JsonWriter.getPath().

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

@@ -59,7 +59,7 @@ final class AdapterMethodsFactory implements JsonAdapter.Factory {
             throw new AssertionError();
           } catch (InvocationTargetException e) {
             if (e.getCause() instanceof IOException) throw (IOException) e.getCause();
-            throw new JsonDataException(e.getCause()); // TODO: more context?
+            throw new JsonDataException(e.getCause() + " at " + writer.getPath());
           }
         }
       }
@@ -77,7 +77,7 @@ final class AdapterMethodsFactory implements JsonAdapter.Factory {
             throw new AssertionError();
           } catch (InvocationTargetException e) {
             if (e.getCause() instanceof IOException) throw (IOException) e.getCause();
-            throw new JsonDataException(e.getCause()); // TODO: more context?
+            throw new JsonDataException(e.getCause() + " at " + reader.getPath());
           }
         }
       }

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

@@ -248,14 +248,6 @@ public final class JsonReader implements Closeable {
     stack[stackSize++] = JsonScope.EMPTY_DOCUMENT;
   }
 
-  /*
-   * The path members. It corresponds directly to stack: At indices where the
-   * stack contains an object (EMPTY_OBJECT, DANGLING_NAME or NONEMPTY_OBJECT),
-   * pathNames contains the name at this scope. Where it contains an array
-   * (EMPTY_ARRAY, NONEMPTY_ARRAY) pathIndices contains the current index in
-   * that array. Otherwise the value is undefined, and we take advantage of that
-   * by incrementing pathIndices when doing so isn't useful.
-   */
   private String[] pathNames = new String[32];
   private int[] pathIndices = new int[32];
 
@@ -1269,30 +1261,7 @@ public final class JsonReader implements Closeable {
    * the current location in the JSON value.
    */
   public String getPath() {
-    StringBuilder result = new StringBuilder().append('$');
-    for (int i = 0, size = stackSize; i < size; i++) {
-      switch (stack[i]) {
-        case JsonScope.EMPTY_ARRAY:
-        case JsonScope.NONEMPTY_ARRAY:
-          result.append('[').append(pathIndices[i]).append(']');
-          break;
-
-        case JsonScope.EMPTY_OBJECT:
-        case JsonScope.DANGLING_NAME:
-        case JsonScope.NONEMPTY_OBJECT:
-          result.append('.');
-          if (pathNames[i] != null) {
-            result.append(pathNames[i]);
-          }
-          break;
-
-        case JsonScope.NONEMPTY_DOCUMENT:
-        case JsonScope.EMPTY_DOCUMENT:
-        case JsonScope.CLOSED:
-          break;
-      }
-    }
-    return result.toString();
+    return JsonScope.getPath(stackSize, stack, pathNames, pathIndices);
   }
 
   /**

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

@@ -15,53 +15,65 @@
  */
 package com.squareup.moshi;
 
-/**
- * Lexical scoping elements within a JSON reader or writer.
- */
+/** Lexical scoping elements within a JSON reader or writer. */
 final class JsonScope {
 
-  /**
-   * An array with no elements requires no separators or newlines before
-   * it is closed.
-   */
+  /** An array with no elements requires no separators or newlines before it is closed. */
   static final int EMPTY_ARRAY = 1;
 
-  /**
-   * A array with at least one value requires a comma and newline before
-   * the next element.
-   */
+  /** A array with at least one value requires a comma and newline before the next element. */
   static final int NONEMPTY_ARRAY = 2;
 
-  /**
-   * An object with no name/value pairs requires no separators or newlines
-   * before it is closed.
-   */
+  /** An object with no name/value pairs requires no separators or newlines before it is closed. */
   static final int EMPTY_OBJECT = 3;
 
-  /**
-   * An object whose most recent element is a key. The next element must
-   * be a value.
-   */
+  /** An object whose most recent element is a key. The next element must be a value. */
   static final int DANGLING_NAME = 4;
 
