Port FSTDocumentKeySet to C++ DocumentKeySet (#1229)

* Define a Comparator for DocumentKey

* Automated migration from FSTDocumentKeySet to DocumentKeySet

* Manual fixups for DocumentKeySet

* Delete FSTDocumentKeySet

2 files changed, 24 insertions, 1 deletions

diff --git a/Firestore/core/src/firebase/firestore/immutable/sorted_set.h b/Firestore/core/src/firebase/firestore/immutable/sorted_set.h
index 6828106..d78fd61 100644
--- a/Firestore/core/src/firebase/firestore/immutable/sorted_set.h
+++ b/Firestore/core/src/firebase/firestore/immutable/sorted_set.h
@@ -61,6 +61,13 @@ class SortedSet {
   explicit SortedSet(M&& map) : map_{std::move(map)} {
   }
 
+  SortedSet(std::initializer_list<value_type> entries, const C& comparator = {})
+      : map_{comparator} {
+    for (auto&& value : entries) {
+      map_ = map_.insert(value, {});
+    }
+  }
+
   bool empty() const {
     return map_.empty();
   }
@@ -124,7 +131,14 @@ class SortedSet {
   }
 
   friend bool operator==(const SortedSet& lhs, const SortedSet& rhs) {
-    return std::equal(lhs.begin(), lhs.end(), rhs.begin(), rhs.end());
+    if (lhs.size() != rhs.size()) {
+      return false;
+    }
+    return std::equal(lhs.begin(), lhs.end(), rhs.begin());
+  }
+
+  friend bool operator!=(const SortedSet& lhs, const SortedSet& rhs) {
+    return !(lhs == rhs);
   }
 
  private:
diff --git a/Firestore/core/src/firebase/firestore/model/document_key.h b/Firestore/core/src/firebase/firestore/model/document_key.h
index 7f6478f..6532b2e 100644
--- a/Firestore/core/src/firebase/firestore/model/document_key.h
+++ b/Firestore/core/src/firebase/firestore/model/document_key.h
@@ -17,6 +17,7 @@
 #ifndef FIRESTORE_CORE_SRC_FIREBASE_FIRESTORE_MODEL_DOCUMENT_KEY_H_
 #define FIRESTORE_CORE_SRC_FIREBASE_FIRESTORE_MODEL_DOCUMENT_KEY_H_
 
+#include <functional>
 #include <initializer_list>
 #include <memory>
 #include <string>
@@ -26,6 +27,7 @@
 #endif  // defined(__OBJC__)
 
 #include "Firestore/core/src/firebase/firestore/model/resource_path.h"
+#include "Firestore/core/src/firebase/firestore/util/comparison.h"
 #include "Firestore/core/src/firebase/firestore/util/hashing.h"
 #include "absl/strings/string_view.h"
 
@@ -118,6 +120,13 @@ inline bool operator>=(const DocumentKey& lhs, const DocumentKey& rhs) {
 }
 
 }  // namespace model
+
+namespace util {
+
+template <>
+struct Comparator<model::DocumentKey> : public std::less<model::DocumentKey> {};
+
+}  // namespace util
 }  // namespace firestore
 }  // namespace firebase