feat: allow replacements in startup command

Author: liam-mackie

go.mod

@@ -4,6 +4,7 @@ go 1.21
 
 require (
 	github.com/pelletier/go-toml/v2 v2.2.1
+	github.com/petar-dambovaliev/aho-corasick v0.0.0-20250424160509-463d218d4745
 	github.com/stretchr/testify v1.9.0
 	github.com/urfave/cli/v2 v2.27.1
 )

go.sum

@@ -5,6 +5,8 @@ github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/pelletier/go-toml/v2 v2.2.1 h1:9TA9+T8+8CUCO2+WYnDLCgrYi9+omqKXyjDtosvtEhg=
 github.com/pelletier/go-toml/v2 v2.2.1/go.mod h1:1t835xjRzz80PqgE6HHgN2JOsmgYu/h4qDAS4n929Rs=
+github.com/petar-dambovaliev/aho-corasick v0.0.0-20250424160509-463d218d4745 h1:Vpr4VgAizEgEZsaMohpw6JYDP+i9Of9dmdY4ufNP6HI=
+github.com/petar-dambovaliev/aho-corasick v0.0.0-20250424160509-463d218d4745/go.mod h1:EHPiTAKtiFmrMldLUNswFwfZ2eJIYBHktdaUTZxYWRw=
 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 v2.1.0 h1:JIOH55/0cWyOuilr9/qlrm0BSXldqnqwMsf35Ld67mk=

replacer/replacer.go

@@ -0,0 +1,38 @@
+package replacer
+
+import (
+	ahocorasick "github.com/petar-dambovaliev/aho-corasick"
+)
+
+type Replacer interface {
+	Replace(command string, replacements map[string]string) string
+}
+
+type RealReplacer struct{}
+
+func NewReplacer() Replacer {
+	return &RealReplacer{}
+}
+
+func (r *RealReplacer) Replace(command string, replacements map[string]string) string {
+	dict := make([]string, 0, len(replacements))
+	replacementArray := make([]string, 0, len(replacements))
+	for k, v := range replacements {
+		dict = append(dict, k)
+		replacementArray = append(replacementArray, v)
+	}
+	ac := getAhoCorasick(dict)
+	replacer := ahocorasick.NewReplacer(ac)
+	return replacer.ReplaceAll(command, replacementArray)
+}
+
+func getAhoCorasick(dictionary []string) ahocorasick.AhoCorasick {
+	builder := ahocorasick.NewAhoCorasickBuilder(ahocorasick.Opts{
+		AsciiCaseInsensitive: true,
+		MatchOnlyWholeWords:  true,
+		MatchKind:            ahocorasick.LeftMostFirstMatch,
+		DFA:                  true,
+	})
+
+	return builder.Build(dictionary)
+}

replacer/replacer_test.go

@@ -0,0 +1,44 @@
+package replacer
+
+import (
+	"testing"
+)
+
+type testCase struct {
+	input    string
+	expected string
+}
+
+func TestReplace(t *testing.T) {
+	defaultReplacements := map[string]string{
+		"{}": "hello",
+		"~":  "/home/test",
+	}
+
+	testCases := map[string]testCase{
+		"multiple replacements": {
+			"~/.local/bin/rat {}{}",
+			"/home/test/.local/bin/rat hellohello",
+		},
+		"single replacement": {
+			"/bin/rat {}",
+			"/bin/rat hello",
+		},
+		"no replacement": {
+			"/bin/rat",
+			"/bin/rat",
+		},
+	}
+
+	for name, test := range testCases {
+		t.Run(name, func(t *testing.T) {
+			replacer := NewReplacer()
+			result := replacer.Replace(test.input, defaultReplacements)
+			if result != test.expected {
+				t.Errorf("expected %s, got %s", test.expected, result)
+			}
+		})
+	}
+	t.Run("", func(t *testing.T) {
+	})
+}

seshcli/seshcli.go

@@ -20,6 +20,7 @@ import (
 	"github.com/joshmedeski/sesh/v2/oswrap"
 	"github.com/joshmedeski/sesh/v2/pathwrap"
 	"github.com/joshmedeski/sesh/v2/previewer"
+	"github.com/joshmedeski/sesh/v2/replacer"
 	"github.com/joshmedeski/sesh/v2/runtimewrap"
 	"github.com/joshmedeski/sesh/v2/shell"
 	"github.com/joshmedeski/sesh/v2/startup"
@@ -39,6 +40,7 @@ func App(version string) cli.App {
 	home := home.NewHome(os)
 	shell := shell.NewShell(exec, home)
 	json := json.NewJson()
+	replacer := replacer.NewReplacer()
 