-  /**
-   * An object with at least one name/value pair requires a comma and
-   * newline before the next element.
-   */
+  /** An object with at least one name/value pair requires a separator before the next element. */
   static final int NONEMPTY_OBJECT = 5;
 
-  /**
-   * No object or array has been started.
-   */
+  /** No object or array has been started. */
   static final int EMPTY_DOCUMENT = 6;
 
-  /**
-   * A document with at an array or object.
-   */
+  /** A document with at an array or object. */
   static final int NONEMPTY_DOCUMENT = 7;
 
-  /**
-   * A document that's been closed and cannot be accessed.
-   */
+  /** A document that's been closed and cannot be accessed. */
   static final int CLOSED = 8;
+
+  /**
+   * Renders the path in a JSON document to a string. The {@code pathNames} and {@code pathIndices}
+   * parameters corresponds directly to stack: At indices where the stack contains an object
+   * (EMPTY_OBJECT, DANGLING_NAME or NONEMPTY_OBJECT), pathNames contains the name at this scope.
+   * Where it contains an array (EMPTY_ARRAY, NONEMPTY_ARRAY) pathIndices contains the current index
+   * in that array. Otherwise the value is undefined, and we take advantage of that by incrementing
+   * pathIndices when doing so isn't useful.
+   */
+  static String getPath(int stackSize, int[] stack, String[] pathNames, int[] pathIndices) {
+    StringBuilder result = new StringBuilder().append('$');
+    for (int i = 0, size = stackSize; i < size; i++) {
+      switch (stack[i]) {
+        case EMPTY_ARRAY:
+        case NONEMPTY_ARRAY:
+          result.append('[').append(pathIndices[i]).append(']');
+          break;
+
+        case EMPTY_OBJECT:
+        case DANGLING_NAME:
+        case NONEMPTY_OBJECT:
+          result.append('.');
+          if (pathNames[i] != null) {
+            result.append(pathNames[i]);
+          }
+          break;
+
+        case NONEMPTY_DOCUMENT:
+        case EMPTY_DOCUMENT:
+        case CLOSED:
+          break;
+      }
+    }
+    return result.toString();
+  }
 }

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

@@ -160,6 +160,9 @@ public final class JsonWriter implements Closeable, Flushable {
     push(EMPTY_DOCUMENT);
   }
 
+  private String[] pathNames = new String[32];
+  private int[] pathIndices = new int[32];
+
   /**
    * A string containing a full set of spaces for a single level of
    * indentation, or null for no pretty printing.
@@ -290,6 +293,7 @@ public final class JsonWriter implements Closeable, Flushable {
    */
   private JsonWriter open(int empty, String openBracket) throws IOException {
     beforeValue(true);
+    pathIndices[stackSize] = 0;
     push(empty);
     sink.writeUtf8(openBracket);
     return this;
@@ -310,6 +314,8 @@ public final class JsonWriter implements Closeable, Flushable {
     }
 
     stackSize--;
+    pathNames[stackSize] = null; // Free the last path name so that it can be garbage collected!
+    pathIndices[stackSize - 1]++;
     if (context == nonempty) {
       newline();
     }
@@ -360,6 +366,7 @@ public final class JsonWriter implements Closeable, Flushable {
       throw new IllegalStateException("JsonWriter is closed.");
     }
     deferredName = name;
+    pathNames[stackSize - 1] = name;
     return this;
   }
 
@@ -384,6 +391,7 @@ public final class JsonWriter implements Closeable, Flushable {
     writeDeferredName();
     beforeValue(false);
     string(value);
+    pathIndices[stackSize - 1]++;
     return this;
   }
 
@@ -403,6 +411,7 @@ public final class JsonWriter implements Closeable, Flushable {
     }
     beforeValue(false);
     sink.writeUtf8("null");
+    pathIndices[stackSize - 1]++;
     return this;
   }
 
@@ -415,6 +424,7 @@ public final class JsonWriter implements Closeable, Flushable {
     writeDeferredName();
     beforeValue(false);
     sink.writeUtf8(value ? "true" : "false");
+    pathIndices[stackSize - 1]++;
     return this;
   }
 
