cli/command/task: keep multiline errors in table rows

cli/command/task/formatter.go

@@ -60,6 +60,7 @@ func formatWrite(fmtCtx formatter.Context, tasks client.TaskListResult, names ma
 		for _, task := range tasks.Items {
 			if err := format(&taskContext{
 				trunc: fmtCtx.Trunc,
+				table: fmtCtx.Format.IsTable(),
 				task:  task,
 				name:  names[task.ID],
 				node:  nodes[task.ID],
@@ -74,6 +75,7 @@ func formatWrite(fmtCtx formatter.Context, tasks client.TaskListResult, names ma
 type taskContext struct {
 	formatter.HeaderContext
 	trunc bool
+	table bool
 	task  swarm.Task
 	name  string
 	node  string
@@ -128,6 +130,15 @@ func (c *taskContext) CurrentState() string {
 func (c *taskContext) Error() string {
 	// Trim and quote the error message.
 	taskErr := c.task.Status.Err
+	if c.table {
+		// Avoid embedding multiline task errors into table output. Daemon-side
+		// task errors can include stack traces; newlines make one task span many
+		// rows and corrupt the columns.
+		taskErr = strings.ReplaceAll(taskErr, "\r\n", " ")
+		taskErr = strings.ReplaceAll(taskErr, "\n", " ")
+		taskErr = strings.ReplaceAll(taskErr, "\r", " ")
+		taskErr = strings.ReplaceAll(taskErr, "	", " ")
+	}
 	if c.trunc {
 		taskErr = formatter.Ellipsis(taskErr, maxErrLength)
 	}

cli/command/task/formatter_test.go

@@ -111,3 +111,45 @@ func TestTaskContextWriteJSONField(t *testing.T) {
 		assert.Check(t, is.Equal(tasks.Items[i].ID, s))
 	}
 }
+
+func TestTaskContextErrorReplacesNewlines(t *testing.T) {
+	tasks := client.TaskListResult{
+		Items: []swarm.Task{
+			{
+				ID: "taskID1",
+				Status: swarm.TaskStatus{
+					Err: "failed to start shim:\n	/usr/local/go/src/runtime/proc.go:211: fatal error: newosproc",
+				},
+			},
+		},
+	}
+	names := map[string]string{"taskID1": "foobar_baz"}
+	out := bytes.NewBufferString("")
+
+	err := formatWrite(formatter.Context{Format: newTaskFormat("table {{.Error}}", false), Output: out}, tasks, names, map[string]string{})
+
+	assert.NilError(t, err)
+	assert.Check(t, is.Contains(out.String(), "/usr/local/go/src/runtime/proc.go:211: fatal error: newosproc"))
+	assert.Check(t, !strings.Contains(out.String(), "failed to start shim:\n	/usr/local/go/src/runtime/proc.go:211: fatal error: newosproc"))
+	assert.Check(t, is.Equal(`"failed to start shim:  /usr/local/go/src/runtime/proc.go:211: fatal error: newosproc"`, (&taskContext{table: true, task: tasks.Items[0]}).Error()))
+}
+
+func TestTaskContextErrorPreservesNewlinesForCustomFormat(t *testing.T) {
+	tasks := client.TaskListResult{
+		Items: []swarm.Task{
+			{
+				ID: "taskID1",
+				Status: swarm.TaskStatus{
+					Err: "failed to start shim:\nfatal error: newosproc",
+				},
+			},
+		},
+	}
+	names := map[string]string{"taskID1": "foobar_baz"}
+	out := bytes.NewBufferString("")
+
+	err := formatWrite(formatter.Context{Format: newTaskFormat("{{.Error}}", false), Output: out}, tasks, names, map[string]string{})
+
+	assert.NilError(t, err)
+	assert.Check(t, is.Contains(out.String(), "failed to start shim:\nfatal error: newosproc"))
+}