Introduce $edit:command:-duration

The `edit:command:-duration` variable is the elapsed seconds of the most
recently run interactive command. It is currently marked experimental by
virtue of a `-` prefix since it might be removed in favor of the command
execution callback solution.

Related elves#1029

0.16.0-release-notes.md

@@ -28,3 +28,6 @@ New features in the interactive editor:
     bindings.
 
 -   A new `edit:clear` builtin to clear the screen has been added.
+
+-   A new, experimental, `edit:command:-duration` variable that is the number of
+    seconds to run the most recent command.

pkg/edit/command_api.go

@@ -3,18 +3,34 @@ package edit
 import (
 	"src.elv.sh/pkg/cli/mode"
 	"src.elv.sh/pkg/eval"
+	"src.elv.sh/pkg/eval/vars"
 )
 
-//elv:fn command:start
+//elvdoc:fn command:start
 //
-// Starts the command mode.
+// Start command mode.
+
+//elvdoc:var command:-duration
+//
+// Duration, in seconds, of the most recent interactive command. This can be useful in your prompt
+// (left or right) to provide feedback on how long a command took to run. The initial value of this
+// variable is the time to evaluate your *~/.elvish/rc.elv* script before issuing the first prompt.
+
+var CommandDuration float64
 
 func initCommandAPI(ed *Editor, ev *eval.Evaler, nb eval.NsBuilder) {
 	bindingVar := newBindingVar(emptyBindingsMap)
 	bindings := newMapBindings(ed, ev, bindingVar)
 	nb.AddNs("command",
 		eval.NsBuilder{
 			"binding": bindingVar,
+			// This is marked as an experimental variable because it might be preferable to provide
+			// this info via a callback. See https://github.com/elves/elvish/issues/1029.
+			//
+			// TODO: Change this to a read-only var, possibly by introducing a vars.FromPtrReadonly
+			// function, to guard against attempts to modify the value from Elvish code. Assuming,
+			// of course, we continue to expose it as a variable rather than via a callback.
+			"-duration": vars.FromPtr(&CommandDuration),
 		}.AddGoFns("<edit:command>:", map[string]interface{}{
 			"start": func() {
 				w := mode.NewStub(mode.StubSpec{

pkg/eval/compile_effect.go

@@ -171,7 +171,6 @@ func (cp *compiler) formOp(n *parse.Form) effectOp {
 			lvalues := cp.parseIndexingLValue(a.Left)
 			tempLValues = append(tempLValues, lvalues.lvalues...)
 		}
-		logger.Println("temporary assignment of", len(n.Assignments), "pairs")
 	}
 
 	redirOps := cp.redirOps(n.Redirs)
@@ -291,7 +290,6 @@ func (op *formOp) exec(fm *Frame) (errRet Exception) {
 			}
 			val := v.Get()
 			saveVals = append(saveVals, val)
-			logger.Printf("saved %s = %s", v, val)
 		}
 		// Do assignment.
 		for _, subop := range op.tempAssignOps {
@@ -315,7 +313,6 @@ func (op *formOp) exec(fm *Frame) (errRet Exception) {
 				if err != nil {
 					errRet = fm.errorp(op, err)
 				}
-				logger.Printf("restored %s = %s", v, val)
 			}
 		}()
 	}

pkg/shell/interact.go

@@ -5,6 +5,7 @@ import (
 	"io"
 	"os"
 	"path/filepath"
+	"strings"
 	"syscall"
 	"time"
 
@@ -79,7 +80,6 @@ func Interact(fds [3]*os.File, cfg *InteractConfig) {
 		cmdNum++
 
 		line, err := ed.ReadCode()
-
 		if err == io.EOF {
 			break
 		} else if err != nil {
@@ -101,8 +101,15 @@ func Interact(fds [3]*os.File, cfg *InteractConfig) {
 		// No error; reset cooldown.
 		cooldown = time.Second
 
-		err = evalInTTY(ev, fds,
+		// We only bother evaluating the statement(s) if the line is not entirely whitespace. This
+		// isn't especially important but keeps things like the `edit:command:-duration` variable
+		// from being updated when we didn't actually evaluate any statements.
+		if strings.TrimSpace(line) == "" {
+			continue
+		}
+		duration, err := evalInTTY(ev, fds,
 			parse.Source{Name: fmt.Sprintf("[tty %v]", cmdNum), Code: line})
+		edit.CommandDuration = duration
 		term.Sanitize(fds[0], fds[2])
 		if err != nil {
 			diag.ShowError(fds[2], err)
@@ -122,7 +129,8 @@ func sourceRC(fds [3]*os.File, ev *eval.Evaler, rcPath string) error {
 		}
 		return err
 	}
-	err = evalInTTY(ev, fds, parse.Source{Name: absPath, Code: code, IsFile: true})
+	duration, err := evalInTTY(ev, fds, parse.Source{Name: absPath, Code: code, IsFile: true})
+	edit.CommandDuration = duration
 	if err != nil {
 		return err
 	}

pkg/shell/script.go

@@ -67,7 +67,7 @@ func Script(fds [3]*os.File, args []string, cfg *ScriptConfig) int {
 			return 2
 		}
 	} else {
-		err := evalInTTY(ev, fds, src)
+		_, err := evalInTTY(ev, fds, src)
 		if err != nil {
 			diag.ShowError(fds[2], err)
 			return 2

pkg/shell/shell.go

@@ -5,6 +5,7 @@ import (
 	"os"
 	"os/signal"
 	"strconv"
+	"time"
 
 	"src.elv.sh/pkg/cli/term"
 	"src.elv.sh/pkg/env"
@@ -62,11 +63,14 @@ func setupShell(fds [3]*os.File, p Paths, spawn bool) (*eval.Evaler, func()) {
 	}
 }
 
-func evalInTTY(ev *eval.Evaler, fds [3]*os.File, src parse.Source) error {
+func evalInTTY(ev *eval.Evaler, fds [3]*os.File, src parse.Source) (float64, error) {
+	start := time.Now()
 	ports, cleanup := eval.PortsFromFiles(fds, ev.ValuePrefix())
 	defer cleanup()
-	return ev.Eval(src, eval.EvalCfg{
+	err := ev.Eval(src, eval.EvalCfg{
 		Ports: ports, Interrupt: eval.ListenInterrupts, PutInFg: true})
+	end := time.Now()
+	return end.Sub(start).Seconds(), err
 }
 
 func incSHLVL() func() {