Add SUPFILE_DIR as default environment variable

This will allow Supfiles to be run different directories and
consistently resolve files relative to the Supfile.

This CL contains refactors the resolution order of environment
variables such that it's a bit easier to reason about.

Fixes #99

cmd/sup/main.go

@@ -109,6 +109,11 @@ func cmdUsage(conf *sup.Supfile) {
 func parseArgs(conf *sup.Supfile) (*sup.Network, []*sup.Command, error) {
 	var commands []*sup.Command
 
+	// In case of the conf.Env needs an initialization
+	if conf.Env == nil {
+		conf.Env = make(sup.EnvList, 0)
+	}
+
 	args := flag.Args()
 	if len(args) < 1 {
 		networkUsage(conf)
@@ -122,26 +127,14 @@ func parseArgs(conf *sup.Supfile) (*sup.Network, []*sup.Command, error) {
 		return nil, nil, ErrUnknownNetwork
 	}
 
-	// Parse CLI --env flag env vars, override values defined in Network env.
-	for _, env := range envVars {
-		if len(env) == 0 {
-			continue
-		}
-		i := strings.Index(env, "=")
-		if i < 0 {
-			if len(env) > 0 {
-				network.Env.Set(env, "")
-			}
-			continue
-		}
-		network.Env.Set(env[:i], env[i+1:])
-	}
-
-	hosts, err := network.ParseInventory()
+	hosts, err := network.ParseInventory(conf.Env)
 	if err != nil {
 		return nil, nil, err
 	}
 	network.Hosts = append(network.Hosts, hosts...)
+	if network.Env == nil {
+		network.Env = make(sup.EnvList, 0)
+	}
 
 	// Does the <network> have at least one host?
 	if len(network.Hosts) == 0 {
@@ -155,27 +148,9 @@ func parseArgs(conf *sup.Supfile) (*sup.Network, []*sup.Command, error) {
 		return nil, nil, ErrUsage
 	}
 
-	// In case of the network.Env needs an initialization
-	if network.Env == nil {
-		network.Env = make(sup.EnvList, 0)
-	}
-
 	// Add default env variable with current network
 	network.Env.Set("SUP_NETWORK", args[0])
 
-	// Add default nonce
-	network.Env.Set("SUP_TIME", time.Now().UTC().Format(time.RFC3339))
-	if os.Getenv("SUP_TIME") != "" {
-		network.Env.Set("SUP_TIME", os.Getenv("SUP_TIME"))
-	}
-
-	// Add user
-	if os.Getenv("SUP_USER") != "" {
-		network.Env.Set("SUP_USER", os.Getenv("SUP_USER"))
-	} else {
-		network.Env.Set("SUP_USER", os.Getenv("USER"))
-	}
-
 	for _, cmd := range args[1:] {
 		// Target?
 		target, isTarget := conf.Targets.Get(cmd)
@@ -248,7 +223,14 @@ func main() {
 			os.Exit(1)
 		}
 	}
-	conf, err := sup.NewSupfile(data)
+	conf, err := sup.NewSupfile(data,
+		// SUPFILE_DIR might change as sup invocations are chained.
+		sup.WithEnv("SUPFILE_DIR", filepath.Dir(supfile)),
+		// Add default nonce, but inherit from previous invocation.
+		sup.WithInheritEnv("SUP_TIME", time.Now().UTC().Format(time.RFC3339)),
+		// Add user, but inherit from previous invocation.
+		sup.WithInheritEnv("SUP_USER", os.Getenv("USER")),
+	)
 	if err != nil {
 		fmt.Fprintln(os.Stderr, err)
 		os.Exit(1)
@@ -331,15 +313,6 @@ func main() {
 		}
 	}
 
