Improve JsonReader.skipValue()

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

@@ -96,6 +96,7 @@ public JsonTreeReader(JsonElement element) {
     popStack(); // empty iterator
     popStack(); // object
     if (stackSize > 0) {
+      pathNames[stackSize - 1] = null; // Free the last path name so that it can be garbage collected
       pathIndices[stackSize - 1]++;
     }
   }
@@ -269,14 +270,18 @@ JsonElement nextJsonElement() throws IOException {
   }
 
   @Override public void skipValue() throws IOException {
-    if (peek() == JsonToken.NAME) {
+    JsonToken peeked = peek();
+    if (peeked == JsonToken.NAME) {
       nextName();
-      pathNames[stackSize - 2] = "null";
+      pathNames[stackSize - 2] = "<skipped>";
+    } else if (peeked == JsonToken.END_ARRAY) {
+      endArray();
+    } else if (peeked == JsonToken.END_OBJECT) {
+      endObject();
+    } else if (peeked == JsonToken.END_DOCUMENT) {
+      throw new IllegalStateException("Cannot skip at end of document");
     } else {
       popStack();
-      if (stackSize > 0) {
-        pathNames[stackSize - 1] = "null";
-      }
     }
     if (stackSize > 0) {
       pathIndices[stackSize - 1]++;

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

@@ -1233,9 +1233,16 @@ public int nextInt() throws IOException {
   }
 
   /**
-   * Skips the next value recursively. If it is an object or array, all nested
-   * elements are skipped. This method is intended for use when the JSON token
-   * stream contains unrecognized or unhandled values.
+   * Skips the next value recursively. This method is intended for use when
+   * the JSON token stream contains unrecognized or unhandled values.
+   *
+   * <p>If the next value is a JSON object or array, all nested elements are
+   * skipped. For JSON objects when called before the name of a property has been
+   * consumed, only the name is skipped. When called at the end of a JSON array
+   * or object, the end of the array or object is skipped.
+   *
+   * @throws IllegalStateException when called at the end of the document, that is,
+   *     after the last value.
    */
   public void skipValue() throws IOException {
     int count = 0;
@@ -1255,22 +1262,45 @@ public void skipValue() throws IOException {
         stackSize--;
         count--;
       } else if (p == PEEKED_END_OBJECT) {
+        // Only update when object end is explicitly skipped, otherwise stack is not updated anyways
+        if (count == 0) {
+          pathNames[stackSize - 1] = null; // Free the last path name so that it can be garbage collected
+        }
         stackSize--;
         count--;
-      } else if (p == PEEKED_UNQUOTED_NAME || p == PEEKED_UNQUOTED) {
+      } else if (p == PEEKED_UNQUOTED) {
         skipUnquotedValue();
-      } else if (p == PEEKED_SINGLE_QUOTED || p == PEEKED_SINGLE_QUOTED_NAME) {
+      } else if (p == PEEKED_SINGLE_QUOTED) {
         skipQuotedValue('\'');
-      } else if (p == PEEKED_DOUBLE_QUOTED || p == PEEKED_DOUBLE_QUOTED_NAME) {
+      } else if (p == PEEKED_DOUBLE_QUOTED) {
         skipQuotedValue('"');
+      } else if (p == PEEKED_UNQUOTED_NAME) {
+        skipUnquotedValue();
+        // Only update when name is explicitly skipped, otherwise stack is not updated anyways
+        if (count == 0) {
+          pathNames[stackSize - 1] = "<skipped>";
+        }
+      } else if (p == PEEKED_SINGLE_QUOTED_NAME) {
+        skipQuotedValue('\'');
+        // Only update when name is explicitly skipped, otherwise stack is not updated anyways
+        if (count == 0) {
+          pathNames[stackSize - 1] = "<skipped>";
+        }
+      } else if (p == PEEKED_DOUBLE_QUOTED_NAME) {
+        skipQuotedValue('"');
+        // Only update when name is explicitly skipped, otherwise stack is not updated anyways
+        if (count == 0) {
+          pathNames[stackSize - 1] = "<skipped>";
+        }
       } else if (p == PEEKED_NUMBER) {
         pos += peekedNumberLength;
+      } else if (p == PEEKED_EOF) {
+        throw new IllegalStateException("Cannot skip at end of document");
       }
       peeked = PEEKED_NONE;
-    } while (count != 0);
+    } while (count > 0);
 