 	// resource dependencies
 	git := git.NewGit(shell)
@@ -60,7 +62,7 @@ func App(version string) cli.App {
 	// core dependencies
 	ls := ls.NewLs(config, shell)
 	lister := lister.NewLister(config, home, tmux, zoxide, tmuxinator)
-	startup := startup.NewStartup(config, lister, tmux, home)
+	startup := startup.NewStartup(config, lister, tmux, home, replacer)
 	namer := namer.NewNamer(path, git, home)
 	connector := connector.NewConnector(config, dir, home, lister, namer, startup, tmux, zoxide, tmuxinator)
 	icon := icon.NewIcon(config)

shell/shell_test.go

@@ -55,4 +55,14 @@ func TestShellPrepareCmd(t *testing.T) {
 		assert.Nil(t, err)
 		assert.Equal(t, []string{"/home/test/.local/bin/rat", "hello"}, cmdParts)
 	})
+
+	// This test case asserts the existing behaviour when the desired replacement is not separated by spaces
+	t.Run("should not use a partial match", func(t *testing.T) {
+		mockHome := new(home.MockHome)
+		shell := &RealShell{home: mockHome}
+		mockHome.On("ExpandHome", "~/.local/bin/rat").Return("/home/test/.local/bin/rat", nil)
+		cmdParts, err := shell.PrepareCmd("~/.local/bin/rat localVar={}", map[string]string{"{}": "hello"})
+		assert.Nil(t, err)
+		assert.Equal(t, []string{"/home/test/.local/bin/rat", "localVar={}"}, cmdParts)
+	})
 }

startup/config.go

@@ -10,7 +10,11 @@ func configStrategy(s *RealStartup, session model.SeshSession) (string, error) {
 	}
 
 	if exists && config.StartupCommand != "" {
-		return config.StartupCommand, nil
+		replacements := map[string]string{
+			"{}": session.Path,
+		}
+
+		return s.replacer.Replace(config.StartupCommand, replacements), nil
 	}
 	return "", nil
 }

startup/defaultconfig.go

@@ -9,7 +9,11 @@ func defaultConfigStrategy(s *RealStartup, session model.SeshSession) (string, e
 
 	defaultConfig := s.config.DefaultSessionConfig
 	if defaultConfig.StartupCommand != "" {
-		return defaultConfig.StartupCommand, nil
+		replacements := map[string]string{
+			"{}": session.Path,
+		}
+
+		return s.replacer.Replace(defaultConfig.StartupCommand, replacements), nil
 	}
 
 	return "", nil

startup/startup.go

@@ -6,6 +6,7 @@ import (
 	"github.com/joshmedeski/sesh/v2/home"
 	"github.com/joshmedeski/sesh/v2/lister"
 	"github.com/joshmedeski/sesh/v2/model"
+	"github.com/joshmedeski/sesh/v2/replacer"
 	"github.com/joshmedeski/sesh/v2/tmux"
 )
 
@@ -14,14 +15,17 @@ type Startup interface {
 }
 
 type RealStartup struct {
-	lister lister.Lister
-	tmux   tmux.Tmux
-	config model.Config
-	home   home.Home
+	lister   lister.Lister
+	tmux     tmux.Tmux
+	config   model.Config
+	home     home.Home
+	replacer replacer.Replacer
 }
 
-func NewStartup(config model.Config, lister lister.Lister, tmux tmux.Tmux, home home.Home) Startup {
-	return &RealStartup{lister, tmux, config, home}
+func NewStartup(
+	config model.Config, lister lister.Lister, tmux tmux.Tmux, home home.Home, replacer replacer.Replacer,
+) Startup {
+	return &RealStartup{lister, tmux, config, home, replacer}
 }
 
 func (s *RealStartup) Exec(session model.SeshSession) (string, error) {