cli/command/container: inline uses of streams.Out.CheckTty

cli/command/container/attach.go

@@ -89,13 +89,20 @@ func RunAttach(ctx context.Context, dockerCLI command.Cli, containerID string, o
 		return err
 	}
 
-	if err := dockerCLI.In().CheckTty(!opts.NoStdin, c.Config.Tty); err != nil {
-		return err
+	attachStdin := !opts.NoStdin
+	if attachStdin {
+		// TODO(thaJeztah): should this also check if c.Config.OpenStdin is true, and produce an error otherwise?
+		if !c.Config.Tty {
+			return errors.New("cannot attach stdin because the container is not a TTY-enabled container")
+		}
+		if !dockerCLI.In().IsTerminal() {
+			return errors.New("cannot attach stdin because stdin is not a terminal")
+		}
 	}
 
 	options := client.ContainerAttachOptions{
 		Stream:     true,
-		Stdin:      !opts.NoStdin && c.Config.OpenStdin,
+		Stdin:      attachStdin && c.Config.OpenStdin,
 		Stdout:     true,
 		Stderr:     true,
 		DetachKeys: detachKeys,

cli/command/container/exec.go

@@ -101,8 +101,8 @@ func RunExec(ctx context.Context, dockerCLI command.Cli, containerIDorName strin
 		return err
 	}
 	if !options.Detach {
-		if err := dockerCLI.In().CheckTty(execOptions.AttachStdin, execOptions.TTY); err != nil {
-			return err
+		if execOptions.AttachStdin && execOptions.TTY && !dockerCLI.In().IsTerminal() {
+			return errors.New("cannot attach stdin to a TTY-enabled container because stdin is not a terminal")
 		}
 	}
 

cli/command/container/run.go

@@ -126,8 +126,8 @@ func runContainer(ctx context.Context, dockerCli command.Cli, runOpts *runOption
 	config.ArgsEscaped = false
 
 	if !runOpts.detach {
-		if err := dockerCli.In().CheckTty(config.AttachStdin, config.Tty); err != nil {
-			return err
+		if config.AttachStdin && config.Tty && !dockerCli.In().IsTerminal() {
+			return errors.New("cannot attach stdin to a TTY-enabled container because stdin is not a terminal")
 		}
 	} else {
 		if copts.attach.Len() != 0 {