     pathIndices[stackSize - 1]++;
-    pathNames[stackSize - 1] = "null";
   }
 
   private void push(int newTop) {

gson/src/test/java/com/google/gson/internal/bind/JsonTreeReaderTest.java

@@ -55,6 +55,34 @@ public void testSkipValue_filledJsonObject() throws IOException {
     assertEquals(JsonToken.END_DOCUMENT, in.peek());
   }
 
+  public void testSkipValue_afterEndOfDocument() throws IOException {
+    JsonTreeReader reader = new JsonTreeReader(new JsonObject());
+    reader.beginObject();
+    reader.endObject();
+    assertEquals(JsonToken.END_DOCUMENT, reader.peek());
+
+    try {
+      reader.skipValue();
+      fail();
+    } catch (IllegalStateException e) {
+      assertEquals("Cannot skip at end of document", e.getMessage());
+    }
+  }
+
+  public void testSkipValue_atArrayEnd() throws IOException {
+    JsonTreeReader reader = new JsonTreeReader(new JsonArray());
+    reader.beginArray();
+    reader.skipValue();
+    assertEquals(JsonToken.END_DOCUMENT, reader.peek());
+  }
+
+  public void testSkipValue_atObjectEnd() throws IOException {
+    JsonTreeReader reader = new JsonTreeReader(new JsonObject());
+    reader.beginObject();
+    reader.skipValue();
+    assertEquals(JsonToken.END_DOCUMENT, reader.peek());
+  }
+
   public void testHasNext_endOfDocument() throws IOException {
     JsonTreeReader reader = new JsonTreeReader(new JsonObject());
     reader.beginObject();

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

@@ -225,8 +225,8 @@ public static List<Object[]> parameters() {
     JsonReader reader = factory.create("{\"a\":1}");
     reader.beginObject();
     reader.skipValue();
-    assertEquals("$.null", reader.getPreviousPath());
-    assertEquals("$.null", reader.getPath());
+    assertEquals("$.<skipped>", reader.getPreviousPath());
+    assertEquals("$.<skipped>", reader.getPath());
   }
 
   @Test public void skipObjectValues() throws IOException {
@@ -236,8 +236,8 @@ public static List<Object[]> parameters() {
     assertEquals("$.", reader.getPath());
     reader.nextName();
     reader.skipValue();
-    assertEquals("$.null", reader.getPreviousPath());
-    assertEquals("$.null", reader.getPath());
+    assertEquals("$.a", reader.getPreviousPath());
+    assertEquals("$.a", reader.getPath());
     reader.nextName();
     assertEquals("$.b", reader.getPreviousPath());
     assertEquals("$.b", reader.getPath());

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

@@ -164,6 +164,34 @@ public void testSkipDouble() throws IOException {
     assertEquals(JsonToken.END_DOCUMENT, reader.peek());
   }
 
+  public void testSkipValueAfterEndOfDocument() throws IOException {
+    JsonReader reader = new JsonReader(reader("{}"));
+    reader.beginObject();
+    reader.endObject();
+    assertEquals(JsonToken.END_DOCUMENT, reader.peek());
+
+    try {
+      reader.skipValue();
+      fail();
+    } catch (IllegalStateException e) {
+      assertEquals("Cannot skip at end of document", e.getMessage());
+    }
+  }
+
+  public void testSkipValueAtArrayEnd() throws IOException {
+    JsonReader reader = new JsonReader(reader("[]"));
+    reader.beginArray();
+    reader.skipValue();
+    assertEquals(JsonToken.END_DOCUMENT, reader.peek());
+  }
+
+  public void testSkipValueAtObjectEnd() throws IOException {
+    JsonReader reader = new JsonReader(reader("{}"));
+    reader.beginObject();
+    reader.skipValue();
+    assertEquals(JsonToken.END_DOCUMENT, reader.peek());
+  }
+
   public void testHelloWorld() throws IOException {
     String json = "{\n" +
         "   \"hello\": true,\n" +