstyle.autofix.recipe.Header;
 import org.checkstyle.autofix.recipe.HexLiteralCase;
+import org.checkstyle.autofix.recipe.NewlineAtEndOfFile;
 import org.checkstyle.autofix.recipe.RedundantImport;
 import org.checkstyle.autofix.recipe.UpperEll;
 import org.openrewrite.Recipe;
@@ -48,6 +49,7 @@ public final class CheckstyleRecipeRegistry {
         RECIPE_MAP.put(CheckstyleCheck.HEX_LITERAL_CASE, HexLiteralCase::new);
         RECIPE_MAP.put(CheckstyleCheck.FINAL_LOCAL_VARIABLE, FinalLocalVariable::new);
         RECIPE_MAP_WITH_CONFIG.put(CheckstyleCheck.HEADER, Header::new);
+        RECIPE_MAP_WITH_CONFIG.put(CheckstyleCheck.NEWLINE_AT_END_OF_FILE, NewlineAtEndOfFile::new);
         RECIPE_MAP.put(CheckstyleCheck.REDUNDANT_IMPORT, RedundantImport::new);
     }
 

src/main/java/org/checkstyle/autofix/recipe/Header.java

@@ -39,7 +39,7 @@ public class Header extends Recipe {
     private static final String HEADER_PROPERTY = "header";
     private static final String HEADER_FILE_PROPERTY = "headerFile";
     private static final String CHARSET_PROPERTY = "charset";
-    private static final String LINE_SEPARATOR = "\n";
+    private static final String LINE_SEPARATOR = System.lineSeparator();
 
     private final List<CheckstyleViolation> violations;
     private final CheckConfiguration config;
@@ -75,7 +75,7 @@ private static String extractLicenseHeader(CheckConfiguration config) {
                     .getPropertyOrDefault(CHARSET_PROPERTY, Charset.defaultCharset().name()));
             final String headerFilePath = config.getProperty(HEADER_FILE_PROPERTY);
             try {
-                header = toLfLineEnding(Files.readString(Path.of(headerFilePath), charsetToUse));
+                header = Files.readString(Path.of(headerFilePath), charsetToUse);
             }
             catch (IOException exception) {
                 throw new IllegalArgumentException("Failed to extract header from config",
@@ -85,10 +85,6 @@ private static String extractLicenseHeader(CheckConfiguration config) {
         return header;
     }
 
-    private static String toLfLineEnding(String text) {
-        return text.replaceAll("(?x)\\\\r(?=\\\\n)|\\r(?=\\n)", "");
-    }
-
     private static class HeaderVisitor extends JavaIsoVisitor<ExecutionContext> {
         private final List<CheckstyleViolation> violations;
         private final String licenseHeader;
@@ -121,8 +117,7 @@ public J visit(Tree tree, ExecutionContext executionContext) {
         private String extractCurrentHeader(JavaSourceFile sourceFile) {
             return sourceFile.getComments().stream()
                     .map(comment -> {
-                        return comment.printComment(getCursor())
-                                + toLfLineEnding(comment.getSuffix());
+                        return comment.printComment(getCursor()) + comment.getSuffix();
                     })
                     .collect(Collectors.joining(""));
         }

