SERVER-33568 Support StringBuilder << streaming for Status and StatusWith<T>

4 files changed, 41 insertions, 11 deletions

diff --git a/src/mongo/base/status.cpp b/src/mongo/base/status.cpp
index 30cc3558497..b6776bd7bf5 100644
--- a/src/mongo/base/status.cpp
+++ b/src/mongo/base/status.cpp
@@ -110,28 +110,35 @@ std::ostream& operator<<(std::ostream& os, const Status& status) {
     return os << status.codeString() << " " << status.reason();
 }
 
-std::string Status::toString() const {
-    StringBuilder ss;
-    ss << codeString();
-    if (!isOK()) {
+template <typename Allocator>
+StringBuilderImpl<Allocator>& operator<<(StringBuilderImpl<Allocator>& sb, const Status& status) {
+    sb << status.codeString();
+    if (!status.isOK()) {
         try {
-            if (auto extra = extraInfo()) {
+            if (auto extra = status.extraInfo()) {
                 BSONObjBuilder bob;
                 extra->serialize(&bob);
-                ss << bob.obj();
+                sb << bob.obj();
             }
         } catch (const DBException&) {
             // This really shouldn't happen but it would be really annoying if it broke error
             // logging in production.
             if (kDebugBuild) {
-                severe() << "Error serializing extra info for " << code()
+                severe() << "Error serializing extra info for " << status.code()
                          << " in Status::toString()";
                 std::terminate();
             }
         }
-        ss << ": " << reason();
+        sb << ": " << status.reason();
     }
-    return ss.str();
+    return sb;
+}
+template StringBuilder& operator<<(StringBuilder& sb, const Status& status);
+
+std::string Status::toString() const {
+    StringBuilder sb;
+    sb << *this;
+    return sb.str();
 }
 
 }  // namespace mongo
diff --git a/src/mongo/base/status.h b/src/mongo/base/status.h
index 11c14bc57ad..2bb524ee413 100644
--- a/src/mongo/base/status.h
+++ b/src/mongo/base/status.h
@@ -43,6 +43,10 @@ class stream;
 
 namespace mongo {
 
+// Including builder.h here would cause a cycle.
+template <typename Allocator>
+class StringBuilderImpl;
+
 /**
  * Status represents an error state or the absence thereof.
  *
@@ -259,6 +263,10 @@ inline bool operator!=(const ErrorCodes::Error lhs, const Status& rhs);
 
 std::ostream& operator<<(std::ostream& os, const Status& status);
 
+// This is only implemented for StringBuilder, not StackStringBuilder.
+template <typename Allocator>
+StringBuilderImpl<Allocator>& operator<<(StringBuilderImpl<Allocator>& os, const Status& status);
+
 }  // namespace mongo
 
 #include "mongo/base/status-inl.h"
diff --git a/src/mongo/base/status_with.h b/src/mongo/base/status_with.h
index 1092f9bdc87..c4d60d2fb81 100644
--- a/src/mongo/base/status_with.h
+++ b/src/mongo/base/status_with.h
@@ -43,6 +43,10 @@
 
 namespace mongo {
 
+// Including builder.h here would cause a cycle.
+template <typename Allocator>
+class StringBuilderImpl;
+
 template <typename T>
 class StatusWith;
 
@@ -155,7 +159,18 @@ StatusWith<T> makeStatusWith(Args&&... args) {
 }
 
 template <typename T>
-std::ostream& operator<<(std::ostream& stream, const StatusWith<T>& sw) {
+auto operator<<(std::ostream& stream, const StatusWith<T>& sw)
+    -> decltype(stream << sw.getValue())  // SFINAE on T streamability.
+{
+    if (sw.isOK())
+        return stream << sw.getValue();
+    return stream << sw.getStatus();
+}
+
+template <typename Allocator, typename T>
+auto operator<<(StringBuilderImpl<Allocator>& stream, const StatusWith<T>& sw)
+    -> decltype(stream << sw.getValue())  // SFINAE on T streamability.
+{
     if (sw.isOK())
         return stream << sw.getValue();
     return stream << sw.getStatus();
diff --git a/src/mongo/client/dbclient.cpp b/src/mongo/client/dbclient.cpp
index 90dc9388cf8..7ca8bd55540 100644
--- a/src/mongo/client/dbclient.cpp
+++ b/src/mongo/client/dbclient.cpp
@@ -970,7 +970,7 @@ Status DBClientConnection::connectSocketOnly(const HostAndPort& serverAddress) {
         return Status(ErrorCodes::HostUnreachable,
                       str::stream() << "couldn't connect to server " << _serverAddress.toString()
                                     << ", connection attempt failed: "
-                                    << sws.getStatus().toString());
+                                    << sws.getStatus());
     }
 
     _session = std::move(sws.getValue());