-	var vars sup.EnvList
-	for _, val := range append(conf.Env, network.Env...) {
-		vars.Set(val.Key, val.Value)
-	}
-	if err := vars.ResolveValues(); err != nil {
-		fmt.Fprintln(os.Stderr, err)
-		os.Exit(1)
-	}
-
 	// Parse CLI --env flag env vars, define $SUP_ENV and override values defined in Supfile.
 	var cliVars sup.EnvList
 	for _, env := range envVars {
@@ -349,11 +322,10 @@ func main() {
 		i := strings.Index(env, "=")
 		if i < 0 {
 			if len(env) > 0 {
-				vars.Set(env, "")
+				cliVars.Set(env, "")
 			}
 			continue
 		}
-		vars.Set(env[:i], env[i+1:])
 		cliVars.Set(env[:i], env[i+1:])
 	}
 
@@ -363,7 +335,7 @@ func main() {
 	for _, v := range cliVars {
 		supEnv += fmt.Sprintf(" -e %v=%q", v.Key, v.Value)
 	}
-	vars.Set("SUP_ENV", strings.TrimSpace(supEnv))
+	cliVars.Set("SUP_ENV", strings.TrimSpace(supEnv))
 
 	// Create new Stackup app.
 	app, err := sup.New(conf)
@@ -375,7 +347,7 @@ func main() {
 	app.Prefix(!disablePrefix)
 
 	// Run all the commands in the given network.
-	err = app.Run(network, vars, commands...)
+	err = app.Run(network, cliVars, commands...)
 	if err != nil {
 		fmt.Fprintln(os.Stderr, err)
 		os.Exit(1)

example/Supfile

@@ -14,6 +14,8 @@ env:
 networks:
   # Groups of hosts
   local:
+    env:
+      SUP_LOCAL: yessir
     hosts:
       - localhost
 
@@ -53,7 +55,7 @@ commands:
     upload:
       - src: ./
         dst: /tmp/$IMAGE
-    script: ./scripts/docker-build.sh
+    script: $SUPFILE_DIR/scripts/docker-build.sh
     once: true
 
   pull:
@@ -126,6 +128,10 @@ commands:
       curl -X POST --data-urlencode 'payload={"channel": "#_team_", "text": "['$SUP_NETWORK'] '$SUP_USER' deployed '$NAME'"}' \
         https://hooks.slack.com/services/X/Y/Z
 
+  env:
+    desc: Print environment
+    local: env
+
   bash:
     desc: Interactive shell on all hosts
     stdin: true

localhost.go

@@ -6,11 +6,9 @@ import (
 	"os"
 	"os/exec"
 	"os/user"
-
-	"github.com/pkg/errors"
 )
 
-// Client is a wrapper over the SSH connection/sessions.
+// LocalhostClient is a wrapper over the SSH connection/sessions.
 type LocalhostClient struct {
 	cmd     *exec.Cmd
 	user    string
@@ -105,15 +103,3 @@ func (c *LocalhostClient) WriteClose() error {
 func (c *LocalhostClient) Signal(sig os.Signal) error {
 	return c.cmd.Process.Signal(sig)
 }
-
-func ResolveLocalPath(cwd, path, env string) (string, error) {
-	// Check if file exists first. Use bash to resolve $ENV_VARs.
-	cmd := exec.Command("bash", "-c", env+"echo -n "+path)
-	cmd.Dir = cwd
-	resolvedFilename, err := cmd.Output()
-	if err != nil {
-		return "", errors.Wrap(err, "resolving path failed")
-	}
-
-	return string(resolvedFilename), nil
-}

ssh.go

@@ -15,7 +15,7 @@ import (
 	"golang.org/x/crypto/ssh/agent"
 )
 
-// Client is a wrapper over the SSH connection/sessions.
+// SSHClient is a wrapper over the SSH connection/sessions.
 type SSHClient struct {
 	conn         *ssh.Client
 	sess         *ssh.Session
@@ -219,16 +219,16 @@ func (c *SSHClient) Wait() error {
 }
 
