fix: properly write digit separators

Author: marhali

src/main/java/de/marhali/json5/stream/Json5Writer.java

@@ -173,7 +173,7 @@ public void writePrimitive(Json5Primitive primitive) throws IOException {
                 writer.write(quote(instant.toString()));
             }
         } else if (primitive.isNumber()) {
-            writer.append(formatNumberString(primitive.getAsString()));
+            writer.append(formatNumberString(primitive.getAsString(), primitive.getNumberRadix()));
         } else {
             writer.append(primitive.getAsString());
         }
@@ -276,25 +276,49 @@ public void writeArray(Json5Array array, int depth) throws IOException {
 
         writer.append(']');
     }
-
-    public String applyNumberSeparator(String numberString, char separator) {
+    private String applyNumberSeparator(String numberString, int numberRadix, char separator) {
         StringBuilder sb = new StringBuilder(numberString);
+
+        boolean hasSign = numberString.startsWith("+")  || numberString.startsWith("-");
+        int offset, separatorOffset;
+
+        switch (numberRadix) {
+            case 2:
+                offset = hasSign ? 3 : 2;
+                separatorOffset = 4;
+                break;
+            case 8:
+                offset = hasSign ? 3 : 2;
+                separatorOffset = 3;
+                break;
+            case 10:
+                offset = 0;
+                separatorOffset = 3;
+                break;
+            case 16:
+                offset = hasSign ? 3 : 2;
+                separatorOffset = 2;
+                break;
+            default:
+                throw new IllegalArgumentException("Invalid number radix: " + numberRadix);
+        }
+
         int len = sb.length();
 
-        for (int i = len - 3; i > 0; i -= 3) {
+        for (int i = len - separatorOffset; i > offset; i -= separatorOffset) {
             sb.insert(i, separator);
         }
 
         return sb.toString();
     }
 
-    public String formatNumberString(String numberString) {
+    public String formatNumberString(String numberString, int numberRadix) {
         var strategy = options.getDigitSeparatorStrategy();
         switch (strategy) {
             case JAVA_STYLE:
-                return applyNumberSeparator(numberString, '_');
+                return applyNumberSeparator(numberString, numberRadix, '_');
             case C_STYLE:
-                return applyNumberSeparator(numberString, '\'');
+                return applyNumberSeparator(numberString, numberRadix, '\'');
             default:
                 return numberString;
         }

src/test/java/de/marhali/json5/e2e/roundtrips/ParserAndWriterTest.java

@@ -148,4 +148,28 @@ void arrayRoundtripMinifyToPretty() throws IOException {
 
         assertEquals(expectedStringifiedElement, stringifiedElement);
     }
+
+    @Test
+    void extensionsRoundtripCStyle() throws IOException {
+        var json5 = new Json5(Json5OptionsFixtures.EXTENSIONS_C_STYLE);
+
+        var element = json5.parse(TestResourceHelper.getTestResource("e2e/roundtrips/extensions-c-style.parser.json5"));
+        var stringifiedElement = json5.serialize(element);
+
+        var expectedStringifiedElement = TestResourceHelper.getTestResourceContent("e2e/roundtrips/extensions-c-style.writer.json5");
+
+        assertEquals(expectedStringifiedElement, stringifiedElement);
+    }
+
+    @Test
+    void extensionsRoundtripJavaStyle() throws IOException {
+        var json5 = new Json5(Json5OptionsFixtures.EXTENSIONS_JAVA_STYLE);
+
+        var element = json5.parse(TestResourceHelper.getTestResource("e2e/roundtrips/extensions-java-style.parser.json5"));
+        var stringifiedElement = json5.serialize(element);
+
+        var expectedStringifiedElement = TestResourceHelper.getTestResourceContent("e2e/roundtrips/extensions-java-style.writer.json5");
+
+        assertEquals(expectedStringifiedElement, stringifiedElement);
+    }
 }

