cli/command/container: improve CID-file errors

cli/command/container/create.go

@@ -177,8 +177,8 @@ func (cid *cidFile) Close() error {
 	if cid.written {
 		return nil
 	}
-	if err := os.Remove(cid.path); err != nil {
-		return fmt.Errorf("failed to remove the CID file '%s': %w", cid.path, err)
+	if err := os.Remove(cid.path); err != nil && !errors.Is(err, os.ErrNotExist) {
+		return fmt.Errorf("failed to remove the CID file: %w", err)
 	}
 
 	return nil
@@ -188,8 +188,8 @@ func (cid *cidFile) Write(id string) error {
 	if cid.file == nil {
 		return nil
 	}
-	if _, err := cid.file.Write([]byte(id)); err != nil {
-		return fmt.Errorf("failed to write the container ID to the file: %w", err)
+	if _, err := cid.file.WriteString(id); err != nil {
+		return fmt.Errorf("failed to write the container ID (%s) to file: %w", id, err)
 	}
 	cid.written = true
 	return nil

cli/command/container/create_test.go

@@ -5,6 +5,7 @@ import (
 	"errors"
 	"io"
 	"os"
+	"path/filepath"
 	"runtime"
 	"sort"
 	"strings"
@@ -42,17 +43,31 @@ func TestNewCIDFileWhenFileAlreadyExists(t *testing.T) {
 }
 
 func TestCIDFileCloseWithNoWrite(t *testing.T) {
-	tempdir := fs.NewDir(t, "test-cid-file")
-	defer tempdir.Remove()
+	// Closing should remove the file if it was not written to.
+	t.Run("closing should remove file", func(t *testing.T) {
+		filename := filepath.Join(t.TempDir(), "cidfile-1")
+		file, err := newCIDFile(filename)
+		assert.NilError(t, err)
+		assert.Check(t, is.Equal(file.path, filename))
 
-	path := tempdir.Join("cidfile")
-	file, err := newCIDFile(path)
-	assert.NilError(t, err)
-	assert.Check(t, is.Equal(file.path, path))
+		assert.NilError(t, file.Close())
+		_, err = os.Stat(filename)
+		assert.Check(t, os.IsNotExist(err))
+	})
 
-	assert.NilError(t, file.Close())
-	_, err = os.Stat(path)
-	assert.Check(t, os.IsNotExist(err))
+	// Closing (and removing) the file should not produce an error if the file no longer exists.
+	t.Run("close should remove file", func(t *testing.T) {
+		filename := filepath.Join(t.TempDir(), "cidfile-2")
+		file, err := newCIDFile(filename)
+		assert.NilError(t, err)
+		assert.Check(t, is.Equal(file.path, filename))
+
+		assert.NilError(t, os.Remove(filename))
+		_, err = os.Stat(filename)
+		assert.Check(t, os.IsNotExist(err))
+
+		assert.NilError(t, file.Close())
+	})
 }
 
 func TestCIDFileCloseWithWrite(t *testing.T) {