Make Serializer fully support converting FieldValues (#3659)

This involved support for reference values and taking server timestamps into account (by crashing, because they are not supposed to ever be serialized).

The biggest change is from making every function that decodes a `FieldValue` a member function (as well as any function called by those functions). That is because decoding a reference requires comparing database IDs, and the database ID of this Firestore instance is stored on the `Serializer`.

Author: var-const

Firestore/Source/Remote/FSTSerializerBeta.mm

@@ -390,7 +390,7 @@ - (FieldValue)decodedReferenceValue:(NSString *)resourceName {
   const DocumentKey key{[self localResourcePathForQualifiedResourcePath:path]};
 
   const DatabaseId database_id(project, database);
-  HARD_ASSERT(database_id == _databaseID, "Database %s:%s cannot encode reference from %s:%s",
+  HARD_ASSERT(database_id == _databaseID, "Database %s:%s cannot decode reference from %s:%s",
               _databaseID.project_id(), _databaseID.database_id(), database_id.project_id(),
               database_id.database_id());
   return FieldValue::FromReference(_databaseID, key);

Firestore/core/src/firebase/firestore/local/local_serializer.cc

@@ -123,8 +123,7 @@ google_firestore_v1_Document LocalSerializer::EncodeDocument(
     const Document& doc) const {
   google_firestore_v1_Document result{};
 
-  result.name =
-      rpc_serializer_.EncodeString(rpc_serializer_.EncodeKey(doc.key()));
+  result.name = rpc_serializer_.EncodeKey(doc.key());
 
   // Encode Document.fields (unless it's empty)
   pb_size_t count = CheckedSize(doc.data().GetInternalValue().size());
@@ -148,8 +147,7 @@ firestore_client_NoDocument LocalSerializer::EncodeNoDocument(
     const NoDocument& no_doc) const {
   firestore_client_NoDocument result{};
 
-  result.name =
-      rpc_serializer_.EncodeString(rpc_serializer_.EncodeKey(no_doc.key()));
+  result.name = rpc_serializer_.EncodeKey(no_doc.key());
   result.read_time = rpc_serializer_.EncodeVersion(no_doc.version());
 
   return result;
@@ -163,18 +161,15 @@ NoDocument LocalSerializer::DecodeNoDocument(
   // TODO(rsgowman): Fix hardcoding of has_committed_mutations.
   // Instead, we should grab this from the proto (see other ports). However,
   // we'll defer until the nanopb-master gets merged to master.
-  return NoDocument(rpc_serializer_.DecodeKey(
-                        reader, rpc_serializer_.DecodeString(proto.name)),
-                    version,
+  return NoDocument(rpc_serializer_.DecodeKey(reader, proto.name), version,
                     /*has_committed_mutations=*/false);
 }
 
 firestore_client_UnknownDocument LocalSerializer::EncodeUnknownDocument(
     const UnknownDocument& unknown_doc) const {
   firestore_client_UnknownDocument result{};
 
-  result.name = rpc_serializer_.EncodeString(
-      rpc_serializer_.EncodeKey(unknown_doc.key()));
+  result.name = rpc_serializer_.EncodeKey(unknown_doc.key());
   result.version = rpc_serializer_.EncodeVersion(unknown_doc.version());
 
   return result;
@@ -185,8 +180,7 @@ UnknownDocument LocalSerializer::DecodeUnknownDocument(
   SnapshotVersion version =
       rpc_serializer_.DecodeSnapshotVersion(reader, proto.version);
 
-  return UnknownDocument(rpc_serializer_.DecodeKey(
-                             reader, rpc_serializer_.DecodeString(proto.name)),
+  return UnknownDocument(rpc_serializer_.DecodeKey(reader, proto.name),
                          version);
 }
 

Firestore/core/src/firebase/firestore/model/database_id.cc

@@ -16,6 +16,8 @@
 
 #include "Firestore/core/src/firebase/firestore/model/database_id.h"
 
+#include <ostream>
+
 #include "Firestore/core/src/firebase/firestore/util/hard_assert.h"
 #include "Firestore/core/src/firebase/firestore/util/hashing.h"
 
@@ -40,6 +42,14 @@ util::ComparisonResult DatabaseId::CompareTo(
   return util::Compare(database_id(), rhs.database_id());
 }
 
+std::string DatabaseId::ToString() const {
+  return absl::StrCat("DatabaseId(", project_id(), ":", database_id(), ")");
+}
+
+std::ostream& operator<<(std::ostream& out, const DatabaseId& database_id) {
+  return out << database_id.ToString();
+}
+
 size_t DatabaseId::Hash() const {
   return util::Hash(project_id(), database_id());
 }

Firestore/core/src/firebase/firestore/model/database_id.h

@@ -17,6 +17,7 @@
 #ifndef FIRESTORE_CORE_SRC_FIREBASE_FIRESTORE_MODEL_DATABASE_ID_H_
 #define FIRESTORE_CORE_SRC_FIREBASE_FIRESTORE_MODEL_DATABASE_ID_H_
 
+#include <iosfwd>
 #include <memory>
 #include <string>
 #include <utility>
@@ -60,6 +61,10 @@ class DatabaseId : public util::Comparable<DatabaseId> {
 
   util::ComparisonResult CompareTo(const DatabaseId& rhs) const;
 
+  std::string ToString() const;
+  friend std::ostream& operator<<(std::ostream& out,
+                                  const DatabaseId& database_id);
+
   size_t Hash() const;
 
  private:

Firestore/core/src/firebase/firestore/nanopb/byte_string.cc

@@ -16,9 +16,12 @@
 
 #include "Firestore/core/src/firebase/firestore/nanopb/byte_string.h"
 
+#include <cctype>
 #include <cstdlib>
 #include <cstring>
+#include <iomanip>
 #include <ostream>
+#include <sstream>
 
 #include "Firestore/core/src/firebase/firestore/nanopb/nanopb_util.h"
 #include "Firestore/core/src/firebase/firestore/util/hashing.h"
@@ -87,14 +90,18 @@ size_t ByteString::Hash() const {
 }
 
 std::string ByteString::ToString() const {
-  std::string hex = absl::BytesToHexString(MakeStringView(*this));
-  return absl::StrCat("<", hex, ">");
+  return absl::CEscape(MakeStringView(*this));
 }
 
 std::ostream& operator<<(std::ostream& out, const ByteString& str) {
   return out << str.ToString();
 }
 
+std::string ByteString::ToHexString() const {
+  std::string hex = absl::BytesToHexString(MakeStringView(*this));
+  return absl::StrCat("<", hex, ">");
+}
+
 }  // namespace nanopb
 }  // namespace firestore
 }  // namespace firebase

Firestore/core/src/firebase/firestore/nanopb/byte_string.h

@@ -147,9 +147,14 @@ class ByteString : public util::Comparable<ByteString> {
 
   size_t Hash() const;
 
+  // Interprets the value as an ASCII string; the way control characters are
+  // represented is implementation-defined.
   std::string ToString() const;
   friend std::ostream& operator<<(std::ostream& out, const ByteString& str);
 
+  // Represents the value as hexademical values.
+  std::string ToHexString() const;
+
  private:
   /**
    * Private constructor directly assigns to bytes_. The extra integer tag