Ensure too large documents cause error on insert

GODRIVER-510

Change-Id: Ief2fa6b04df3dd98e7861b47aa3208db780a093d

Author: skriptble

core/command/errors.go

@@ -22,6 +22,9 @@ var (
 	ErrMultiDocCommandResponse = errors.New("command returned multiple documents")
 	// ErrNoDocCommandResponse occurs when the server indicated a response existed, but none was found.
 	ErrNoDocCommandResponse = errors.New("command returned no documents")
+	// ErrDocumentTooLarge occurs when a document that is larger than the maximum size accepted by a
+	// server is passed to an insert command.
+	ErrDocumentTooLarge = errors.New("an inserted document is too large")
 )
 
 // QueryFailureError is an error representing a command failure as a document.

core/command/insert.go

@@ -64,6 +64,9 @@ splitInserts:
 				return nil, err
 			}
 
+			if int(itsize) > targetBatchSize {
+				return nil, ErrDocumentTooLarge
+			}
 			if size+int(itsize) > targetBatchSize {
 				break assembleBatch
 			}

core/command/insert_test.go

@@ -78,4 +78,12 @@ func TestInsertCommandSplitting(t *testing.T) {
 		}
 
 	})
+	t.Run("document_larger_than_max_size", func(t *testing.T) {
+		i := &Insert{}
+		i.Docs = append(i.Docs, bson.NewDocument(bson.EC.String("a", "bcdefghijklmnopqrstuvwxyz")))
+		_, err := i.split(100, 5)
+		if err != ErrDocumentTooLarge {
+			t.Errorf("Expected a too large error. got %v; want %v", err, ErrDocumentTooLarge)
+		}
+	})
 }