Migrate Writer APIs to Appendable parameter

gson/src/main/java/com/google/gson/Gson.java

@@ -16,6 +16,7 @@
 
 package com.google.gson;
 
+import com.google.errorprone.annotations.InlineMe;
 import com.google.gson.annotations.JsonAdapter;
 import com.google.gson.internal.ConstructorConstructor;
 import com.google.gson.internal.Excluder;
@@ -119,9 +120,9 @@
  * <ol>
  *   <li>Use {@link #getAdapter(Class)} to obtain the adapter for the type to be serialized
  *   <li>When using an existing {@code JsonWriter}, manually apply the writer settings of this
- *       {@code Gson} instance listed by {@link #newJsonWriter(Writer)}.<br>
+ *       {@code Gson} instance listed by {@link #newJsonWriter(Appendable)}.<br>
  *       Otherwise, when not using an existing {@code JsonWriter}, use {@link
- *       #newJsonWriter(Writer)} to construct one.
+ *       #newJsonWriter(Appendable)} to construct one.
  *   <li>Call {@link TypeAdapter#write(JsonWriter, Object)}
  * </ol>
  *
@@ -809,8 +810,8 @@ public JsonElement toJsonTree(Object src, Type typeOfSrc) {
    * the generic type information because of the Type Erasure feature of Java. Note that this method
    * works fine if any of the object fields are of generic type, just the object itself should not
    * be of a generic type. If the object is of generic type, use {@link #toJson(Object, Type)}
-   * instead. If you want to write out the object to a {@link Writer}, use {@link #toJson(Object,
-   * Appendable)} instead.
+   * instead. If you want to write out the object to an {@link Appendable}, use {@link
+   * #toJson(Object, Appendable)} instead.
    *
    * @param src the object for which JSON representation is to be created
    * @return JSON representation of {@code src}.
@@ -828,7 +829,7 @@ public String toJson(Object src) {
    * This method serializes the specified object, including those of generic types, into its
    * equivalent JSON representation. This method must be used if the specified object is a generic
    * type. For non-generic objects, use {@link #toJson(Object)} instead. If you want to write out
-   * the object to a {@link Appendable}, use {@link #toJson(Object, Type, Appendable)} instead.
+   * the object to an {@link Appendable}, use {@link #toJson(Object, Type, Appendable)} instead.
    *
    * @param src the object for which JSON representation is to be created
    * @param typeOfSrc The specific genericized type of src. You can obtain this type by using the
@@ -894,7 +895,7 @@ public void toJson(Object src, Appendable writer) throws JsonIOException {
    */
   public void toJson(Object src, Type typeOfSrc, Appendable writer) throws JsonIOException {
     try {
-      JsonWriter jsonWriter = newJsonWriter(Streams.writerForAppendable(writer));
+      JsonWriter jsonWriter = newJsonWriter(writer);
       toJson(src, typeOfSrc, jsonWriter);
     } catch (IOException e) {
       throw new JsonIOException(e);
@@ -976,7 +977,7 @@ public String toJson(JsonElement jsonElement) {
    */
   public void toJson(JsonElement jsonElement, Appendable writer) throws JsonIOException {
     try {
-      JsonWriter jsonWriter = newJsonWriter(Streams.writerForAppendable(writer));
+      JsonWriter jsonWriter = newJsonWriter(writer);
       toJson(jsonElement, jsonWriter);
     } catch (IOException e) {
       throw new JsonIOException(e);
@@ -1032,6 +1033,16 @@ public void toJson(JsonElement jsonElement, JsonWriter writer) throws JsonIOExce
     }
   }
 
