support passing arguments to the started executable (#13)

README.md

@@ -37,6 +37,7 @@ The tool supports the following flags for more custom configuration:
 * `--glob-exclude, -ge` - Specifies a glob pattern for files and directories that should be excluded. Can be specified multiple times. The pattern works only for a single path segment (e.g. `vendor`, `.DS_Store`, `*_test.go`)
 * `--run, -r` - Specifies the folder that includes the `main` package to be run.
 * `--cache, -c` - Specifies a pre-build executable to use the first time. This is useful when using `gocrane` with Docker images that have the built executable available to avoid unnecessary initial builds on startup.
+* `--args` - Specifies arguments to pass when starting the built executable.
 
 By default `gocrane` excludes the following glob patterns:
 

go.mod

@@ -4,6 +4,7 @@ go 1.15
 
 require (
 	github.com/fsnotify/fsnotify v1.4.9
+	github.com/google/shlex v0.0.0-20191202100458-e7afc7fbc510
 	github.com/satori/go.uuid v1.2.0
 	github.com/urfave/cli/v2 v2.3.0
 	golang.org/x/sync v0.0.0-20201207232520-09787c993a3a

go.sum

@@ -3,6 +3,8 @@ github.com/cpuguy83/go-md2man/v2 v2.0.0-20190314233015-f79a8a8ca69d h1:U+s90UTSY
 github.com/cpuguy83/go-md2man/v2 v2.0.0-20190314233015-f79a8a8ca69d/go.mod h1:maD7wRr/U5Z6m/iR4s+kqSMx2CaBsrgA7czyZG/E6dU=
 github.com/fsnotify/fsnotify v1.4.9 h1:hsms1Qyu0jgnwNXIxa+/V/PDsU6CfLf6CNO8H7IWoS4=
 github.com/fsnotify/fsnotify v1.4.9/go.mod h1:znqG4EE+3YCdAaPaxE2ZRY/06pZUdp0tY4IgpuI1SZQ=
+github.com/google/shlex v0.0.0-20191202100458-e7afc7fbc510 h1:El6M4kTTCOh6aBiKaUGG7oYTSPP8MxqL4YI3kZKwcP4=
+github.com/google/shlex v0.0.0-20191202100458-e7afc7fbc510/go.mod h1:pupxD2MaaD3pAXIBCelhxNneeOaAeabZDe5s4K6zSpQ=
 github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
 github.com/russross/blackfriday/v2 v2.0.1 h1:lPqVAte+HuHNfhJ/0LC98ESWRz8afy9tM/0RK8m9o+Q=

internal/crane/run.go

@@ -20,6 +20,7 @@ type Settings struct {
 	ExcludeGlobs    []string
 	RunDir          string
 	CachedBuild     string
+	Args            []string
 	ShutdownTimeout time.Duration
 }
 
@@ -49,7 +50,7 @@ func Run(ctx context.Context, settings Settings) error {
 		return fmt.Errorf("failed to create builder: %w", err)
 	}
 	defer builder.Cleanup()
-	runner := project.NewRunner()
+	runner := project.NewRunner(settings.Args)
 
 	// Trigger an initial build by faking a change if we don't have
 	// a cached executable to use.

internal/flag/shlex.go

@@ -0,0 +1,37 @@
+// Package flag provides types to be used as command-line flag arguments with
+// the github.com/urfave/cli package.
+package flag
+
+import (
+	"fmt"
+
+	"github.com/google/shlex"
+)
+
+type ShlexStringSlice []string
+
+func (s *ShlexStringSlice) Set(value string) error {
+	v, err := shlex.Split(value)
+	if err != nil {
+		return err
+	}
+	*s = v
+	return nil
+}
+
+func (s *ShlexStringSlice) String() string {
+	return fmt.Sprintf("%v", []string(*s))
+}
+
+func ShlexStrings(val interface{}) []string {
+	s, ok := val.(*ShlexStringSlice)
+	if !ok {
+		return nil
+	}
+
+	if s == nil {
+		return nil
+	}
+
+	return []string(*s)
+}

internal/project/runner.go

@@ -9,11 +9,14 @@ import (
 	"syscall"
 )
 
-func NewRunner() *Runner {
-	return &Runner{}
+func NewRunner(args []string) *Runner {
+	return &Runner{
+		args: args,
+	}
 }
 
 type Runner struct {
+	args []string
 }
 
 func (r *Runner) Run(ctx context.Context, path string) (*Process, error) {
@@ -22,7 +25,7 @@ func (r *Runner) Run(ctx context.Context, path string) (*Process, error) {
 	}
 
 	runCtx, killFunc := context.WithCancel(ctx)
-	cmd := exec.CommandContext(runCtx, path)
+	cmd := exec.CommandContext(runCtx, path, r.args...)
 	cmd.Stdout = output
 	cmd.Stderr = output
 	if err := cmd.Start(); err != nil {

main.go

@@ -9,6 +9,7 @@ import (
 	"time"
 
 	"github.com/mokiat/gocrane/internal/crane"
+	"github.com/mokiat/gocrane/internal/flag"
 	"github.com/urfave/cli/v2"
 )
 
@@ -59,6 +60,12 @@ func main() {
 				Aliases: []string{"c"},
 				EnvVars: []string{"GOCRANE_CACHE"},
 			},
+			&cli.GenericFlag{
+				Name:    "args",
+				Usage:   "arguments to use when running the built executable",
+				EnvVars: []string{"GOCRANE_ARGS"},
+				Value:   &flag.ShlexStringSlice{},
+			},
 			&cli.DurationFlag{
 				Name:    "shutdown-timeout",
 				Usage:   "amount of time to wait for program to exit gracefully",
@@ -74,6 +81,7 @@ func main() {
 				ExcludeGlobs:    c.StringSlice("glob-exclude"),
 				RunDir:          c.String("run"),
 				CachedBuild:     c.String("cache"),
+				Args:            flag.ShlexStrings(c.Generic("args")),
 				ShutdownTimeout: c.Duration("shutdown-timeout"),
 			})
 		},