Add support for fish

internal/nix/shell.go

@@ -19,19 +19,25 @@ import (
 	"go.jetpack.io/devbox/internal/boxcli/featureflag"
 	"go.jetpack.io/devbox/internal/boxcli/usererr"
 	"go.jetpack.io/devbox/internal/debug"
+	"go.jetpack.io/devbox/internal/xdg"
 )
 
 //go:embed shellrc.tmpl
 var shellrcText string
 var shellrcTmpl = template.Must(template.New("shellrc").Parse(shellrcText))
 
+//go:embed shellrc_fish.tmpl
+var fishrcText string
+var fishrcTmpl = template.Must(template.New("shellrc_fish").Parse(fishrcText))
+
 type name string
 
 const (
 	shUnknown name = ""
 	shBash    name = "bash"
 	shZsh     name = "zsh"
 	shKsh     name = "ksh"
+	shFish    name = "fish"
 	shPosix   name = "posix"
 )
 
@@ -85,6 +91,9 @@ func DetectShell(opts ...ShellOption) (*Shell, error) {
 	case "ksh":
 		sh.name = shKsh
 		sh.userShellrcPath = rcfilePath(".kshrc")
+	case "fish":
+		sh.name = shFish
+		sh.userShellrcPath = fishConfig()
 	case "dash", "ash", "sh":
 		sh.name = shPosix
 		sh.userShellrcPath = os.Getenv("ENV")
@@ -172,6 +181,10 @@ func rcfilePath(basename string) string {
 	return filepath.Join(home, basename)
 }
 
+func fishConfig() string {
+	return filepath.Join(xdg.ConfigDir(), "fish", "config.fish")
+}
+
 func (s *Shell) Run(nixShellFilePath, nixFlakesFilePath string) error {
 	// Copy the current PATH into nix-shell, but clean and remove some
 	// directories that are incompatible.
@@ -342,6 +355,13 @@ func (s *Shell) shellRCOverrides(shellrc string) (extraEnv []string, extraArgs [
 		extraEnv = []string{fmt.Sprintf(`ZDOTDIR=%s`, shellescape.Quote(filepath.Dir(shellrc)))}
 	case shKsh, shPosix:
 		extraEnv = []string{fmt.Sprintf(`ENV=%s`, shellescape.Quote(shellrc))}
+	case shFish:
+		if featureflag.UnifiedEnv.Enabled() {
+			extraArgs = []string{"-C", ". " + shellrc}
+		} else {
+			// Needs quotes because it's wrapped inside the nix-shell command
+			extraArgs = []string{"-C", shellescape.Quote(". " + shellrc)}
+		}
 	}
 	return extraEnv, extraArgs
 }
@@ -394,7 +414,12 @@ func (s *Shell) writeDevboxShellrc() (path string, err error) {
 		pathPrepend = s.pkgConfigDir + ":" + pathPrepend
 	}
 
-	err = shellrcTmpl.Execute(shellrcf, struct {
+	tmpl := shellrcTmpl
+	if s.name == shFish {
+		tmpl = fishrcTmpl
+	}
+
+	err = tmpl.Execute(shellrcf, struct {
 		ProjectDir       string
 		OriginalInit     string
 		OriginalInitPath string

internal/nix/shellrc_fish.tmpl

@@ -0,0 +1,107 @@
+{{- /*
+
+This template defines the shellrc file that the devbox shell will run at
+startup when using the fish shell.
+
+It does _not_ include the user's original fish config, because unlike other
+shells, fish has multiple files as part of its config, and it's difficult
+to start a fish shell with a custom fish config. Instead, we let fish read
+the user's original config directly, and run these commands next.
+
+Devbox needs to ensure that the shell's PATH, prompt, and a few other things are
+set correctly after the user's shellrc runs. The commands to do this are in
+the "Devbox Post-init Hook" section.
+
+This file is useful for debugging shell errors, so try to keep the generated
+content readable.
+
+*/ -}}
+
+{{- if .UnifiedEnv -}}
+# Run the shell hook defined in shell.nix or flake.nix
+eval $shellHook
+
+{{ end -}}
+
+# Begin Devbox Post-init Hook
+
+{{- /*
+NOTE: fish_add_path doesn't play nicely with colon:separated:paths, and I'd rather not
+add string-splitting logic here nor parametrize computeNixEnv based on the shell being
+used. So here we (ab)use the fact that using "export" ahead of the variable definition
+makes fish do exactly what we want and behave in the same way as other shells.
+*/ -}}
+{{ if .UnifiedEnv -}}
+export PATH="$DEVBOX_PATH_PREPEND:$PATH"
+{{- else -}}
+export PATH="{{ .PathPrepend }}:$PATH"
+{{- end }}
+
+{{- /*
+Set the history file by setting fish_history. This is not exactly the same as with other
+shells, because we're not setting the file, but rather the session name, but it's a good
+enough approximation for now.
+*/ -}}
+{{- if .HistoryFile }}
+set fish_history devbox
+{{- end }}
+
+# Prepend to the prompt to make it clear we're in a devbox shell.
+functions -c fish_prompt __devbox_fish_prompt_orig
+function fish_prompt
+    echo "(devbox)" (__devbox_fish_prompt_orig)
+end
+
+{{- if .ShellStartTime }}
+# log that the shell is ready now!
+devbox log shell-ready {{ .ShellStartTime }}
+{{ end }}
+
+# End Devbox Post-init Hook
+
+# Switch to the directory where devbox.json config is
+set workingDir $(pwd)
+cd {{ .ProjectDir }}
+
+{{- if .PluginInitHook }}
+
+# Begin Plugin Init Hook
+
+{{ .PluginInitHook }}
+
+# End Plugin Init Hook
+
+{{- end }}
+
+{{- if .UserHook }}
+
+# Begin Devbox User Hook
+
+{{ .UserHook }}
+
+# End Devbox User Hook
+
+{{- end }}
+
+cd $workingDir
+
+{{- if .ShellStartTime }}
+# log that the shell is interactive now!
+devbox log shell-interactive {{ .ShellStartTime }}
+{{ end }}
+
+# Begin Script command
+
+{{- if .ScriptCommand }}
+
+function run_script
+    set workingDir $(pwd)
+    cd {{ .ProjectDir }}
+
+    {{  .ScriptCommand }}
+
+    cd $workingDir
+end
+{{- end }}
+
+# End Script command