Add pseudo tty support for tests

Signed-off-by: apostasie <[email protected]>

Author: apostasie

pkg/testutil/test/command.go

@@ -45,6 +45,7 @@ type GenericCommand struct {
 	envBlackList []string
 	stdin        io.Reader
 	async        bool
+	pty          bool
 	timeout      time.Duration
 	workingDir   string
 
@@ -65,6 +66,10 @@ func (gc *GenericCommand) WithWrapper(binary string, args ...string) {
 	gc.helperArgs = args
 }
 
+func (gc *GenericCommand) WithPseudoTTY() {
+	gc.pty = true
+}
+
 func (gc *GenericCommand) WithStdin(r io.Reader) {
 	gc.stdin = r
 }
@@ -77,6 +82,7 @@ func (gc *GenericCommand) WithCwd(path string) {
 // Primitives (gc.timeout) is here, it is just a matter of exposing a WithTimeout method
 // - UX to be decided
 // - validate use case: would we ever need this?
+
 func (gc *GenericCommand) Run(expect *Expected) {
 	if gc.t != nil {
 		gc.t.Helper()
@@ -90,6 +96,16 @@ func (gc *GenericCommand) Run(expect *Expected) {
 	} else {
 		iCmdCmd := gc.boot()
 		env = iCmdCmd.Env
+
+		if gc.pty {
+			pty, tty, _ := Open()
+			iCmdCmd.Stdin = tty
+			iCmdCmd.Stdout = tty
+			iCmdCmd.Stderr = tty
+			defer pty.Close()
+			defer tty.Close()
+		}
+
 		// Run it
 		result = icmd.RunCmd(iCmdCmd)
 	}

pkg/testutil/test/pty.go

@@ -0,0 +1,74 @@
+/*
+   Copyright The containerd Authors.
+
+   Licensed under the Apache License, Version 2.0 (the "License");
+   you may not use this file except in compliance with the License.
+   You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
+*/
+
+package test
+
+import (
+	"errors"
+	"os"
+	"strconv"
+	"syscall"
+	"unsafe"
+)
+
+// Inspiration from https://github.com/creack/pty/tree/2cde18bfb702199728dd43bf10a6c15c7336da0a
+
+var ErrPTY = errors.New("pty failure")
+
+func Open() (pty, tty *os.File, err error) {
+	defer func() {
+		if err != nil && pty != nil {
+			err = errors.Join(pty.Close(), err)
+		}
+		if err != nil {
+			err = errors.Join(ErrPTY, err)
+		}
+	}()
+
+	pty, err = os.OpenFile("/dev/ptmx", os.O_RDWR, 0)
+	if err != nil {
+		return nil, nil, err
+	}
+
+	var n uint32
+	err = ioctl(pty, syscall.TIOCGPTN, uintptr(unsafe.Pointer(&n)))
+	if err != nil {
+		return nil, nil, err
+	}
+
+	sname := "/dev/pts/" + strconv.Itoa(int(n))
+
+	var u int32
+	err = ioctl(pty, syscall.TIOCSPTLCK, uintptr(unsafe.Pointer(&u)))
+	if err != nil {
+		return nil, nil, err
+	}
+
+	tty, err = os.OpenFile(sname, os.O_RDWR|syscall.O_NOCTTY, 0)
+	if err != nil {
+		return nil, nil, err
+	}
+
+	return pty, tty, nil
+}
+
+func ioctl(f *os.File, cmd, ptr uintptr) error {
+	_, _, e := syscall.Syscall(syscall.SYS_IOCTL, f.Fd(), cmd, ptr)
+	if e != 0 {
+		return e
+	}
+	return nil
+}

pkg/testutil/test/test.go

@@ -97,6 +97,8 @@ type TestableCommand interface {
 	WithArgs(args ...string)
 	// WithWrapper allows wrapping a command with another command (for example: `time`, `unbuffer`)
 	WithWrapper(binary string, args ...string)
+	// WithPseudoTTY
+	WithPseudoTTY()
 	// WithStdin allows passing a reader to be used for stdin for the command
 	WithStdin(r io.Reader)
 	// WithCwd allows specifying the working directory for the command