Includes mmctl into the mono-repo (#23091)

* Includes mmctl into the mono-repo

* Update to use the new public module paths

* Adds docs check to the mmctl CI

* Fix public utils import path

* Tidy up modules

* Fix linter

* Update CI tasks to use the new file structure

* Update CI references

server/cmd/mmctl/printer/human/entry.go

@@ -0,0 +1,52 @@
+// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
+// See LICENSE.txt for license information.
+
+package human
+
+import (
+	"fmt"
+	"strings"
+	"time"
+
+	"github.com/mattermost/mattermost-server/server/public/shared/mlog"
+)
+
+type LogEntry struct {
+	Time    time.Time
+	Level   string
+	Message string
+	Caller  string
+	Fields  []mlog.Field
+}
+
+// Provide default string representation. Used by SimpleWriter
+func (f LogEntry) String() string {
+	var sb strings.Builder
+	if !f.Time.IsZero() {
+		sb.WriteString(f.Time.Format(time.RFC3339Nano))
+		sb.WriteRune(' ')
+	}
+	if f.Level != "" {
+		sb.WriteString(f.Level)
+		sb.WriteRune(' ')
+	}
+	if f.Caller != "" {
+		sb.WriteString(f.Caller)
+		sb.WriteRune(' ')
+	}
+	for _, field := range f.Fields {
+		sb.WriteString(field.Key)
+		sb.WriteRune('=')
+		sb.WriteString(fmt.Sprint(field.Interface))
+		sb.WriteRune(' ')
+	}
+	if f.Message != "" {
+		// If the message is multiple lines, start the whole message on a new line
+		if strings.ContainsRune(f.Message, '\n') {
+			sb.WriteRune('\n')
+		}
+		sb.WriteString(f.Message)
+	}
+
+	return sb.String()
+}

server/cmd/mmctl/printer/human/logrus_writer.go

@@ -0,0 +1,77 @@
+// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
+// See LICENSE.txt for license information.
+
+package human
+
+import (
+	"fmt"
+	"io"
+	"time"
+
+	"github.com/sirupsen/logrus"
+)
+
+type LogrusWriter struct {
+	logger *logrus.Logger
+}
+
+func (w *LogrusWriter) Write(e LogEntry) {
+	if e.Level == "" {
+		fmt.Fprintln(w.logger.Out, e.Message)
+		return
+	}
+
+	lvl, err := logrus.ParseLevel(e.Level)
+	if err != nil {
+		fmt.Fprintln(w.logger.Out, err)
+		lvl = logrus.TraceLevel + 1 // will invoke Println
+	}
+
+	logger := w.logger.WithTime(e.Time)
+
+	if e.Caller != "" {
+		// logrus has a system of reporting the caller, but there's no easy way to override it
+		logger = logger.WithField("caller", e.Caller)
+	}
+
+	for _, field := range e.Fields {
+		logger = logger.WithField(field.Key, field.Interface)
+	}
+
+	switch lvl {
+	case logrus.PanicLevel:
+		// Prevent panic from causing us to exit
+		defer func() {
+			_ = recover()
+		}()
+		logger.Panic(e.Message)
+	case logrus.FatalLevel:
+		logger.Fatal(e.Message)
+	case logrus.ErrorLevel:
+		logger.Error(e.Message)
+	case logrus.WarnLevel:
+		logger.Warn(e.Message)
+	case logrus.InfoLevel:
+		logger.Info(e.Message)
+	case logrus.DebugLevel:
+		logger.Debug(e.Message)
+	case logrus.TraceLevel:
+		logger.Trace(e.Message)
+	default:
+		logger.Println(e.Message)
+	}
+}
+
+func NewLogrusWriter(output io.Writer) *LogrusWriter {
+	w := new(LogrusWriter)
+	w.logger = logrus.New()
+	w.logger.SetLevel(logrus.TraceLevel) // don't filter any logs
+	w.logger.ExitFunc = func(int) {}     // prevent Fatal from causing us to exit
+	w.logger.SetReportCaller(false)
+	w.logger.SetOutput(output)
+	var tf logrus.TextFormatter
+	tf.FullTimestamp = true
+	tf.TimestampFormat = time.RFC3339Nano
+	w.logger.SetFormatter(&tf)
+	return w
+}