+  /**
+   * For compatibility only!
+   *
+   * @see Gson#newJsonWriter(Appendable)
+   */
+  @InlineMe(replacement = "this.newJsonWriter((Appendable) writer)")
+  public JsonWriter newJsonWriter(Writer writer) throws IOException {
+    return newJsonWriter((Appendable) writer);
+  }
+
   /**
    * Returns a new JSON writer configured for the settings on this Gson instance.
    *
@@ -1049,9 +1060,9 @@ public void toJson(JsonElement jsonElement, JsonWriter writer) throws JsonIOExce
    *   <li>{@link GsonBuilder#setFormattingStyle(FormattingStyle)}
    * </ul>
    */
-  public JsonWriter newJsonWriter(Writer writer) throws IOException {
+  public JsonWriter newJsonWriter(Appendable writer) throws IOException {
     if (generateNonExecutableJson) {
-      writer.write(JSON_NON_EXECUTABLE_PREFIX);
+      writer.append(JSON_NON_EXECUTABLE_PREFIX);
     }
     JsonWriter jsonWriter = new JsonWriter(writer);
     jsonWriter.setFormattingStyle(formattingStyle);

gson/src/main/java/com/google/gson/JsonElement.java

@@ -422,7 +422,7 @@ public short getAsShort() {
   public String toString() {
     try {
       StringBuilder stringBuilder = new StringBuilder();
-      JsonWriter jsonWriter = new JsonWriter(Streams.writerForAppendable(stringBuilder));
+      JsonWriter jsonWriter = new JsonWriter(stringBuilder);
       // Make writer lenient because toString() must not fail, even if for example JsonPrimitive
       // contains NaN
       jsonWriter.setStrictness(Strictness.LENIENT);

gson/src/main/java/com/google/gson/TypeAdapter.java

@@ -16,7 +16,7 @@
 
 package com.google.gson;
 
-import com.google.gson.internal.Streams;
+import com.google.errorprone.annotations.InlineMe;
 import com.google.gson.internal.bind.JsonTreeReader;
 import com.google.gson.internal.bind.JsonTreeWriter;
 import com.google.gson.stream.JsonReader;
@@ -129,6 +129,16 @@ public TypeAdapter() {}
    */
   public abstract void write(JsonWriter out, T value) throws IOException;
 
+  /**
+   * For compatibility only!
+   *
+   * @see TypeAdapter#toJson(Appendable, Object)
+   */
+  @InlineMe(replacement = "this.toJson((Appendable) out, value)")
+  public final void toJson(Writer out, T value) throws IOException {
+    toJson((Appendable) out, value);
+  }
+
   /**
    * Converts {@code value} to a JSON document and writes it to {@code out}.
    *
@@ -139,7 +149,7 @@ public TypeAdapter() {}
    * @param value the Java object to convert. May be {@code null}.
    * @since 2.2
    */
-  public final void toJson(Writer out, T value) throws IOException {
+  public final void toJson(Appendable out, T value) throws IOException {
     JsonWriter writer = new JsonWriter(out);
     write(writer, value);
   }
@@ -159,7 +169,7 @@ public final void toJson(Writer out, T value) throws IOException {
   public final String toJson(T value) {
     StringBuilder stringBuilder = new StringBuilder();
     try {
-      toJson(Streams.writerForAppendable(stringBuilder), value);
+      toJson(stringBuilder, value);
     } catch (IOException e) {
       throw new JsonIOException(e);
     }

gson/src/main/java/com/google/gson/internal/bind/JsonTreeWriter.java

@@ -31,7 +31,7 @@
 
 /** This writer creates a JsonElement. */
 public final class JsonTreeWriter extends JsonWriter {
-  private static final Writer UNWRITABLE_WRITER =
+  private static final Appendable UNWRITABLE_WRITER =
       new Writer() {
         @Override
         public void write(char[] buffer, int offset, int counter) {

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

@@ -25,6 +25,7 @@
 import static com.google.gson.stream.JsonScope.NONEMPTY_OBJECT;
 
 import com.google.errorprone.annotations.CanIgnoreReturnValue;
+import com.google.errorprone.annotations.InlineMe;
 import com.google.gson.FormattingStyle;
 import com.google.gson.Gson;
 import com.google.gson.GsonBuilder;
@@ -200,7 +201,7 @@ public class JsonWriter implements Closeable, Flushable {
   }
 
