remove fmt.Errorf

package_test.go

@@ -8,6 +8,8 @@ import (
 	"reflect"
 	"runtime"
 	"testing"
+
+	"github.com/pkg/errors"
 )
 
 func testContext(t *testing.T, opts ...func(*Context) error) *Context {
@@ -28,13 +30,14 @@ func TestResolvePackage(t *testing.T) {
 		pkg: "a",
 	}, {
 		pkg: "localimport",
-		err: fmt.Errorf(`import "../localimport": relative import not supported`),
+		err: &importErr{path: "../localimport", msg: "relative import not supported"},
 	}}
 	proj := testProject(t)
 	for _, tt := range tests {
 		ctx, err := NewContext(proj, tt.opts...)
 		defer ctx.Destroy()
 		_, err = ctx.ResolvePackage(tt.pkg)
+		err = errors.Cause(err)
 		if !reflect.DeepEqual(err, tt.err) {
 			t.Errorf("ResolvePackage(%q): want: %v, got %v", tt.pkg, tt.err, err)
 		}

resolver.go

@@ -72,17 +72,26 @@ type importer struct {
 	Root string // root directory
 }
 
+type importErr struct {
+	path string
+	msg  string
+}
+
+func (e *importErr) Error() string {
+	return fmt.Sprintf("import %q: %v", e.path, e.msg)
+}
+
 func (i *importer) Import(path string) (*build.Package, error) {
 	if path == "" {
-		return nil, fmt.Errorf("import %q: invalid import path", path)
+		return nil, errors.WithStack(&importErr{path: path, msg: "invalid import path"})
 	}
 
 	if path == "." || path == ".." || strings.HasPrefix(path, "./") || strings.HasPrefix(path, "../") {
-		return nil, fmt.Errorf("import %q: relative import not supported", path)
+		return nil, errors.WithStack(&importErr{path: path, msg: "relative import not supported"})
 	}
 
 	if strings.HasPrefix(path, "/") {
-		return nil, fmt.Errorf("import %q: cannot import absolute path", path)
+		return nil, errors.WithStack(&importErr{path: path, msg: "cannot import absolute path"})
 	}
 
 	var p *build.Package