server/cmd/mmctl/printer/human/parser.go

@@ -0,0 +1,180 @@
+// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
+// See LICENSE.txt for license information.
+
+package human
+
+import (
+	"encoding/json"
+	"errors"
+	"fmt"
+	"io"
+	"strconv"
+	"strings"
+	"time"
+
+	"github.com/mattermost/mattermost-server/server/public/shared/mlog"
+)
+
+func ParseLogMessage(msg string) LogEntry {
+	result, err := parseLogMessage(msg)
+	if err != nil {
+		// If failed to parse, just output a LogEntry where all fields are blank, but Message is the original string
+		var result2 LogEntry
+		result2.Message = msg
+		return result2
+	}
+	return result
+}
+
+func parseLogMessage(msg string) (result LogEntry, err error) {
+	// Note: This implementation uses a custom json decoding loop.
+	// The primary advantage of this versus decoding directly into a map is to
+	// preserve the order of the fields. This can be simplified if we end up
+	// having the formatter sort fields alphabetically (logrus does by default)
+
+	dec := json.NewDecoder(strings.NewReader(msg))
+
+	// look for an initial "{"
+	token, err := dec.Token()
+	if err != nil {
+		return result, err
+	}
+	d, ok := token.(json.Delim)
+	if !ok || d != '{' {
+		return result, fmt.Errorf("input is not a JSON object, found: %v", token)
+	}
+
+	// read all key-value pairs
+	for dec.More() {
+		key, err2 := dec.Token()
+		if err2 != nil {
+			return result, err2
+		}
+		skey, ok2 := key.(string)
+		if !ok2 {
+			return result, errors.New("key is not a value string")
+		}
+		if !dec.More() {
+			return result, errors.New("missing value pair")
+		}
+
+		switch skey {
+		case "ts":
+			var ts json.Number
+			if err2 := dec.Decode(&ts); err2 != nil {
+				return result, err2
+			}
+			timeVal, err2 := numberToTime(ts)
+			if err2 != nil {
+				return result, err2
+			}
+			result.Time = timeVal
+
+		case "level":
+			s, err2 := decodeAsString(dec)
+			if err2 != nil {
+				return result, err2
+			}
+			result.Level = s
+
+		case "msg":
+			s, err2 := decodeAsString(dec)
+			if err2 != nil {
+				return result, err2
+			}
+			result.Message = s
+
+		case "caller":
+			s, err2 := decodeAsString(dec)
+			if err2 != nil {
+				return result, err2
+			}
+			result.Caller = s
+
+		default:
+			var p interface{}
+			if err2 := dec.Decode(&p); err2 != nil {
+				return result, err2
+			}
+			var f mlog.Field
+			f.Key = skey
+			f.Interface = p
+			result.Fields = append(result.Fields, f)
+		}
+	}
+
+	// read the "}"
+	token, err = dec.Token()
+	if err != nil {
+		return result, err
+	}
+	d, ok = token.(json.Delim)
+	if !ok || d != '}' {
+		return result, fmt.Errorf("failed to read '}', read: %v", token)
+	}
+
+	// make sure nothing else trailing
+	if token, err := dec.Token(); err != io.EOF {
+		return result, err
+	} else if token != nil {
+		return result, errors.New("found trailing data")
+	}
+
+	return result, nil
+}
+
+// Translate a number into a time
+func numberToTime(v json.Number) (time.Time, error) {
+	// Using floating point math to extract the nanoseconds leads to a time that doesn't exactly match the input
+	// Instead, parse out the components from the string representation
+
+	var t time.Time
+
+	// First make sure it is a number...
+	flt, err := v.Float64()
+	if err != nil {
+		return t, err
+	}
+
+	s := v.String()
+
+	if strings.ContainsAny(s, "eE") {
+		// input is in scientific notation. Convert to standard decimal notation
+		s = strconv.FormatFloat(flt, 'f', -1, 64)
+	}
+
+	// extract the seconds and nanoseconds separately
+	var nanos, sec int64
+
+	parts := strings.SplitN(s, ".", 2)
+	sec, err = strconv.ParseInt(parts[0], 10, 64)
+	if err != nil {
+		return t, err
+	}
+
+	if len(parts) == 2 {
+		nanosText := parts[1] + "000000000"
+		nanosText = nanosText[:9]
+		nanos, err = strconv.ParseInt(nanosText, 10, 64)
+		if err != nil {
+			return t, err
+		}
+	}
+
+	t = time.Unix(sec, nanos)
+	return t, nil
+}
+
+// Decodes a value from JSON, coercing it to a string value as necessary
+func decodeAsString(dec *json.Decoder) (s string, err error) {
+	var v interface{}
+	if err = dec.Decode(&v); err != nil {
+		return s, err
+	}
+	var ok bool
+	if s, ok = v.(string); ok {
+		return s, err
+	}
+	s = fmt.Sprint(v)
+	return s, err
+}