   /** The JSON output destination */
-  private final Writer out;
+  private final Appendable out;
 
   private int[] stack = new int[32];
   private int stackSize = 0;
@@ -229,7 +230,16 @@ public class JsonWriter implements Closeable, Flushable {
    * ensure {@link Writer} is buffered; wrapping in {@link java.io.BufferedWriter BufferedWriter} if
    * necessary.
    */
+  @InlineMe(replacement = "this((Appendable) out)")
   public JsonWriter(Writer out) {
+    this((Appendable) out);
+  }
+
+  /**
+   * Creates a new instance that writes a JSON-encoded stream to {@code out}. For best performance,
+   * ensure the {@link Appendable} is buffered if there are actual IO operations.
+   */
+  public JsonWriter(Appendable out) {
     this.out = Objects.requireNonNull(out, "out == null");
     setFormattingStyle(FormattingStyle.COMPACT);
   }
@@ -447,7 +457,7 @@ public JsonWriter endObject() throws IOException {
   private JsonWriter openScope(int empty, char openBracket) throws IOException {
     beforeValue();
     push(empty);
-    out.write(openBracket);
+    out.append(openBracket);
     return this;
   }
 
@@ -466,7 +476,7 @@ private JsonWriter closeScope(int empty, int nonempty, char closeBracket) throws
     if (context == nonempty) {
       newline();
     }
-    out.write(closeBracket);
+    out.append(closeBracket);
     return this;
   }
 
@@ -544,7 +554,7 @@ public JsonWriter value(String value) throws IOException {
   public JsonWriter value(boolean value) throws IOException {
     writeDeferredName();
     beforeValue();
-    out.write(value ? "true" : "false");
+    out.append(value ? "true" : "false");
     return this;
   }
 
@@ -561,7 +571,7 @@ public JsonWriter value(Boolean value) throws IOException {
     }
     writeDeferredName();
     beforeValue();
-    out.write(value ? "true" : "false");
+    out.append(value ? "true" : "false");
     return this;
   }
 
@@ -615,7 +625,7 @@ public JsonWriter value(double value) throws IOException {
   public JsonWriter value(long value) throws IOException {
     writeDeferredName();
     beforeValue();
-    out.write(Long.toString(value));
+    out.append(Long.toString(value));
     return this;
   }
 
@@ -675,7 +685,7 @@ public JsonWriter nullValue() throws IOException {
       }
     }
     beforeValue();
-    out.write("null");
+    out.append("null");
     return this;
   }
 
@@ -701,24 +711,32 @@ public JsonWriter jsonValue(String value) throws IOException {
   }
 
   /**
-   * Ensures all buffered data is written to the underlying {@link Writer} and flushes that writer.
+   * Ensures all buffered data is written to the underlying {@link Appendable} and flushes it if it
+   * is an instance of {@link Flushable}.
+   *
+   * @throws IllegalStateException if this writer is closed.
    */
   @Override
   public void flush() throws IOException {
     if (stackSize == 0) {
       throw new IllegalStateException("JsonWriter is closed.");
     }
-    out.flush();
+    if (out instanceof Flushable) {
+      ((Flushable) out).flush();
+    }
   }
 
   /**
-   * Flushes and closes this writer and the underlying {@link Writer}.
+   * Flushes and closes this writer and the underlying {@link Appendable} if it is an instance of
+   * {@link Closeable}.
    *
    * @throws IOException if the JSON document is incomplete.
    */
   @Override
   public void close() throws IOException {
-    out.close();
+    if (out instanceof Closeable) {
+      ((Closeable) out).close();
+    }
 
     int size = stackSize;
     if (size > 1 || (size == 1 && stack[size - 1] != NONEMPTY_DOCUMENT)) {
@@ -743,7 +761,7 @@ private static boolean alwaysCreatesValidJsonNumber(Class<? extends Number> c) {
 
   private void string(String value) throws IOException {
     String[] replacements = htmlSafe ? HTML_SAFE_REPLACEMENT_CHARS : REPLACEMENT_CHARS;
-    out.write('\"');
+    out.append('\"');
     int last = 0;
     int length = value.length();
     for (int i = 0; i < length; i++) {
@@ -762,25 +780,25 @@ private void string(String value) throws IOException {
         continue;
       }
       if (last < i) {
-        out.write(value, last, i - last);
+        out.append(value, last, i);
       }
-      out.write(replacement);
+      out.append(replacement);
       last = i + 1;
     }
     if (last < length) {
-      out.write(value, last, length - last);
+      out.append(value, last, length);
     }
-    out.write('\"');
+    out.append('\"');
   }
 
   private void newline() throws IOException {
     if (usesEmptyNewlineAndIndent) {
       return;
     }
 
