[shellenv] Remove nix profile from path, add shellenv command (#667)

## Summary

This removes nix profile from path when using unified environment. It
adds a new shellenv command and prints instructions when package is
added inside devbox shell.

@gcurtis I chose `eval $(devbox shellenv)` over `. <(devbox shellenv)`
to be consistent with the global instructions and also because it's easy
to miss the period when we print it. Not sure if there's a difference.
Also is this fish compatible or do we need different instructions for
fish?

Lastly, you'll notice `hash -r` is not there anymore. In my experiments
running `eval $(devbox shellenv)` causes the hash table to clear. I
believe this happens because `PATH` has changed, but I'm not 100% sure.

## How was it tested?

<img width="762" alt="image"
src="https://user-images.githubusercontent.com/544948/220529645-42a6578f-e733-4943-9478-bb415a904a40.png">


```bash
➜ devbox shell
➜ devbox add php82 php82Extensions.memcached
➜ which php
php not found
➜ eval $(devbox shellenv)
➜ which php
/nix/store/5yylkc71wmlzii2vl40021vgbfwqmajb-php-with-extensions-8.2.1/bin/php
➜ php -m | grep memcached
memcached
```

Author: mikeland73

devbox.go

@@ -31,7 +31,7 @@ type Devbox interface {
 	GenerateEnvrc(force bool, source string) error
 	Info(pkg string, markdown bool) error
 	ListScripts() []string
-	PrintEnv() (string, error)
+	PrintEnv(setFullPath bool) (string, error)
 	PrintGlobalList() error
 	PullGlobal(path string) error
 	// Remove removes Nix packages from the config so that it no longer exists in

devbox.json

@@ -13,7 +13,8 @@
       "build-linux": "GOOS=linux go build -o dist/devbox-linux cmd/devbox/main.go",
       "build-linux-amd64": "GOOS=linux GOARCH=amd64 go build -o dist/devbox-linux-amd64 cmd/devbox/main.go",
       "code": "code .",
-      "lint": "golangci-lint run"
+      "lint": "golangci-lint run",
+      "test": "go test -race -cover ./..."
     }
   },
   "nixpkgs": {

internal/boxcli/global.go

@@ -103,7 +103,7 @@ func globalPullCmd() *cobra.Command {
 func globalShellenvCmd() *cobra.Command {
 	return &cobra.Command{
 		Use:   "shellenv",
-		Short: "Print shell commands that add Devbox packages to your PATH",
+		Short: "Print shell commands that add global Devbox packages to your PATH",
 		Run: func(*cobra.Command, []string) {
 			fmt.Print(impl.GenerateShellEnv())
 		},

internal/boxcli/root.go

@@ -51,6 +51,7 @@ func RootCmd() *cobra.Command {
 	command.AddCommand(ServicesCmd())
 	command.AddCommand(SetupCmd())
 	command.AddCommand(ShellCmd())
+	command.AddCommand(shellEnvCmd())
 	command.AddCommand(VersionCmd())
 	command.AddCommand(genDocsCmd())
 

internal/boxcli/shell.go

@@ -65,7 +65,7 @@ func runShellCmd(cmd *cobra.Command, args []string, flags shellCmdFlags) error {
 	}
 
 	if flags.PrintEnv {
-		script, err := box.PrintEnv()
+		script, err := box.PrintEnv(false)
 		if err != nil {
 			return err
 		}

internal/boxcli/shellenv.go

@@ -0,0 +1,45 @@
+// Copyright 2022 Jetpack Technologies Inc and contributors. All rights reserved.
+// Use of this source code is governed by the license in the LICENSE file.
+
+package boxcli
+
+import (
+	"fmt"
+
+	"github.com/spf13/cobra"
+	"go.jetpack.io/devbox"
+)
+
+type shellEnvCmdFlags struct {
+	config configFlags
+}
+
+func shellEnvCmd() *cobra.Command {
+	flags := shellEnvCmdFlags{}
+	command := &cobra.Command{
+		Use:     "shellenv",
+		Short:   "Print shell commands that add Devbox packages to your PATH",
+		Args:    cobra.ExactArgs(0),
+		PreRunE: ensureNixInstalled,
+		RunE: func(cmd *cobra.Command, args []string) error {
+			s, err := shellEnvFunc(cmd, flags)
+			if err != nil {
+				return err
+			}
+			fmt.Fprintln(cmd.OutOrStdout(), s)
+			return nil
+		},
+	}
+
+	flags.config.register(command)
+	return command
+}
+
+func shellEnvFunc(cmd *cobra.Command, flags shellEnvCmdFlags) (string, error) {
+	box, err := devbox.Open(flags.config.path, cmd.ErrOrStderr())
+	if err != nil {
+		return "", err
+	}
+
+	return box.PrintEnv(true)
+}

