Make JsonReader.promoteNameToValue() a public API

moshi/src/main/java/com/squareup/moshi/JsonReader.java

@@ -514,8 +514,19 @@ public abstract class JsonReader implements Closeable {
   /**
    * Changes the reader to treat the next name as a string value. This is useful for map adapters so
    * that arbitrary type adapters can use {@link #nextString} to read a name value.
+   *
+   * <p>In this example, calling this method allows two sequential calls to {@link #nextString()}:
+   * <pre> {@code
+   *
+   *     JsonReader reader = JsonReader.of(new Buffer().writeUtf8("{\"a\":\"b\"}"));
+   *     reader.beginObject();
+   *     reader.promoteNameToValue();
+   *     assertEquals("a", reader.nextString());
+   *     assertEquals("b", reader.nextString());
+   *     reader.endObject();
+   * }</pre>
    */
-  abstract void promoteNameToValue() throws IOException;
+  public abstract void promoteNameToValue() throws IOException;
 
   /**
    * A set of strings to be chosen with {@link #selectName} or {@link #selectString}. This prepares

moshi/src/main/java/com/squareup/moshi/JsonUtf8Reader.java

@@ -1158,7 +1158,7 @@ final class JsonUtf8Reader extends JsonReader {
     }
   }
 
-  @Override void promoteNameToValue() throws IOException {
+  @Override public void promoteNameToValue() throws IOException {
     if (hasNext()) {
       peekedString = nextName();
       peeked = PEEKED_BUFFERED;

moshi/src/main/java/com/squareup/moshi/JsonUtf8Writer.java

@@ -162,12 +162,13 @@ final class JsonUtf8Writer extends JsonWriter {
       throw new IllegalStateException("JsonWriter is closed.");
     }
     int context = peekScope();
-    if ((context != EMPTY_OBJECT && context != NONEMPTY_OBJECT) || deferredName != null) {
+    if ((context != EMPTY_OBJECT && context != NONEMPTY_OBJECT)
+        || deferredName != null
+        || promoteValueToName) {
       throw new IllegalStateException("Nesting problem.");
     }
     deferredName = name;
     pathNames[stackSize - 1] = name;
-    promoteValueToName = false;
     return this;
   }
 
@@ -184,6 +185,7 @@ final class JsonUtf8Writer extends JsonWriter {
       return nullValue();
     }
     if (promoteValueToName) {
+      promoteValueToName = false;
       return name(value);
     }
     writeDeferredName();
@@ -236,6 +238,7 @@ final class JsonUtf8Writer extends JsonWriter {
       throw new IllegalArgumentException("Numeric values must be finite, but was " + value);
     }
     if (promoteValueToName) {
+      promoteValueToName = false;
       return name(Double.toString(value));
     }
     writeDeferredName();
@@ -247,6 +250,7 @@ final class JsonUtf8Writer extends JsonWriter {
 
   @Override public JsonWriter value(long value) throws IOException {
     if (promoteValueToName) {
+      promoteValueToName = false;
       return name(Long.toString(value));
     }
     writeDeferredName();
@@ -267,6 +271,7 @@ final class JsonUtf8Writer extends JsonWriter {
       throw new IllegalArgumentException("Numeric values must be finite, but was " + value);
     }
     if (promoteValueToName) {
+      promoteValueToName = false;
       return name(string);
     }
     writeDeferredName();

moshi/src/main/java/com/squareup/moshi/JsonValueReader.java

@@ -330,7 +330,7 @@ final class JsonValueReader extends JsonReader {
     return new JsonValueReader(this);
   }
 
-  @Override void promoteNameToValue() throws IOException {
+  @Override public void promoteNameToValue() throws IOException {
     if (hasNext()) {
       String name = nextName();
       push(name);

moshi/src/main/java/com/squareup/moshi/JsonValueWriter.java

@@ -130,17 +130,17 @@ final class JsonValueWriter extends JsonWriter {
     if (stackSize == 0) {
       throw new IllegalStateException("JsonWriter is closed.");
     }
-    if (peekScope() != EMPTY_OBJECT || deferredName != null) {
+    if (peekScope() != EMPTY_OBJECT || deferredName != null || promoteValueToName) {
       throw new IllegalStateException("Nesting problem.");
     }
     deferredName = name;
     pathNames[stackSize - 1] = name;
-    promoteValueToName = false;
     return this;
   }
 
