Close implicit sessions if an error occurs for cursor commands.

Change-Id: Ic795ecbff2b8e97eafa617feca53cf86dcfd050d

Author: Divjot Arora

x/mongo/driver/aggregate.go

@@ -114,5 +114,10 @@ func Aggregate(
 		cmd.Opts = append(cmd.Opts, hintElem)
 	}
 
-	return cmd.RoundTrip(ctx, desc, ss, conn)
+	c, err := cmd.RoundTrip(ctx, desc, ss, conn)
+	if err != nil {
+		closeImplicitSession(cmd.Session)
+	}
+
+	return c, err
 }

x/mongo/driver/dispatch.go

@@ -12,6 +12,7 @@ import (
 	"github.com/mongodb/mongo-go-driver/bson"
 	"github.com/mongodb/mongo-go-driver/bson/bsoncodec"
 	"github.com/mongodb/mongo-go-driver/x/bsonx"
+	"github.com/mongodb/mongo-go-driver/x/mongo/driver/session"
 )
 
 // ErrCollation is caused if a collation is given for an invalid server version.
@@ -58,3 +59,9 @@ func interfaceToElement(key string, i interface{}, registry *bsoncodec.Registry)
 		return bsonx.Elem{key, bsonx.Document(doc)}, nil
 	}
 }
+
+func closeImplicitSession(sess *session.Client) {
+	if sess != nil && sess.SessionType == session.Implicit {
+		sess.EndSession()
+	}
+}

x/mongo/driver/find.go

@@ -159,5 +159,10 @@ func Find(
 		cmd.Opts = append(cmd.Opts, sortElem)
 	}
 
-	return cmd.RoundTrip(ctx, desc, ss, conn)
+	c, err := cmd.RoundTrip(ctx, desc, ss, conn)
+	if err != nil {
+		closeImplicitSession(cmd.Session)
+	}
+
+	return c, err
 }

x/mongo/driver/list_collections.go

@@ -60,5 +60,10 @@ func ListCollections(
 		cmd.Opts = append(cmd.Opts, bsonx.Elem{"nameOnly", bsonx.Boolean(*lc.NameOnly)})
 	}
 
-	return cmd.RoundTrip(ctx, ss.Description(), ss, conn)
+	c, err := cmd.RoundTrip(ctx, ss.Description(), ss, conn)
+	if err != nil {
+		closeImplicitSession(cmd.Session)
+	}
+
+	return c, err
 }

x/mongo/driver/list_indexes.go

@@ -61,5 +61,10 @@ func ListIndexes(
 		}
 	}
 
-	return cmd.RoundTrip(ctx, ss.Description(), ss, conn)
+	c, err := cmd.RoundTrip(ctx, ss.Description(), ss, conn)
+	if err != nil {
+		closeImplicitSession(cmd.Session)
+	}
+
+	return c, err
 }