server/cmd/mmctl/printer/human/process.go

@@ -0,0 +1,23 @@
+// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
+// See LICENSE.txt for license information.
+
+package human
+
+import (
+	"bufio"
+	"io"
+)
+
+type LogWriter interface {
+	Write(e LogEntry)
+}
+
+// Read JSON logs from input and write formatted logs to the output
+func ProcessLogs(reader io.Reader, writer LogWriter) {
+	scanner := bufio.NewScanner(reader)
+	for scanner.Scan() {
+		s := scanner.Text()
+		e := ParseLogMessage(s)
+		writer.Write(e)
+	}
+}

server/cmd/mmctl/printer/human/simple_writer.go

@@ -0,0 +1,23 @@
+// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
+// See LICENSE.txt for license information.
+
+package human
+
+import (
+	"fmt"
+	"io"
+)
+
+type SimpleWriter struct {
+	out io.Writer
+}
+
+func (w *SimpleWriter) Write(e LogEntry) {
+	fmt.Fprintln(w.out, e)
+}
+
+func NewSimpleWriter(out io.Writer) *SimpleWriter {
+	w := new(SimpleWriter)
+	w.out = out
+	return w
+}

server/cmd/mmctl/printer/keys.go

@@ -0,0 +1,57 @@
+// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
+// See LICENSE.txt for license information.
+
+package printer
+
+// These are the key that aliases
+const (
+	ArrowLeft  = rune(KeyCtrlB)
+	ArrowRight = rune(KeyCtrlF)
+	ArrowUp    = rune(KeyCtrlP)
+	ArrowDown  = rune(KeyCtrlN)
+	Space      = ' '
+	Enter      = '\r'
+	NewLine    = '\n'
+	Backspace  = rune(KeyCtrlH)
+	Backspace2 = rune(KeyDEL)
+)
+
+// Key is the ascii codes of a keys
+type Key int16
+
+// These are the control keys.  Note that they overlap with other keys.
+const (
+	KeyCtrlSpace      Key = iota
+	KeyCtrlA              // KeySOH
+	KeyCtrlB              // KeySTX
+	KeyCtrlC              // KeyETX
+	KeyCtrlD              // KeyEOT
+	KeyCtrlE              // KeyENQ
+	KeyCtrlF              // KeyACK
+	KeyCtrlG              // KeyBEL
+	KeyCtrlH              // KeyBS
+	KeyCtrlI              // KeyTAB
+	KeyCtrlJ              // KeyLF
+	KeyCtrlK              // KeyVT
+	KeyCtrlL              // KeyFF
+	KeyCtrlM              // KeyCR
+	KeyCtrlN              // KeySO
+	KeyCtrlO              // KeySI
+	KeyCtrlP              // KeyDLE
+	KeyCtrlQ              // KeyDC1
+	KeyCtrlR              // KeyDC2
+	KeyCtrlS              // KeyDC3
+	KeyCtrlT              // KeyDC4
+	KeyCtrlU              // KeyNAK
+	KeyCtrlV              // KeySYN
+	KeyCtrlW              // KeyETB
+	KeyCtrlX              // KeyCAN
+	KeyCtrlY              // KeyEM
+	KeyCtrlZ              // KeySUB
+	KeyESC                // KeyESC
+	KeyCtrlBackslash      // KeyFS
+	KeyCtrlRightSq        // KeyGS
+	KeyCtrlCarat          // KeyRS
+	KeyCtrlUnderscore     // KeyUS
+	KeyDEL            = 0x7F
+)

