Implement peekJson() for JsonUtf8Reader

This required an upgrade to Okio 1.16.0.

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

@@ -497,8 +497,7 @@ public abstract class JsonReader implements Closeable {
    *   jsonReader.nextInt() // Returns 456, reader contains 789 and ].
    * }</pre>
    */
-  // TODO(jwilson): make this public once it's supported in JsonUtf8Reader.
+  public abstract JsonReader peekJson();
-  abstract JsonReader peekJson();
 
   /**
    * Returns a <a href="http://goessner.net/articles/JsonPath/">JsonPath</a> to

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

@@ -98,6 +98,27 @@ final class JsonUtf8Reader extends JsonReader {
     pushScope(JsonScope.EMPTY_DOCUMENT);
   }
 
+  /** Copy-constructor makes a deep copy for peeking. */
+  JsonUtf8Reader(JsonUtf8Reader copyFrom) {
+    super(copyFrom);
+
+    BufferedSource sourcePeek = copyFrom.source.peek();
+    this.source = sourcePeek;
+    this.buffer = sourcePeek.getBuffer();
+    this.peeked = copyFrom.peeked;
+    this.peekedLong = copyFrom.peekedLong;
+    this.peekedNumberLength = copyFrom.peekedNumberLength;
+    this.peekedString = copyFrom.peekedString;
+
+    // Make sure our buffer has as many bytes as the source's buffer. This is necessary because
+    // JsonUtf8Reader assumes any data it has peeked (like the peekedNumberLength) are buffered.
+    try {
+      sourcePeek.require(copyFrom.buffer.size());
+    } catch (IOException e) {
+      throw new AssertionError();
+    }
+  }
+
   @Override public void beginArray() throws IOException {
     int p = peeked;
     if (p == PEEKED_NONE) {
@@ -1051,8 +1072,8 @@ final class JsonUtf8Reader extends JsonReader {
     return found;
   }
 
-  @Override JsonReader peekJson() {
+  @Override public JsonReader peekJson() {
-    throw new UnsupportedOperationException("TODO");
+    return new JsonUtf8Reader(this);
   }
 
   @Override public String toString() {

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

@@ -318,7 +318,7 @@ final class JsonValueReader extends JsonReader {
     }
   }
 
-  @Override JsonReader peekJson() {
+  @Override public JsonReader peekJson() {
     return new JsonValueReader(this);
   }
 

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

@@ -33,6 +33,7 @@ import static com.squareup.moshi.JsonReader.Token.STRING;
 import static com.squareup.moshi.TestUtil.repeat;
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNotNull;
 import static org.junit.Assert.fail;
 import static org.junit.Assume.assumeTrue;
 
@@ -988,7 +989,6 @@ public final class JsonReaderTest {
 
   @Test public void basicPeekJson() throws IOException {
     JsonReader reader = newReader("{\"a\":12,\"b\":[34,56],\"c\":78}");
-    assumeTrue(reader instanceof JsonValueReader); // Not implemented for JsonUtf8Reader yet!
     reader.beginObject();
     assertThat(reader.nextName()).isEqualTo("a");
     assertThat(reader.nextInt()).isEqualTo(12);
@@ -1021,7 +1021,6 @@ public final class JsonReaderTest {
    */
   @Test public void peekJsonReader() throws IOException {
     JsonReader reader = newReader("[12,34,{\"a\":56,\"b\":78},90]");
-    assumeTrue(reader instanceof JsonValueReader); // Not implemented for JsonUtf8Reader yet!
     for (int i = 0; i < 12; i++) {
       readPeek12Steps(reader.peekJson(), i, 12);
       readPeek12Steps(reader, i, i + 1);
@@ -1084,4 +1083,67 @@ public final class JsonReaderTest {
         assertThat(reader.getPath()).isEqualTo("$");
     }
   }
+
+  /** Confirm that we can peek in every state of the UTF-8 reader. */
+  @Test public void peekAfterPeek() throws IOException {
+    JsonReader reader = newReader(
+        "[{\"a\":\"aaa\",'b':'bbb',c:c,\"d\":\"d\"},true,false,null,1,2.0]");
+    reader.setLenient(true);
+    readValue(reader, true);
+    reader.peekJson();
+  }
+
+  @Test public void peekAfterPromoteNameToValue() throws IOException {
+    JsonReader reader = newReader("{\"a\":\"b\"}");
+    reader.beginObject();
+    reader.promoteNameToValue();
+    assertEquals("a", reader.peekJson().nextString());
+    assertEquals("a", reader.nextString());
+    assertEquals("b", reader.peekJson().nextString());
+    assertEquals("b", reader.nextString());
+    reader.endObject();
+  }
+
+  /** Peek a value, then read it, recursively. */
+  private void readValue(JsonReader reader, boolean peekJsonFirst) throws IOException {
+    JsonReader.Token token = reader.peek();
+    if (peekJsonFirst) {
+      readValue(reader.peekJson(), false);
+    }
+
+    switch (token) {
+      case BEGIN_ARRAY:
+        reader.beginArray();
+        while (reader.hasNext()) {
+          readValue(reader, peekJsonFirst);
+        }
+        reader.peekJson().endArray();
+        reader.endArray();
+        break;
+      case BEGIN_OBJECT:
+        reader.beginObject();
+        while (reader.hasNext()) {
+          assertNotNull(reader.peekJson().nextName());
+          assertNotNull(reader.nextName());
+          readValue(reader, peekJsonFirst);
+        }
+        reader.peekJson().endObject();
+        reader.endObject();
+        break;
+      case STRING:
+        reader.nextString();
+        break;
+      case NUMBER:
+        reader.nextDouble();
+        break;
+      case BOOLEAN:
+        reader.nextBoolean();
+        break;
+      case NULL:
+        reader.nextNull();
+        break;
+      default:
+        throw new AssertionError();
+    }
+  }
 }

pom.xml

@@ -35,7 +35,7 @@
     <maven-assembly.version>3.1.0</maven-assembly.version>
 
     <!-- Dependencies -->
-    <okio.version>1.15.0</okio.version>
+    <okio.version>1.16.0</okio.version>
 
     <!-- Test Dependencies -->
     <compile-testing.version>0.15</compile-testing.version>