Feat: support reading CLI options from a file

* Configuration is performed inside a YAML file.
* If the config file doesn't exist, it will be ignored.
* Command-line arguments take priority over options set in the file.

.gitignore

@@ -24,4 +24,4 @@ go.work
 /.envrc
 /bin
 /certs
-/result
+/result

cli/cli.go

@@ -19,6 +19,6 @@ func Run() error {
 	app.Authors = []*cli.Author{
 		{Name: "Murtaza Udaipurwala", Email: "murtaza@murtazau.xyz"},
 	}
-	app.Commands = []*cli.Command{runCmd, serveCmd}
+	app.Commands = []*cli.Command{runCmd(), serveCmd()}
 	return app.Run(os.Args)
 }

cli/config.go

@@ -0,0 +1,28 @@
+package cli
+
+import (
+	"fmt"
+	"os"
+
+	"github.com/urfave/cli/v2"
+	"github.com/urfave/cli/v2/altsrc"
+)
+
+func loadConfigIfExists(flags []cli.Flag) cli.BeforeFunc {
+	def := altsrc.NewMapInputSource("", make(map[interface{}]interface{}))
+	return altsrc.InitInputSourceWithContext(
+		flags,
+		func(ctx *cli.Context) (altsrc.InputSourceContext, error) {
+			path := ctx.Path("config")
+			stat, err := os.Stat(path)
+			if err != nil {
+				return def, nil
+			}
+			if stat.IsDir() {
+				return def, fmt.Errorf("provided config %q is a directory",
+					path)
+			}
+			return altsrc.NewYamlSourceFromFile(path)
+		},
+	)
+}

cli/run.go

@@ -6,96 +6,113 @@ import (
 	"github.com/murtaza-u/fleet/srv"
 
 	"github.com/urfave/cli/v2"
+	"github.com/urfave/cli/v2/altsrc"
 )
 
-var runCmd = &cli.Command{
-	Name:  "run",
-	Usage: "run the fleet server",
-	Args:  false,
-	Flags: []cli.Flag{
-		&cli.UintFlag{
+func runFlags() []cli.Flag {
+	return []cli.Flag{
+		altsrc.NewUintFlag(&cli.UintFlag{
 			Name:    "rpc-port",
 			Usage:   "Port for the gRPC server",
 			Value:   2035,
 			EnvVars: []string{"FLEET_RPC_PORT"},
-		},
-		&cli.UintFlag{
+		}),
+		altsrc.NewUintFlag(&cli.UintFlag{
 			Name:    "http-port",
 			Usage:   "Port for the http web server",
 			Value:   8080,
 			EnvVars: []string{"FLEET_HTTP_PORT"},
-		},
-		&cli.BoolFlag{
+		}),
+		altsrc.NewBoolFlag(&cli.BoolFlag{
 			Name:    "reflect",
 			Usage:   "Enable gRPC reflection",
 			EnvVars: []string{"FLEET_REFLECT"},
-		},
-		&cli.BoolFlag{
+		}),
+		altsrc.NewBoolFlag(&cli.BoolFlag{
 			Name:    "tls",
 			Usage:   "Enable server-side gRPC TLS",
 			EnvVars: []string{"FLEET_TLS"},
-		},
-		&cli.PathFlag{
+		}),
+		altsrc.NewPathFlag(&cli.PathFlag{
 			Name:      "certificate",
-			Usage:     "path to certificate file",
+			Usage:     "Path to certificate file",
 			Value:     filepath.Join("certs", "srv-cert.pem"),
 			TakesFile: true,
 			EnvVars:   []string{"FLEET_CERTIFICATE_PATH"},
-		},
-		&cli.PathFlag{
+		}),
+		altsrc.NewPathFlag(&cli.PathFlag{
 			Name:      "private-key",
-			Usage:     "path to private key file",
+			Usage:     "Path to private key file",
 			Value:     filepath.Join("certs", "srv-key.pem"),
 			TakesFile: true,
 			EnvVars:   []string{"FLEET_PRIVATE_KEY_FILE"},
-		},
-		&cli.Int64Flag{
+		}),
+		altsrc.NewInt64Flag(&cli.Int64Flag{
 			Name:    "max-http-request-body-size",
 			Usage:   "Maximum size of the HTTP request body",
 			Value:   1024 * 1024,
 			EnvVars: []string{"FLEET_MAX_HTTP_REQUEST_BODY_SIZE"},
-		},
-		&cli.IntFlag{
+		}),
+		altsrc.NewIntFlag(&cli.IntFlag{
 			Name:    "max-grpc-recv-size",
 			Usage:   "Maximum gRPC receive message size",
 			Value:   1024 * 1024,
 			EnvVars: []string{"FLEET_MAX_GRPC_RECV_SIZE"},
-		},
-		&cli.IntFlag{
+		}),
+		altsrc.NewIntFlag(&cli.IntFlag{
 			Name:    "max-grpc-send-size",
 			Usage:   "Maximum gRPC send message size.",
 			Value:   1024 * 1024,
 			EnvVars: []string{"FLEET_MAX_GRPC_SEND_SIZE"},
-		},
-		&cli.StringFlag{
+		}),
+		altsrc.NewStringFlag(&cli.StringFlag{
 			Name:    "serving-url-format",
 			Usage:   "Serving url format",
 			Value:   "http://%s.localhost:8080",
 			EnvVars: []string{"FLEET_SERVING_URL_FORMAT"},
+		}),
+		&cli.PathFlag{
+			Name:    "config",
+			Aliases: []string{"c"},
+			Usage:   "Path to config file",
+			Value:   filepath.Join(".", "config.yaml"),
+			EnvVars: []string{"FLEET_CONFIG_FILE"},
 		},
-	},
-	Action: func(ctx *cli.Context) error {
-		opts := []srv.OptFunc{
-			srv.WithRPCPort(uint16(ctx.Uint("rpc-port"))),
-			srv.WithHTTPPort(uint16(ctx.Uint("http-port"))),
-			srv.WithPathToCertificate(ctx.Path("certificate")),
-			srv.WithPathToPrivateKey(ctx.Path("private-key")),
-			srv.WithMaxRequestBodySize(ctx.Int64("max-http-request-body-size")),
-			srv.WithMaxMsgRecvSize(ctx.Int("max-grpc-recv-size")),
-			srv.WithMaxMsgRecvSize(ctx.Int("max-grpc-send-size")),
-			srv.WithServingUrlFormat(ctx.String("serving-url-format")),
-		}
-		if ctx.Bool("tls") {
-			opts = append(opts, srv.WithTLS())
-		}
-		if ctx.Bool("reflect") {
-			opts = append(opts, srv.WithReflection())
-		}
+	}
+}
+
+func runCmd() *cli.Command {
+	flags := runFlags()
 
