Merge pull request 'feat(cli): setup interactif déclaratif avec champs typés' (#17) from feat/setup-declaratif-typed-fields into release/v1.2

Reviewed-on: https://gitea.lclr.dev/AI/mcp-framework/pulls/17

README.md

@@ -275,6 +275,58 @@ if err != nil {
 }
 ```
 
+Pour décrire un setup complet sans réécrire la boucle interactive :
+
+```go
+result, err := cli.RunSetup(cli.SetupOptions{
+	Stdin:  os.Stdin,
+	Stdout: os.Stdout,
+	Fields: []cli.SetupField{
+		{
+			Name:     "base_url",
+			Label:    "Base URL",
+			Type:     cli.SetupFieldURL,
+			Required: true,
+		},
+		{
+			Name:           "api_token",
+			Label:          "API token",
+			Type:           cli.SetupFieldSecret,
+			Required:       true,
+			ExistingSecret: storedToken, // conserve la valeur existante si l'utilisateur laisse vide
+		},
+		{
+			Name:    "enabled",
+			Label:   "Enable integration",
+			Type:    cli.SetupFieldBool,
+			Default: "true",
+		},
+		{
+			Name:      "scopes",
+			Label:     "Scopes",
+			Type:      cli.SetupFieldList,
+			Default:   "read,write",
+			Normalize: func(value string) string { return strings.TrimSpace(strings.ToLower(value)) },
+		},
+	},
+})
+if err != nil {
+	return err
+}
+
+baseURL, _ := result.Get("base_url")
+apiToken, _ := result.Get("api_token")
+enabled, _ := result.Get("enabled")
+scopes, _ := result.Get("scopes")
+
+if apiToken.KeptStoredSecret {
+	fmt.Println("Stored token kept.")
+}
+```
+
+Chaque champ peut déclarer ses propres hooks de validation (`Validate`, `ValidateBool`, `ValidateList`).
+Les validations sont appliquées de manière cohérente en TTY et en stdin non interactif.
+
 Pour standardiser la résolution `flag > env > config > secret` avec provenance :
 
 ```go

cli/setup.go

@@ -0,0 +1,530 @@
+package cli
+
+import (
+	"bufio"
+	"errors"
+	"fmt"
+	"io"
+	"os"
+	"slices"
+	"strings"
+
+	"golang.org/x/term"
+)
+
+type SetupFieldType string
+
+const (
+	SetupFieldString SetupFieldType = "string"
+	SetupFieldURL    SetupFieldType = "url"
+	SetupFieldSecret SetupFieldType = "secret"
+	SetupFieldBool   SetupFieldType = "bool"
+	SetupFieldList   SetupFieldType = "list"
+)
+
+var ErrInvalidSetupDefinition = errors.New("invalid setup definition")
+
+type SetupField struct {
+	Name           string
+	Label          string
+	Type           SetupFieldType
+	Required       bool
+	Default        string
+	ExistingSecret string
+	ListSeparator  string
+	Normalize      func(string) string
+	Validate       func(string) error
+	ValidateBool   func(bool) error
+	ValidateList   func([]string) error
+}
+
+type SetupOptions struct {
+	Fields []SetupField
+	Stdin  *os.File
+	Stdout io.Writer
+}
+
+type SetupValue struct {
+	Type             SetupFieldType
+	String           string
+	Bool             bool
+	List             []string
+	Set              bool
+	KeptStoredSecret bool
+}
+
+type SetupResultField struct {
+	Name  string
+	Value SetupValue
+}
+
+type SetupResult struct {
+	Fields []SetupResultField
+}
+
+func (r SetupResult) Get(name string) (SetupValue, bool) {
+	needle := strings.TrimSpace(name)
+	for _, field := range r.Fields {
+		if field.Name == needle {
+			return field.Value, true
+		}
+	}
+
+	return SetupValue{}, false
+}
+
+type SetupValidationError struct {
+	Field   string
+	Label   string
+	Message string
+}
+
+func (e *SetupValidationError) Error() string {
+	label := strings.TrimSpace(e.Label)
+	if label == "" {
+		label = strings.TrimSpace(e.Field)
+	}
+
+	if label == "" {
+		return strings.TrimSpace(e.Message)
