Firestore project: Import of API interfaces.

-- 197713382 by zxu <zxu>: Implement more on listener class and implement ListenerRegistration. TESTED: blaze test //sensored/testapp:testapp_build_test blaze test //sensored/testapp:testapp_build_test --config=android_x86 blaze test //sensored/testapp:android_testapp_test --config=android_x86 --define firebase_build=stable blaze test //sensored/cpp:firestore_kokoro blaze test //sensored/cpp:listener_registration_test -- 196551381 by zxu <zxu>: Implement more on listener class and implement the DocumentReference::AddSnapshotListener. Also added a few test case and fixed a bug in DocumentReferenceInternal. ListenerRegistration will be implemented in subsequent CL. TESTED: blaze test //sensored/testapp:testapp_build_test blaze test //sensored/testapp:testapp_build_test --config=android_x86 blaze test //sensored/testapp:android_testapp_test --config=android_x86 --define firebase_build=stable blaze test //sensored/cpp:firestore_kokoro blaze test //sensored/cpp:firestore_test -- 196276752 by zxu <zxu>: Implement the SnapshotMetadata with inline methods and (non-)Wrapper for Firestore C++. TESTED: blaze test //sensored/testapp:testapp_build_test blaze test //sensored/testapp:testapp_build_test --config=android_x86 blaze test //sensored/testapp:android_testapp_test --config=android_x86 --experimental_one_version_enforcement=warning blaze test //sensored/cpp:firestore_kokoro blaze test //sensored/cpp:firestore_test -- 195841793 by zxu <zxu>: Implement the wrapper class for callback (EventListener). People unlike huge CL. So sending this short one for review. In subsequent CLs, I'll do: * cache/uncache or the CppEventListener class and the wiring of native method; * actually using this to implement DocumentReference::AddSnapshotListener; * update the testapp to run android_test with callback. -- 194112388 by zxu <zxu>: Add Android-Wrapper for DocumentReference's non-callback methods. Tested: blaze test //sensored/testapp:testapp_build_test blaze test //sensored/testapp:testapp_build_test --config=android_x86 blaze test //sensored/cpp:firestore_kokoro blaze test //sensored/cpp:firestore_test -- 192445183 by zxu <zxu>: Add Android-Wrapper for Firestore's remaining methods. Tested: blaze test //sensored/testapp:testapp_build_test blaze test //sensored/testapp:testapp_build_test --config=android_x86 blaze test //sensored/cpp:firestore_kokoro blaze test //sensored/cpp:firestore_test -- 190986604 by mcg <mcg>: Manually import the public portion of - 22c226a C++ migration: make Timestamp class a part of public API ... by Konstantin Varlamov <var-const@users.noreply.github.com> Note that this only imports the header, which otherewise won't come over with a regular copybara run because we're currently excluding the public headers from the Firestore import with cl/188810622. The .cc implementation of this will come over with a regular copybara import, coming shortly. -- 189013767 by zxu <zxu>: Add Android-Wrapper for Firestore's method that does not involve other Firestore types. Tested: blaze test //sensored/testapp:testapp_build_test blaze test //sensored/testapp:testapp_build_test --config=android_x86 blaze test //sensored/cpp:firestore_kokoro -- 188809445 by mcg <mcg>: Import of firebase-ios-sdk from Github. - 07f4695 Updates Changelog for 4.5.0 release (firebase#908) by Zsika Phillip <protocol86@users.noreply.github.com> - 2b82a2e Allow serializing arbitrary length FieldValues (firebase#889) by rsgowman <rgowman> - 3e41f25 Fix test failures that occur during prod build (firebase#910) by rsgowman <rgowman> - f122cf7 Fix MutationQueue issue resulting in re-sending acknowled... by Michael Lehenbauer <mikelehen@gmail.com> - 7522314 Partial wrapping of pb_ostream_t (pt2) (firebase#903) by rsgowman <rgowman> - 0d3adb1 Partial wrapping of pb_ostream_t (pt1) (firebase#899) by rsgowman <rgowman> - e41f4b1 Merge Release 4.10.1 into Master (firebase#896) by zxu <zxu> - 2ae36f1 [De]Serialize FieldValue map_values ("Objects") (firebase#878) by rsgowman <rgowman> - 5930ad2 Factor out a universal build script (firebase#884) by Gil <mcg> - 8ef0f14 Adds Email link sign-in (firebase#882) by Paul Beusterien <paulbeusterien> - 0b8f216 Merge pull request firebase#880 from firebase/release-4.10.0 by Paul Beusterien <paulbeusterien> - 8311c64 port paths to FSTDocumentKey (firebase#877) by zxu <zxu> - 34ebf10 Add 10 second timeout waiting for connection before clien... by Michael Lehenbauer <mikelehen@gmail.com> - 1c40e7a add converters and port paths to FSTQuery (firebase#869) by zxu <zxu> - 9b5b4d8 Serialize (and deserialize) string values (firebase#864) by rsgowman <rgowman> - c6f73f7 Fix the issue completion handler is not triggered in subs... by Chen Liang <chliang> - 1ecf690 Add FieldValue.boolean_value() (firebase#862) by rsgowman <rgowman> - 3e7c062 replacing Auth by C++ auth implementation (firebase#802) by zxu <zxu> - 13aeb61 Eliminate TypedValue and serialize direct from FieldValue... by rsgowman <rgowman> -- 187049498 by mcg <mcg>: Import of firebase-ios-sdk from Github. - f7d9f29 Fix lint warnings (firebase#840) by Gil <mcg> - b5c60ad Refactor [En|De]codeVarint to be symetric wrt tags (firebase#837) by rsgowman <rgowman> - ddc12c0 Merge pull request firebase#694 from morganchen12/auth-docs by Morgan Chen <morganchen12@gmail.com> - 442d46f Avoid warnings about failing to override a designated ini... by Gil <mcg> - 4dc63f8 Fix Firestore tests for M22 (firebase#834) by Gil <mcg> - 935f3ca Avoid wrapping and rewrapping NSStrings when constructin... by Gil <mcg> - 6ce954a Serialize (and deserialize) int64 values (firebase#818) (firebase#829) by rsgowman <rgowman> - 41dcd4b Fix trivial mem leak in the test suite (firebase#828) by rsgowman <rgowman> - 50f9df9 Accept FIRTimestamp where NSDate is currently accepted as... by Konstantin Varlamov <var-const@users.noreply.github.com> - 67b068e Fix implicit retain self warnings (firebase#808) by rsgowman <rgowman> - 14ea068 Make FSTTimestamp into a public Firestore class (firebase#698) by Konstantin Varlamov <var-const@users.noreply.github.com> - de00de2 [En|De]codeUnsignedVarint -> [En|De]codeVarint (firebase#817) by rsgowman <rgowman> - 9bf73ab Fix two stream close issues (b/73167987, b/73382103). (firebase#8... by Michael Lehenbauer <mikelehen@gmail.com> - 7a4a2ea replacing FSTGetTokenResult by C++ Token implementation (... by zxu <zxu> - a9f3f35 Delete stale Firestore instances after FIRApp is deleted.... by Ryan Wilson <wilsonryan> - aa6f1ae Disable -Wrange-loop-analysis for abseil (firebase#807) by rsgowman <rgowman> - ef55eef Require official 1.4.0 for min CocoaPods version (firebase#806) by Paul Beusterien <paulbeusterien> - 7cddb97 Serialize (and deserialize) bool values (firebase#791) by rsgowman <rgowman> - 7a97f6c Enable -Wcomma for our build; disable it for abseil. (firebase#799) by rsgowman <rgowman> - 81ee594 DispatchQueue delayed callback improvements + testing (firebase#7... by Michael Lehenbauer <mikelehen@gmail.com> - fd9fd27 replacing Auth/FSTUser by C++ auth implementation (firebase#804) by zxu <zxu> - 6889850 Merge pull request firebase#801 from firebase/release-4.9.0 by Paul Beusterien <paulbeusterien> - e4be254 Fixed capitalization of init in test function. (firebase#797) by Ryan Wilson <wilsonryan> - 933be73 Improve documentation on auto-init property in FCM. (firebase#792) by Chen Liang <chliang> - 0f3c24b Actually ignore events on inactive streams, rather than j... by Greg Soltis <gsoltis> - fe19fca Serialize and deserialize null (firebase#783) by rsgowman <rgowman> - 95d0411 fix flaky test (firebase#788) by zxu <zxu> - b6613bd Cleaning up implicit retain for the RTDB and Storage by Sebastian Schmidt <mrschmidt> - 5f5f808 Keep track of number of queries in the query cache (firebase#776) by Greg Soltis <gsoltis> - c7c51a7 Fix double parsing on 32 bit devices. (firebase#787) by