allow repl to intercept ctrl+c when running a command, closes #275

Author: odino

Makefile

@@ -28,4 +28,4 @@ wasm:
 	GOOS=js GOARCH=wasm go build -o docs/abs.wasm js/js.go
 tapes: build_simple
 	docker build -t abs-tapes docs/vhs
-	docker run -ti -v $$(pwd)/builds/abs:/usr/bin/abs -v $$(pwd):/abs abs-tapes
+	docker run -ti -v $$(pwd)/builds/abs:/usr/bin/abs -v $$(pwd):/abs -e TAPE=$(tape) abs-tapes

docs/vhs/images/ip.gif

@@ -0,0 +1,18 @@
+Output "/abs/docs/vhs/images/repl-quit-command.gif"
+
+Set FontSize 24
+Set Width 1200
+Set Height 400
+Set BorderRadius 10
+Set Margin 10
+Set MarginFill "#a1a1a1"
+Set TypingSpeed 75ms
+
+Source "/abs/docs/vhs/tapes/config.tape"
+
+Type "`sleep 10`"
+Enter
+Sleep 1
+
+Ctrl+C
+Sleep 2

docs/vhs/images/readme-sample.gif

@@ -1,6 +1,6 @@
 f run_tape(t) {
-    echo("running tape %s", tape)
-    res = `vhs /abs/docs/vhs/tapes/$tape`
+    echo("running tape %s", t)
+    res = `vhs /abs/docs/vhs/tapes/$t`
 
     if !res.ok {
         exit(99, res)

docs/vhs/images/repl-quit-command.gif

@@ -1,6 +1,7 @@
 package terminal
 
 import (
+	"context"
 	"crypto/rand"
 	"fmt"
 	"io"
@@ -82,6 +83,7 @@ type Model struct {
 	// to determine that while ABS is executing,
 	// we should relay stdin from the terminal
 	isEvaluating bool
+	cancelEval   context.CancelFunc
 	// function to print the prompt 'prefix'
 	prompt func() string
 	// dirty input -- input I may have typed on
@@ -155,7 +157,12 @@ func (m Model) Update(msg tea.Msg) (tea.Model, tea.Cmd) {
 		// so if we type during this time,
 		// we should forward this to ABS' stdin
 		if m.isEvaluating {
-			return m.interceptStdin(msg)
+			switch msg.Type {
+			case tea.KeyCtrlC:
+				return m.abortEval()
+			default:
+				return m.interceptStdin(msg)
+			}
 		}
 
 		if m.IsSuggesting() {
@@ -253,6 +260,22 @@ func (m Model) Update(msg tea.Msg) (tea.Model, tea.Cmd) {
 	return m, tiCmd
 }
 
+func (m Model) abortEval() (tea.Model, tea.Cmd) {
+	return m, func() tea.Msg {
+		// *if* a command was running, let's
+		// notify it that it should be canceled
+		if m.cancelEval != nil {
+			m.cancelEval()
+		}
+
+		// 'fake' a command being done
+		return doneEval{
+			out: object.NULL,
+			ok:  false,
+		}
+	}
+}
+
 func (m Model) search() Model {
 	if !m.isSearching {
 		m.isSearching = true
@@ -597,10 +620,27 @@ type doneEval struct {
 
 func (m Model) eval() (Model, tea.Cmd) {
 	m.isEvaluating = true
+	ctx, cancel := context.WithCancel(context.Background())
+	m.cancelEval = cancel
+
 	done := make(chan doneEval)
 
 	go func() {
+		defer m.cancelEval()
+		// obviously we should pass the context to the runner
+		// but this is for another day. The current implementation
+		// makes it so that the command will keep running in background,
+		// but we'll give the user the impression the command is
+		// terminated (which is bad). Again, I think the real solution
+		// over time is to introduce a CancelContext to the runner
+		// that gets passed down all the way to running the commands.
 		out, ok, parseErrors := runner.Run(m.in.Value(), m.env)
+
+		// someone cancelled the eval operation
+		if err := ctx.Err(); err != nil {
+			return
+		}
+
 		done <- doneEval{out, ok, parseErrors}
 	}()