JsonAdapter.fromJson(String) must fully consume. (#441)

* JsonAdapter.fromJson(String) must fully consume.

* Replace field with method.

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

@@ -37,7 +37,12 @@ public abstract class JsonAdapter<T> {
   }
 
   @CheckReturnValue public final @Nullable T fromJson(String string) throws IOException {
-    return fromJson(new Buffer().writeUtf8(string));
+    JsonReader reader = JsonReader.of(new Buffer().writeUtf8(string));
+    T result = fromJson(reader);
+    if (!isLenient() && reader.peek() != JsonReader.Token.END_DOCUMENT) {
+      throw new JsonDataException("JSON document was not fully consumed.");
+    }
+    return result;
   }
 
   public abstract void toJson(JsonWriter writer, @Nullable T value) throws IOException;
@@ -109,6 +114,9 @@ public abstract class JsonAdapter<T> {
           writer.setSerializeNulls(serializeNulls);
         }
       }
+      @Override boolean isLenient() {
+        return delegate.isLenient();
+      }
       @Override public String toString() {
         return delegate + ".serializeNulls()";
       }
@@ -136,6 +144,9 @@ public abstract class JsonAdapter<T> {
           delegate.toJson(writer, value);
         }
       }
+      @Override boolean isLenient() {
+        return delegate.isLenient();
+      }
       @Override public String toString() {
         return delegate + ".nullSafe()";
       }
@@ -164,6 +175,9 @@ public abstract class JsonAdapter<T> {
           writer.setLenient(lenient);
         }
       }
+      @Override boolean isLenient() {
+        return true;
+      }
       @Override public String toString() {
         return delegate + ".lenient()";
       }
@@ -191,6 +205,9 @@ public abstract class JsonAdapter<T> {
       @Override public void toJson(JsonWriter writer, @Nullable T value) throws IOException {
         delegate.toJson(writer, value);
       }
+      @Override boolean isLenient() {
+        return delegate.isLenient();
+      }
       @Override public String toString() {
         return delegate + ".failOnUnknown()";
       }
@@ -223,12 +240,19 @@ public abstract class JsonAdapter<T> {
           writer.setIndent(originalIndent);
         }
       }
+      @Override boolean isLenient() {
+        return delegate.isLenient();
+      }
       @Override public String toString() {
         return delegate + ".indent(\"" + indent + "\")";
       }
     };
   }
 
+  boolean isLenient() {
+    return false;
+  }
+
   public interface Factory {
     /**
      * Attempts to create an adapter for {@code type} annotated with {@code annotations}. This

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

@@ -21,6 +21,7 @@ import java.util.Collections;
 import java.util.List;
 import java.util.Locale;
 import java.util.Map;
+import javax.annotation.Nullable;
 import org.junit.Test;
 import org.junit.runner.RunWith;
 import org.junit.runners.Parameterized;
@@ -182,4 +183,67 @@ public final class JsonAdapterTest {
     serializeNulls.toJson(writer, Collections.<String, String>singletonMap("a", null));
     assertThat(factory.json()).isEqualTo("{\"a\":null}");
   }
+
+  @Test public void stringDocumentMustBeFullyConsumed() throws IOException {
+    JsonAdapter<String> brokenAdapter = new JsonAdapter<String>() {
+      @Override public String fromJson(JsonReader reader) throws IOException {
+        return "Forgot to call reader.nextString().";
+      }
+
+      @Override public void toJson(JsonWriter writer, @Nullable String value) throws IOException {
+        throw new AssertionError();
+      }
+    };
+    try {
+      brokenAdapter.fromJson("\"value\"");
+      fail();
+    } catch (JsonDataException e) {
+      assertThat(e).hasMessage("JSON document was not fully consumed.");
+    }
+  }
+
+  @Test public void adapterFromJsonStringPeeksAtEnd() throws IOException {
+    JsonAdapter<Boolean> adapter = new JsonAdapter<Boolean>() {
+      @Override public Boolean fromJson(JsonReader reader) throws IOException {
+        return reader.nextBoolean();
+      }
+
+      @Override public void toJson(JsonWriter writer, @Nullable Boolean value) throws IOException {
+        throw new AssertionError();
+      }
+    };
+    try {
+      adapter.fromJson("true true");
+      fail();
+    } catch (JsonEncodingException e) {
+      assertThat(e).hasMessage(
+          "Use JsonReader.setLenient(true) to accept malformed JSON at path $");
+    }
+  }
+
+  @Test public void lenientAdapterFromJsonStringDoesNotPeekAtEnd() throws IOException {
+    JsonAdapter<Boolean> adapter = new JsonAdapter<Boolean>() {
+      @Override public Boolean fromJson(JsonReader reader) throws IOException {
+        return reader.nextBoolean();
+      }
+
+      @Override public void toJson(JsonWriter writer, @Nullable Boolean value) throws IOException {
+        throw new AssertionError();
+      }
+    }.lenient();
+    assertThat(adapter.fromJson("true true")).isEqualTo(true);
+  }
+
+  @Test public void adaptersDelegateLeniency() throws IOException {
+    JsonAdapter<Boolean> adapter = new JsonAdapter<Boolean>() {
+      @Override public Boolean fromJson(JsonReader reader) throws IOException {
+        return reader.nextBoolean();
+      }
+
+      @Override public void toJson(JsonWriter writer, @Nullable Boolean value) throws IOException {
+        throw new AssertionError();
+      }
+    }.lenient().nullSafe();
+    assertThat(adapter.fromJson("true true")).isEqualTo(true);
+  }
 }