More expressive return type from generator

Instead of returning just a String with the Java source file
(compilation unit), instead include all information needed to correctly
write the source to a file.

generator/src/main/java/no/rune/record/matcher/JavaCompilationUnit.java

@@ -0,0 +1,33 @@
+package no.rune.record.matcher;
+
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.NotDirectoryException;
+import java.nio.file.Path;
+import java.util.Optional;
+
+import static java.nio.file.Files.isDirectory;
+
+public record JavaCompilationUnit(String content, String name, Optional<String> packageName) {
+
+    public JavaCompilationUnit(String content, String name, Package location) {
+        this(content, name, Optional.of(location).map(Package::getName));
+    }
+
+    Path writeToBaseDirectory(Path baseDirectory) throws NotDirectoryException, IOException {
+        if (!isDirectory(baseDirectory)) {
+            throw new NotDirectoryException(baseDirectory.toString());
+        }
+        var targetDirectory = packageName.map(p -> baseDirectory.resolve(p.replace('.', '/'))).orElse(baseDirectory);
+        var targetFile = targetDirectory.resolve(name + ".java");
+        try {
+            if (!baseDirectory.equals(targetDirectory)) {
+                Files.createDirectories(targetDirectory);
+            }
+            return Files.writeString(targetFile, content);
+        } catch (IOException e) {
+            throw new IOException("Unable to write to " + targetFile + ", " +
+                    "because " + e.getClass().getSimpleName() + ": " + e.getMessage(), e);
+        }
+    }
+}

generator/src/main/java/no/rune/record/matcher/RecordMatcherGenerator.java

@@ -25,11 +25,11 @@ public class RecordMatcherGenerator {
 
     public static final RecordMatcherClassNameResolver DEFAULT_MATCHER_NAME_RESOLVER = new DefaultRecordMatcherClassNameResolver();
 
-    public String generateFromRecord(Class<? extends Record> record) {
+    public JavaCompilationUnit generateFromRecord(Class<? extends Record> record) {
         return generateFromRecord(record, record.getPackage(), DEFAULT_MATCHER_NAME_RESOLVER.resolve(record));
     }
 
-    public String generateFromRecord(Class<? extends Record> record, Package target, String matcherSimpleClassName) {
+    public JavaCompilationUnit generateFromRecord(Class<? extends Record> record, Package target, String matcherSimpleClassName) {
 
         var codeFactory = new CodeFactory(record, ClassName.get(target.getName(), matcherSimpleClassName));
 
@@ -140,10 +140,11 @@ public String generateFromRecord(Class<? extends Record> record, Package target,
             .addMethod(matchesSafelyMethodBuilder.build());
 
 
-        return JavaFile.builder(target.getName(), matcherClassBuilder.build())
+        String compilationUnitContent = JavaFile.builder(target.getName(), matcherClassBuilder.build())
                 .indent("    ")
                 .skipJavaLangImports(true)
                 .build().toString();
+        return new JavaCompilationUnit(compilationUnitContent, matcherSimpleClassName, target);
     }
 
 

generator/src/test/java/no/rune/record/matcher/DefaultRecordMatcherClassNameResolverTest.java

@@ -1,6 +1,5 @@
 package no.rune.record.matcher;
 
-import no.rune.record.matcher.DefaultRecordMatcherClassNameResolver;
 import org.junit.jupiter.api.Test;
 
 import static org.hamcrest.MatcherAssert.assertThat;

generator/src/test/java/no/rune/record/matcher/ExpectedMatcher.java

@@ -33,15 +33,15 @@ public static ExpectedMatcher expectedMatcherFor(Class<? extends Record> record)
 
     private static final RecordMatcherGenerator generator = new RecordMatcherGenerator();
 
-    public String generatedSourceCode() {
+    public JavaCompilationUnit generatedSourceCode() {
         return generator.generateFromRecord(record());
     }
 
     public void assertEqualToGeneratedMatcherSourceCode() {
         var generatedSourceCode = generatedSourceCode();
-        assertEquals(sourceCode(), generatedSourceCode);
+        assertEquals(sourceCode(), generatedSourceCode.content());
 
-        var compiledGeneratedMatcher = javac().compile(JavaFileObjects.forSourceString(fullyQualifiedClassName(), generatedSourceCode));
+        var compiledGeneratedMatcher = javac().compile(JavaFileObjects.forSourceString(fullyQualifiedClassName(), generatedSourceCode.content()));
         assertAll(
                 () -> assertThat(compiledGeneratedMatcher, where(Compilation::status, is(SUCCESS))),
                 () -> assertThat(compiledGeneratedMatcher, where(Compilation::errors, empty())));

maven-plugin/src/main/java/no/rune/record/matcher/GenerateRecordMatcherMojo.java

@@ -79,17 +79,15 @@ public void execute() throws MojoExecutionException, MojoFailureException {
             }
             var generator = new RecordMatcherGenerator();
             resolveIncludedRecords().forEach(recordClass -> {
-                var recordMatcherSourceCode = generator.generateFromRecord(recordClass);
-                var matcherClassFileTargetDirectory = outputDirectory.resolve(Path.of(recordClass.getPackageName().replace('.', '/')));
-                var matcherTargetFile = matcherClassFileTargetDirectory.resolve(recordClass.getSimpleName() + "Matcher.java");
+                var recordMatcherCompilationUnit = generator.generateFromRecord(recordClass);
                 try {
-                    Files.createDirectories(matcherClassFileTargetDirectory);
-                    Files.writeString(matcherTargetFile, recordMatcherSourceCode);
+                    var writtenFile = recordMatcherCompilationUnit.writeToBaseDirectory(outputDirectory);
+                    LOG.info("Generated matcher {}", outputDirectory.relativize(writtenFile));
                 } catch (IOException e) {
-                    throw new UncheckedIOException("Unable to write to " + matcherTargetFile + ", " +
+                    throw new UncheckedIOException(
+                            "Unable to write " + recordMatcherCompilationUnit + " to file, " +
                             "because " + e.getClass().getSimpleName() + ": " + e.getMessage(), e);
                 }
-                LOG.info("Generated matcher {}", outputDirectory.relativize(matcherTargetFile));
             });
         } else {
             LOG.warn("No records to generate Hamcrest matchers from!");