Ryan Wilson <wilsonryan> - 9504582 Port Firestore Document to C++ (firebase#777) by zxu <zxu> - adf9fb3 Update FieldValue of type Reference (firebase#775) by zxu <zxu> - 4afcfb1 Move to explicit nil check. (firebase#782) by Ryan Wilson <wilsonryan> - fd83e07 Strawman C++ API (firebase#763) by rsgowman <rgowman> - 8003348 C++ port: add C++ equivalent of FSTDocumentKey. (firebase#762) by Konstantin Varlamov <var-const@users.noreply.github.com> - 612d99c Fix Core CLANG_WARN_OBJC_IMPLICIT_RETAIN_SELF warnings (#... by Paul Beusterien <paulbeusterien> - bf45a15 port Firestore SnapshotVersion in C++ (firebase#767) by zxu <zxu> - d70c23e port Firestore Auth module in C++ (firebase#733) by zxu <zxu> - 633eb7b Let Travis run for `CMake` test and `lint.sh` (firebase#769) by zxu <zxu> - 274fe52 cmake build fixes (firebase#770) by rsgowman <rgowman> -- 184568931 by mcg <mcg>: Import of firebase-ios-sdk from Github. - 32266c5 Make sure Firestore/core/include is in the podspec (firebase#748) by Gil <mcg> - 070c0ea Merge pull request firebase#746 from morganchen12/unguarded-block by Morgan Chen <morganchen12@gmail.com> - 13f572e Increase expectation timeout to 25 seconds. (firebase#744) by Michael Lehenbauer <mikelehen@gmail.com> - 47d81fd fix (firebase#739) by Chen Liang <chliang> - 515625c Remove predecessorKey,Object,Document, etc (firebase#735) by Gil <mcg> - ac30522 Start on ArraySortedMap in C++ (firebase#721) by Gil <mcg> - 729b8d1 Move all Firestore Objective-C to Objective-C++ (firebase#734) by Gil <mcg> - 693d064 Merge pull request firebase#732 from OleksiyA/FCM-subscribe-compl... by Oleksiy Ivanov <oleksiy@informationrd.com> - 3cbdbf2 Schema migrations for LevelDB (firebase#728) by Greg Soltis <gsoltis> - 6474a82 Firestore DatabaseId in C++ (firebase#727) by zxu <zxu> - 05ef5ae Add absl_strings to firebase_firestore_util_test dependen... by rsgowman <rgowman> - 03a0069 Add changelog entry for my last PR (oops) and also add a ... by Michael Lehenbauer <mikelehen@gmail.com> - 5a280ca Import iterator_adaptors from google3 (firebase#718) by Gil <mcg> - 63a380b Use fixed-sized types (firebase#719) by Gil <mcg> - 6dc1373 Version updates to 4.8.2 (firebase#722) by Paul Beusterien <paulbeusterien> - a74d39f Fix a number of c++ build errors (firebase#715) by rsgowman <rgowman> - cceeec3 travis: check for copyright in sources (firebase#717) by Paul Beusterien <paulbeusterien> - 4d7c973 Fix b/72502745: OnlineState changes cause limbo document ... by Michael Lehenbauer <mikelehen@gmail.com> - af6976a normalize and port the rest of Firebase/Port code (firebase#713) by zxu <zxu> - 7226b4a port TargetIdGenerator to iOS (firebase#709) by zxu <zxu> - 5306474 adding unit test for auto init enable function (firebase#710) by Chen Liang <chliang> - 821fb90 implement `TargetIdGenerator` in C++ for Firestore (firebase#701) by zxu <zxu> - 5fdda3f normalize string_util (firebase#708) by zxu <zxu> - 15a2926 Update CHANGELOG for M21.1 release (firebase#679) by Ryan Wilson <wilsonryan> - f027214 Fix incorrect deprecation message (firebase#688) by Iulian Onofrei <6d0847b9@opayq.com> - bfa0e40 Implement the rest of FieldValue types for C++ (firebase#687) by zxu <zxu> - 1f77212 Properly publish Abseil sources as a part of the podspec ... by Gil <mcg> ORIGINAL_AUTHOR=Firebase <firebase-noreply> PiperOrigin-RevId: 197713382
zxu123 · May 23, 2018 · ec72ca8 · ec72ca8
1 parent 2593e20
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diff --git a/Firestore/core/include/firebase/firestore/CMakeLists.txt b/Firestore/core/include/firebase/firestore/CMakeLists.txt
@@ -12,7 +12,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-# Hack to make the headers show up in IDEs
+# feature to make the headers show up in IDEs
 # (see https://stackoverflow.com/questions/27039019/ and open issue on CMake
 # issue tracker: https://gitlab.kitware.com/cmake/cmake/issues/15234)
 add_custom_target(firebase_firestore_types_ide SOURCES

