devbox: clean up profile history after sync (#2449)

After syncing the flake packages to the profile, remove all old
generations of the Nix profile. This allows the Nix garbage collector to
eventually remove any old packages.

Opted for a Go implementation instead of calling `nix profile
wipe-history` because deleting the history is pretty simple and this is
faster.

Author: gcurtis

internal/devbox/nixprofile.go

@@ -5,6 +5,8 @@ import (
 	"errors"
 	"fmt"
 	"log/slog"
+	"os"
+	"path/filepath"
 	"strings"
 
 	"github.com/samber/lo"
@@ -84,5 +86,42 @@ func (d *Devbox) syncNixProfileFromFlake(ctx context.Context) error {
 			return fmt.Errorf("error installing packages in nix profile %s: %w", add, err)
 		}
 	}
+	if len(add) > 0 || len(remove) > 0 {
+		err := wipeProfileHistory(profilePath)
+		if err != nil {
+			// Log the error, but nothing terrible happens if this
+			// fails.
+			slog.DebugContext(ctx, "error cleaning up profile history", "err", err)
+		}
+	}
+	return nil
+}
+
+// wipeProfileHistory removes all old generations of a Nix profile, similar to
+// nix profile wipe-history. profile should be a path to the "default" symlink,
+// like .devbox/nix/profile/default.
+func wipeProfileHistory(profile string) error {
+	link, err := os.Readlink(profile)
+	if errors.Is(err, os.ErrNotExist) {
+		return nil
+	}
+	if err != nil {
+		return err
+	}
+
+	dir := filepath.Dir(profile)
+	entries, err := os.ReadDir(dir)
+	if err != nil {
+		return err
+	}
+	for _, dent := range entries {
+		if dent.Name() == "default" || dent.Name() == link {
+			continue
+		}
+		err := os.Remove(filepath.Join(dir, dent.Name()))
+		if err != nil && !errors.Is(err, os.ErrNotExist) {
+			return err
+		}
+	}
 	return nil
 }

testscripts/rm/multi.test.txt

@@ -10,6 +10,10 @@ exec devbox rm vim hello
 
 json.superset devbox.json expected.json
 
+# Check that profile history was cleaned up. There should only be
+# default and default-N-link.
+glob -count=2 .devbox/nix/profile/*
+
 -- expected.json --
 {
   "packages": []

testscripts/testrunner/testrunner.go

@@ -80,6 +80,54 @@ func copyFileCmd(script *testscript.TestScript, neg bool, args []string) {
 	script.Check(err)
 }
 
+func globCmd(script *testscript.TestScript, neg bool, args []string) {
+	count := -1
+	if neg {
+		count = 0
+	}
+	if len(args) != 0 {
+		after, ok := strings.CutPrefix(args[0], "-count=")
+		if ok {
+			var err error
+			count, err = strconv.Atoi(after)
+			if err != nil {
+				script.Fatalf("invalid -count=: %v", err)
+			}
+			if count < 1 {
+				script.Fatalf("invalid -count=: must be at least 1")
+			}
+			args = args[1:]
+		}
+	}
+	if len(args) == 0 {
+		script.Fatalf("usage: glob [-count=N] pattern")
+	}
+
+	var matches []string
+	for _, a := range args {
+		glob := script.MkAbs(a)
+		m, err := filepath.Glob(glob)
+		if err != nil {
+			script.Fatalf("invalid glob pattern: %v", err)
+		}
+		for _, match := range m {
+			script.Logf("glob %q matched: %s", glob, match)
+		}
+		matches = append(matches, m...)
+	}
+
+	// -1 means that no -count= was given, so we want at least 1 match.
+	if count == -1 {
+		if len(matches) == 0 && !neg {
+			script.Fatalf("no matches for globs %q, want at least 1", strings.Join(args, " "))
+		}
+		return
+	}
+	if len(matches) != count {
+		script.Fatalf("got %d matches for globs %q, want %d", len(matches), strings.Join(args, " "), count)
+	}
+}
+
 func getTestscriptParams(dir string) testscript.Params {
 	return testscript.Params{
 		Dir:                 dir,
@@ -91,6 +139,7 @@ func getTestscriptParams(dir string) testscript.Params {
 			"devboxjson.packages.contains": assertDevboxJSONPackagesContains,
 			"devboxlock.packages.contains": assertDevboxLockPackagesContains,
 			"env.path.len":                 assertPathLength,
+			"glob":                         globCmd,
 			"json.superset":                assertJSONSuperset,
 			"path.order":                   assertPathOrder,
 			"source.path":                  sourcePath,