Update tengo vendor and load the stdlib. Fixes #789 (#792)

vendor/github.com/d5/tengo/compiler/bytecode_decode.go

@@ -0,0 +1,97 @@
+package compiler
+
+import (
+	"encoding/gob"
+	"fmt"
+	"io"
+
+	"github.com/d5/tengo/objects"
+)
+
+// Decode reads Bytecode data from the reader.
+func (b *Bytecode) Decode(r io.Reader, modules *objects.ModuleMap) error {
+	if modules == nil {
+		modules = objects.NewModuleMap()
+	}
+
+	dec := gob.NewDecoder(r)
+
+	if err := dec.Decode(&b.FileSet); err != nil {
+		return err
+	}
+	// TODO: files in b.FileSet.File does not have their 'set' field properly set to b.FileSet
+	// as it's private field and not serialized by gob encoder/decoder.
+
+	if err := dec.Decode(&b.MainFunction); err != nil {
+		return err
+	}
+
+	if err := dec.Decode(&b.Constants); err != nil {
+		return err
+	}
+	for i, v := range b.Constants {
+		fv, err := fixDecoded(v, modules)
+		if err != nil {
+			return err
+		}
+		b.Constants[i] = fv
+	}
+
+	return nil
+}
+
+func fixDecoded(o objects.Object, modules *objects.ModuleMap) (objects.Object, error) {
+	switch o := o.(type) {
+	case *objects.Bool:
+		if o.IsFalsy() {
+			return objects.FalseValue, nil
+		}
+		return objects.TrueValue, nil
+	case *objects.Undefined:
+		return objects.UndefinedValue, nil
+	case *objects.Array:
+		for i, v := range o.Value {
+			fv, err := fixDecoded(v, modules)
+			if err != nil {
+				return nil, err
+			}
+			o.Value[i] = fv
+		}
+	case *objects.ImmutableArray:
+		for i, v := range o.Value {
+			fv, err := fixDecoded(v, modules)
+			if err != nil {
+				return nil, err
+			}
+			o.Value[i] = fv
+		}
+	case *objects.Map:
+		for k, v := range o.Value {
+			fv, err := fixDecoded(v, modules)
+			if err != nil {
+				return nil, err
+			}
+			o.Value[k] = fv
+		}
+	case *objects.ImmutableMap:
+		modName := moduleName(o)
+		if mod := modules.GetBuiltinModule(modName); mod != nil {
+			return mod.AsImmutableMap(modName), nil
+		}
+
+		for k, v := range o.Value {
+			// encoding of user function not supported
+			if _, isUserFunction := v.(*objects.UserFunction); isUserFunction {
+				return nil, fmt.Errorf("user function not decodable")
+			}
+
+			fv, err := fixDecoded(v, modules)
+			if err != nil {
+				return nil, err
+			}
+			o.Value[k] = fv
+		}
+	}
+
+	return o, nil
+}