diff --git a/Firestore/core/include/firebase/firestore/collection_reference.h b/Firestore/core/include/firebase/firestore/collection_reference.h
@@ -0,0 +1,98 @@
+/*
+ * Copyright 2018 Google
+ *
+ * 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.
+ */
+
+#ifndef FIRESTORE_CORE_INCLUDE_FIREBASE_FIRESTORE_COLLECTION_REFERENCE_H_
+#define FIRESTORE_CORE_INCLUDE_FIREBASE_FIRESTORE_COLLECTION_REFERENCE_H_
+
+namespace firebase {
+namespace firestore {
+
+class CollectionReferenceInternal;
+class FirestoreInternal;
+
+/**
+ * A CollectionReference refers to a collection of documents location in a
+ * Firestore database and can be used for adding documents, getting document
+ * references, and querying for documents.
+ */
+// TODO(zxu123): add more methods to complete the class and make it useful.
+class CollectionReference {
+ public:
+  /**
+   * @brief Default constructor. This creates an invalid CollectionReference.
+   * Attempting to perform any operations on this reference will fail unless a
+   * valid CollectionReference has been assigned to it.
+   */
+  CollectionReference();
+
+  /**
+   * @brief Copy constructor. It's totally okay (and efficient) to copy
+   * CollectionReference instances, as they simply point to the same location in
+   * the database.
+   *
+   * @param[in] reference CollectionReference to copy from.
+   */
+  CollectionReference(const CollectionReference& reference);
+
+  /**
+   * @brief Move constructor. Moving is an efficient operation for
+   * CollectionReference instances.
+   *
+   * @param[in] reference CollectionReference to move data from.
+   */
+  CollectionReference(CollectionReference&& reference);
+
+  /** @brief Required virtual destructor. */
+  virtual ~CollectionReference();
+
+  /**
+   * @brief Copy assignment operator. It's totally okay (and efficient) to copy
+   * CollectionReference instances, as they simply point to the same location in
+   * the database.
+   *
+   * @param[in] reference CollectionReference to copy from.
+   *
+   * @returns Reference to the destination CollectionReference.
+   */
+  CollectionReference& operator=(const CollectionReference& reference);
+
+  /**
+   * @brief Move assignment operator. Moving is an efficient operation for
+   * CollectionReference instances.
+   *
+   * @param[in] reference CollectionReference to move data from.
+   *
+   * @returns Reference to the destination CollectionReference.
+   */
+  CollectionReference& operator=(CollectionReference&& reference);
+
+ protected:
+  explicit CollectionReference(CollectionReferenceInternal* internal);
+
+ private:
+  friend class DocumentReference;
+  friend class DocumentReferenceInternal;
+  friend class FirestoreInternal;
+
+  // TODO(zxu123): investigate possibility to use std::unique_ptr or
+  // firebase::UniquePtr.
+  CollectionReferenceInternal* internal_ = nullptr;
+};
+
+}  // namespace firestore
+}  // namespace firebase
+
+#endif  // FIRESTORE_CORE_INCLUDE_FIREBASE_FIRESTORE_COLLECTION_REFERENCE_H_
diff --git a/Firestore/core/include/firebase/firestore/document_change.h b/Firestore/core/include/firebase/firestore/document_change.h
@@ -0,0 +1,34 @@
+/*
+ * Copyright 2018 Google
+ *
+ * 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.
+ */
+
+#ifndef FIRESTORE_CORE_INCLUDE_FIREBASE_FIRESTORE_DOCUMENT_CHANGE_H_
+#define FIRESTORE_CORE_INCLUDE_FIREBASE_FIRESTORE_DOCUMENT_CHANGE_H_
+
+namespace firebase {
+namespace firestore {
+
+/**
+ * A DocumentChange represents a change to the documents matching a query. It
+ * contains the document affected and the type of change that occurred (added,
+ * modified, or removed).
+ */
+// TODO(zxu123): add more methods to complete the class and make it useful.
+class DocumentChange {};
+
+}  // namespace firestore
+}  // namespace firebase
+
+#endif  // FIRESTORE_CORE_INCLUDE_FIREBASE_FIRESTORE_DOCUMENT_CHANGE_H_
diff --git a/Firestore/core/include/firebase/firestore/document_reference.h b/Firestore/core/include/firebase/firestore/document_reference.h
@@ -16,7 +16,7 @@
 
