Enhancement - Add option to add a state to an auth code url request

apps/confidential/confidential.go

@@ -343,7 +343,7 @@ func New(authority, clientID string, cred Credential, options ...Option) (Client
 
 // authCodeURLOptions contains options for AuthCodeURL
 type authCodeURLOptions struct {
-	claims, loginHint, tenantID, domainHint string
+	claims, loginHint, tenantID, domainHint, state string
 }
 
 // AuthCodeURLOption is implemented by options for AuthCodeURL
@@ -363,12 +363,36 @@ func (cca Client) AuthCodeURL(ctx context.Context, clientID, redirectURI string,
 	if err != nil {
 		return "", err
 	}
+	ap.State = o.state
 	ap.Claims = o.claims
 	ap.LoginHint = o.loginHint
 	ap.DomainHint = o.domainHint
 	return cca.base.AuthCodeURL(ctx, clientID, redirectURI, scopes, ap)
 }
 
+// WithState adds a user-generated state to the request.
+func WithState(state string) interface {
+	AuthCodeURLOption
+	options.CallOption
+} {
+	return struct {
+		AuthCodeURLOption
+		options.CallOption
+	}{
+		CallOption: options.NewCallOption(
+			func(a any) error {
+				switch t := a.(type) {
+				case *authCodeURLOptions:
+					t.state = state
+				default:
+					return fmt.Errorf("unexpected options type %T", a)
+				}
+				return nil
+			},
+		),
+	}
+}
+
 // WithLoginHint pre-populates the login prompt with a username.
 func WithLoginHint(username string) interface {
 	AuthCodeURLOption

apps/confidential/confidential_test.go

@@ -1256,6 +1256,46 @@ func TestWithLoginHint(t *testing.T) {
 	}
 }
 
+func TestWithState(t *testing.T) {
+	state := "abc-123-secure-string"
+	cred, err := NewCredFromSecret(fakeSecret)
+	if err != nil {
+		t.Fatal(err)
+	}
+	client, err := New(fakeAuthority, fakeClientID, cred, WithHTTPClient(&errorClient{}))
+	if err != nil {
+		t.Fatal(err)
+	}
+	client.base.Token.Resolver = &fake.ResolveEndpoints{}
+	for _, expectState := range []bool{true, false} {
+		t.Run(fmt.Sprint(expectState), func(t *testing.T) {
+			opts := []AuthCodeURLOption{}
+			if expectState {
+				opts = append(opts, WithState(state))
+			}
+			u, err := client.AuthCodeURL(context.Background(), "id", localhost, tokenScope, opts...)
+			if err != nil {
+				t.Fatal(err)
+			}
+			parsed, err := url.Parse(u)
+			if err != nil {
+				t.Fatal(err)
+			}
+			if !parsed.Query().Has("state") {
+				if !expectState {
+					return
+				}
+				t.Fatal("expected a state")
+			} else if !expectState {
+				t.Fatal("expected no state")
+			}
+			if actual := parsed.Query()["state"]; len(actual) != 1 || actual[0] != state {
+				t.Fatalf(`unexpected state "%v"`, actual)
+			}
+		})
+	}
+}
+
 func TestWithDomainHint(t *testing.T) {
 	domain := "contoso.com"
 	cred, err := NewCredFromSecret(fakeSecret)