cmd/geth, jsre: improve the js command

geth js stopped the JS runtime after running the first input file
and blocked for pending callbacks. This commit makes it process
all files and enables quitting with Ctrl-C regardless of callbacks.

Error reporting is also improved. If a script fails to load, the error
is printed and includes the backtrace. package jsre now ensures that
otto is aware of the filename, the backtrace will contain them.

Before:

$ geth js bad.js; echo "exit $?"
... log messages ...
exit 0

After:

$ geth js bad.js; echo "exit $?"
... log messages ...
Fatal: JavaScript Error: Invalid number of input parameters
    at web3.js:3109:20
    at web3.js:4917:15
    at web3.js:4960:5
    at web3.js:4984:23
    at checkWork (bad.js:11:9)
    at bad.js:19:1

exit 1

2 files changed, 26 insertions, 12 deletions

diff --git a/cmd/geth/js.go b/cmd/geth/js.go
index 767b513c1..2b64303b2 100644
--- a/cmd/geth/js.go
+++ b/cmd/geth/js.go
@@ -123,7 +123,7 @@ func (self *jsre) batch(statement string) {
 	err := self.re.EvalAndPrettyPrint(statement)
 
 	if err != nil {
-		fmt.Printf("error: %v", err)
+		fmt.Printf("%v", jsErrorString(err))
 	}
 
 	if self.atexit != nil {
@@ -301,21 +301,19 @@ func (self *jsre) preloadJSFiles(ctx *cli.Context) error {
 		for _, file := range jsFiles {
 			filename := common.AbsolutePath(assetPath, strings.TrimSpace(file))
 			if err := self.re.Exec(filename); err != nil {
-				return fmt.Errorf("%s: %v", file, err)
+				return fmt.Errorf("%s: %v", file, jsErrorString(err))
 			}
 		}
 	}
 	return nil
 }
 
-// exec executes the JS file with the given filename and stops the JSRE
-func (self *jsre) exec(filename string) error {
-	if err := self.re.Exec(filename); err != nil {
-		self.re.Stop(false)
-		return fmt.Errorf("Javascript Error: %v", err)
+// jsErrorString adds a backtrace to errors generated by otto.
+func jsErrorString(err error) string {
+	if ottoErr, ok := err.(*otto.Error); ok {
+		return ottoErr.String()
 	}
-	self.re.Stop(true)
-	return nil
+	return err.Error()
 }
 
 func (self *jsre) interactive() {
diff --git a/cmd/geth/main.go b/cmd/geth/main.go
index 512a5f183..4f3946200 100644
--- a/cmd/geth/main.go
+++ b/cmd/geth/main.go
@@ -21,6 +21,7 @@ import (
 	"fmt"
 	"io/ioutil"
 	"os"
+	"os/signal"
 	"path/filepath"
 	"runtime"
 	"strconv"
@@ -353,7 +354,7 @@ func console(ctx *cli.Context) {
 	// preload user defined JS files into the console
 	err = repl.preloadJSFiles(ctx)
 	if err != nil {
-		utils.Fatalf("unable to preload JS file %v", err)
+		utils.Fatalf("%v", err)
 	}
 
 	// in case the exec flag holds a JS statement execute it and return
@@ -372,6 +373,7 @@ func execScripts(ctx *cli.Context) {
 	// Create and start the node based on the CLI flags
 	node := utils.MakeSystemNode(ClientIdentifier, nodeNameVersion, makeDefaultExtra(), ctx)
 	startNode(ctx, node)
+	defer node.Stop()
 
 	// Attach to the newly started node and execute the given scripts
 	client, err := node.Attach()
@@ -383,10 +385,24 @@ func execScripts(ctx *cli.Context) {
 		ctx.GlobalString(utils.RPCCORSDomainFlag.Name),
 		client, false)
 
+	// Run all given files.
 	for _, file := range ctx.Args() {
-		repl.exec(file)
+		if err = repl.re.Exec(file); err != nil {
+			break
+		}
 	}
-	node.Stop()
+	if err != nil {
+		utils.Fatalf("JavaScript Error: %v", jsErrorString(err))
+	}
+	// JS files loaded successfully.
+	// Wait for pending callbacks, but stop for Ctrl-C.
+	abort := make(chan os.Signal, 1)
+	signal.Notify(abort, os.Interrupt)
+	go func() {
+		<-abort
+		repl.re.Stop(false)
+	}()
+	repl.re.Stop(true)
 }
 
 // startNode boots up the system node and all registered protocols, after which