 // TODO(rsgowman): This file isn't intended to be used just yet. It's just an
 // outline of what the API might eventually look like. Most of this was
-// shamelessly stolen and modified from RTDB's header file, melded with the
+// shamelessly stolen and modified from rtdb's header file, melded with the
 // (java) firestore api.
 
 #ifndef FIRESTORE_CORE_INCLUDE_FIREBASE_FIRESTORE_DOCUMENT_REFERENCE_H_
@@ -29,41 +29,30 @@
 #include <functional>
 #endif
 
+#include "firebase/app.h"
+#include "firebase/firestore/collection_reference.h"
+#include "firebase/firestore/document_snapshot.h"
+#include "firebase/firestore/event_listener.h"
+#include "firebase/firestore/field_value.h"
+#include "firebase/firestore/firestore.h"
+#include "firebase/firestore/firestore_errors.h"
+#include "firebase/firestore/listener_registration.h"
+#include "firebase/firestore/set_options.h"
+#include "firebase/future.h"
+
 // TODO(rsgowman): Note that RTDB uses:
 //   #if defined(FIREBASE_USE_MOVE_OPERATORS) || defined(DOXYGEN
 // to protect move operators from older compilers. But all our supported
 // compilers support this, so we've skipped the #if guard. This TODO comment is
 // here so we don't forget to mention this during the API review, and should be
 // removed once this note has migrated to the API review doc.
 