+	}
+
+	return fmt.Sprintf("%s: %s", label, strings.TrimSpace(e.Message))
+}
+
+type normalizedSetupField struct {
+	Name           string
+	Label          string
+	Type           SetupFieldType
+	Required       bool
+	DefaultString  string
+	DefaultBool    *bool
+	DefaultList    []string
+	ExistingSecret string
+	ListSeparator  string
+	Normalize      func(string) string
+	Validate       func(string) error
+	ValidateBool   func(bool) error
+	ValidateList   func([]string) error
+}
+
+func RunSetup(options SetupOptions) (SetupResult, error) {
+	stdin, stdout := normalizeSetupIO(options)
+
+	fields, err := normalizeSetupFields(options.Fields)
+	if err != nil {
+		return SetupResult{}, err
+	}
+
+	reader := bufio.NewReader(stdin)
+	fd := int(stdin.Fd())
+	isTTY := term.IsTerminal(fd)
+
+	result := SetupResult{
+		Fields: make([]SetupResultField, 0, len(fields)),
+	}
+
+	for _, field := range fields {
+		value, err := promptSetupField(reader, stdin, stdout, fd, isTTY, field)
+		if err != nil {
+			return result, err
+		}
+
+		result.Fields = append(result.Fields, SetupResultField{
+			Name:  field.Name,
+			Value: value,
+		})
+	}
+
+	return result, nil
+}
+
+func normalizeSetupIO(options SetupOptions) (*os.File, io.Writer) {
+	stdin := options.Stdin
+	if stdin == nil {
+		stdin = os.Stdin
+	}
+
+	stdout := options.Stdout
+	if stdout == nil {
+		stdout = os.Stdout
+	}
+
+	return stdin, stdout
+}
+
+func normalizeSetupFields(fields []SetupField) ([]normalizedSetupField, error) {
+	normalized := make([]normalizedSetupField, 0, len(fields))
+	seenNames := make(map[string]struct{}, len(fields))
+
+	for i, field := range fields {
+		name := strings.TrimSpace(field.Name)
+		if name == "" {
+			return nil, fmt.Errorf("%w: field at index %d has empty name", ErrInvalidSetupDefinition, i)
+		}
+		if _, exists := seenNames[name]; exists {
+			return nil, fmt.Errorf("%w: duplicate field name %q", ErrInvalidSetupDefinition, name)
+		}
+		seenNames[name] = struct{}{}
+
+		if !isKnownSetupFieldType(field.Type) {
+			return nil, fmt.Errorf("%w: field %q uses unknown type %q", ErrInvalidSetupDefinition, name, field.Type)
+		}
+
+		label := strings.TrimSpace(field.Label)
+		if label == "" {
+			label = name
+		}
+
+		normalizer := field.Normalize
+		if normalizer == nil {
+			normalizer = strings.TrimSpace
+		}
+
+		listSeparator := field.ListSeparator
+		if listSeparator == "" {
+			listSeparator = ","
+		}
+
+		entry := normalizedSetupField{
+			Name:           name,
+			Label:          label,
+			Type:           field.Type,
+			Required:       field.Required,
+			ExistingSecret: strings.TrimSpace(field.ExistingSecret),
+			ListSeparator:  listSeparator,
+			Normalize:      normalizer,
+			Validate:       field.Validate,
+			ValidateBool:   field.ValidateBool,
+			ValidateList:   field.ValidateList,
+		}
+
+		switch field.Type {
+		case SetupFieldString, SetupFieldURL, SetupFieldSecret:
+			entry.DefaultString = normalizer(field.Default)
+			if field.Type == SetupFieldURL && entry.DefaultString != "" {
+				if err := ValidateBaseURL(entry.DefaultString); err != nil {
+					return nil, fmt.Errorf("%w: field %q default URL is invalid: %v", ErrInvalidSetupDefinition, name, err)
+				}
+			}
+		case SetupFieldBool:
+			defaultRaw := strings.TrimSpace(field.Default)
+			if defaultRaw != "" {
+				defaultValue, err := parseBoolValue(defaultRaw)
+				if err != nil {
+					return nil, fmt.Errorf("%w: field %q default bool is invalid: %v", ErrInvalidSetupDefinition, name, err)