-    out.write(formattingStyle.getNewline());
+    out.append(formattingStyle.getNewline());
     for (int i = 1, size = stackSize; i < size; i++) {
-      out.write(formattingStyle.getIndent());
+      out.append(formattingStyle.getIndent());
     }
   }
 
@@ -791,7 +809,7 @@ private void newline() throws IOException {
   private void beforeName() throws IOException {
     int context = peek();
     if (context == NONEMPTY_OBJECT) { // first in object
-      out.write(formattedComma);
+      out.append(formattedComma);
     } else if (context != EMPTY_OBJECT) { // not in an object!
       throw new IllegalStateException("Nesting problem.");
     }

gson/src/test/java/com/google/gson/GsonBuilderTest.java

@@ -23,7 +23,6 @@
 import com.google.gson.stream.JsonWriter;
 import java.io.IOException;
 import java.io.StringReader;
-import java.io.StringWriter;
 import java.lang.reflect.Modifier;
 import java.lang.reflect.Type;
 import java.text.DateFormat;
@@ -222,7 +221,7 @@ public void testDefaultStrictness() throws IOException {
     Gson gson = builder.create();
     assertThat(gson.newJsonReader(new StringReader("{}")).getStrictness())
         .isEqualTo(Strictness.LEGACY_STRICT);
-    assertThat(gson.newJsonWriter(new StringWriter()).getStrictness())
+    assertThat(gson.newJsonWriter(new StringBuilder()).getStrictness())
         .isEqualTo(Strictness.LEGACY_STRICT);
   }
 
@@ -234,7 +233,7 @@ public void testSetLenient() throws IOException {
     Gson gson = builder.create();
     assertThat(gson.newJsonReader(new StringReader("{}")).getStrictness())
         .isEqualTo(Strictness.LENIENT);
-    assertThat(gson.newJsonWriter(new StringWriter()).getStrictness())
+    assertThat(gson.newJsonWriter(new StringBuilder()).getStrictness())
         .isEqualTo(Strictness.LENIENT);
   }
 
@@ -245,7 +244,7 @@ public void testSetStrictness() throws IOException {
     builder.setStrictness(strictness);
     Gson gson = builder.create();
     assertThat(gson.newJsonReader(new StringReader("{}")).getStrictness()).isEqualTo(strictness);
-    assertThat(gson.newJsonWriter(new StringWriter()).getStrictness()).isEqualTo(strictness);
+    assertThat(gson.newJsonWriter(new StringBuilder()).getStrictness()).isEqualTo(strictness);
   }
 
   @Test

gson/src/test/java/com/google/gson/GsonTest.java

@@ -27,7 +27,6 @@
 import com.google.gson.stream.MalformedJsonException;
 import java.io.IOException;
 import java.io.StringReader;
-import java.io.StringWriter;
 import java.text.DateFormat;
 import java.util.ArrayList;
 import java.util.Collections;
@@ -455,7 +454,7 @@ public int hashCode() {
 
   @Test
   public void testNewJsonWriter_Default() throws IOException {
-    StringWriter writer = new StringWriter();
+    StringBuilder writer = new StringBuilder();
     JsonWriter jsonWriter = new Gson().newJsonWriter(writer);
     jsonWriter.beginObject();
     jsonWriter.name("test");
@@ -475,7 +474,7 @@ public void testNewJsonWriter_Default() throws IOException {
   @SuppressWarnings({"deprecation", "InlineMeInliner"}) // for GsonBuilder.setLenient
   @Test
   public void testNewJsonWriter_Custom() throws IOException {
-    StringWriter writer = new StringWriter();
+    StringBuilder writer = new StringBuilder();
     JsonWriter jsonWriter =
         new GsonBuilder()
             .disableHtmlEscaping()