   @Override public JsonWriter value(@Nullable String value) throws IOException {
     if (promoteValueToName) {
+      promoteValueToName = false;
       return name(value);
     }
     add(value);
@@ -184,6 +184,7 @@ final class JsonValueWriter extends JsonWriter {
       throw new IllegalArgumentException("Numeric values must be finite, but was " + value);
     }
     if (promoteValueToName) {
+      promoteValueToName = false;
       return name(Double.toString(value));
     }
     add(value);
@@ -193,6 +194,7 @@ final class JsonValueWriter extends JsonWriter {
 
   @Override public JsonWriter value(long value) throws IOException {
     if (promoteValueToName) {
+      promoteValueToName = false;
       return name(Long.toString(value));
     }
     add(value);
@@ -223,6 +225,7 @@ final class JsonValueWriter extends JsonWriter {
         ? ((BigDecimal) value)
         : new BigDecimal(value.toString());
     if (promoteValueToName) {
+      promoteValueToName = false;
       return name(bigDecimalValue.toString());
     }
     add(bigDecimalValue);

moshi/src/main/java/com/squareup/moshi/JsonWriter.java

@@ -443,8 +443,20 @@ public abstract class JsonWriter implements Closeable, Flushable {
   /**
    * Changes the writer to treat the next value as a string name. This is useful for map adapters so
    * that arbitrary type adapters can use {@link #value} to write a name value.
+   *
+   * <p>In this example, calling this method allows two sequential calls to {@link #value(String)}
+   * to produce the object, {@code {"a": "b"}}.
+   * <pre> {@code
+   *
+   *     JsonWriter writer = JsonWriter.of(...);
+   *     writer.beginObject();
+   *     writer.promoteValueToName();
+   *     writer.value("a");
+   *     writer.value("b");
+   *     writer.endObject();
+   * }</pre>
    */
-  final void promoteValueToName() throws IOException {
+  public final void promoteValueToName() throws IOException {
     int context = peekScope();
     if (context != NONEMPTY_OBJECT && context != EMPTY_OBJECT) {
       throw new IllegalStateException("Nesting problem.");

moshi/src/test/java/com/squareup/moshi/JsonReaderTest.java

@@ -20,7 +20,6 @@ import java.io.IOException;
 import java.util.Arrays;
 import java.util.Collections;
 import java.util.List;
-import java.util.Set;
 import org.junit.Test;
 import org.junit.runner.RunWith;
 import org.junit.runners.Parameterized;
@@ -1158,6 +1157,85 @@ public final class JsonReaderTest {
     reader.endObject();
   }
 
+  @Test public void promoteStringNameToValue() throws IOException {
+    JsonReader reader = newReader("{\"a\":\"b\"}");
+    reader.beginObject();
+    reader.promoteNameToValue();
+    assertEquals("a", reader.nextString());
+    assertEquals("b", reader.nextString());
+    reader.endObject();
+  }
+
+  @Test public void promoteDoubleNameToValue() throws IOException {
+    JsonReader reader = newReader("{\"5\":\"b\"}");
+    reader.beginObject();
+    reader.promoteNameToValue();
+    assertEquals(5.0, reader.nextDouble(), 0.0);
+    assertEquals("b", reader.nextString());
+    reader.endObject();
+  }
+
+  @Test public void promoteLongNameToValue() throws IOException {
+    JsonReader reader = newReader("{\"5\":\"b\"}");
+    reader.beginObject();
+    reader.promoteNameToValue();
+    assertEquals(5L, reader.nextLong());
+    assertEquals("b", reader.nextString());
+    reader.endObject();
+  }
+
+  @Test public void promoteNullNameToValue() throws IOException {
+    JsonReader reader = newReader("{\"null\":\"b\"}");
+    reader.beginObject();
+    reader.promoteNameToValue();
+    try {
+      reader.nextNull();
+      fail();
+    } catch (JsonDataException expected) {
+    }
+    assertEquals("null", reader.nextString());
+  }
+
+  @Test public void promoteBooleanNameToValue() throws IOException {
+    JsonReader reader = newReader("{\"true\":\"b\"}");
+    reader.beginObject();
+    reader.promoteNameToValue();
+    try {
+      reader.nextBoolean();
+      fail();
+    } catch (JsonDataException expected) {
+    }
+    assertEquals("true", reader.nextString());
+  }
+
+  @Test public void promoteBooleanNameToValueCannotBeReadAsName() throws IOException {
+    JsonReader reader = newReader("{\"true\":\"b\"}");
+    reader.beginObject();
+    reader.promoteNameToValue();
+    try {
+      reader.nextName();
+      fail();
+    } catch (JsonDataException expected) {
+    }
+    assertEquals("true", reader.nextString());
+  }
+
+  @Test public void promoteSkippedNameToValue() throws IOException {
+    JsonReader reader = newReader("{\"true\":\"b\"}");
+    reader.beginObject();
+    reader.promoteNameToValue();
+    reader.skipValue();
+    assertEquals("b", reader.nextString());
+  }
+
+  @Test public void promoteNameToValueAtEndOfObject() throws IOException {
+    JsonReader reader = newReader("{}");
+    reader.beginObject();
+    reader.promoteNameToValue();
+    assertThat(reader.hasNext()).isFalse();
+    reader.endObject();
+  }
+
   @Test public void optionsStrings() {
     String[] options = new String[] { "a", "b", "c" };
     JsonReader.Options abc = JsonReader.Options.of("a", "b", "c");