-		srv, err := srv.New(opts...)
-		if err != nil {
-			return err
-		}
-		return srv.Run()
-	},
+	return &cli.Command{
+		Name:   "run",
+		Usage:  "Runs the fleet server",
+		Args:   false,
+		Flags:  flags,
+		Before: loadConfigIfExists(flags),
+		Action: func(ctx *cli.Context) error {
+			opts := []srv.OptFunc{
+				srv.WithRPCPort(uint16(ctx.Uint("rpc-port"))),
+				srv.WithHTTPPort(uint16(ctx.Uint("http-port"))),
+				srv.WithPathToCertificate(ctx.Path("certificate")),
+				srv.WithPathToPrivateKey(ctx.Path("private-key")),
+				srv.WithMaxRequestBodySize(ctx.Int64("max-http-request-body-size")),
+				srv.WithMaxMsgRecvSize(ctx.Int("max-grpc-recv-size")),
+				srv.WithMaxMsgRecvSize(ctx.Int("max-grpc-send-size")),
+				srv.WithServingUrlFormat(ctx.String("serving-url-format")),
+			}
+			if ctx.Bool("tls") {
+				opts = append(opts, srv.WithTLS())
+			}
+			if ctx.Bool("reflect") {
+				opts = append(opts, srv.WithReflection())
+			}
+
+			srv, err := srv.New(opts...)
+			if err != nil {
+				return err
+			}
+			return srv.Run()
+		},
+	}
 }

cli/serve.go

@@ -3,6 +3,7 @@ package cli
 import (
 	"errors"
 	"fmt"
+	"log"
 	"net/http"
 	"net/http/httputil"
 	"net/url"
@@ -13,40 +14,64 @@ import (
 
 	"github.com/lucasepe/codename"
 	"github.com/urfave/cli/v2"
+	"github.com/urfave/cli/v2/altsrc"
 )
 