src/main/java/org/checkstyle/autofix/recipe/NewlineAtEndOfFile.java

@@ -0,0 +1,151 @@
+///////////////////////////////////////////////////////////////////////////////////////////////
+// checkstyle-openrewrite-recipes: Automatically fix Checkstyle violations with OpenRewrite.
+// Copyright (C) 2025 The Checkstyle OpenRewrite Recipes Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+///////////////////////////////////////////////////////////////////////////////////////////////
+
+package org.checkstyle.autofix.recipe;
+
+import java.nio.file.Path;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.function.UnaryOperator;
+
+import org.checkstyle.autofix.parser.CheckConfiguration;
+import org.checkstyle.autofix.parser.CheckstyleViolation;
+import org.openrewrite.ExecutionContext;
+import org.openrewrite.Recipe;
+import org.openrewrite.Tree;
+import org.openrewrite.TreeVisitor;
+import org.openrewrite.java.JavaIsoVisitor;
+import org.openrewrite.java.format.AutodetectGeneralFormatStyle;
+import org.openrewrite.java.tree.Comment;
+import org.openrewrite.java.tree.J;
+import org.openrewrite.java.tree.JavaSourceFile;
+import org.openrewrite.java.tree.Space;
+import org.openrewrite.style.GeneralFormatStyle;
+import org.openrewrite.style.Style;
+
+public class NewlineAtEndOfFile extends Recipe {
+
+    private final List<CheckstyleViolation> violations;
+    private final CheckConfiguration config;
+
+    public NewlineAtEndOfFile(List<CheckstyleViolation> violations, CheckConfiguration config) {
+        this.violations = violations;
+        this.config = config;
+    }
+
+    @Override
+    public String getDisplayName() {
+        return "End files with a single newline";
+    }
+
+    @Override
+    public String getDescription() {
+        return "Some tools work better when files end with an empty line.";
+    }
+
+    @Override
+    public TreeVisitor<?, ExecutionContext> getVisitor() {
+        final String lineSeparator = config.getProperty("lineSeparator");
+        return new NewLineAtEndOfFileVisitor(violations, lineSeparator);
+    }
+
+    private static class NewLineAtEndOfFileVisitor extends JavaIsoVisitor<ExecutionContext> {
+        private final List<CheckstyleViolation> violations;
+        private final String lineSeparatorConfig;
+
+        NewLineAtEndOfFileVisitor(List<CheckstyleViolation> violations,
+                                         String lineSeparatorConfig) {
+            this.violations = violations;
+            this.lineSeparatorConfig = lineSeparatorConfig.toLowerCase();
+        }
+
+        @Override
+        public J visit(Tree tree, ExecutionContext executionContext) {
+            J result = (J) tree;
+
+            if (tree instanceof JavaSourceFile sourceFile) {
+
+                final Path filePath = sourceFile.getSourcePath().toAbsolutePath();
+
+                if (hasViolation(filePath)) {
+                    final String expectedLineEnding = determineLineEnding(sourceFile);
+
+                    final Space eof = sourceFile.getEof();
+                    final String lastWhitespace = eof.getLastWhitespace();
+
+                    if (!expectedLineEnding.equals(lastWhitespace)) {
+                        final List<Comment> comments = eof.getComments();
+                        if (comments.isEmpty()) {
+                            result = sourceFile.withEof(Space.format(expectedLineEnding));
+                        }
+                        else {
+                            result = sourceFile.withEof(sourceFile.getEof().withComments(mapLast(
+                                    comments, comment -> comment.withSuffix(expectedLineEnding))));
+                        }
+                    }
+                }
+            }
+
+            return result;
+        }
+
+        private String determineLineEnding(JavaSourceFile sourceFile) {
+            return switch (lineSeparatorConfig) {
+                case "lf" -> "\n";
+                case "crlf" -> "\r\n";
+                case "cr" -> "\r";
+                case "system" -> System.lineSeparator();
+                case "lf_cr_crlf" -> getAutodetectedLineEnding(sourceFile);
+                default -> {
+                    throw new IllegalStateException("Unexpected value: " + lineSeparatorConfig);
+                }
+            };
+        }
+
+        private String getAutodetectedLineEnding(JavaSourceFile sourceFile) {
+            final GeneralFormatStyle generalFormatStyle =
+                    Style.from(GeneralFormatStyle.class, sourceFile, () -> {
+                        return AutodetectGeneralFormatStyle
+                                .autodetectGeneralFormatStyle(sourceFile);
+                    });
+            return generalFormatStyle.newLine();
+        }
+
+        private static List<Comment> mapLast(List<Comment> comments,
+                                             UnaryOperator<Comment> mapper) {
+            List<Comment> result = comments;
+
+            if (comments != null && !comments.isEmpty()) {
+                final int lastIndex = comments.size() - 1;
+                final Comment last = comments.get(lastIndex);
+                final Comment newLast = mapper.apply(last);
+
+                if (last != newLast) {
+                    result = new ArrayList<>(comments);
+                    result.set(lastIndex, newLast);
+                }
+            }
+
+            return result;
+        }
+
+        private boolean hasViolation(Path filePath) {
+            return violations.stream()
+                    .anyMatch(violation -> violation.getFilePath().endsWith(filePath));
+        }
+    }
+}

