GODRIVER-2156 Enable makezero linter. (#801)

Author: matthewdale

.golangci.yml

@@ -12,6 +12,7 @@ linters:
     - gosimple
     - govet
     - ineffassign
+    - makezero
     # - misspell
     - nakedret
     - revive

mongo/collection.go

@@ -1274,9 +1274,9 @@ func (coll *Collection) FindOne(ctx context.Context, filter interface{},
 		ctx = context.Background()
 	}
 
-	findOpts := make([]*options.FindOptions, len(opts))
-	for i, opt := range opts {
-		findOpts[i] = &options.FindOptions{
+	findOpts := make([]*options.FindOptions, 0, len(opts))
+	for _, opt := range opts {
+		findOpts = append(findOpts, &options.FindOptions{
 			AllowPartialResults: opt.AllowPartialResults,
 			BatchSize:           opt.BatchSize,
 			Collation:           opt.Collation,
@@ -1295,7 +1295,7 @@ func (coll *Collection) FindOne(ctx context.Context, filter interface{},
 			Skip:                opt.Skip,
 			Snapshot:            opt.Snapshot,
 			Sort:                opt.Sort,
-		}
+		})
 	}
 	// Unconditionally send a limit to make sure only one document is returned and the cursor is not kept open
 	// by the server.

x/mongo/driver/topology/server.go

@@ -180,8 +180,7 @@ func NewServer(addr address.Address, topologyID primitive.ObjectID, opts ...Serv
 		PoolMonitor: cfg.poolMonitor,
 	}
 
-	connectionOpts := make([]ConnectionOption, len(cfg.connectionOpts))
-	copy(connectionOpts, cfg.connectionOpts)
+	connectionOpts := copyConnectionOpts(cfg.connectionOpts)
 	connectionOpts = append(connectionOpts, withErrorHandlingCallback(s.ProcessHandshakeError))
 	s.pool = newPool(pc, connectionOpts...)
 	s.publishServerOpeningEvent(s.address)
@@ -590,8 +589,7 @@ func (s *Server) updateDescription(desc description.Server) {
 // createConnection creates a new connection instance but does not call connect on it. The caller must call connect
 // before the connection can be used for network operations.
 func (s *Server) createConnection() (*connection, error) {
-	opts := make([]ConnectionOption, len(s.cfg.connectionOpts))
-	copy(opts, s.cfg.connectionOpts)
+	opts := copyConnectionOpts(s.cfg.connectionOpts)
 	opts = append(opts,
 		WithConnectTimeout(func(time.Duration) time.Duration { return s.cfg.heartbeatTimeout }),
 		WithReadTimeout(func(time.Duration) time.Duration { return s.cfg.heartbeatTimeout }),
@@ -609,6 +607,12 @@ func (s *Server) createConnection() (*connection, error) {
 	return newConnection(s.address, opts...)
 }
 
+func copyConnectionOpts(opts []ConnectionOption) []ConnectionOption {
+	optsCopy := make([]ConnectionOption, len(opts))
+	copy(optsCopy, opts)
+	return optsCopy
+}
+
 func (s *Server) setupHeartbeatConnection() error {
 	conn, err := s.createConnection()
 	if err != nil {