server/cmd/mmctl/printer/printer.go

@@ -0,0 +1,325 @@
+// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
+// See LICENSE.txt for license information.
+
+package printer
+
+import (
+	"bytes"
+	"encoding/json"
+	"fmt"
+	"io"
+	"os"
+	"os/exec"
+	"strings"
+	"text/template"
+
+	"github.com/fatih/color"
+	"github.com/spf13/cobra"
+)
+
+const (
+	FormatPlain = "plain"
+	FormatJSON  = "json"
+)
+
+type Printer struct { //nolint
+	writer  io.Writer
+	eWriter io.Writer
+
+	Format        string
+	Single        bool
+	NoNewline     bool
+	templateFuncs template.FuncMap
+	pager         bool
+	Quiet         bool
+	Lines         []interface{}
+	ErrorLines    []interface{}
+
+	cmd        *cobra.Command
+	serverAddr string
+}
+
+type printOpts struct {
+	format    string
+	pagerPath string
+	single    bool
+	usePager  bool
+	shortStat bool
+	noNewline bool
+}
+
+var printer Printer
+
+func init() {
+	printer.writer = os.Stdout
+	printer.eWriter = os.Stderr
+	printer.pager = true
+	printer.templateFuncs = make(template.FuncMap)
+}
+
+// SetFormat sets the format for the final output of the printer
+func SetFormat(t string) {
+	printer.Format = t
+}
+
+func SetCommand(cmd *cobra.Command) {
+	printer.cmd = cmd
+}
+
+func SetServerAddres(addr string) {
+	printer.serverAddr = addr
+}
+
+func OverrideEnablePager(enable bool) {
+	printer.pager = enable
+}
+
+// SetFormat sets the format for the final output of the printer
+func SetQuiet(q bool) {
+	printer.Quiet = q
+}
+
+// SetNoNewline prevents the addition of a newline at the end of the plain output.
+// This may be useful when you want to handle newlines yourself.
+func SetNoNewline(no bool) {
+	printer.NoNewline = no
+}
+
+func SetTemplateFunc(name string, f interface{}) {
+	printer.templateFuncs[name] = f
+}
+
+// SetSingle sets the single flag on the printer. If this flag is set, the
+// printer will check the size of stored elements before printing, and
+// if there is only one, it will be printed on its own instead of
+// inside a list
+func SetSingle(single bool) {
+	printer.Single = single
+}
+
+// PrintT prints an element. Depending on the format, the element can be
+// formatted and printed as a structure or used to populate the
+// template
+func PrintT(templateString string, v interface{}) {
+	if printer.Quiet {
+		return
+	}
+	switch printer.Format {
+	case FormatPlain:
+		tpl := template.Must(template.New("").Funcs(printer.templateFuncs).Parse(templateString))
+		sb := &strings.Builder{}
+		if err := tpl.Execute(sb, v); err != nil {
+			PrintError("Can't print the message using the provided template: " + templateString)
+			return
+		}
+		printer.Lines = append(printer.Lines, sb.String())
+	case FormatJSON:
+		printer.Lines = append(printer.Lines, v)
+	}
+}
+
+func PrintPreparedT(tpl *template.Template, v interface{}) {
+	if printer.Quiet {
+		return
+	}
+	switch printer.Format {
+	case FormatPlain:
+		sb := &strings.Builder{}
+		if err := tpl.Execute(sb, v); err != nil {
+			PrintError("Can't print the message using the provided template: " + err.Error())
+			return
+		}
+		printer.Lines = append(printer.Lines, sb.String())
+	case FormatJSON:
+		printer.Lines = append(printer.Lines, v)
+	}
+}
+
+// Print an element. If the format requires a template, the element
+// will be printed as a structure with field names using the print
+// verb %+v
+func Print(v interface{}) {
+	PrintT("{{printf \"%+v\" .}}", v)
+}
+
+// Flush writes the elements accumulated in the printer
+func Flush() error {
+	if printer.Quiet {
+		return nil
+	}
+
+	opts := printOpts{
+		format:    printer.Format,
+		single:    printer.Single,
+		noNewline: printer.NoNewline,
+	}
+
+	cmd := printer.cmd
+	if cmd != nil {
+		shortStat, err := printer.cmd.Flags().GetBool("short-stat")
+		if err == nil && printer.cmd.Name() == "list" && printer.cmd.Parent().Name() != "auth" {