 // DialThrough will create a new connection from the ssh server sc is connected to. DialThrough is an SSHDialer.
-func (sc *SSHClient) DialThrough(net, addr string, config *ssh.ClientConfig) (*ssh.Client, error) {
-	conn, err := sc.conn.Dial(net, addr)
+func (c *SSHClient) DialThrough(net, addr string, config *ssh.ClientConfig) (*ssh.Client, error) {
+	conn, err := c.conn.Dial(net, addr)
 	if err != nil {
 		return nil, err
 	}
-	c, chans, reqs, err := ssh.NewClientConn(conn, addr, config)
+	sc, chans, reqs, err := ssh.NewClientConn(conn, addr, config)
 	if err != nil {
 		return nil, err
 	}
-	return ssh.NewClient(c, chans, reqs), nil
+	return ssh.NewClient(sc, chans, reqs), nil
 
 }
 

sup.go

@@ -30,12 +30,18 @@ func New(conf *Supfile) (*Stackup, error) {
 // Run runs set of commands on multiple hosts defined by network sequentially.
 // TODO: This megamoth method needs a big refactor and should be split
 //       to multiple smaller methods.
-func (sup *Stackup) Run(network *Network, envVars EnvList, commands ...*Command) error {
+func (sup *Stackup) Run(network *Network, cliVars EnvList, commands ...*Command) error {
 	if len(commands) == 0 {
 		return errors.New("no commands to be run")
 	}
 
-	env := envVars.AsExport()
+	// Order is important here.
+	// Least specific (most general) env vars first,
+	// then the network specific ones and finally
+	// the command line vars.
+	// Semantics are last-write-wins.
+	env := append(sup.conf.Env, network.Env...)
+	env = append(env, cliVars...)
 
 	// Create clients for every host (either SSH or Localhost).
 	var bastion *SSHClient
@@ -58,7 +64,7 @@ func (sup *Stackup) Run(network *Network, envVars EnvList, commands ...*Command)
 			// Localhost client.
 			if host == "localhost" {
 				local := &LocalhostClient{
-					env: env + `export SUP_HOST="` + host + `";`,
+					env: env.AsExport() + `export SUP_HOST="` + host + `";`,
 				}
 				if err := local.Connect(host); err != nil {
 					errCh <- errors.Wrap(err, "connecting to localhost failed")
@@ -70,7 +76,7 @@ func (sup *Stackup) Run(network *Network, envVars EnvList, commands ...*Command)
 
 			// SSH client.
 			remote := &SSHClient{
-				env:   env + `export SUP_HOST="` + host + `";`,
+				env:   env.AsExport() + `export SUP_HOST="` + host + `";`,
 				user:  network.User,
 				color: Colors[i%len(Colors)],
 			}
@@ -112,7 +118,7 @@ func (sup *Stackup) Run(network *Network, envVars EnvList, commands ...*Command)
 	// Run command or run multiple commands defined by target sequentially.
 	for _, cmd := range commands {
 		// Translate command into task(s).
-		tasks, err := sup.createTasks(cmd, clients, env)
+		tasks, err := sup.createTasks(cmd, clients)
 		if err != nil {
 			return errors.Wrap(err, "creating task failed")
 		}

supfile.go

@@ -262,14 +262,47 @@ func (e ErrUnsupportedSupfileVersion) Error() string {
 	return fmt.Sprintf("%v\n\nCheck your Supfile version (available latest version: v0.5)", e.Msg)
 }
 
+// SupfileOption modifies a Supfile in some way and maybe returns an error.
+type SupfileOption func(*Supfile) error
+
+// WithInheritEnv exports the environment variable env as value, val, in the context of a supfile.
+// env will be read from the process runtime and the values here have precedence. This allows users
+// to chain Supfile invocation and only have the top-level value set the SUP_* env vars.
+func WithInheritEnv(env, val string) SupfileOption {
+	if envVal := os.Getenv(env); envVal != "" {
+		val = envVal
+	}
+	return WithEnv(env, val)
+}
+
+// WithEnv forces the environment variable env to val in the context of a Supfile.
+func WithEnv(env, val string) SupfileOption {
+	return func(s *Supfile) error {
+		for network := range s.Networks.nets {
+			n := s.Networks.nets[network]
+			n.Env.Set(env, val)
+			s.Networks.nets[network] = n
+		}
+		s.Env.Set(env, val)
+		return nil
+	}
+}
+
 // NewSupfile parses configuration file and returns Supfile or error.
-func NewSupfile(data []byte) (*Supfile, error) {
+func NewSupfile(data []byte, opts ...SupfileOption) (*Supfile, error) {
 	var conf Supfile
 