internal/impl/devbox.go

@@ -443,7 +443,7 @@ func (d *Devbox) Exec(cmds ...string) error {
 	}
 }
 
-func (d *Devbox) PrintEnv() (string, error) {
+func (d *Devbox) PrintEnv(setFullPath bool) (string, error) {
 	script := ""
 	if featureflag.UnifiedEnv.Disabled() {
 		envs, err := plugin.Env(d.packages(), d.projectDir)
@@ -455,7 +455,7 @@ func (d *Devbox) PrintEnv() (string, error) {
 		}
 		return script, nil
 	}
-	envs, err := d.computeNixEnv(false)
+	envs, err := d.computeNixEnv(setFullPath)
 	if err != nil {
 		return "", err
 	}
@@ -760,8 +760,7 @@ func (d *Devbox) printPackageUpdateMessage(
 // 1. Start with the PATH as defined by nix (through nix print-dev-env).
 // 2. Clean the host PATH of any nix paths.
 // 3. Append the cleaned host PATH (tradeoff between reproducibility and ease of use).
-// 4. Prepend the devbox-managed nix profile path (which is needed to support devbox add inside shell--can we do without it?).
-// 5. Prepend the paths of any plugins (tbd whether it's actually needed).
+// 4. Prepend the paths of any plugins (tbd whether it's actually needed).
 func (d *Devbox) computeNixEnv(setFullPath bool) (map[string]string, error) {
 
 	vaf, err := nix.PrintDevEnv(d.nixShellFilePath(), d.nixFlakesFilePath())
@@ -826,18 +825,14 @@ func (d *Devbox) computeNixEnv(setFullPath bool) (map[string]string, error) {
 
 	// PATH handling.
 	pluginVirtenvPath := d.pluginVirtenvPath() // TODO: consider removing this; not being used?
-	nixProfilePath, err := d.profileBinPath()
-	if err != nil {
-		return nil, err
-	}
 	nixPath := env["PATH"]
 	hostPath := nix.CleanEnvPath(os.Getenv("PATH"), os.Getenv("NIX_PROFILES"))
 
 	// NOTE: for devbox shell, we need to defer the PATH setting, because a user's init file may prepend
 	// stuff to PATH, which will then take precedence over the devbox-set PATH. Instead, we do the path
 	// prepending in shellrc.tmpl. I chose to use the `setFullPath` variable instead of something like
 	// `isShell` to discourage the addition of more logic that makes shell/run differ more.
-	pathPrepend := fmt.Sprintf("%s:%s:%s", pluginVirtenvPath, nixProfilePath, nixPath)
+	pathPrepend := fmt.Sprintf("%s:%s", pluginVirtenvPath, nixPath)
 	if setFullPath {
 		env["PATH"] = fmt.Sprintf("%s:%s", pathPrepend, hostPath)
 	} else {

internal/plugin/info.go

@@ -10,6 +10,7 @@ import (
 	"github.com/fatih/color"
 	"github.com/pkg/errors"
 	"github.com/samber/lo"
+	"go.jetpack.io/devbox/internal/boxcli/featureflag"
 )
 
 func PrintReadme(
@@ -134,6 +135,14 @@ func printInfoInstructions(pkg string, w io.Writer) error {
 }
 
 func PrintEnvUpdateMessage(pkgs []string, projectDir string, w io.Writer) error {
+	if featureflag.UnifiedEnv.Enabled() {
+		color.New(color.FgYellow).Fprint(
+			w,
+			"\nTo update your shell and ensure your new packages are usable, "+
+				"please run:\n\neval $(devbox shellenv)\n\n\n",
+		)
+		return nil
+	}
 	commands := []string{"hash -r"}
 	for _, pkg := range pkgs {
 		if path := getEnvFilePathIfExist(pkg, projectDir); path != "" {

testscripts/run/path.test.txt

@@ -22,13 +22,10 @@ stdout '/some/clean/path'
 # Path contains plugin virtual env path
 stdout '.devbox/virtenv/bin'
 
-# Path contains devbox-managed nix profile path
-stdout '.devbox/nix/profile/default/bin'
-
 # Path contains path to installed nix packages
 stdout '-which-'
 
-# Verify PATH is set in correct order: virtual env path, nix profile, nix packages, host path.
-path.order '.devbox/virtenv/bin' '.devbox/nix/profile/default/bin' '-which-' 'some/clean/path'
+# Verify PATH is set in correct order: virtual env path nix packages, host path.
+path.order '.devbox/virtenv/bin' '-which-' 'some/clean/path'
 
-# TODO: verify that bashrc file prepends do not prepend before nix paths.
+# TODO: verify that bashrc file prepends do not prepend before nix paths.

testscripts/shell/shellenv.test.txt

@@ -0,0 +1,12 @@
+exec devbox init
+
+# test adding and running hello
+exec devbox add hello
+! exec hello
+! stdout .
+
+# source shellenv and test again
+exec devbox shellenv
+source.path
+exec hello
+stdout 'Hello, world!'