@@ -432,6 +442,7 @@ public final class JsonWriter implements Closeable, Flushable {
     writeDeferredName();
     beforeValue(false);
     sink.writeUtf8(Double.toString(value));
+    pathIndices[stackSize - 1]++;
     return this;
   }
 
@@ -444,6 +455,7 @@ public final class JsonWriter implements Closeable, Flushable {
     writeDeferredName();
     beforeValue(false);
     sink.writeUtf8(Long.toString(value));
+    pathIndices[stackSize - 1]++;
     return this;
   }
 
@@ -467,6 +479,7 @@ public final class JsonWriter implements Closeable, Flushable {
     }
     beforeValue(false);
     sink.writeUtf8(string);
+    pathIndices[stackSize - 1]++;
     return this;
   }
 
@@ -598,4 +611,12 @@ public final class JsonWriter implements Closeable, Flushable {
         throw new IllegalStateException("Nesting problem.");
     }
   }
+
+  /**
+   * Returns a <a href="http://goessner.net/articles/JsonPath/">JsonPath</a> to
+   * the current location in the JSON value.
+   */
+  public String getPath() {
+    return JsonScope.getPath(stackSize, stack, pathNames, pathIndices);
+  }
 }

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

@@ -233,6 +233,37 @@ public final class AdapterMethodsTest {
   @interface Nullable {
   }
 
+  @Test public void adapterThrows() throws Exception {
+    Moshi moshi = new Moshi.Builder()
+        .add(new ExceptionThrowingPointJsonAdapter())
+        .build();
+    JsonAdapter<Point[]> arrayOfPointAdapter = moshi.adapter(Point[].class).lenient();
+    try {
+      arrayOfPointAdapter.toJson(new Point[] { null, null, new Point(0, 0) });
+      fail();
+    } catch (JsonDataException expected) {
+      assertThat(expected.getMessage())
+          .isEqualTo("java.lang.Exception: pointToJson fail! at $[2]");
+    }
+    try {
+      arrayOfPointAdapter.fromJson("[null,null,[0,0]]");
+      fail();
+    } catch (JsonDataException expected) {
+      assertThat(expected.getMessage())
+          .isEqualTo("java.lang.Exception: pointFromJson fail! at $[2]");
+    }
+  }
+
+  static class ExceptionThrowingPointJsonAdapter {
+    @ToJson void pointToJson(JsonWriter writer, Point point) throws Exception {
+      throw new Exception("pointToJson fail!");
+    }
+
+    @FromJson Point pointFromJson(JsonReader reader) throws Exception {
+      throw new Exception("pointFromJson fail!");
+    }
+  }
+
   static class Point {
     final int x;
     final int y;

