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-rw-r--r--sidecar/store.go329
-rw-r--r--sidecar/store_test.go164
2 files changed, 493 insertions, 0 deletions
diff --git a/sidecar/store.go b/sidecar/store.go
new file mode 100644
index 0000000..76e626f
--- /dev/null
+++ b/sidecar/store.go
@@ -0,0 +1,329 @@
+// Package sidecar stores vr's append-only JSONL log in a private jj change.
+//
+// The change is an anonymous direct child of root(), so it is visible and
+// durable in the jj repository without becoming part of project history or the
+// working copy. A repo-local revset alias names it and git.private-commits keeps
+// accidental --change pushes from publishing it.
+package sidecar
+
+import (
+ "errors"
+ "fmt"
+ "os"
+ "os/exec"
+ "path/filepath"
+ "strconv"
+ "strings"
+ "syscall"
+)
+
+const (
+ Alias = "vr_log"
+ LogFile = "vr-log.jsonl"
+ Description = "private: vr log"
+)
+
+var ErrNoLog = errors.New("vr log has not been initialized")
+
+// Store is a repository's vr log. Open is read-only with respect to jj; the
+// sidecar change and its config are created lazily by Append.
+type Store struct {
+ root string
+ lockPath string
+}
+
+// Open finds the jj workspace containing dir.
+func Open(dir string) (*Store, error) {
+ root, err := jjOutput(dir, "workspace", "root")
+ if err != nil {
+ return nil, err
+ }
+ root = strings.TrimSpace(root)
+ configPath, err := jjOutput(root, "config", "path", "--repo")
+ if err != nil {
+ return nil, err
+ }
+ return &Store{
+ root: root,
+ lockPath: filepath.Join(filepath.Dir(strings.TrimSpace(configPath)), "vr-agent-logger.lock"),
+ }, nil
+}
+
+func (s *Store) Root() string { return s.root }
+
+func (s *Store) String() string {
+ return fmt.Sprintf("jj sidecar %s:%s", Alias, LogFile)
+}
+
+// Read returns the current log. Before the first sidecar write it falls back
+// to a repo-root legacy log, which makes migration transparent.
+func (s *Store) Read() ([]byte, error) {
+ var data []byte
+ err := s.withLock(syscall.LOCK_SH, func() error {
+ rev, found, _, err := s.resolveExisting()
+ if err != nil {
+ return err
+ }
+ if found {
+ data, err = s.readRevision(rev)
+ return err
+ }
+ data, err = os.ReadFile(filepath.Join(s.root, LogFile))
+ if errors.Is(err, os.ErrNotExist) {
+ return ErrNoLog
+ }
+ return err
+ })
+ return data, err
+}
+
+// Generation is a cheap identity for the current contents, used by vrsite to
+// notice appends. A sidecar rewrite gets a new commit id.
+func (s *Store) Generation() (string, error) {
+ var generation string
+ err := s.withLock(syscall.LOCK_SH, func() error {
+ rev, found, _, err := s.resolveExisting()
+ if err != nil {
+ return err
+ }
+ if found {
+ generation, err = s.logValue(rev, "commit_id")
+ return err
+ }
+ info, err := os.Stat(filepath.Join(s.root, LogFile))
+ if errors.Is(err, os.ErrNotExist) {
+ generation = "empty"
+ return nil
+ }
+ if err != nil {
+ return err
+ }
+ generation = fmt.Sprintf("legacy:%d:%d", info.Size(), info.ModTime().UnixNano())
+ return nil
+ })
+ return generation, err
+}
+
+// Append serializes sidecar rewrites across vr processes. makePayload runs
+// while holding that lock and receives the complete current log, allowing note
+// numbering and reply validation to be atomic with the append.
+func (s *Store) Append(makePayload func(current []byte) ([]byte, error)) error {
+ return s.withLock(syscall.LOCK_EX, func() error {
+ rev, err := s.ensure()
+ if err != nil {
+ return err
+ }
+ sidecarData, err := s.readRevision(rev)
+ if err != nil {
+ return err
+ }
+ current := sidecarData
+ if len(current) == 0 {
+ legacy, legacyErr := os.ReadFile(filepath.Join(s.root, LogFile))
+ if legacyErr == nil {
+ current = legacy
+ } else if !errors.Is(legacyErr, os.ErrNotExist) {
+ return legacyErr
+ }
+ }
+ payload, err := makePayload(current)
+ if err != nil {
+ return err
+ }
+ if len(payload) == 0 {
+ return errors.New("refusing to append an empty vr log payload")
+ }
+
+ var appendData []byte
+ if len(sidecarData) == 0 && len(current) > 0 {
+ appendData = append(appendData, current...)