src/test/java/org/checkstyle/autofix/generator/GenerateDiffFilesTest.java

@@ -84,6 +84,7 @@ private void createDiff(Path inputFile) throws IOException, InterruptedException
         }
 
         final String diff = out.toString();
-        Files.writeString(diffFile, diff);
+        final String normalizedDiff = diff.replaceAll("\\r\\n?", "\n");
+        Files.writeString(diffFile, normalizedDiff);
     }
 }

src/test/java/org/checkstyle/autofix/recipe/AbstractRecipeTestSupport.java

@@ -100,8 +100,9 @@ private void verify(Configuration config, Path reportPath, String inputPath, Str
         try {
             final Recipe mainRecipe = new CheckstyleAutoFix(reportPath.toString(),
                     configPath.toString());
-            final String beforeCode = readFile(getPath(inputPath));
-            final String expectedAfterCode = readFile(getPath(outputPath));
+            final String beforeCode = Files.readString(Path.of(getPath(inputPath)));
+            final String expectedAfterCode = Files.readString(Path.of(getPath(outputPath)));
+
             testRecipe(beforeCode, expectedAfterCode,
                     getPath(inputPath), new InputClassRenamer(),
                     mainRecipe, new RemoveViolationComments());
@@ -194,8 +195,14 @@ private Configuration getCheckConfigurations(String inputPath) throws Exception
     private String[] convertToExpectedMessages(List<CheckstyleViolation> violations) {
         return violations.stream()
                 .map(violation -> {
-                    return violation.getLine() + ":"
-                                + violation.getColumn() + ": " + violation.getMessage();
+                    String message = violation.getLine() + ":";
+                    if (violation.getColumn() != -1) {
+                        message += violation.getColumn() + ": ";
+                    }
+                    else {
+                        message += " ";
+                    }
+                    return message + violation.getMessage();
                 })
                 .toArray(String[]::new);
     }
@@ -205,7 +212,7 @@ private void testRecipe(String beforeCode, String expectedAfterCode,
         assertDoesNotThrow(() -> {
             rewriteRun(
                     spec -> spec.recipes(recipes),
-                    java(beforeCode, expectedAfterCode, spec -> spec.path(filePath))
+                    java(beforeCode, expectedAfterCode, spec -> spec.path(filePath).noTrim())
             );
         });
     }

src/test/java/org/checkstyle/autofix/recipe/NewLineAtEndOfFileTest.java

@@ -0,0 +1,37 @@
+///////////////////////////////////////////////////////////////////////////////////////////////
+// checkstyle-openrewrite-recipes: Automatically fix Checkstyle violations with OpenRewrite.
+// Copyright (C) 2025 The Checkstyle OpenRewrite Recipes Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+///////////////////////////////////////////////////////////////////////////////////////////////
+
+package org.checkstyle.autofix.recipe;
+
+import org.checkstyle.autofix.parser.ReportParser;
+
+public class NewLineAtEndOfFileTest extends AbstractRecipeTestSupport {
+    @Override
+    protected String getSubpackage() {
+        return "newlineatendoffile";
+    }
+
+    @RecipeTest
+    void newLineCrlf(ReportParser parser) throws Exception {
+        verify(parser, "NewlineAtEndOfFileCrlf");
+    }
+
+    @RecipeTest
+    void noNewLine(ReportParser parser) throws Exception {
+        verify(parser, "NewlineAtEndOfFileNoNewLine");
+    }
+}

src/test/resources/org/checkstyle/autofix/recipe/newlineatendoffile/newlineatendoffilecrlf/DiffNewlineAtEndOfFileCrlf.diff