+				}
+				entry.DefaultBool = &defaultValue
+			}
+		case SetupFieldList:
+			defaultRaw := strings.TrimSpace(field.Default)
+			if defaultRaw != "" {
+				entry.DefaultList = splitSetupList(defaultRaw, listSeparator, normalizer)
+			}
+		}
+
+		normalized = append(normalized, entry)
+	}
+
+	return normalized, nil
+}
+
+func promptSetupField(
+	reader *bufio.Reader,
+	stdin *os.File,
+	stdout io.Writer,
+	fd int,
+	isTTY bool,
+	field normalizedSetupField,
+) (SetupValue, error) {
+	for {
+		if err := renderSetupPrompt(stdout, field); err != nil {
+			return SetupValue{}, err
+		}
+
+		raw, err := readSetupInput(reader, stdout, fd, isTTY, field.Type)
+		if err != nil {
+			return SetupValue{}, fmt.Errorf("read %q: %w", field.Name, err)
+		}
+
+		value, validationErr := parseSetupValue(field, raw)
+		if validationErr == nil {
+			return value, nil
+		}
+
+		setupErr := &SetupValidationError{
+			Field:   field.Name,
+			Label:   field.Label,
+			Message: validationErr.Error(),
+		}
+		if !isTTY {
+			return SetupValue{}, setupErr
+		}
+
+		if _, err := fmt.Fprintf(stdout, "Invalid value for %s: %s\n", field.Label, validationErr.Error()); err != nil {
+			return SetupValue{}, err
+		}
+	}
+}
+
+func readSetupInput(
+	reader *bufio.Reader,
+	stdout io.Writer,
+	fd int,
+	isTTY bool,
+	fieldType SetupFieldType,
+) (string, error) {
+	if fieldType == SetupFieldSecret && isTTY {
+		secret, err := term.ReadPassword(fd)
+		fmt.Fprintln(stdout)
+		if err != nil {
+			return "", err
+		}
+		return string(secret), nil
+	}
+
+	line, err := reader.ReadString('\n')
+	if err != nil && !errors.Is(err, io.EOF) {
+		return "", err
+	}
+	return line, nil
+}
+
+func parseSetupValue(field normalizedSetupField, raw string) (SetupValue, error) {
+	switch field.Type {
+	case SetupFieldString:
+		return parseSetupStringValue(field, raw)
+	case SetupFieldURL:
+		value, err := parseSetupStringValue(field, raw)
+		if err != nil {
+			return SetupValue{}, err
+		}
+		if value.Set {
+			if err := ValidateBaseURL(value.String); err != nil {
+				return SetupValue{}, fmt.Errorf("must be a valid URL with scheme and host")
+			}
+		}
+		return value, nil
+	case SetupFieldSecret:
+		return parseSetupSecretValue(field, raw)
+	case SetupFieldBool:
+		return parseSetupBoolValue(field, raw)
+	case SetupFieldList:
+		return parseSetupListValue(field, raw)
+	default:
+		return SetupValue{}, fmt.Errorf("unsupported field type %q", field.Type)
+	}
+}
+
+func parseSetupStringValue(field normalizedSetupField, raw string) (SetupValue, error) {
+	value := field.Normalize(raw)
+	set := value != ""
+	if !set && field.DefaultString != "" {
+		value = field.DefaultString
+		set = true
+	}
+
+	if field.Required && !set {
+		return SetupValue{}, fmt.Errorf("value is required")
+	}
+
+	if set && field.Validate != nil {
+		if err := field.Validate(value); err != nil {
+			return SetupValue{}, err
+		}
+	}
+
+	return SetupValue{
+		Type:   field.Type,
+		String: value,
+		Set:    set,
+	}, nil
+}
+
+func parseSetupSecretValue(field normalizedSetupField, raw string) (SetupValue, error) {
+	value := field.Normalize(raw)
+	set := value != ""
+	keptStored := false
+
+	if !set && field.ExistingSecret != "" {
+		value = field.ExistingSecret
+		set = true
+		keptStored = true
+	} else if !set && field.DefaultString != "" {
+		value = field.DefaultString
+		set = true
+	}
+
+	if field.Required && !set {
+		return SetupValue{}, fmt.Errorf("value is required")
+	}
+