+ }
+ if len(current) > 0 && current[len(current)-1] != '\n' {
+ appendData = append(appendData, '\n')
+ }
+ appendData = append(appendData, payload...)
+ if appendData[len(appendData)-1] != '\n' {
+ appendData = append(appendData, '\n')
+ }
+ return s.runAppend(appendData)
+ })
+}
+
+func (s *Store) withLock(kind int, fn func() error) error {
+ if err := os.MkdirAll(filepath.Dir(s.lockPath), 0o755); err != nil {
+ return err
+ }
+ f, err := os.OpenFile(s.lockPath, os.O_CREATE|os.O_RDWR, 0o600)
+ if err != nil {
+ return err
+ }
+ defer f.Close()
+ if err := syscall.Flock(int(f.Fd()), kind); err != nil {
+ return err
+ }
+ defer syscall.Flock(int(f.Fd()), syscall.LOCK_UN) //nolint:errcheck
+ return fn()
+}
+
+func (s *Store) ensure() (string, error) {
+ rev, found, configured, err := s.resolveExisting()
+ if err != nil {
+ return "", err
+ }
+ if !found {
+ if _, err := s.jj("new", "--no-edit", "root()", "-m", Description); err != nil {
+ return "", err
+ }
+ ids, err := s.descriptionMatches()
+ if err != nil {
+ return "", err
+ }
+ if len(ids) != 1 {
+ return "", fmt.Errorf("created %q sidecar but found %d matching root children", Description, len(ids))
+ }
+ rev = ids[0]
+ }
+ if !configured {
+ if _, err := s.jj("config", "set", "--repo", "revset-aliases."+Alias, strconv.Quote(rev)); err != nil {
+ return "", err
+ }
+ }
+ private, err := s.jj("config", "get", "git.private-commits")
+ if err != nil {
+ return "", err
+ }
+ if !containsRevsetName(private, Alias) {
+ expr := fmt.Sprintf("(%s) | %s", strings.TrimSpace(private), Alias)
+ if _, err := s.jj("config", "set", "--repo", "git.private-commits", strconv.Quote(expr)); err != nil {
+ return "", err
+ }
+ }
+ return rev, nil
+}
+
+func (s *Store) resolveExisting() (rev string, found, configured bool, err error) {
+ configuredValue, configErr := s.jj("config", "get", "revset-aliases."+Alias)
+ if configErr == nil {
+ rev, err = s.logValue("exactly("+Alias+", 1)", "change_id")
+ if err != nil {
+ return "", false, true, fmt.Errorf("repo-local revset alias %s is invalid: %w", Alias, err)
+ }
+ valid := fmt.Sprintf("exactly(%s & root()+ & subject(exact:%s), 1)", Alias, strconv.Quote(Description))
+ if _, err := s.logValue(valid, "change_id"); err != nil {
+ return "", false, true, fmt.Errorf("repo-local revset alias %s=%q does not name vr's sidecar: %w",
+ Alias, strings.TrimSpace(configuredValue), err)
+ }
+ return rev, true, true, nil
+ }
+
+ ids, err := s.descriptionMatches()
+ if err != nil {
+ return "", false, false, err
+ }
+ switch len(ids) {
+ case 0:
+ return "", false, false, nil
+ case 1:
+ return ids[0], true, false, nil
+ default:
+ return "", false, false, fmt.Errorf("found %d root children described %q; cannot choose a vr sidecar", len(ids), Description)
+ }
+}
+
+func (s *Store) descriptionMatches() ([]string, error) {
+ revset := fmt.Sprintf("root()+ & subject(exact:%s)", strconv.Quote(Description))
+ out, err := s.jj("log", "-G", "-r", revset, "-T", "change_id ++ \"\\n\"")
+ if err != nil {
+ return nil, err
+ }
+ var ids []string
+ for _, id := range strings.Fields(out) {
+ ids = append(ids, id)
+ }
+ return ids, nil
+}
+
+func (s *Store) logValue(revset, template string) (string, error) {
+ out, err := s.jj("log", "-G", "-r", revset, "-T", template)
+ if err != nil {
+ return "", err
+ }
+ value := strings.TrimSpace(out)
+ if value == "" {
+ return "", fmt.Errorf("revision %q produced no %s", revset, template)
+ }
+ return value, nil
+}
+
+func (s *Store) readRevision(rev string) ([]byte, error) {
+ listed, err := s.jj("file", "list", "-r", rev, "--", LogFile)
+ if err != nil {
+ return nil, err
+ }
+ if strings.TrimSpace(listed) == "" {
+ return nil, nil
+ }
+ out, err := s.jj("file", "show", "-r", rev, "--", LogFile)
+ return []byte(out), err
+}
+
+func (s *Store) runAppend(data []byte) error {
+ f, err := os.CreateTemp(filepath.Dir(s.lockPath), "vr-log-append-*")
+ if err != nil {
+ return err
+ }
+ tmp := f.Name()
+ defer os.Remove(tmp) //nolint:errcheck
+ if _, err := f.Write(data); err != nil {
+ f.Close()
+ return err
+ }
+ if err := f.Close(); err != nil {
+ return err
+ }
+ _, err = s.jj("--config", "snapshot.auto-track=\"all()\"",
+ "--config", "snapshot.max-new-file-size=\"1GiB\"",
+ "run", "--clean", "--root", "-r", "exactly("+Alias+", 1)", "--",
+ "sh", "-c", "cat \"$1\" >> "+LogFile, "sh", tmp)
+ return err
+}
+
+func (s *Store) jj(args ...string) (string, error) {
+ return jjOutput(s.root, args...)
