Return null in RubyFileTypeDetector#findEncoding if no magic encoding comment

* Like before and to pass the unit tests.

Author: eregon

src/main/java/org/truffleruby/RubyFileTypeDetector.java

@@ -16,8 +16,8 @@
 import java.util.Locale;
 import java.util.regex.Pattern;
 
-import org.jcodings.Encoding;
 import org.truffleruby.core.encoding.Encodings;
+import org.truffleruby.core.encoding.RubyEncoding;
 import org.truffleruby.core.encoding.TStringUtils;
 import org.truffleruby.core.string.TStringWithEncoding;
 import org.truffleruby.parser.lexer.RubyLexer;
@@ -68,14 +68,17 @@ public Charset findEncoding(TruffleFile file) {
         // We use ISO-8859-1 because every byte is valid in that encoding and
         // we only care about US-ASCII characters for magic encoding comments.
         try (BufferedReader fileContent = file.newBufferedReader(StandardCharsets.ISO_8859_1)) {
-            return findEncoding(fileContent).getCharset();
+            var encoding = findEncoding(fileContent);
+            if (encoding != null) {
+                return encoding.jcoding.getCharset();
+            }
         } catch (IOException | SecurityException e) {
             // Reading random files could cause all sorts of errors
-            return StandardCharsets.UTF_8;
         }
+        return null; // no magic encoding comment
     }
 
-    public static Encoding findEncoding(BufferedReader reader) {
+    public static RubyEncoding findEncoding(BufferedReader reader) {
         try {
             final String firstLine = reader.readLine();
             if (firstLine != null) {
@@ -91,15 +94,14 @@ public static Encoding findEncoding(BufferedReader reader) {
                             TStringUtils.fromJavaString(encodingCommentLine, Encodings.BINARY), Encodings.BINARY);
                     var encoding = RubyLexer.parseMagicEncodingComment(encodingComment);
                     if (encoding != null) {
-                        return encoding.jcoding;
+                        return encoding;
                     }
                 }
             }
         } catch (IOException e) {
             // Use the default encoding if reading failed somehow
         }
 
-        // The default encoding
-        return Encodings.UTF_8.jcoding;
+        return null;
     }
 }

src/main/java/org/truffleruby/parser/RubySource.java

@@ -63,8 +63,10 @@ public RubySource(Source source, String sourcePath, TStringWithEncoding code, bo
             // The sourcePath might not exist, so we cannot reread from the filesystem.
             // So we look for the magic encoding comment and if not found use UTF-8.
             var sourceString = source.getCharacters().toString();
-            var jcoding = RubyFileTypeDetector.findEncoding(new BufferedReader(new StringReader(sourceString)));
-            var encoding = Encodings.getBuiltInEncoding(jcoding);
+            var encoding = RubyFileTypeDetector.findEncoding(new BufferedReader(new StringReader(sourceString)));
+            if (encoding == null) {
+                encoding = Encodings.UTF_8;
+            }
             code = new TStringWithEncoding(TStringUtils.fromJavaString(sourceString, encoding), encoding);
         }
         assert checkMagicEncoding(code);

src/test-internal/java/org/truffleruby/test/internal/RubyFileTypeDetectorTest.java

@@ -84,20 +84,17 @@ public void testIndirect() throws IOException {
     @Test
     public void testEncoding() {
         final RubyFileTypeDetector fileTypeDetector = new RubyFileTypeDetector();
-        testWithAST("", new Consumer<RubyRootNode>() {
-            @Override
-            public void accept(RubyRootNode rootNode) {
-                TruffleLanguage.Env env = RubyLanguage.getCurrentContext().getEnv();
-                try {
-                    for (TestCase testCase : getTestCases()) {
-                        if (testCase.hasRubyMimeType) {
-                            TruffleFile file = env.getPublicTruffleFile(testCase.path.toString());
-                            assertEquals(testCase.encoding, fileTypeDetector.findEncoding(file));
-                        }
+        testWithAST("", rootNode -> {
+            TruffleLanguage.Env env = RubyLanguage.getCurrentContext().getEnv();
+            try {
+                for (TestCase testCase : getTestCases()) {
+                    if (testCase.hasRubyMimeType) {
+                        TruffleFile file = env.getPublicTruffleFile(testCase.path.toString());
+                        assertEquals(testCase.encoding, fileTypeDetector.findEncoding(file));
                     }
-                } catch (IOException ioe) {
-                    throw new RuntimeException(ioe);
                 }
+            } catch (IOException ioe) {
+                throw new RuntimeException(ioe);
             }
         });
     }