+	if set && field.Validate != nil {
+		if err := field.Validate(value); err != nil {
+			return SetupValue{}, err
+		}
+	}
+
+	return SetupValue{
+		Type:             field.Type,
+		String:           value,
+		Set:              set,
+		KeptStoredSecret: keptStored,
+	}, nil
+}
+
+func parseSetupBoolValue(field normalizedSetupField, raw string) (SetupValue, error) {
+	trimmed := strings.TrimSpace(raw)
+	if trimmed == "" {
+		if field.DefaultBool != nil {
+			value := *field.DefaultBool
+			if field.ValidateBool != nil {
+				if err := field.ValidateBool(value); err != nil {
+					return SetupValue{}, err
+				}
+			}
+			return SetupValue{
+				Type: SetupFieldBool,
+				Bool: value,
+				Set:  true,
+			}, nil
+		}
+
+		if field.Required {
+			return SetupValue{}, fmt.Errorf("value is required")
+		}
+
+		return SetupValue{
+			Type: SetupFieldBool,
+			Set:  false,
+		}, nil
+	}
+
+	value, err := parseBoolValue(trimmed)
+	if err != nil {
+		return SetupValue{}, err
+	}
+	if field.ValidateBool != nil {
+		if err := field.ValidateBool(value); err != nil {
+			return SetupValue{}, err
+		}
+	}
+
+	return SetupValue{
+		Type: SetupFieldBool,
+		Bool: value,
+		Set:  true,
+	}, nil
+}
+
+func parseSetupListValue(field normalizedSetupField, raw string) (SetupValue, error) {
+	trimmed := strings.TrimSpace(raw)
+
+	var list []string
+	set := false
+	if trimmed != "" {
+		list = splitSetupList(trimmed, field.ListSeparator, field.Normalize)
+		set = true
+	} else if len(field.DefaultList) > 0 {
+		list = slices.Clone(field.DefaultList)
+		set = true
+	}
+
+	if field.Required && len(list) == 0 {
+		return SetupValue{}, fmt.Errorf("value is required")
+	}
+
+	if field.ValidateList != nil {
+		if err := field.ValidateList(list); err != nil {
+			return SetupValue{}, err
+		}
+	}
+
+	return SetupValue{
+		Type: SetupFieldList,
+		List: list,
+		Set:  set,
+	}, nil
+}
+
+func renderSetupPrompt(w io.Writer, field normalizedSetupField) error {
+	switch field.Type {
+	case SetupFieldSecret:
+		if field.ExistingSecret != "" {
+			_, err := fmt.Fprintf(w, "%s [stored, leave blank to keep]: ", field.Label)
+			return err
+		}
+		if field.DefaultString != "" {
+			_, err := fmt.Fprintf(w, "%s [%s]: ", field.Label, field.DefaultString)
+			return err
+		}
+		_, err := fmt.Fprintf(w, "%s: ", field.Label)
+		return err
+	case SetupFieldBool:
+		defaultLabel := "y/n"
+		if field.DefaultBool != nil {
+			if *field.DefaultBool {
+				defaultLabel = "Y/n"
+			} else {
+				defaultLabel = "y/N"
+			}
+		}
+		_, err := fmt.Fprintf(w, "%s [%s]: ", field.Label, defaultLabel)
+		return err
+	case SetupFieldList:
+		if len(field.DefaultList) > 0 {
+			_, err := fmt.Fprintf(
+				w,
+				"%s [%s]: ",
+				field.Label,
+				strings.Join(field.DefaultList, field.ListSeparator),
+			)
+			return err
+		}
+		_, err := fmt.Fprintf(w, "%s: ", field.Label)
+		return err
+	case SetupFieldString, SetupFieldURL:
+		if field.DefaultString != "" {
+			_, err := fmt.Fprintf(w, "%s [%s]: ", field.Label, field.DefaultString)
+			return err
+		}
+		_, err := fmt.Fprintf(w, "%s: ", field.Label)
+		return err
+	default:
+		_, err := fmt.Fprintf(w, "%s: ", field.Label)
+		return err
+	}
+}
+
+func splitSetupList(raw, separator string, normalize func(string) string) []string {
+	parts := strings.Split(raw, separator)
+	list := make([]string, 0, len(parts))
+	for _, part := range parts {
+		normalized := normalize(part)
+		if normalized == "" {
+			continue
+		}
+		list = append(list, normalized)