@@ -0,0 +1,14 @@
+--- src/test/resources/org/checkstyle/autofix/recipe/newlineatendoffile/newlineatendoffilecrlf/InputNewlineAtEndOfFileCrlf.java
++++ src/test/resources/org/checkstyle/autofix/recipe/newlineatendoffile/newlineatendoffilecrlf/OutputNewlineAtEndOfFileCrlf.java
+@@ -4,9 +4,8 @@
+ fileExtensions = (default)""
+
+ */
+-// violation 6 lines above 'Expected line ending for file is LF(\\n), but CRLF(\\r\\n) is detected.'
+
+ package org.checkstyle.autofix.recipe.newlineatendoffile.newlineatendoffilecrlf;
+
+-public class InputNewlineAtEndOfFileCrlf {
+-}
++public class OutputNewlineAtEndOfFileCrlf {
++}

src/test/resources/org/checkstyle/autofix/recipe/newlineatendoffile/newlineatendoffilecrlf/InputNewlineAtEndOfFileCrlf.java

@@ -0,0 +1,12 @@
+/*
+com.puppycrawl.tools.checkstyle.checks.NewlineAtEndOfFileCheck
+lineSeparator = lf
+fileExtensions = (default)""
+
+*/
+// violation 6 lines above 'Expected line ending for file is LF(\\n), but CRLF(\\r\\n) is detected.'
+
+package org.checkstyle.autofix.recipe.newlineatendoffile.newlineatendoffilecrlf;
+
+public class InputNewlineAtEndOfFileCrlf {
+}

src/test/resources/org/checkstyle/autofix/recipe/newlineatendoffile/newlineatendoffilecrlf/OutputNewlineAtEndOfFileCrlf.java

@@ -0,0 +1,11 @@
+/*
+com.puppycrawl.tools.checkstyle.checks.NewlineAtEndOfFileCheck
+lineSeparator = lf
+fileExtensions = (default)""
+
+*/
+
+package org.checkstyle.autofix.recipe.newlineatendoffile.newlineatendoffilecrlf;
+
+public class OutputNewlineAtEndOfFileCrlf {
+}

src/test/resources/org/checkstyle/autofix/recipe/newlineatendoffile/newlineatendoffilenonewline/DiffNewlineAtEndOfFileNoNewLine.diff

@@ -0,0 +1,16 @@
+--- src/test/resources/org/checkstyle/autofix/recipe/newlineatendoffile/newlineatendoffilenonewline/InputNewlineAtEndOfFileNoNewLine.java
++++ src/test/resources/org/checkstyle/autofix/recipe/newlineatendoffile/newlineatendoffilenonewline/OutputNewlineAtEndOfFileNoNewLine.java
+@@ -4,10 +4,9 @@
+ fileExtensions = (default)""
+
+ */
+-// violation 6 lines above 'File does not end with a newline.'
+
+ package org.checkstyle.autofix.recipe.newlineatendoffile.newlineatendoffilenonewline;
+
+-public interface InputNewlineAtEndOfFileNoNewLine
++public interface OutputNewlineAtEndOfFileNoNewLine
+ {
+-}
+\ No newline at end of file
++}

src/test/resources/org/checkstyle/autofix/recipe/newlineatendoffile/newlineatendoffilenonewline/InputNewlineAtEndOfFileNoNewLine.java

@@ -0,0 +1,13 @@
+/*
+com.puppycrawl.tools.checkstyle.checks.NewlineAtEndOfFileCheck
+lineSeparator = LF
+fileExtensions = (default)""
+
+*/
+// violation 6 lines above 'File does not end with a newline.'
+
+package org.checkstyle.autofix.recipe.newlineatendoffile.newlineatendoffilenonewline;
+
+public interface InputNewlineAtEndOfFileNoNewLine
+{
+}

src/test/resources/org/checkstyle/autofix/recipe/newlineatendoffile/newlineatendoffilenonewline/OutputNewlineAtEndOfFileNoNewLine.java

@@ -0,0 +1,12 @@
+/*
+com.puppycrawl.tools.checkstyle.checks.NewlineAtEndOfFileCheck
+lineSeparator = LF
+fileExtensions = (default)""
+
+*/
+
+package org.checkstyle.autofix.recipe.newlineatendoffile.newlineatendoffilenonewline;
+
+public interface OutputNewlineAtEndOfFileNoNewLine
+{
+}