-// TODO(rsgowman): replace these forward decls with appropriate includes (once
-// they exist)
-namespace firebase {
-class App;
-template <typename T>
-class Future;
-}  // namespace firebase
-
 namespace firebase {
 namespace firestore {
 
-// TODO(rsgowman): replace these forward decls with appropriate includes (once
-// they exist)
-class FieldValue;
-class DocumentSnapshot;
+class DocumentReferenceInternal;
 class Firestore;
-class Error;
-template <typename T>
-class EventListener;
-class ListenerRegistration;
-class CollectionReference;
-class DocumentListenOptions;
-// TODO(rsgowman): not quite a forward decl, but required to make the default
-// parameter to Set() "compile".
-class SetOptions {
- public:
-  SetOptions();
-};
+class FirestoreInternal;
 
 // TODO(rsgowman): move this into the FieldValue header
 #ifdef STLPORT
@@ -80,12 +69,19 @@ using MapFieldValue = std::unordered_map<std::string, FieldValue>;
  *
  * Create a DocumentReference via Firebase::Document(const string& path).
  *
+ * NOT thread-safe: an instance should not be used from multiple threads
+ *
  * Subclassing Note: Firestore classes are not meant to be subclassed except for
  * use in test mocks. Subclassing is not supported in production code and new
  * SDK releases may break code that does so.
  */
 class DocumentReference {
  public:
+  enum class MetadataChanges {
+    kExclude,
+    kInclude,
+  };
+
   /**
    * @brief Default constructor. This creates an invalid DocumentReference.
    * Attempting to perform any operations on this reference will fail (and cause
@@ -269,28 +265,13 @@ class DocumentReference {
    * this DocumentReference. (Ownership is not transferred; you are responsible
    * for making sure that listener is valid as long as this DocumentReference is
    * valid and the listener is registered.)
+   * @param[in] option The option whether to listen metadata-changes or not.
    *
    * @return A registration object that can be used to remove the listener.
    */
   virtual ListenerRegistration AddSnapshotListener(
-      EventListener<DocumentSnapshot>* listener);
-
-  /**
-   * @brief Starts listening to the document referenced by this
-   * DocumentReference.
-   *
-   * @param[in] options The options to use for this listen.
-   * @param[in] listener The event listener that will be called with the
-   * snapshots, which must remain in memory until you remove the listener from
-   * this DocumentReference. (Ownership is not transferred; you are responsible
-   * for making sure that listener is valid as long as this DocumentReference is
-   * valid and the listener is registered.)
-   *
-   * @return A registration object that can be used to remove the listener.
-   */
-  virtual ListenerRegistration AddSnapshotListener(
-      const DocumentListenOptions& options,
-      EventListener<DocumentSnapshot>* listener);
+      EventListener<DocumentSnapshot>* listener,
+      MetadataChanges option = MetadataChanges::kExclude);
 
 #if defined(FIREBASE_USE_STD_FUNCTION) || defined(DOXYGEN)
   /**
@@ -299,35 +280,29 @@ class DocumentReference {
    *
    * @param[in] callback function or lambda to call. When this function is
    * called, exactly one of the parameters will be non-null.
+   * @param[in] option The option whether to listen metadata-changes or not.
    *
    * @return A registration object that can be used to remove the listener.
    *
    * @note This method is not available when using STLPort on Android, as
    * std::function is not supported on STLPort.
    */
   virtual ListenerRegistration AddSnapshotListener(
-      std::function<void(const DocumentSnapshot*, const Error*)> callback);
-
-  /**
-   * @brief Starts listening to the document referenced by this
-   * DocumentReference.
-   *
-   * @param[in] options The options to use for this listen.
-   * @param[in] callback function or lambda to call. When this function is
-   * called, exactly one of the parameters will be non-null.
-   *
-   * @return A registration object that can be used to remove the listener.
-   *
-   * @note This method is not available when using STLPort on Android, as
-   * std::function is not supported on STLPort.
-   */
-  virtual ListenerRegistration AddSnapshotListener(
-      const DocumentListenOptions& options,
-      std::function<void(const DocumentSnapshot*, const Error*)> callback);
+      std::function<void(const DocumentSnapshot*, const Error*)> callback,
+      MetadataChanges option = MetadataChanges::kExclude);
 #endif  // defined(FIREBASE_USE_STD_FUNCTION) || defined(DOXYGEN)
+
+ protected:
+  explicit DocumentReference(DocumentReferenceInternal* internal);
+
+ private:
+  friend class FirestoreInternal;
+
+  // TODO(zxu123): investigate possibility to use std::unique_ptr or
+  // firebase::UniquePtr.
+  DocumentReferenceInternal* internal_ = nullptr;
 };
 