+}
+
+func jjOutput(dir string, args ...string) (string, error) {
+ full := append([]string{"--ignore-working-copy", "--no-pager"}, args...)
+ cmd := exec.Command("jj", full...)
+ cmd.Dir = dir
+ out, err := cmd.Output()
+ if err != nil {
+ message := strings.TrimSpace(string(out))
+ if ee, ok := err.(*exec.ExitError); ok {
+ message = strings.TrimSpace(string(ee.Stderr))
+ }
+ if message != "" {
+ return "", fmt.Errorf("jj %s: %w: %s", strings.Join(args, " "), err, message)
+ }
+ return "", fmt.Errorf("jj %s: %w", strings.Join(args, " "), err)
+ }
+ return string(out), nil
+}
+
+func containsRevsetName(expr, name string) bool {
+ for i := 0; i+len(name) <= len(expr); i++ {
+ if expr[i:i+len(name)] != name {
+ continue
+ }
+ before := i == 0 || !isNameByte(expr[i-1])
+ after := i+len(name) == len(expr) || !isNameByte(expr[i+len(name)])
+ if before && after {
+ return true
+ }
+ }
+ return false
+}
+
+func isNameByte(b byte) bool {
+ return b == '_' || b == '-' || b >= 'a' && b <= 'z' || b >= 'A' && b <= 'Z' || b >= '0' && b <= '9'
+}
diff --git a/sidecar/store_test.go b/sidecar/store_test.go
new file mode 100644
index 0000000..85f50e1
--- /dev/null
+++ b/sidecar/store_test.go
@@ -0,0 +1,164 @@
+package sidecar
+
+import (
+ "fmt"
+ "os"
+ "os/exec"
+ "path/filepath"
+ "strings"
+ "sync"
+ "testing"
+)
+
+func TestAppendCreatesPrivateUnrelatedSidecar(t *testing.T) {
+ repo := testRepo(t)
+ // Store must be independent of a user's restrictive auto-track setting.
