extract: process interface wrapper method with variadic parameter

Fixes #1055

extract/extract.go

@@ -202,7 +202,15 @@ func (e *Extractor) genContent(importPath string, p *types.Package) ([]byte, err
 						if args[j] = v.Name(); args[j] == "" {
 							args[j] = fmt.Sprintf("a%d", j)
 						}
-						params[j] = args[j] + " " + types.TypeString(v.Type(), qualify)
+						// process interface method variadic parameter
+						if sign.Variadic() && j == len(args)-1 { // check is last arg
+							// only replace the first "[]" to "..."
+							at := types.TypeString(v.Type(), qualify)[2:]
+							params[j] = args[j] + " ..." + at
+							args[j] += "..."
+						} else {
+							params[j] = args[j] + " " + types.TypeString(v.Type(), qualify)
+						}
 					}
 					arg := "(" + strings.Join(args, ", ") + ")"
 					param := "(" + strings.Join(params, ", ") + ")"

extract/extract_test.go

@@ -85,6 +85,41 @@ func TestPackages(t *testing.T) {
 			importPath: "guthib.com/baz",
 			expected:   expectedOutput,
 		},
+		{
+			desc:       "using relative path, interface method parameter is variadic",
+			wd:         "./testdata/7/src/guthib.com/variadic",
+			arg:        "../variadic",
+			importPath: "guthib.com/variadic",
+			expected: `
+// Code generated by 'yaegi extract guthib.com/variadic'. DO NOT EDIT.
+
+package variadic
+
+import (
+	"guthib.com/variadic"
+	"reflect"
+)
+
+func init() {
+	Symbols["guthib.com/variadic"] = map[string]reflect.Value{
+		// type definitions
+		"Variadic": reflect.ValueOf((*variadic.Variadic)(nil)),
+
+		// interface wrapper definitions
+		"_Variadic": reflect.ValueOf((*_guthib_com_variadic_Variadic)(nil)),
+	}
+}
+
+// _guthib_com_variadic_Variadic is an interface wrapper for Variadic type
+type _guthib_com_variadic_Variadic struct {
+	WCall func(method string, args ...[]interface{}) (interface{}, error)
+}
+
+func (W _guthib_com_variadic_Variadic) Call(method string, args ...[]interface{}) (interface{}, error) {
+	return W.WCall(method, args...)
+}
+`[1:],
+		},
 	}
 
 	for _, test := range testCases {

extract/testdata/7/src/guthib.com/variadic/go.mod

@@ -0,0 +1 @@
+module guthib.com/baz-baz/variadic

extract/testdata/7/src/guthib.com/variadic/variadic.go

@@ -0,0 +1,5 @@
+package variadic
+
+type Variadic interface {
+	Call(method string, args ...[]interface{}) (interface{}, error)
+}