cli/addons/instant: Add new addon for "instant mode".

cli/addons/instant/instant.go

@@ -0,0 +1,90 @@
+// Package instant implements an addon that executes code whenever it changes
+// and shows the result.
+package instant
+
+import (
+	"github.com/elves/elvish/cli"
+	"github.com/elves/elvish/cli/el"
+	"github.com/elves/elvish/cli/el/layout"
+	"github.com/elves/elvish/cli/el/textview"
+	"github.com/elves/elvish/cli/term"
+	"github.com/elves/elvish/ui"
+)
+
+// Config keeps the configuration for the instant addon.
+type Config struct {
+	// Keybinding.
+	Binding el.Handler
+	// The function to execute code and returns the output.
+	Execute func(code string) ([]string, error)
+}
+
+type widget struct {
+	Config
+	app      cli.App
+	textView textview.Widget
+	lastCode string
+	lastErr  error
+}
+
+func (w *widget) Render(width, height int) *term.Buffer {
+	bb := term.NewBufferBuilder(width).
+		WriteStyled(layout.ModeLine(" INSTANT ", false)).SetDotHere()
+	if w.lastErr != nil {
+		bb.Newline().Write(w.lastErr.Error(), ui.Red)
+	}
+	buf := bb.Buffer()
+	if len(buf.Lines) >= height {
+		buf.TrimToLines(0, height)
+		return buf
+	}
+	bufTextView := w.textView.Render(width, height-len(buf.Lines))
+	buf.Extend(bufTextView, false)
+	return buf
+}
+
+func (w *widget) Focus() bool { return false }
+
+func (w *widget) Handle(event term.Event) bool {
+	handled := w.Binding.Handle(event)
+	if !handled {
+		codeArea := w.app.CodeArea()
+		handled = codeArea.Handle(event)
+	}
+	w.update(false)
+	return handled
+}
+
+func (w *widget) update(force bool) {
+	code := w.app.CodeArea().CopyState().Buffer.Content
+	if code == w.lastCode && !force {
+		return
+	}
+	w.lastCode = code
+	output, err := w.Execute(code)
+	w.lastErr = err
+	if err == nil {
+		w.textView.MutateState(func(s *textview.State) {
+			*s = textview.State{Lines: output, First: 0}
+		})
+	}
+}
+
+// Start starts the addon.
+func Start(app cli.App, cfg Config) {
+	if cfg.Execute == nil {
+		app.Notify("executor is required")
+		return
+	}
+	if cfg.Binding == nil {
+		cfg.Binding = el.DummyHandler{}
+	}
+	w := widget{
+		Config:   cfg,
+		app:      app,
+		textView: textview.New(textview.Spec{Scrollable: true}),
+	}
+	app.MutateState(func(s *cli.State) { s.Addon = &w })
+	w.update(true)
+	app.Redraw()
+}

cli/addons/instant/instant_test.go

@@ -0,0 +1,78 @@
+package instant
+
+import (
+	"errors"
+	"testing"
+
+	. "github.com/elves/elvish/cli/apptest"
+	"github.com/elves/elvish/cli/term"
+	"github.com/elves/elvish/ui"
+)
+
+var styles = ui.RuneStylesheet{
+	'*': ui.Stylings(ui.Bold, ui.LightGray, ui.BgMagenta),
+	'!': ui.Red,
+}
+
+func setupStarted(t *testing.T) *Fixture {
+	f := Setup()
+	Start(f.App, Config{
+		Execute: func(code string) ([]string, error) {
+			var err error
+			if code == "!" {
+				err = errors.New("error")
+			}
+			return []string{"result of", code}, err
+		},
+	})
+	f.TestTTY(t,
+		term.DotHere, "\n",
+		" INSTANT \n", styles,
+		"*********",
+		"result of\n",
+		"",
+	)
+	return f
+}
+
+func TestUpdate(t *testing.T) {
+	f := setupStarted(t)
+	defer f.Stop()
+
+	f.TTY.Inject(term.K('a'))
+	bufA := f.MakeBuffer(
+		"a", term.DotHere, "\n",
+		" INSTANT \n", styles,
+		"*********",
+		"result of\n",
+		"a",
+	)
+	f.TTY.TestBuffer(t, bufA)
+
+	f.TTY.Inject(term.K(ui.Right))
+	f.TTY.TestBuffer(t, bufA)
+}
+
+func TestError(t *testing.T) {
+	f := setupStarted(t)
+	defer f.Stop()
+
+	f.TTY.Inject(term.K('!'))
+	f.TestTTY(t,
+		"!", term.DotHere, "\n",
+		" INSTANT \n", styles,
+		"*********",
+		// Error shown.
+		"error\n", styles,
+		"!!!!!",
+		// Buffer not updated.
+		"result of\n",
+		"",
+	)
+}
+
+func TestStart_NoExecutor(t *testing.T) {
+	f := Setup()
+	Start(f.App, Config{})
+	f.TestTTYNotes(t, "executor is required")
+}