-var serveCmd = &cli.Command{
-	Name:        "serve",
-	Usage:       "connect to the fleet server and serve incoming requests",
-	UsageText:   "[options] static|proxy",
-	Subcommands: []*cli.Command{staticCmd, proxyCmd},
-	Flags: []cli.Flag{
-		&cli.BoolFlag{
-			Name:  "tls",
-			Usage: "Use TLS to connect to the Fleet gRPC server",
-		},
-		&cli.StringFlag{
+func serveFlags() []cli.Flag {
+	conf, err := os.UserConfigDir()
+	if err != nil {
+		log.Fatal(err)
+	}
+	path := filepath.Join(conf, "fleet", "config.yaml")
+
+	return []cli.Flag{
+		altsrc.NewStringFlag(&cli.StringFlag{
 			Name:    "address",
-			Aliases: []string{"addr", "rpc-addr", "rpc-address"},
-			Usage:   "address(host:port) of the Fleet gRPC server",
+			Aliases: []string{"addr"},
+			Usage:   "Address(host:port) of the Fleet gRPC server",
 			Value:   "localhost:2035",
-		},
-		&cli.PathFlag{
+		}),
+		altsrc.NewBoolFlag(&cli.BoolFlag{
+			Name:  "tls",
+			Usage: "Use TLS to connect to the Fleet gRPC server",
+		}),
+		altsrc.NewPathFlag(&cli.PathFlag{
 			Name:      "ca-cert",
+			Usage:     "Path to the CA's certificate file",
 			Value:     filepath.Join("certs", "ca-cert.pem"),
 			TakesFile: true,
-		},
+		}),
 		&cli.StringFlag{
 			Name:    "propose-subdomain",
-			Aliases: []string{"subdomain", "propose", "p"},
-			Usage:   "propose a subdomain to register yourself for the current session",
+			Aliases: []string{"p"},
+			Usage:   "Propose a subdomain to register yourself for the current session",
 		},
-	},
+		&cli.PathFlag{
+			Name:      "config",
+			Aliases:   []string{"c"},
+			Usage:     "Path to config file",
+			Value:     path,
+			TakesFile: true,
+		},
+	}
+}
+
+func serveCmd() *cli.Command {
+	flags := serveFlags()
+
+	return &cli.Command{
+		Name:        "serve",
+		Usage:       "Connect to the fleet server and serve incoming requests",
+		UsageText:   "[options] static|proxy",
+		Subcommands: []*cli.Command{staticCmd, proxyCmd},
+		Flags:       flags,
+		Before:      loadConfigIfExists(flags),
+	}
 }
 
 var staticCmd = &cli.Command{
 	Name:      "static",
-	Usage:     "serves files from the provided directory",
+	Usage:     "Serves files from the provided directory",
 	UsageText: "[path]",
 	ArgsUsage: "[path]",
 	Args:      true,
@@ -80,7 +105,7 @@ var staticCmd = &cli.Command{
 
 var proxyCmd = &cli.Command{
 	Name:      "proxy",
-	Usage:     "proxies incoming requests to the provided URL",
+	Usage:     "Proxies incoming requests to the provided URL",
 	UsageText: "URL",
 	ArgsUsage: "URL",
 	Args:      true,

flake.nix

@@ -14,7 +14,7 @@
           pname = "fleet";
           version = version;
           src = ./.;
-          vendorHash = "sha256-N29GLrnkLQAZYuU5OzmV2QOAdwv4FWeLbzaJVKP+/J0=";
+          vendorHash = "sha256-TM9ZfQ/YfSYdLbdhDgJUMHbhFfm+iOc70zVRKclAjf0=";
           CGO_ENABLED = 0;
           subPackages = [ "cmd/fleet" ];
           nativeBuildInputs = [ pkgs.installShellFiles ];

go.mod

@@ -13,6 +13,7 @@ require (
 )
 
 require (
+	github.com/BurntSushi/toml v1.3.2 // indirect
 	github.com/cpuguy83/go-md2man/v2 v2.0.3 // indirect
 	github.com/davecgh/go-spew v1.1.1 // indirect
 	github.com/golang/protobuf v1.5.3 // indirect

go.sum

@@ -1,3 +1,5 @@
+github.com/BurntSushi/toml v1.3.2 h1:o7IhLm0Msx3BaB+n3Ag7L8EVlByGnpq14C4YWiu/gL8=
+github.com/BurntSushi/toml v1.3.2/go.mod h1:CxXYINrC8qIiEnFrOxCa7Jy5BFHlXnUU2pbicEuybxQ=
 github.com/cpuguy83/go-md2man/v2 v2.0.3 h1:qMCsGGgs+MAzDFyp9LpAe1Lqy/fY/qCovCm0qnXZOBM=
 github.com/cpuguy83/go-md2man/v2 v2.0.3/go.mod h1:tgQtvFlXSQOSOSIRvRPT7W67SCa46tRHOmNcaadrF8o=
 github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=