Make pkg compatible with Go <1.20

Author: MDobak

xerrors_go120_test.go

@@ -0,0 +1,61 @@
+//go:build go1.20
+// +build go1.20
+
+package xerrors
+
+import (
+	"errors"
+	"fmt"
+	"testing"
+)
+
+func TestJoinf_Go120(t *testing.T) {
+	err1 := Message("first error")
+	err2 := Message("second error")
+	tests := []struct {
+		format string
+		args   []any
+		want   string
+	}{
+		{format: "multiple errors: %w: %w", args: []any{err1, err2}, want: "multiple errors: first error: second error"},
+	}
+	for n, tt := range tests {
+		t.Run(fmt.Sprintf("case-%d", n+1), func(t *testing.T) {
+			got := Joinf(tt.format, tt.args...)
+			if got == nil {
+				t.Errorf("Joinf(%q, %#v): expected non-nil error", tt.format, tt.args)
+				return
+			}
+			if got.Error() != tt.want {
+				t.Errorf("Joinf(%q, %#v): got: %q, want %q", tt.format, tt.args, got, tt.want)
+			}
+			if len(StackTrace(got)) != 0 {
+				t.Errorf("Joinf(%q, %#v): returned error must not contain a stack trace", tt.format, tt.args)
+			}
+			for _, v := range tt.args {
+				if err, ok := v.(error); ok {
+					if !errors.Is(got, err) {
+						t.Errorf("errors.Is(Joinf(errs...), err): must return true")
+					}
+				}
+			}
+		})
+	}
+}
+
+func TestJoinf_Unwrap(t *testing.T) {
+	err1 := Message("first error")
+	err2 := Message("second error")
+	got := Joinf("%w: %w", err1, err2)
+	unwrapper, ok := got.(interface{ Unwrap() error })
+	if !ok {
+		t.Fatalf("Join(err1, err2) must implement Unwrap()")
+	}
+	unwrapped := unwrapper.Unwrap()
+	if unwrapped == nil {
+		t.Fatalf("Join(err1, err2).Unwrap() must not return nil")
+	}
+	if !(!errors.Is(unwrapped, err1) && errors.Is(unwrapped, err2)) {
+		t.Fatalf("Join(err1, err2).Unwrap() must return the second error")
+	}
+}