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

@@ -0,0 +1,219 @@
+/*
+ * Copyright (C) 2014 Google Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.squareup.moshi;
+
+import java.io.IOException;
+import java.math.BigInteger;
+import okio.Buffer;
+import org.junit.Test;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+public final class JsonWriterPathTest {
+  @Test public void path() throws IOException {
+    JsonWriter writer = new JsonWriter(new Buffer());
+    assertThat(writer.getPath()).isEqualTo("$");
+    writer.beginObject();
+    assertThat(writer.getPath()).isEqualTo("$.");
+    writer.name("a");
+    assertThat(writer.getPath()).isEqualTo("$.a");
+    writer.beginArray();
+    assertThat(writer.getPath()).isEqualTo("$.a[0]");
+    writer.value(2);
+    assertThat(writer.getPath()).isEqualTo("$.a[1]");
+    writer.value(true);
+    assertThat(writer.getPath()).isEqualTo("$.a[2]");
+    writer.value(false);
+    assertThat(writer.getPath()).isEqualTo("$.a[3]");
+    writer.nullValue();
+    assertThat(writer.getPath()).isEqualTo("$.a[4]");
+    writer.value("b");
+    assertThat(writer.getPath()).isEqualTo("$.a[5]");
+    writer.beginObject();
+    assertThat(writer.getPath()).isEqualTo("$.a[5].");
+    writer.name("c");
+    assertThat(writer.getPath()).isEqualTo("$.a[5].c");
+    writer.value("d");
+    assertThat(writer.getPath()).isEqualTo("$.a[5].c");
+    writer.endObject();
+    assertThat(writer.getPath()).isEqualTo("$.a[6]");
+    writer.beginArray();
+    assertThat(writer.getPath()).isEqualTo("$.a[6][0]");
+    writer.value(3);
+    assertThat(writer.getPath()).isEqualTo("$.a[6][1]");
+    writer.endArray();
+    assertThat(writer.getPath()).isEqualTo("$.a[7]");
+    writer.endArray();
+    assertThat(writer.getPath()).isEqualTo("$.a");
+    writer.endObject();
+    assertThat(writer.getPath()).isEqualTo("$");
+  }
+
+  @Test public void arrayOfObjects() throws IOException {
+    JsonWriter writer = new JsonWriter(new Buffer());
+    writer.beginArray();
+    assertThat(writer.getPath()).isEqualTo("$[0]");
+    writer.beginObject();
+    assertThat(writer.getPath()).isEqualTo("$[0].");
+    writer.endObject();
+    assertThat(writer.getPath()).isEqualTo("$[1]");
+    writer.beginObject();
+    assertThat(writer.getPath()).isEqualTo("$[1].");
+    writer.endObject();
+    assertThat(writer.getPath()).isEqualTo("$[2]");
+    writer.beginObject();
+    assertThat(writer.getPath()).isEqualTo("$[2].");
+    writer.endObject();
+    assertThat(writer.getPath()).isEqualTo("$[3]");
+    writer.endArray();
+    assertThat(writer.getPath()).isEqualTo("$");
+  }
+
+  @Test public void arrayOfArrays() throws IOException {
+    JsonWriter writer = new JsonWriter(new Buffer());
+    writer.beginArray();
+    assertThat(writer.getPath()).isEqualTo("$[0]");
+    writer.beginArray();
+    assertThat(writer.getPath()).isEqualTo("$[0][0]");
+    writer.endArray();
+    assertThat(writer.getPath()).isEqualTo("$[1]");
+    writer.beginArray();
+    assertThat(writer.getPath()).isEqualTo("$[1][0]");
+    writer.endArray();
+    assertThat(writer.getPath()).isEqualTo("$[2]");
+    writer.beginArray();
+    assertThat(writer.getPath()).isEqualTo("$[2][0]");
+    writer.endArray();
+    assertThat(writer.getPath()).isEqualTo("$[3]");
+    writer.endArray();
+    assertThat(writer.getPath()).isEqualTo("$");
+  }
+
+  @Test public void objectPath() throws IOException {
+    JsonWriter writer = new JsonWriter(new Buffer());
+    assertThat(writer.getPath()).isEqualTo("$");
+    writer.beginObject();
+    assertThat(writer.getPath()).isEqualTo("$.");
+    writer.name("a");
+    assertThat(writer.getPath()).isEqualTo("$.a");
+    writer.value(1);
+    assertThat(writer.getPath()).isEqualTo("$.a");
+    writer.name("b");
+    assertThat(writer.getPath()).isEqualTo("$.b");