+			opts.shortStat = shortStat
+		}
+	}
+
+	b, err := printer.linesToBytes(opts)
+	if err != nil {
+		return err
+	}
+	lines := lineCount(b)
+
+	isTTY := checkInteractiveTerminal() == nil
+	var enablePager bool
+	termHeight, err := termHeight(os.Stdout)
+	if err == nil {
+		enablePager = isTTY && (termHeight < lines) // calculate if we should enable paging
+	}
+
+	pager := os.Getenv("PAGER")
+	if enablePager {
+		enablePager = pager != ""
+	}
+
+	opts.usePager = enablePager && printer.pager
+	opts.pagerPath = pager
+
+	err = printer.printBytes(b, opts)
+	if err != nil {
+		return err
+	}
+
+	// after all, print errors
+	printer.printErrors()
+
+	defer func() {
+		printer.Lines = []interface{}{}
+		printer.ErrorLines = []interface{}{}
+	}()
+
+	if cmd == nil || cmd.Name() != "list" || printer.cmd.Parent().Name() == "auth" {
+		return nil
+	}
+
+	// the command is a list command, we may want to
+	// take care of the stat flags
+	noStat, err := cmd.Flags().GetBool("no-stat")
+	if err != nil {
+		return err
+	}
+
+	// print stats
+	switch {
+	case noStat:
+		// do nothing
+	case !opts.shortStat:
+		// should not go to pager
+		if isTTY && !enablePager {
+			fmt.Fprintf(printer.eWriter, "\n") // add a one line space before statistical data
+		}
+		fallthrough
+	case len(printer.Lines) > 0:
+		entity := cmd.Parent().Name()
+		container := strings.TrimSuffix(printer.serverAddr, "api/v4")
+		if container != "" {
+			container = fmt.Sprintf(" on %s", container)
+		}
+		fmt.Fprintf(printer.eWriter, "There are %d %ss%s\n", len(printer.Lines), entity, container)
+	}
+
+	return nil
+}
+
+// Clean resets the printer's accumulated lines
+func Clean() {
+	printer.Lines = []interface{}{}
+	printer.ErrorLines = []interface{}{}
+}
+
+// GetLines returns the printer's accumulated lines
+func GetLines() []interface{} {
+	return printer.Lines
+}
+
+// GetErrorLines returns the printer's accumulated error lines
+func GetErrorLines() []interface{} {
+	return printer.ErrorLines
+}
+
+// PrintError prints to the stderr.
+func PrintError(msg string) {
+	printer.ErrorLines = append(printer.ErrorLines, msg)
+}
+
+// PrintWarning prints warning message to the error output, unlike Print and PrintError
+// functions, PrintWarning writes the output immediately instead of waiting command to finish.
+func PrintWarning(msg string) {
+	if printer.Quiet {
+		return
+	}
+	fmt.Fprintf(printer.eWriter, "%s\n", color.YellowString("WARNING: %s", msg))
+}
+
+func (p Printer) linesToBytes(opts printOpts) (b []byte, err error) {
+	if opts.shortStat {
+		return
+	}
+
+	newline := "\n"
+	if opts.noNewline {
+		newline = ""
+	}
+
+	switch opts.format {
+	case FormatPlain:
+		var buf bytes.Buffer
+		for i := range p.Lines {
+			fmt.Fprintf(&buf, "%s%s", p.Lines[i], newline)
+		}
+		b = buf.Bytes()
+	case FormatJSON:
+		switch {
+		case opts.single && len(p.Lines) == 0:
+			return
+		case opts.single && len(p.Lines) == 1:
+			b, err = json.MarshalIndent(p.Lines[0], "", "  ")
+		default:
+			b, err = json.MarshalIndent(p.Lines, "", "  ")
+		}
+		b = append(b, '\n')
+	}
+	return
+}
+
+func (p Printer) printBytes(b []byte, opts printOpts) error {
+	if !opts.usePager {
+		fmt.Fprintf(p.writer, "%s", b)
+		return nil
+	}
+
+	c := exec.Command(opts.pagerPath) // nolint:gosec
+
+	in, err := c.StdinPipe()
+	if err != nil {
+		return fmt.Errorf("could not create the stdin pipe: %w", err)
+	}
+
+	c.Stdout = p.writer
+	c.Stderr = p.eWriter
+
+	go func() {
+		defer in.Close()
+		_, _ = io.Copy(in, bytes.NewReader(b))
+	}()
+
+	if err := c.Start(); err != nil {
+		return fmt.Errorf("could not start the pager: %w", err)
+	}
+
+	return c.Wait()
+}
+
+func (p Printer) printErrors() {
+	for i := range printer.ErrorLines {
+		fmt.Fprintln(printer.eWriter, printer.ErrorLines[i])
+	}
+}