+	}
+	return list
+}
+
+func parseBoolValue(raw string) (bool, error) {
+	switch strings.ToLower(strings.TrimSpace(raw)) {
+	case "1", "t", "true", "y", "yes", "on":
+		return true, nil
+	case "0", "f", "false", "n", "no", "off":
+		return false, nil
+	default:
+		return false, fmt.Errorf("must be one of: yes/no, y/n, true/false, 1/0")
+	}
+}
+
+func isKnownSetupFieldType(fieldType SetupFieldType) bool {
+	switch fieldType {
+	case SetupFieldString, SetupFieldURL, SetupFieldSecret, SetupFieldBool, SetupFieldList:
+		return true
+	default:
+		return false
+	}
+}

cli/setup_test.go

@@ -0,0 +1,265 @@
+package cli
+
+import (
+	"bytes"
+	"errors"
+	"os"
+	"slices"
+	"strings"
+	"testing"
+)
+
+func TestRunSetupParsesTypedFieldsWithDefaultsAndNormalization(t *testing.T) {
+	stdin := setupTestInputFile(t, strings.Join([]string{
+		" https://api.example.com ",
+		"",
+		"",
+		"Read, WRITE, admin",
+		"  eu-west  ",
+	}, "\n")+"\n")
+
+	var stdout bytes.Buffer
+	result, err := RunSetup(SetupOptions{
+		Stdin:  stdin,
+		Stdout: &stdout,
+		Fields: []SetupField{
+			{
+				Name:     "base_url",
+				Label:    "Base URL",
+				Type:     SetupFieldURL,
+				Required: true,
+			},
+			{
+				Name:           "api_token",
+				Label:          "API token",
+				Type:           SetupFieldSecret,
+				Required:       true,
+				ExistingSecret: "stored-token",
+			},
+			{
+				Name:    "enabled",
+				Label:   "Enabled",
+				Type:    SetupFieldBool,
+				Default: "true",
+			},
+			{
+				Name:    "scopes",
+				Label:   "Scopes",
+				Type:    SetupFieldList,
+				Default: "read,write",
+				Normalize: func(raw string) string {
+					return strings.ToLower(strings.TrimSpace(raw))
+				},
+			},
+			{
+				Name:      "region",
+				Label:     "Region",
+				Type:      SetupFieldString,
+				Default:   "eu-central",
+				Normalize: strings.TrimSpace,
+			},
+		},
+	})
+	if err != nil {
+		t.Fatalf("RunSetup returned error: %v", err)
+	}
+
+	baseURL, ok := result.Get("base_url")
+	if !ok {
+		t.Fatalf("missing base_url field")
+	}
+	if !baseURL.Set || baseURL.String != "https://api.example.com" {
+		t.Fatalf("base_url = %#v, want normalized URL", baseURL)
+	}
+
+	token, ok := result.Get("api_token")
+	if !ok {
+		t.Fatalf("missing api_token field")
+	}
+	if token.String != "stored-token" {
+		t.Fatalf("token.String = %q, want stored-token", token.String)
+	}
+	if !token.KeptStoredSecret {
+		t.Fatalf("token should keep stored secret when blank")
+	}
+
+	enabled, ok := result.Get("enabled")
+	if !ok {
+		t.Fatalf("missing enabled field")
+	}
+	if !enabled.Bool || !enabled.Set {
+		t.Fatalf("enabled = %#v, want true from default", enabled)
+	}
+
+	scopes, ok := result.Get("scopes")
+	if !ok {
+		t.Fatalf("missing scopes field")
+	}
+	wantScopes := []string{"read", "write", "admin"}
+	if !slices.Equal(scopes.List, wantScopes) {
+		t.Fatalf("scopes.List = %v, want %v", scopes.List, wantScopes)
+	}
+
+	region, ok := result.Get("region")
+	if !ok {
+		t.Fatalf("missing region field")
+	}
+	if region.String != "eu-west" {
+		t.Fatalf("region.String = %q, want eu-west", region.String)
+	}
+
+	promptOutput := stdout.String()
+	for _, needle := range []string{
+		"Base URL:",
+		"API token [stored, leave blank to keep]:",
+		"Enabled [Y/n]:",
+		"Scopes [read,write]:",
+		"Region [eu-central]:",
+	} {
+		if !strings.Contains(promptOutput, needle) {
+			t.Fatalf("prompt output = %q, want substring %q", promptOutput, needle)
+		}
+	}
+}
+
