Start pseudo terminal with explicit window size

Ref: #254

Make sure to start pseudo terminal with fixed size in case the columns
flag was used.

Refactor `ptexec` package to allow for more flexibility.

Introduce test cases for `ptexec` package.

internal/cmd/root.go

@@ -73,12 +73,14 @@ window including all terminal colors and text decorations.
 
 		var scaffold = img.NewImageCreator()
 		var buf bytes.Buffer
+		var pt = ptexec.New()
 
 		// Initialise scaffold with a column sizing so that the
 		// content can be wrapped accordingly
 		//
 		if columns, err := cmd.Flags().GetInt("columns"); err == nil && columns > 0 {
 			scaffold.SetColumns(columns)
+			pt.Cols(uint16(columns))
 		}
 
 		// Disable window shadow if requested
@@ -110,7 +112,7 @@ window including all terminal colors and text decorations.
 		// Run the provided command in a pseudo terminal and capture
 		// the output to be later rendered into the screenshot
 		//
-		bytes, err := ptexec.RunCommandInPseudoTerminal(args[0], args[1:]...)
+		bytes, err := pt.Command(args[0], args[1:]...).Run()
 		if err != nil {
 			return err
 		}
@@ -135,7 +137,7 @@ window including all terminal colors and text decorations.
 				editor = "vi"
 			}
 
-			if _, err := ptexec.RunCommandInPseudoTerminal(editor, tmpFile.Name()); err != nil {
+			if _, err := ptexec.New().Command(editor, tmpFile.Name()).Run(); err != nil {
 				return err
 			}
 

internal/ptexec/exec.go

@@ -35,23 +35,64 @@ import (
 	"golang.org/x/term"
 )
 
-// RunCommandInPseudoTerminal runs the provided program with the given
-// arguments in a pseudo terminal (PTY) so that the behavior is the same
-// if it would be executed in a terminal
-func RunCommandInPseudoTerminal(name string, args ...string) ([]byte, error) {
-	var errors = []error{}
+type PseudoTerminal struct {
+	name string
+	args []string
+
+	shell string
+
+	cols   uint16
+	rows   uint16
+	resize bool
+
+	stdout io.Writer
+}
+
+func New() *PseudoTerminal {
+	return &PseudoTerminal{
+		shell:  "/bin/sh",
+		resize: true,
+		stdout: os.Stdout,
+	}
+}
+
+func (c *PseudoTerminal) Cols(cols uint16) *PseudoTerminal {
+	c.cols = cols
+	return c
+}
+
+func (c *PseudoTerminal) Rows(rows uint16) *PseudoTerminal {
+	c.rows = rows
+	return c
+}
+
+func (c *PseudoTerminal) Stdout(stdout io.Writer) *PseudoTerminal {
+	c.stdout = stdout
+	return c
+}
+
+func (c *PseudoTerminal) Command(name string, args ...string) *PseudoTerminal {
+	c.name = name
+	c.args = args
+	return c
+}
+
+func (c *PseudoTerminal) Run() ([]byte, error) {
+	if c.name == "" {
+		return nil, fmt.Errorf("no command specified")
+	}
 
 	// Convenience hack in case command contains a space, for example in case
 	// typical construct like "foo | grep" are used.
-	if strings.Contains(name, " ") {
-		args = []string{
+	if strings.Contains(c.name, " ") {
+		c.args = []string{
 			"-c",
 			strings.Join(append(
-				[]string{name},
-				args...,
+				[]string{c.name},
+				c.args...,
 			), " "),
 		}
-		name = "/bin/sh"
+		c.name = c.shell
 	}
 
 	// Set RAW mode for Stdin
@@ -65,13 +106,17 @@ func RunCommandInPseudoTerminal(name string, args ...string) ([]byte, error) {
 		defer func() { _ = term.Restore(int(os.Stdin.Fd()), oldState) }()
 	}
 
-	pt, err := pty.Start(exec.Command(name, args...))
+	// collect all errors along the way
+	var errors = []error{}
+
+	// #nosec G204 -- since this is exactly what we want, arbitrary commands
+	pt, err := c.pseudoTerminal(exec.Command(c.name, c.args...))
 	if err != nil {
 		return nil, err
 	}
 