+    writer.value(2);
+    assertThat(writer.getPath()).isEqualTo("$.b");
+    writer.endObject();
+    assertThat(writer.getPath()).isEqualTo("$");
+    writer.close();
+    assertThat(writer.getPath()).isEqualTo("$");
+  }
+
+  @Test public void nestedObjects() throws IOException {
+    JsonWriter writer = new JsonWriter(new Buffer());
+    assertThat(writer.getPath()).isEqualTo("$");
+    writer.beginObject();
+    assertThat(writer.getPath()).isEqualTo("$.");
+    writer.name("a");
+    assertThat(writer.getPath()).isEqualTo("$.a");
+    writer.beginObject();
+    assertThat(writer.getPath()).isEqualTo("$.a.");
+    writer.name("b");
+    assertThat(writer.getPath()).isEqualTo("$.a.b");
+    writer.beginObject();
+    assertThat(writer.getPath()).isEqualTo("$.a.b.");
+    writer.name("c");
+    assertThat(writer.getPath()).isEqualTo("$.a.b.c");
+    writer.nullValue();
+    assertThat(writer.getPath()).isEqualTo("$.a.b.c");
+    writer.endObject();
+    assertThat(writer.getPath()).isEqualTo("$.a.b");
+    writer.endObject();
+    assertThat(writer.getPath()).isEqualTo("$.a");
+    writer.endObject();
+    assertThat(writer.getPath()).isEqualTo("$");
+  }
+
+  @Test public void arrayPath() throws IOException {
+    JsonWriter writer = new JsonWriter(new Buffer());
+    assertThat(writer.getPath()).isEqualTo("$");
+    writer.beginArray();
+    assertThat(writer.getPath()).isEqualTo("$[0]");
+    writer.value(1);
+    assertThat(writer.getPath()).isEqualTo("$[1]");
+    writer.value(true);
+    assertThat(writer.getPath()).isEqualTo("$[2]");
+    writer.value("a");
+    assertThat(writer.getPath()).isEqualTo("$[3]");
+    writer.value(5.5d);
+    assertThat(writer.getPath()).isEqualTo("$[4]");
+    writer.value(BigInteger.ONE);
+    assertThat(writer.getPath()).isEqualTo("$[5]");
+    writer.endArray();
+    assertThat(writer.getPath()).isEqualTo("$");
+    writer.close();
+    assertThat(writer.getPath()).isEqualTo("$");
+  }
+
+  @Test public void nestedArrays() throws IOException {
+    JsonWriter writer = new JsonWriter(new Buffer());
+    assertThat(writer.getPath()).isEqualTo("$");
+    writer.beginArray();
+    assertThat(writer.getPath()).isEqualTo("$[0]");
+    writer.beginArray();
+    assertThat(writer.getPath()).isEqualTo("$[0][0]");
+    writer.beginArray();
+    assertThat(writer.getPath()).isEqualTo("$[0][0][0]");
+    writer.nullValue();
+    assertThat(writer.getPath()).isEqualTo("$[0][0][1]");
+    writer.endArray();
+    assertThat(writer.getPath()).isEqualTo("$[0][1]");
+    writer.endArray();
+    assertThat(writer.getPath()).isEqualTo("$[1]");
+    writer.endArray();
+    assertThat(writer.getPath()).isEqualTo("$");
+    writer.close();
+    assertThat(writer.getPath()).isEqualTo("$");
+  }
+
+  @Test public void multipleTopLevelValuesInOneDocument() throws IOException {
+    JsonWriter writer = new JsonWriter(new Buffer());
+    writer.setLenient(true);
+    writer.beginArray();
+    writer.endArray();
+    assertThat(writer.getPath()).isEqualTo("$");
+    writer.beginArray();
+    writer.endArray();
+    assertThat(writer.getPath()).isEqualTo("$");
+  }
+
+  @Test public void skipNulls() throws IOException {
+    JsonWriter writer = new JsonWriter(new Buffer());
+    writer.setSerializeNulls(false);
+    assertThat(writer.getPath()).isEqualTo("$");
+    writer.beginObject();
+    assertThat(writer.getPath()).isEqualTo("$.");
+    writer.name("a");
+    assertThat(writer.getPath()).isEqualTo("$.a");
+    writer.nullValue();
+    assertThat(writer.getPath()).isEqualTo("$.a");
+    writer.name("b");
+    assertThat(writer.getPath()).isEqualTo("$.b");
+    writer.nullValue();
+    assertThat(writer.getPath()).isEqualTo("$.b");
+    writer.endObject();
+    assertThat(writer.getPath()).isEqualTo("$");
+  }
+}