-// TODO(rsgowman): probably define and inline here.
 bool operator==(const DocumentReference& lhs, const DocumentReference& rhs);
 
 inline bool operator!=(const DocumentReference& lhs,
@@ -361,7 +336,7 @@ namespace std {
 // C++ style guide. But we think this is probably ok in this case since:
 // a) It's the standard way of doing this outside of Google (as the style guide
 // itself points out), and
-// b) This has a straightforward hash function anyway (just hash the path) so I
+// b) This has a straightfoward hash function anyway (just hash the path) so I
 // don't think the concerns in the style guide are going to bite us.
 //
 // Raise this concern during the API review.

diff --git a/Firestore/core/include/firebase/firestore/document_snapshot.h b/Firestore/core/include/firebase/firestore/document_snapshot.h
@@ -0,0 +1,38 @@
+/*
+ * Copyright 2018 Google
+ *
+ * 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.
+ */
+
+#ifndef FIRESTORE_CORE_INCLUDE_FIREBASE_FIRESTORE_DOCUMENT_SNAPSHOT_H_
+#define FIRESTORE_CORE_INCLUDE_FIREBASE_FIRESTORE_DOCUMENT_SNAPSHOT_H_
+
+namespace firebase {
+namespace firestore {
+
+/**
+ * A DocumentSnapshot contains data read from a document in your Firestore
+ * database. The data can be extracted with the data() method or by using
+ * FooValue() to access a specific field, where Foo is the type of that field.
+ *
+ * For a DocumentSnapshot that points to a non-existing document, any data
+ * access will raise assertion. You can use the exists() method to explicitly
+ * verify a documents existence.
+ */
+// TODO(zxu123): add more methods to complete the class and make it useful.
+class DocumentSnapshot {};
+
+}  // namespace firestore
+}  // namespace firebase
+
+#endif  // FIRESTORE_CORE_INCLUDE_FIREBASE_FIRESTORE_DOCUMENT_SNAPSHOT_H_
diff --git a/Firestore/core/include/firebase/firestore/event_listener.h b/Firestore/core/include/firebase/firestore/event_listener.h
@@ -22,19 +22,18 @@
 #ifndef FIRESTORE_CORE_INCLUDE_FIREBASE_FIRESTORE_EVENT_LISTENER_H_
 #define FIRESTORE_CORE_INCLUDE_FIREBASE_FIRESTORE_EVENT_LISTENER_H_
 
+#include "firebase/firestore/firestore_errors.h"
+
 namespace firebase {
 namespace firestore {
 
-// TODO(rsgowman): replace these forward decl's with appropriate includes (once
-// they exist)
-class Error;
-
 /**
  * @brief An interface for event listeners.
  */
 template <typename T>
 class EventListener {
  public:
+  virtual ~EventListener() {}
   /**
    * @brief OnEvent will be called with the new value or the error if an error
    * occurred.
@@ -44,7 +43,7 @@ class EventListener {
    * @param value The value of the event. null if there was an error.
    * @param error The error if there was error. null otherwise.
    */
-  void OnEvent(const T* value, const Error* error);
+  virtual void OnEvent(const T* value, const Error* error) = 0;
 };
 
 }  // namespace firestore