server/cmd/mmctl/printer/printer_test.go

@@ -0,0 +1,161 @@
+// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
+// See LICENSE.txt for license information.
+
+package printer
+
+import (
+	"bufio"
+	"bytes"
+	"testing"
+	"text/template"
+
+	"github.com/stretchr/testify/assert"
+)
+
+type mockWriter []byte
+
+func (w *mockWriter) Write(b []byte) (n int, err error) {
+	*w = append(*w, b...)
+	return len(*w) - len(b), nil
+}
+
+func TestPrintT(t *testing.T) {
+	w := bufio.NewWriter(&bytes.Buffer{})
+	printer.writer = w
+	printer.Format = FormatPlain
+
+	ts := struct {
+		ID int
+	}{
+		ID: 123,
+	}
+
+	t.Run("should execute template", func(t *testing.T) {
+		tpl := `testing template {{.ID}}`
+		PrintT(tpl, ts)
+		assert.Len(t, GetLines(), 1)
+
+		assert.Equal(t, "testing template 123", printer.Lines[0])
+
+		_ = Flush()
+	})
+
+	t.Run("should fail to execute, no method or field", func(t *testing.T) {
+		Clean()
+		tpl := `testing template {{.Name}}`
+		PrintT(tpl, ts)
+		assert.Len(t, GetErrorLines(), 1)
+
+		assert.Equal(t, "Can't print the message using the provided template: "+tpl, printer.ErrorLines[0])
+		_ = Flush()
+	})
+}
+
+func TestPrintPreparedT(t *testing.T) {
+	w := bufio.NewWriter(&bytes.Buffer{})
+	printer.writer = w
+	printer.Format = FormatPlain
+
+	ts := struct {
+		ID int
+	}{
+		ID: 123,
+	}
+
+	t.Run("should execute template", func(t *testing.T) {
+		tpl := template.Must(template.New("").Parse(`testing template {{.ID}}`))
+		PrintPreparedT(tpl, ts)
+		assert.Len(t, GetLines(), 1)
+
+		assert.Equal(t, "testing template 123", printer.Lines[0])
+
+		_ = Flush()
+	})
+
+	t.Run("should fail to execute, no method or field", func(t *testing.T) {
+		Clean()
+		tpl := template.Must(template.New("").Parse(`testing template {{.Name}}`))
+		PrintPreparedT(tpl, ts)
+		assert.Len(t, GetErrorLines(), 1)
+
+		assert.Contains(t, printer.ErrorLines[0], "Can't print the message using the provided template")
+		_ = Flush()
+	})
+}
+
+func TestFlushJSON(t *testing.T) {
+	printer.Format = FormatJSON
+
+	t.Run("should print a line in JSON format", func(t *testing.T) {
+		mw := &mockWriter{}
+		printer.writer = mw
+		Clean()
+
+		Print("test string")
+		assert.Len(t, GetLines(), 1)
+
+		_ = Flush()
