Fixed goroutine leak and tweaked the API a little. A UI can now be provided a parent context to derive its own Run context from. Also, UI handles Read errors a little better.

Author: Zaba505

README.md

@@ -1,5 +1,6 @@
 [![GoDoc](https://godoc.org/github.com/Zaba505/sand?status.svg)](https://godoc.org/github.com/Zaba505/sand)
 [![Go Report Card](https://goreportcard.com/badge/github.com/Zaba505/sand)](https://goreportcard.com/report/github.com/Zaba505/sand)
+[![Build Status](https://travis-ci.com/Zaba505/sand.svg?branch=master)](https://travis-ci.com/Zaba505/sand)
 
 # sand
 Package for creating interpreters

engine.go

@@ -27,10 +27,11 @@ func (ui *UI) exec(ctx context.Context, line string) int {
 		ui:     ui,
 		respCh: make(chan int),
 	}
-	defer close(req.respCh)
-
-	ui.reqCh <- req
-
+	select {
+	case <-ctx.Done():
+		return 0
+	case ui.reqCh <- req:
+	}
 	return <-req.respCh
 }
 
@@ -46,7 +47,13 @@ func runEngine(ctx context.Context, eng Engine, reqChs chan chan execReq) {
 			go func(rc chan execReq) {
 				for req := range rc {
 					resp := eng.Exec(req.ctx, req.line, req.ui)
-					req.respCh <- resp
+					select {
+					case <-ctx.Done():
+						close(req.respCh)
+						return
+					case req.respCh <- resp:
+					}
+					close(req.respCh)
 				}
 			}(reqCh)
 		}

example/cobra/cmd_test.go

@@ -81,7 +81,7 @@ func TestRootCmd(t *testing.T) {
 				subT.Error(err)
 			}
 
-			if err = ui.Run(); err != io.EOF {
+			if err = ui.Run(nil); err != io.EOF {
 				subT.Error(err)
 			}
 
@@ -95,5 +95,6 @@ func TestRootCmd(t *testing.T) {
 				subT.Fail()
 			}
 		})
+
 	}
 }

example/echo/main.go

@@ -32,6 +32,7 @@ func main() {
 
 	log.SetOutput(os.Stdout)
 	err := ui.Run(
+		nil,
 		sand.WithPrefix(">"),
 		sand.WithIO(os.Stdin, os.Stdout),
 	)

example/tictactoe/main.go

@@ -175,7 +175,7 @@ func main() {
 	ui.SetPrefix(">")
 	ui.SetIO(os.Stdin, os.Stdout)
 
-	if err := ui.Run(); err != nil {
+	if err := ui.Run(nil); err != nil {
 		log.Fatal(err)
 	}
 }

ui.go

@@ -101,13 +101,13 @@ func (ui *UI) SetIO(in io.Reader, out io.Writer) {
 // Run creates a UI and associates the provided Engine to it.
 // It then starts the UI. I/O must be provided for this call
 // to not panic.
-func Run(eng Engine, opts ...Option) error {
+func Run(ctx context.Context, eng Engine, opts ...Option) error {
 	if eng == nil {
 		return ErrNoEngine
 	}
 
 	ui := NewUI(eng)
-	return ui.Run(opts...)
+	return ui.Run(ctx, opts...)
 }
 
 // minRead
@@ -116,11 +116,15 @@ const minRead = 512
 // Run starts the user interface with the provided sources
 // for input and output of the interpreter and engine.
 // The prefix will be printed before every line.
-func (ui *UI) Run(opts ...Option) (err error) {
+func (ui *UI) Run(ctx context.Context, opts ...Option) (err error) {
 	// Make sure engine is set
 	if ui.eng == nil {
 		return ErrNoEngine
 	}
+	// Check if context is nil
+	if ctx == nil {
+		ctx = context.Background()
+	}
 
 	// Set options
 	for _, opt := range opts {
@@ -129,7 +133,9 @@ func (ui *UI) Run(opts ...Option) (err error) {
 
 	// Set signal handling
 	var cancel func()
-	ui.ctx, cancel = context.WithCancel(context.Background())
+	ui.ctx, cancel = context.WithCancel(ctx)
+	defer cancel()
+	defer close(ui.sigs)
 	go func() {
 		for sig := range ui.sigs {
 			handler, exists := ui.sigHandlers[sig]
@@ -159,6 +165,7 @@ func (ui *UI) Run(opts ...Option) (err error) {
 	}()
 	defer close(ui.reqCh)
 
+	var n int
 	for {
 		// Write prefix
 		_, err = ui.Write(nil)
@@ -168,11 +175,11 @@ func (ui *UI) Run(opts ...Option) (err error) {
 
 		// Read line
 		b := make([]byte, minRead)
-		_, err = ui.Read(b)
-		if err != nil {
-			if err == context.Canceled {
-				err = nil
-			}
+		n, err = ui.Read(b)
+		if err == context.Canceled {
+			return nil
+		}
+		if err != nil && err != io.EOF || n == 0 {
 			return
 		}
 
@@ -181,6 +188,11 @@ func (ui *UI) Run(opts ...Option) (err error) {
 		if status != 0 {
 			return
 		}
+
+		// Check if we hit EOF on previous read
+		if err == io.EOF {
+			return
+		}
 	}
 }
 
@@ -219,7 +231,10 @@ type readResp struct {
 func (ui *UI) readAsync(b []byte, readCh chan readResp) {
 	var resp readResp
 	resp.n, resp.err = ui.i.Read(b)
-	readCh <- resp
+	select {
+	case <-ui.ctx.Done():
+	case readCh <- resp:
+	}
 	close(readCh)
 }