fix: avoid emitting version warning when connection error encountered (#3082)

codersdk/error.go

@@ -1,5 +1,11 @@
 package codersdk
 
+import (
+	"net"
+
+	"golang.org/x/xerrors"
+)
+
 // Response represents a generic HTTP response.
 type Response struct {
 	// Message is an actionable message that depicts actions the request took.
@@ -25,3 +31,16 @@ type ValidationError struct {
 	Field  string `json:"field" validate:"required"`
 	Detail string `json:"detail" validate:"required"`
 }
+
+// IsConnectionErr is a convenience function for checking if the source of an
+// error is due to a 'connection refused', 'no such host', etc.
+func IsConnectionErr(err error) bool {
+	var (
+		// E.g. no such host
+		dnsErr *net.DNSError
+		// Eg. connection refused
+		opErr *net.OpError
+	)
+
+	return xerrors.As(err, &dnsErr) || xerrors.As(err, &opErr)
+}

codersdk/error_test.go

@@ -0,0 +1,65 @@
+package codersdk_test
+
+import (
+	"net"
+	"os"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+	"golang.org/x/xerrors"
+
+	"github.com/coder/coder/codersdk"
+)
+
+func TestIsConnectionErr(t *testing.T) {
+	t.Parallel()
+
+	type tc = struct {
+		name           string
+		err            error
+		expectedResult bool
+	}
+
+	cases := []tc{
+		{
+			// E.g. "no such host"
+			name: "DNSError",
+			err: &net.DNSError{
+				Err:         "no such host",
+				Name:        "foofoo",
+				Server:      "1.1.1.1:53",
+				IsTimeout:   false,
+				IsTemporary: false,
+				IsNotFound:  true,
+			},
+			expectedResult: true,
+		},
+		{
+			// E.g. "connection refused"
+			name: "OpErr",
+			err: &net.OpError{
+				Op:     "dial",
+				Net:    "tcp",
+				Source: nil,
+				Addr:   nil,
+				Err:    &os.SyscallError{},
+			},
+			expectedResult: true,
+		},
+		{
+			name:           "OpaqueError",
+			err:            xerrors.Errorf("I'm opaque!"),
+			expectedResult: false,
+		},
+	}
+
+	for _, c := range cases {
+		c := c
+
+		t.Run(c.name, func(t *testing.T) {
+			t.Parallel()
+
+			require.Equal(t, c.expectedResult, codersdk.IsConnectionErr(c.err))
+		})
+	}
+}