feat: add standard CLI options

cli.go

@@ -0,0 +1,50 @@
+/*
+Copyright 2026 The Crossplane Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package function
+
+import "github.com/crossplane/function-sdk-go/logging"
+
+// CLI provides standard flags and environment variables for Composition
+// Functions. Embed it in your own struct to add custom flags.
+//
+//	type CLI struct {
+//	    function.CLI `kong:"embed"`
+//	    MyFlag string `default:"foo" env:"MY_FLAG" help:"My custom flag."`
+//	}
+type CLI struct {
+	Address            string `default:":9443"            env:"ADDRESS"                                                                                                       help:"Address at which to listen for gRPC connections."`
+	Debug              bool   `env:"DEBUG"                help:"Emit debug logs in addition to info logs."                                                                    short:"d"`
+	Insecure           bool   `env:"INSECURE"             help:"Run without mTLS credentials. If you supply this flag --tls-server-certs-dir will be ignored."`
+	MaxRecvMessageSize int    `default:"4"                env:"MAX_RECV_MESSAGE_SIZE"                                                                                         help:"Maximum size of received messages in MB."`
+	Network            string `default:"tcp"              env:"NETWORK"                                                                                                       help:"Network on which to listen for gRPC connections."`
+	TLSCertsDir        string `env:"TLS_SERVER_CERTS_DIR" help:"Directory containing server certs (tls.key, tls.crt) and the CA used to verify client certificates (ca.crt)."`
+}
+
+// StandardOptions returns the ServeOptions derived from standard CLI flags.
+func (c *CLI) StandardOptions() []ServeOption {
+	return []ServeOption{
+		Listen(c.Network, c.Address),
+		MTLSCertificates(c.TLSCertsDir),
+		Insecure(c.Insecure),
+		MaxRecvMessageSize(c.MaxRecvMessageSize * 1024 * 1024),
+	}
+}
+
+// Logger returns a new logger configured from CLI flags.
+func (c *CLI) Logger() (logging.Logger, error) {
+	return NewLogger(c.Debug)
+}