+func TestRunSetupReturnsReadableValidationErrorInNonInteractiveMode(t *testing.T) {
+	stdin := setupTestInputFile(t, "maybe\n")
+	var stdout bytes.Buffer
+
+	_, err := RunSetup(SetupOptions{
+		Stdin:  stdin,
+		Stdout: &stdout,
+		Fields: []SetupField{
+			{
+				Name:  "enabled",
+				Label: "Enabled",
+				Type:  SetupFieldBool,
+			},
+		},
+	})
+
+	var validationErr *SetupValidationError
+	if !errors.As(err, &validationErr) {
+		t.Fatalf("RunSetup error = %v, want SetupValidationError", err)
+	}
+	if validationErr.Field != "enabled" {
+		t.Fatalf("validationErr.Field = %q, want enabled", validationErr.Field)
+	}
+	if !strings.Contains(validationErr.Error(), "must be one of") {
+		t.Fatalf("validationErr = %v, want readable bool error", validationErr)
+	}
+}
+
+func TestRunSetupSupportsValidationHooks(t *testing.T) {
+	stdin := setupTestInputFile(t, "https://example.com\nalpha,beta\n")
+
+	_, err := RunSetup(SetupOptions{
+		Stdin: stdin,
+		Fields: []SetupField{
+			{
+				Name:  "base_url",
+				Label: "Base URL",
+				Type:  SetupFieldURL,
+				Validate: func(value string) error {
+					if !strings.HasSuffix(value, "/v1") {
+						return errors.New("must end with /v1")
+					}
+					return nil
+				},
+			},
+			{
+				Name: "scopes",
+				Type: SetupFieldList,
+				ValidateList: func(values []string) error {
+					if len(values) < 3 {
+						return errors.New("at least 3 scopes are required")
+					}
+					return nil
+				},
+			},
+		},
+	})
+
+	var validationErr *SetupValidationError
+	if !errors.As(err, &validationErr) {
+		t.Fatalf("RunSetup error = %v, want SetupValidationError", err)
+	}
+	if validationErr.Field != "base_url" {
+		t.Fatalf("validationErr.Field = %q, want base_url", validationErr.Field)
+	}
+	if !strings.Contains(validationErr.Error(), "must end with /v1") {
+		t.Fatalf("validationErr = %v", validationErr)
+	}
+}
+
+func TestRunSetupRejectsInvalidDefinitions(t *testing.T) {
+	tests := []struct {
+		name   string
+		fields []SetupField
+	}{
+		{
+			name: "empty field name",
+			fields: []SetupField{
+				{Name: " ", Type: SetupFieldString},
+			},
+		},
+		{
+			name: "duplicate field names",
+			fields: []SetupField{
+				{Name: "base_url", Type: SetupFieldString},
+				{Name: "base_url", Type: SetupFieldURL},
+			},
+		},
+		{
+			name: "unknown type",
+			fields: []SetupField{
+				{Name: "base_url", Type: SetupFieldType("json")},
+			},
+		},
+		{
+			name: "invalid bool default",
+			fields: []SetupField{
+				{Name: "enabled", Type: SetupFieldBool, Default: "sometimes"},
+			},
+		},
+		{
+			name: "invalid url default",
+			fields: []SetupField{
+				{Name: "base_url", Type: SetupFieldURL, Default: "localhost"},
+			},
+		},
+	}
+
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			_, err := RunSetup(SetupOptions{
+				Stdin:  setupTestInputFile(t, ""),
+				Fields: tc.fields,
+			})
+			if !errors.Is(err, ErrInvalidSetupDefinition) {
+				t.Fatalf("RunSetup error = %v, want ErrInvalidSetupDefinition", err)
+			}
+		})
+	}
+}
+
+func setupTestInputFile(t *testing.T, content string) *os.File {
+	t.Helper()
+
+	file, err := os.CreateTemp(t.TempDir(), "setup-input-*.txt")
+	if err != nil {
+		t.Fatalf("CreateTemp returned error: %v", err)
+	}
+	t.Cleanup(func() {
+		_ = file.Close()
+	})
+
+	if _, err := file.WriteString(content); err != nil {
+		t.Fatalf("WriteString returned error: %v", err)
+	}
+	if _, err := file.Seek(0, 0); err != nil {
+		t.Fatalf("Seek returned error: %v", err)
+	}
+
+	return file
+}