fix: Validate value before writing deferred name in JsonWriter

gson/src/main/java/com/google/gson/stream/JsonWriter.java

@@ -576,10 +576,10 @@ public JsonWriter value(Boolean value) throws IOException {
    */
   @CanIgnoreReturnValue
   public JsonWriter value(float value) throws IOException {
-    writeDeferredName();
     if (strictness != Strictness.LENIENT && (Float.isNaN(value) || Float.isInfinite(value))) {
       throw new IllegalArgumentException("Numeric values must be finite, but was " + value);
     }
+    writeDeferredName();
     beforeValue();
     out.append(Float.toString(value));
     return this;
@@ -596,10 +596,10 @@ public JsonWriter value(float value) throws IOException {
    */
   @CanIgnoreReturnValue
   public JsonWriter value(double value) throws IOException {
-    writeDeferredName();
     if (strictness != Strictness.LENIENT && (Double.isNaN(value) || Double.isInfinite(value))) {
       throw new IllegalArgumentException("Numeric values must be finite, but was " + value);
     }
+    writeDeferredName();
     beforeValue();
     out.append(Double.toString(value));
     return this;
@@ -635,7 +635,6 @@ public JsonWriter value(Number value) throws IOException {
       return nullValue();
     }
 
-    writeDeferredName();
     String string = value.toString();
     Class<? extends Number> numberClass = value.getClass();
 
@@ -653,6 +652,7 @@ public JsonWriter value(Number value) throws IOException {
       }
     }
 
+    writeDeferredName();
     beforeValue();
     out.append(string);
     return this;

gson/src/test/java/com/google/gson/stream/JsonWriterTest.java

@@ -423,6 +423,51 @@ public void testNonFiniteNumbersWhenLenient() throws IOException {
     assertThat(stringWriter.toString()).isEqualTo("[NaN,-Infinity,Infinity,Infinity]");
   }
 
+  /**
+   * Regression test for https://github.com/google/gson/issues/1736
+   *
+   * <p>When a non-finite value is rejected, the deferred name should not have been written yet, so
+   * the writer state remains consistent.
+   */
+  @Test
+  public void testNonFiniteValueDoesNotWriteDeferredName() throws IOException {
+    StringWriter stringWriter = new StringWriter();
+    JsonWriter jsonWriter = new JsonWriter(stringWriter);
+    jsonWriter.setSerializeNulls(false);
+    jsonWriter.beginObject();
+
+    // value(float) with NaN should not write the name
+    jsonWriter.name("a");
+    assertThrows(IllegalArgumentException.class, () -> jsonWriter.value(Float.NaN));
+    jsonWriter.nullValue(); // should be suppressed since serializeNulls=false
+
+    // value(double) with NaN should not write the name
+    jsonWriter.name("b");
+    assertThrows(IllegalArgumentException.class, () -> jsonWriter.value(Double.NaN));
+    jsonWriter.nullValue();
+
+    // value(double) with Infinity should not write the name
+    jsonWriter.name("c");
+    assertThrows(IllegalArgumentException.class, () -> jsonWriter.value(Double.POSITIVE_INFINITY));
+    jsonWriter.nullValue();
+
+    // value(Number) with NaN should not write the name
+    jsonWriter.name("d");
+    assertThrows(
+        IllegalArgumentException.class, () -> jsonWriter.value(Double.valueOf(Double.NaN)));
+    jsonWriter.nullValue();
+
+    // value(Number) with invalid number string should not write the name
+    jsonWriter.name("e");
+    assertThrows(
+        IllegalArgumentException.class,
+        () -> jsonWriter.value(new LazilyParsedNumber("not-a-num")));
+    jsonWriter.nullValue();
+
+    jsonWriter.endObject();
+    assertThat(stringWriter.toString()).isEqualTo("{}");
+  }
+
   @Test
   public void testFloats() throws IOException {
     StringWriter stringWriter = new StringWriter();