+		assert.Equal(t, "[\n  \"test string\"\n]\n", string(*mw))
+		assert.Empty(t, GetLines(), 0)
+	})
+
+	t.Run("should print multi line in JSON format", func(t *testing.T) {
+		mw := &mockWriter{}
+		printer.writer = mw
+
+		Clean()
+		Print("test string-1")
+		Print("test string-2")
+		assert.Len(t, GetLines(), 2)
+
+		_ = Flush()
+		assert.Equal(t, "[\n  \"test string-1\",\n  \"test string-2\"\n]\n", string(*mw))
+		assert.Empty(t, GetLines(), 0)
+	})
+}
+
+func TestFlushPlain(t *testing.T) {
+	printer.Format = FormatPlain
+
+	t.Run("should print a line in plain format", func(t *testing.T) {
+		mw := &mockWriter{}
+		printer.writer = mw
+		Clean()
+
+		Print("test string")
+		assert.Len(t, GetLines(), 1)
+
+		_ = Flush()
+		assert.Equal(t, "test string\n", string(*mw))
+		assert.Empty(t, GetLines(), 0)
+	})
+
+	t.Run("should print multi line in plain format", func(t *testing.T) {
+		mw := &mockWriter{}
+		printer.writer = mw
+
+		Clean()
+		Print("test string-1")
+		Print("test string-2")
+		assert.Len(t, GetLines(), 2)
+
+		_ = Flush()
+		assert.Equal(t, "test string-1\ntest string-2\n", string(*mw))
+		assert.Empty(t, GetLines(), 0)
+	})
+
+	t.Run("should print multi line in plain format without a newline", func(t *testing.T) {
+		mw := &mockWriter{}
+		printer.writer = mw
+		printer.NoNewline = true
+
+		Clean()
+		Print("test string-1")
+		Print("test string-2")
+		assert.Len(t, GetLines(), 2)
+
+		_ = Flush()
+		assert.Equal(t, "test string-1test string-2", string(*mw))
+		assert.Empty(t, GetLines(), 0)
+	})
+}

server/cmd/mmctl/printer/util.go

@@ -0,0 +1,38 @@
+// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
+// See LICENSE.txt for license information.
+
+package printer
+
+import (
+	"bytes"
+	"errors"
+	"os"
+
+	"golang.org/x/term"
+)
+
+func checkInteractiveTerminal() error {
+	fileInfo, err := os.Stdout.Stat()
+	if err != nil {
+		return err
+	}
+
+	if (fileInfo.Mode() & os.ModeCharDevice) == 0 {
+		return errors.New("this is not an interactive shell")
+	}
+
+	return nil
+}
+
+func termHeight(file *os.File) (int, error) {
+	_, h, err := term.GetSize(int(file.Fd()))
+	if err != nil {
+		return -1, err
+	}
+
+	return h, nil
+}
+
+func lineCount(b []byte) int {
+	return bytes.Count(b, []byte{'\n'})
+}