 	if err := yaml.Unmarshal(data, &conf); err != nil {
 		return nil, err
 	}
 
+	for _, opt := range opts {
+		err := opt(&conf)
+		if err != nil {
+			return nil, err
+		}
+	}
+
 	// API backward compatibility. Will be deprecated in v1.0.
 	switch conf.Version {
 	case "":
@@ -327,16 +360,28 @@ func NewSupfile(data []byte) (*Supfile, error) {
 	return &conf, nil
 }
 
+func (s *Supfile) ResolveLocalPath(cwd, path string) (string, error) {
+	// Check if file exists first. Use bash to resolve $ENV_VARs.
+	cmd := exec.Command("bash", "-c", s.Env.AsExport()+" echo -n "+path)
+	cmd.Dir = cwd
+	resolvedFilename, err := cmd.Output()
+	if err != nil {
+		return "", errors.Wrap(err, "resolving path failed")
+	}
+
+	return string(resolvedFilename), nil
+}
+
 // ParseInventory runs the inventory command, if provided, and appends
 // the command's output lines to the manually defined list of hosts.
-func (n Network) ParseInventory() ([]string, error) {
+func (n Network) ParseInventory(ctx EnvList) ([]string, error) {
 	if n.Inventory == "" {
 		return nil, nil
 	}
 
 	cmd := exec.Command("/bin/sh", "-c", n.Inventory)
 	cmd.Env = os.Environ()
-	cmd.Env = append(cmd.Env, n.Env.Slice()...)
+	cmd.Env = append(cmd.Env, append(ctx.Slice(), n.Env.Slice()...)...)
 	cmd.Stderr = os.Stderr
 	output, err := cmd.Output()
 	if err != nil {

task.go

@@ -17,7 +17,7 @@ type Task struct {
 	TTY     bool
 }
 
-func (sup *Stackup) createTasks(cmd *Command, clients []Client, env string) ([]*Task, error) {
+func (sup *Stackup) createTasks(cmd *Command, clients []Client) ([]*Task, error) {
 	var tasks []*Task
 
 	cwd, err := os.Getwd()
@@ -27,7 +27,7 @@ func (sup *Stackup) createTasks(cmd *Command, clients []Client, env string) ([]*
 
 	// Anything to upload?
 	for _, upload := range cmd.Upload {
-		uploadFile, err := ResolveLocalPath(cwd, upload.Src, env)
+		uploadFile, err := sup.conf.ResolveLocalPath(cwd, upload.Src)
 		if err != nil {
 			return nil, errors.Wrap(err, "upload: "+upload.Src)
 		}
@@ -64,7 +64,11 @@ func (sup *Stackup) createTasks(cmd *Command, clients []Client, env string) ([]*
 
 	// Script. Read the file as a multiline input command.
 	if cmd.Script != "" {
-		f, err := os.Open(cmd.Script)
+		script, err := sup.conf.ResolveLocalPath(cwd, cmd.Script)
+		if err != nil {
+			return nil, errors.Wrap(err, "can't resolve script path")
+		}
+		f, err := os.Open(script)
 		if err != nil {
 			return nil, errors.Wrap(err, "can't open script")
 		}
@@ -106,7 +110,7 @@ func (sup *Stackup) createTasks(cmd *Command, clients []Client, env string) ([]*
 	// Local command.
 	if cmd.Local != "" {
 		local := &LocalhostClient{
-			env: env + `export SUP_HOST="localhost";`,
+			env: sup.conf.Env.AsExport() + `export SUP_HOST="localhost";`,
 		}
 		local.Connect("localhost")
 		task := &Task{