+ testJJ(t, repo, "config", "set", "--repo", "snapshot.auto-track", `"none()"`)
+ testJJ(t, repo, "config", "set", "--repo", "git.private-commits", `"description(glob:'secret:*')"`)
+ before := testJJ(t, repo, "status")
+ store, err := Open(repo)
+ if err != nil {
+ t.Fatal(err)
+ }
+
+ if err := store.Append(func(current []byte) ([]byte, error) {
+ if len(current) != 0 {
+ t.Fatalf("new store contained %q", current)
+ }
+ return []byte("one\n"), nil
+ }); err != nil {
+ t.Fatal(err)
+ }
+ if err := store.Append(func(current []byte) ([]byte, error) {
+ if string(current) != "one\n" {
+ t.Fatalf("second append saw %q", current)
+ }
+ return []byte("two\n"), nil
+ }); err != nil {
+ t.Fatal(err)
+ }
+
+ got, err := store.Read()
+ if err != nil {
+ t.Fatal(err)
+ }
+ if string(got) != "one\ntwo\n" {
+ t.Fatalf("sidecar log = %q", got)
+ }
+ if after := testJJ(t, repo, "status"); after != before {
+ t.Fatalf("working copy changed:\n--- before\n%s--- after\n%s", before, after)
+ }
+ if _, err := os.Stat(filepath.Join(repo, LogFile)); !os.IsNotExist(err) {
+ t.Fatalf("log materialized in the project working copy: %v", err)
+ }
+
+ alias := strings.TrimSpace(testJJ(t, repo, "config", "get", "revset-aliases."+Alias))
+ if alias == "" {
+ t.Fatal("repo-local sidecar alias was not configured")
+ }
+ private := testJJ(t, repo, "config", "get", "git.private-commits")
+ if !containsRevsetName(private, Alias) {
+ t.Fatalf("private commits = %q, missing %s", private, Alias)
+ }
+ if !strings.Contains(private, "secret:*") {
+ t.Fatalf("private commits = %q, previous setting was overwritten", private)
+ }
+ parent := strings.TrimSpace(testJJ(t, repo, "log", "-G", "-r", "exactly("+Alias+", 1)",
+ "-T", "parents.map(|p| p.commit_id()).join(\"\")"))
+ if parent != strings.Repeat("0", 40) {
+ t.Fatalf("sidecar parent = %q, want virtual root", parent)
+ }
+}
+
+func TestLegacyLogIsReadThenImportedOnFirstAppend(t *testing.T) {
+ repo := testRepo(t)
+ legacy := []byte("legacy\n")
+ if err := os.WriteFile(filepath.Join(repo, LogFile), legacy, 0o644); err != nil {
+ t.Fatal(err)
+ }
+ store, err := Open(repo)
+ if err != nil {
+ t.Fatal(err)
+ }
+ if got, err := store.Read(); err != nil || string(got) != string(legacy) {
+ t.Fatalf("pre-migration read = %q, %v", got, err)
+ }
+ if err := store.Append(func(current []byte) ([]byte, error) {
+ if string(current) != string(legacy) {
+ t.Fatalf("migration callback saw %q", current)
+ }
+ return []byte("sidecar\n"), nil
+ }); err != nil {
+ t.Fatal(err)
+ }
+ if got, err := store.Read(); err != nil || string(got) != "legacy\nsidecar\n" {
+ t.Fatalf("migrated log = %q, %v", got, err)
+ }
+}
+
+func TestConcurrentAppendsAreSerialized(t *testing.T) {
+ repo := testRepo(t)
+ store, err := Open(repo)
+ if err != nil {
+ t.Fatal(err)
+ }
+ const writers = 6
+ errCh := make(chan error, writers)
+ var wg sync.WaitGroup
+ for range writers {
+ wg.Add(1)
+ go func() {
+ defer wg.Done()
+ errCh <- store.Append(func(current []byte) ([]byte, error) {
+ id := len(strings.Fields(string(current))) + 1
+ return []byte(fmt.Sprintf("%d\n", id)), nil
+ })
+ }()
+ }
+ wg.Wait()
+ close(errCh)
+ for err := range errCh {
+ if err != nil {
+ t.Fatal(err)
+ }
+ }
+ got, err := store.Read()
+ if err != nil {
+ t.Fatal(err)
+ }
+ if string(got) != "1\n2\n3\n4\n5\n6\n" {
+ t.Fatalf("serialized appends = %q", got)
+ }
+}
+
+func testRepo(t *testing.T) string {
+ t.Helper()
+ if _, err := exec.LookPath("jj"); err != nil {
+ t.Skip("jj not installed")
+ }
+ home := t.TempDir()
+ t.Setenv("HOME", home)
+ t.Setenv("JJ_USER", "test")
+ t.Setenv("JJ_EMAIL", "[email protected]")
+ repo := filepath.Join(home, "repo")
+ if err := os.Mkdir(repo, 0o755); err != nil {
+ t.Fatal(err)
+ }
+ cmd := exec.Command("jj", "git", "init")
+ cmd.Dir = repo
+ if out, err := cmd.CombinedOutput(); err != nil {
+ t.Fatalf("jj git init: %v\n%s", err, out)
+ }
+ return repo
+}
+
+func testJJ(t *testing.T, repo string, args ...string) string {
+ t.Helper()
+ cmd := exec.Command("jj", append([]string{"--ignore-working-copy", "--no-pager"}, args...)...)
+ cmd.Dir = repo
+ out, err := cmd.CombinedOutput()
+ if err != nil {
+ t.Fatalf("jj %s: %v\n%s", strings.Join(args, " "), err, out)
+ }
+ return string(out)
+}
generated by cgit v1.3 (git 2.53.0) at 2026-10-02 18:57:52 +0000