 	// Support terminal resizing
-	if isTerminal(os.Stdin) {
+	if c.resize && isTerminal(os.Stdin) {
 		ch := make(chan os.Signal, 1)
 		signal.Notify(ch, syscall.SIGWINCH)
 		go func() {
@@ -98,7 +143,7 @@ func RunCommandInPseudoTerminal(name string, args ...string) ([]byte, error) {
 	}()
 
 	var buf bytes.Buffer
-	if err = copy(io.MultiWriter(os.Stdout, &buf), pt); err != nil {
+	if err = copy(io.MultiWriter(c.stdout, &buf), pt); err != nil {
 		return nil, err
 	}
 
@@ -112,6 +157,38 @@ func RunCommandInPseudoTerminal(name string, args ...string) ([]byte, error) {
 	return buf.Bytes(), nil
 }
 
+func (c *PseudoTerminal) pseudoTerminal(cmd *exec.Cmd) (*os.File, error) {
+	if c.cols == 0 && c.rows == 0 {
+		return pty.Start(cmd)
+	}
+
+	size, err := pty.GetsizeFull(os.Stdout)
+	if err != nil {
+		return nil, err
+	}
+
+	if c.rows != 0 {
+		size.Rows = c.rows
+	}
+
+	if c.cols != 0 {
+		size.Cols = c.cols
+	}
+
+	c.resize = false
+
+	return pty.StartWithSize(cmd, size)
+}
+
+// RunCommandInPseudoTerminal runs the provided program with the given
+// arguments in a pseudo terminal (PTY) so that the behavior is the same
+// if it would be executed in a terminal
+//
+// Deprecated: Use New().Command().Run() instead.
+func RunCommandInPseudoTerminal(name string, args ...string) ([]byte, error) {
+	return New().Command(name, args...).Run()
+}
+
 func copy(dst io.Writer, src io.Reader) error {
 	_, err := io.Copy(dst, src)
 	if err != nil {

internal/ptexec/exec_test.go

@@ -0,0 +1,60 @@
+// Copyright © 2024 The Homeport Team
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in
+// all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+// THE SOFTWARE.
+
+package ptexec_test
+
+import (
+	. "github.com/onsi/ginkgo/v2"
+	. "github.com/onsi/gomega"
+
+	. "github.com/homeport/termshot/internal/ptexec"
+)
+
+var _ = Describe("Pseudo Terminal Execute Suite", func() {
+	Context("running commands in pseudo terminal", func() {
+		It("should run a command just fine", func() {
+			out, err := New().Stdout(GinkgoWriter).
+				Command("echo", "hello").
+				Run()
+
+			Expect(err).ToNot(HaveOccurred())
+			Expect(string(out)).To(Equal("hello\r\n"))
+		})
+
+		It("should run a script just fine", func() {
+			out, err := New().Stdout(GinkgoWriter).
+				Command("echo hello").
+				Run()
+
+			Expect(err).ToNot(HaveOccurred())
+			Expect(string(out)).To(Equal("hello\r\n"))
+		})
+
+		It("should run with fixed terminal size", func() {
+			out, err := New().Stdout(GinkgoWriter).Cols(80).Command("tput", "cols").Run()
+			Expect(err).ToNot(HaveOccurred())
+			Expect(string(out)).To(Equal("80\r\n"))
+
+			out, err = New().Stdout(GinkgoWriter).Rows(25).Command("tput", "lines").Run()
+			Expect(err).ToNot(HaveOccurred())
+			Expect(string(out)).To(Equal("25\r\n"))
+		})
+	})
+})

internal/ptexec/ptexec_suite_test.go

@@ -0,0 +1,33 @@
+// Copyright © 2024 The Homeport Team
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in
+// all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+// THE SOFTWARE.
+
+package ptexec_test
+
+import (
+	"testing"
+
+	. "github.com/onsi/ginkgo/v2"
+	. "github.com/onsi/gomega"
+)
+
+func TestPtexec(t *testing.T) {
+	RegisterFailHandler(Fail)
+	RunSpecs(t, "Pseudo Terminal Exec Suite")
+}