moshi/src/test/java/com/squareup/moshi/JsonWriterTest.java

@@ -814,4 +814,88 @@ public final class JsonWriterTest {
       assertThat(e).hasMessage("Map keys must be non-null");
     }
   }
+
+  @Test public void promoteStringNameToValue() throws IOException {
+    JsonWriter writer = factory.newWriter();
+    writer.beginObject();
+    writer.promoteValueToName();
+    writer.value("a");
+    writer.value("b");
+    writer.endObject();
+    assertThat(factory.json()).isEqualTo("{\"a\":\"b\"}");
+  }
+
+  @Test public void promoteDoubleNameToValue() throws IOException {
+    JsonWriter writer = factory.newWriter();
+    writer.beginObject();
+    writer.promoteValueToName();
+    writer.value(5.0);
+    writer.value("b");
+    writer.endObject();
+    assertThat(factory.json()).isEqualTo("{\"5.0\":\"b\"}");
+  }
+
+  @Test public void promoteLongNameToValue() throws IOException {
+    JsonWriter writer = factory.newWriter();
+    writer.beginObject();
+    writer.promoteValueToName();
+    writer.value(5L);
+    writer.value("b");
+    writer.endObject();
+    assertThat(factory.json()).isEqualTo("{\"5\":\"b\"}");
+  }
+
+  @Test public void promoteNumberNameToValue() throws IOException {
+    JsonWriter writer = factory.newWriter();
+    writer.beginObject();
+    writer.promoteValueToName();
+    writer.value(BigInteger.ONE);
+    writer.value("b");
+    writer.endObject();
+    assertThat(factory.json()).isEqualTo("{\"1\":\"b\"}");
+  }
+
+  @Test public void promoteNullNameToValue() throws IOException {
+    JsonWriter writer = factory.newWriter();
+    writer.beginObject();
+    writer.promoteValueToName();
+    try {
+      writer.nullValue();
+      fail();
+    } catch (IllegalStateException expected) {
+      assertThat(expected).hasMessage("null cannot be used as a map key in JSON at path $.");
+    }
+  }
+
+  @Test public void promoteBooleanNameToValue() throws IOException {
+    JsonWriter writer = factory.newWriter();
+    writer.beginObject();
+    writer.promoteValueToName();
+    try {
+      writer.value(true);
+      fail();
+    } catch (IllegalStateException expected) {
+      assertThat(expected).hasMessage("Boolean cannot be used as a map key in JSON at path $.");
+    }
+  }
+
+  @Test public void promoteNameToValueCannotBeWrittenAsName() throws IOException {
+    JsonWriter writer = factory.newWriter();
+    writer.beginObject();
+    writer.promoteValueToName();
+    try {
+      writer.name("a");
+      fail();
+    } catch (IllegalStateException expected) {
+      assertThat(expected).hasMessage("Nesting problem.");
+    }
+  }
+
+  @Test public void promoteNameToValueAtEndOfObject() throws IOException {
+    JsonWriter writer = factory.newWriter();
+    writer.beginObject();
+    writer.promoteValueToName();
+    writer.endObject();
+    assertThat(factory.json()).isEqualTo("{}");
+  }
 }