opts: deprecate ParseEnvFile

It was a wrapper around kvfile.Load, which should be used instead.

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

cli/compose/loader/envfile.go

@@ -0,0 +1,26 @@
+package loader
+
+import (
+	"os"
+
+	"github.com/docker/cli/pkg/kvfile"
+)
+
+// parseEnvFile reads a file with environment variables enumerated by lines
+//
+// “Environment variable names used by the utilities in the Shell and
+// Utilities volume of [IEEE Std 1003.1-2001] consist solely of uppercase
+// letters, digits, and the '_' (underscore) from the characters defined in
+// Portable Character Set and do not begin with a digit. *But*, other
+// characters may be permitted by an implementation; applications shall
+// tolerate the presence of such names.”
+//
+// As of [moby-16585], it's up to application inside docker to validate or not
+// environment variables, that's why we just strip leading whitespace and
+// nothing more.
+//
+// [IEEE Std 1003.1-2001]: http://pubs.opengroup.org/onlinepubs/009695399/basedefs/xbd_chap08.html
+// [moby-16585]: https://github.com/moby/moby/issues/16585
+func parseEnvFile(filename string) ([]string, error) {
+	return kvfile.Parse(filename, os.LookupEnv)
+}

cli/compose/loader/envfile_test.go

@@ -0,0 +1,40 @@
+package loader
+
+import (
+	"os"
+	"path/filepath"
+	"testing"
+
+	"gotest.tools/v3/assert"
+	is "gotest.tools/v3/assert/cmp"
+)
+
+func tmpFileWithContent(t *testing.T, content string) string {
+	t.Helper()
+	fileName := filepath.Join(t.TempDir(), "envfile")
+	err := os.WriteFile(fileName, []byte(content), 0o644)
+	assert.NilError(t, err)
+	return fileName
+}
+
+// Test parseEnvFile for a non existent file
+func TestParseEnvFileNonExistentFile(t *testing.T) {
+	_, err := parseEnvFile("no_such_file")
+	assert.Check(t, is.ErrorType(err, os.IsNotExist))
+}
+
+// parseEnvFile with environment variable import definitions
+func TestParseEnvVariableDefinitionsFile(t *testing.T) {
+	content := `# comment=
+UNDEFINED_VAR
+DEFINED_VAR
+`
+	tmpFile := tmpFileWithContent(t, content)
+
+	t.Setenv("DEFINED_VAR", "defined-value")
+	variables, err := parseEnvFile(tmpFile)
+	assert.NilError(t, err)
+
+	expectedLines := []string{"DEFINED_VAR=defined-value"}
+	assert.Check(t, is.DeepEqual(variables, expectedLines))
+}

cli/compose/loader/loader.go

@@ -469,7 +469,7 @@ func resolveEnvironment(serviceConfig *types.ServiceConfig, workingDir string, l
 
 		for _, file := range serviceConfig.EnvFile {
 			filePath := absPath(workingDir, file)
-			fileVars, err := opts.ParseEnvFile(filePath)
+			fileVars, err := parseEnvFile(filePath)
 			if err != nil {
 				return err
 			}