Prompt can now be customized by modifying le:{,r}prompt.

This fixes #103.

edit/editor.go

@@ -29,6 +29,8 @@ type Editor struct {
 	store  *store.Store
 	evaler *eval.Evaler
 	cmdSeq int
+	ps1    Prompt
+	rps1   Prompt
 	editorState
 }
 
@@ -93,6 +95,8 @@ func NewEditor(file *os.File, sigs chan os.Signal, ev *eval.Evaler, st *store.St
 		}
 	}
 
+	prompt, rprompt := defaultPrompts()
+
 	ed := &Editor{
 		file:   file,
 		writer: newWriter(file),
@@ -101,6 +105,8 @@ func NewEditor(file *os.File, sigs chan os.Signal, ev *eval.Evaler, st *store.St
 		store:  st,
 		evaler: ev,
 		cmdSeq: seq,
+		ps1:    prompt,
+		rps1:   rprompt,
 	}
 	ev.AddModule("le", makeModule(ed))
 	return ed
@@ -282,7 +288,7 @@ func (ed *Editor) finishReadLine(addError func(error)) {
 }
 
 // ReadLine reads a line interactively.
-func (ed *Editor) ReadLine(prompt, rprompt func() string) (lr LineRead) {
+func (ed *Editor) ReadLine() (lr LineRead) {
 	ed.editorState = editorState{active: true}
 	isExternalCh := make(chan map[string]bool, 1)
 	go getIsExternal(ed.evaler, isExternalCh)
@@ -302,8 +308,8 @@ func (ed *Editor) ReadLine(prompt, rprompt func() string) (lr LineRead) {
 
 MainLoop:
 	for {
-		ed.prompt = prompt()
-		ed.rprompt = rprompt()
+		ed.prompt = ed.ps1.Call(ed)
+		ed.rprompt = ed.rps1.Call(ed)
 
 		err := ed.refresh(false, true)
 		if err != nil {

edit/module.go

@@ -39,6 +39,9 @@ func makeModule(ed *Editor) eval.Namespace {
 
 	ns["binding"] = eval.NewRoVariable(binding)
 
+	ns["prompt"] = PromptVariable{&ed.ps1}
+	ns["rprompt"] = PromptVariable{&ed.rps1}
+
 	return ns
 }
 

edit/prompt.go

@@ -2,11 +2,36 @@ package edit
 
 import (
 	"bytes"
+	"errors"
 	"os"
+	"os/user"
 
 	"github.com/elves/elvish/eval"
+	"github.com/elves/elvish/util"
 )
 
+var ErrPromptMustBeStringOrFunc = errors.New("prompt must be string or function")
+
+// PromptVariable implements $le:prompt and $le:rprompt.
+type PromptVariable struct {
+	Prompt *Prompt
+}
+
+func (pv PromptVariable) Get() eval.Value {
+	// XXX Should return a proper eval.Caller
+	return eval.String("<prompt>")
+}
+
+func (pv PromptVariable) Set(v eval.Value) {
+	if s, ok := v.(eval.String); ok {
+		*pv.Prompt = BuiltinPrompt(func(*Editor) string { return string(s) })
+	} else if c, ok := v.(eval.Caller); ok {
+		*pv.Prompt = CallerPrompt{c}
+	} else {
+		throw(ErrPromptMustBeStringOrFunc)
+	}
+}
+
 // Prompt is the interface of prompt functions.
 type Prompt interface {
 	Call(*Editor) string
@@ -29,7 +54,7 @@ func (c CallerPrompt) Call(ed *Editor) string {
 	if err != nil {
 		return ""
 	}
-	ports := []*eval.Port{in, nil, &eval.Port{File: os.Stderr}}
+	ports := []*eval.Port{in, &eval.Port{File: os.Stdout}, &eval.Port{File: os.Stderr}}
 
 	// XXX There is no source to pass to NewTopEvalCtx.
 	ec := eval.NewTopEvalCtx(ed.evaler, "[editor prompt]", "", ports)
@@ -44,3 +69,24 @@ func (c CallerPrompt) Call(ed *Editor) string {
 	}
 	return b.String()
 }
+
+func defaultPrompts() (Prompt, Prompt) {
+	// Make default prompts.
+	username := "???"
+	user, err := user.Current()
+	if err == nil {
+		username = user.Username
+	}
+	hostname, err := os.Hostname()
+	if err != nil {
+		hostname = "???"
+	}
+	rpromptStr := username + "@" + hostname
+	prompt := func(*Editor) string {
+		return util.Getwd() + "> "
+	}
+	rprompt := func(*Editor) string {
+		return rpromptStr
+	}
+	return BuiltinPrompt(prompt), BuiltinPrompt(rprompt)
+}

run/run.go

@@ -8,7 +8,6 @@ import (
 	"io"
 	"os"
 	"os/signal"
-	"os/user"
 	"syscall"
 	"time"
 
@@ -127,27 +126,9 @@ func interact(ev *eval.Evaler, st *store.Store) {
 		}
 	}
 
-	// Build prompt and rprompt.
-	username := "???"
-	user, err := user.Current()
-	if err == nil {
-		username = user.Username
-	}
-	hostname, err := os.Hostname()
-	if err != nil {
-		hostname = "???"
-	}
-	rpromptStr := username + "@" + hostname
-	prompt := func() string {
-		return util.Getwd() + "> "
-	}
-	rprompt := func() string {
-		return rpromptStr
-	}
-
 	// Build readLine function.
 	readLine := func() edit.LineRead {
-		return ed.ReadLine(prompt, rprompt)
+		return ed.ReadLine()
 	}
 
 	cooldown := time.Second