internal/jsre: fix completion of globals

It didn't complete 'St' to 'String' for some reason. Now it does,
and the code is much simpler.

internal/jsre/completion.go

@@ -35,47 +35,29 @@ func (jsre *JSRE) CompleteKeywords(line string) []string {
 
 func getCompletions(vm *goja.Runtime, line string) (results []string) {
 	parts := strings.Split(line, ".")
-	objRef := "this"
-	prefix := line
-
 	if len(parts) == 0 {
 		return nil
 	}
 
-	// Figure out which is the right-most fully named object
-	// in the line. e.g. if line = "x.y.z" and "x.y" is an
-	// object, and that its keys are "zebu" and "zebra", then
-	// objRef will be set to "y" and obj will reference "x.y".
-	v := vm.Get(parts[0])
-	var obj *goja.Object = v.ToObject(vm)
-	switch {
-	case obj != nil && len(parts) > 1: // "x.y.z" case
-		objRef = strings.Join(parts[0:len(parts)-1], ".")
-		prefix = parts[len(parts)-1]
-		for _, part := range parts[1 : len(parts)-1] {
-			v = obj.Get(part)
+	// Find the right-most fully named object in the line. e.g. if line = "x.y.z"
+	// and "x.y" is an object, obj will reference "x.y".
+	obj := vm.GlobalObject()
+	for i := 0; i < len(parts)-1; i++ {
+		v := obj.Get(parts[i])
 		if v == nil {
-				return nil
+			return nil // No object was found
 		}
 		obj = v.ToObject(vm)
 	}
-	case obj != nil:
-		// In this case, there is no "." chain, so the
-		// the right-most object is assumed to be `this`.
-		obj = vm.GlobalObject()
-	default: // No object was found
-		return nil
-	}
 
-	// Go over the keys of the right-most object (which could
-	// be `this`) and retain those keys that are prefixed by
-	// `prefix`. e.g. if line = "x.y.z", that "x.y" exists
-	// and has keys "zebu", "zebra" and "platypus", then only
-	// "zebu" and "zebra" will be added to `results`.
+	// Go over the keys of the object and retain the keys matching prefix.
+	// Example: if line = "x.y.z" and "x.y" exists and has keys "zebu", "zebra"
+	// and "platypus", then "x.y.zebu" and "x.y.zebra" will be added to results.
+	prefix := parts[len(parts)-1]
 	iterOwnAndConstructorKeys(vm, obj, func(k string) {
 		if strings.HasPrefix(k, prefix) {
-			if objRef == "this" {
-				results = append(results, line)
+			if len(parts) == 1 {
+				results = append(results, k)
 			} else {
 				results = append(results, strings.Join(parts[:len(parts)-1], ".")+"."+k)
 			}

internal/jsre/completion_test.go

@@ -41,6 +41,10 @@ func TestCompleteKeywords(t *testing.T) {
 		input string
 		want  []string
 	}{
+		{
+			input: "St",
+			want:  []string{"String"},
+		},
 		{
 			input: "x",
 			want:  []string{"x."},