Use ShortSource in errors thrown from Go

Author: fbogsany

aux.go

@@ -34,7 +34,7 @@ func countLevels(l *State) int {
 		le *= 2
 	}
 	for li < le {
-		m := (li + le)/2
+		m := (li + le) / 2
 		if Stack(l, m, &d) {
 			li = m + 1
 		} else {
@@ -169,7 +169,7 @@ func Where(l *State, level int) {
 	if Stack(l, level, &activationRecord) { // check function at level
 		Info(l, "Sl", &activationRecord)      // get info about it
 		if activationRecord.CurrentLine > 0 { // is there info?
-			PushString(l, fmt.Sprintf("%s:%d: ", activationRecord.Source, activationRecord.CurrentLine))
+			PushString(l, fmt.Sprintf("%s:%d: ", activationRecord.ShortSource, activationRecord.CurrentLine))
 			return
 		}
 	}

vm_test.go

@@ -2,6 +2,7 @@ package lua
 
 import (
 	"fmt"
+	"strings"
 	"testing"
 )
 
@@ -155,7 +156,7 @@ func TestError(t *testing.T) {
 			t.Error("error handler received no arguments")
 		} else if errorMessage, ok := ToString(l, -1); !ok {
 			t.Errorf("error handler received %s instead of string", TypeNameOf(l, -1))
-		} else if errorMessage != program+":1: error" {
+		} else if errorMessage != chunkID(program)+":1: error" {
 			t.Errorf("error handler received '%s' instead of 'error'", errorMessage)
 		}
 		errorHandled = true
@@ -168,6 +169,35 @@ func TestError(t *testing.T) {
 	}
 }
 
+func TestErrorf(t *testing.T) {
+	l := NewState()
+	BaseOpen(l)
+	program := "-- script that is bigger than the max ID size\nhelper()\n" + strings.Repeat("--", idSize)
+	expectedErrorMessage := chunkID(program) + ":2: error"
+	PushGoFunction(l, func(l *State) int {
+		Errorf(l, "error")
+		return 0
+	})
+	SetGlobal(l, "helper")
+	errorHandled := false
+	PushGoFunction(l, func(l *State) int {
+		if Top(l) == 0 {
+			t.Error("error handler received no arguments")
+		} else if errorMessage, ok := ToString(l, -1); !ok {
+			t.Errorf("error handler received %s instead of string", TypeNameOf(l, -1))
+		} else if errorMessage != expectedErrorMessage {
+			t.Errorf("error handler received '%s' instead of '%s'", errorMessage, expectedErrorMessage)
+		}
+		errorHandled = true
+		return 1
+	})
+	LoadString(l, program)
+	ProtectedCall(l, 0, 0, -2)
+	if !errorHandled {
+		t.Error("error not handled")
+	}
+}
+
 func Example() {
 	type step struct {
 		name     string