src/test/java/de/marhali/json5/fixtures/Json5OptionsFixtures.java

@@ -73,4 +73,40 @@ public class Json5OptionsFixtures {
         .duplicateKeyStrategy(DuplicateKeyStrategy.UNIQUE)
         .indentFactor(0)
         .build();
+
+    public static Json5Options EXTENSIONS_C_STYLE = Json5Options.builder()
+        .allowNaN()
+        .allowInfinity()
+        .allowInvalidSurrogates()
+        .allowBinaryLiterals()
+        .allowOctalLiterals()
+        .allowHexFloatingLiterals()
+        .allowLongUnicodeEscapes()
+        .quoteless()
+        .parseComments()
+        .writeComments()
+        .trailingComma()
+        .insertFinalNewline()
+        .digitSeparatorStrategy(DigitSeparatorStrategy.C_STYLE)
+        .duplicateKeyStrategy(DuplicateKeyStrategy.UNIQUE)
+        .prettyPrinting()
+        .build();
+
+    public static Json5Options EXTENSIONS_JAVA_STYLE = Json5Options.builder()
+        .allowNaN()
+        .allowInfinity()
+        .allowInvalidSurrogates()
+        .allowBinaryLiterals()
+        .allowOctalLiterals()
+        .allowHexFloatingLiterals()
+        .allowLongUnicodeEscapes()
+        .quoteless()
+        .parseComments()
+        .writeComments()
+        .trailingComma()
+        .insertFinalNewline()
+        .digitSeparatorStrategy(DigitSeparatorStrategy.JAVA_STYLE)
+        .duplicateKeyStrategy(DuplicateKeyStrategy.UNIQUE)
+        .prettyPrinting()
+        .build();
 }

src/test/resources/e2e/roundtrips/extensions-c-style.parser.json5

@@ -0,0 +1,15 @@
+// Number extensions with digit separator C-style
+{
+  decimalNumber: 1234567,
+  decimalNumberNegative: -11234567,
+  decimalNumberPositive: +111234567,
+  binaryNumber: 0b10101100,
+  binaryNumberNegative: -0b101100,
+  binaryNumberPositive: +0b1101100,
+  octalNumber: 0o1234567,
+  octalNumberNegative: -0o12345671,
+  octalNumberPositive: +0o123456712,
+  hexNumber: 0xDEADBEEF,
+  hexNumberNegative: -0xADBEEFA,
+  hexNumberPositive: +0xEADBEEFB
+}

src/test/resources/e2e/roundtrips/extensions-c-style.writer.json5

@@ -0,0 +1,15 @@
+// Number extensions with digit separator C-style
+{
+  decimalNumber: 1'234'567,
+  decimalNumberNegative: -11'234'567,
+  decimalNumberPositive: 111'234'567,
+  binaryNumber: 0b1010'1100,
+  binaryNumberNegative: -0b10'1100,
+  binaryNumberPositive: 0b110'1100,
+  octalNumber: 0o1'234'567,
+  octalNumberNegative: -0o12'345'671,
+  octalNumberPositive: 0o123'456'712,
+  hexNumber: 0xde'ad'be'ef,
+  hexNumberNegative: -0xa'db'ee'fa,
+  hexNumberPositive: 0xea'db'ee'fb,
+}

src/test/resources/e2e/roundtrips/extensions-java-style.parser.json5

@@ -0,0 +1,15 @@
+// Number extensions with digit separator Java-style
+{
+  decimalNumber: 1234567,
+  decimalNumberNegative: -11234567,
+  decimalNumberPositive: +111234567,
+  binaryNumber: 0b10101100,
+  binaryNumberNegative: -0b101100,
+  binaryNumberPositive: +0b1101100,
+  octalNumber: 0o1234567,
+  octalNumberNegative: -0o12345671,
+  octalNumberPositive: +0o123456712,
+  hexNumber: 0xDEADBEEF,
+  hexNumberNegative: -0xADBEEFA,
+  hexNumberPositive: +0xEADBEEFB
+}

src/test/resources/e2e/roundtrips/extensions-java-style.writer.json5

@@ -0,0 +1,15 @@
+// Number extensions with digit separator Java-style
+{
+  decimalNumber: 1_234_567,
+  decimalNumberNegative: -11_234_567,
+  decimalNumberPositive: 111_234_567,
+  binaryNumber: 0b1010_1100,
+  binaryNumberNegative: -0b10_1100,
+  binaryNumberPositive: 0b110_1100,
+  octalNumber: 0o1_234_567,
+  octalNumberNegative: -0o12_345_671,
+  octalNumberPositive: 0o123_456_712,
+  hexNumber: 0xde_ad_be_ef,
+  hexNumberNegative: -0xa_db_ee_fa,
+  hexNumberPositive: 0xea_db_ee_fb,
+}