Add local cargo registry type

- serve sparse index and config.json for local cargo repos from a cargo_index table
- add Web API publish, yank and unyank under the local repo api root
- drop index lines when the crate file is deleted

internal/api/v1/cargo.go

@@ -0,0 +1,148 @@
+package v1
+
+import (
+	"bytes"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"io"
+	"log/slog"
+	"net/http"
+
+	"github.com/go-chi/chi/v5"
+
+	"git.unkin.net/unkin/artifactapi/internal/database"
+	"git.unkin.net/unkin/artifactapi/internal/provider"
+	"git.unkin.net/unkin/artifactapi/internal/provider/cargo"
+	"git.unkin.net/unkin/artifactapi/pkg/models"
+)
+
+// This file implements the cargo registry Web API (publish, yank, unyank) for
+// local cargo repositories. config.json points api at /api/v1/local/<repo>, so
+// cargo appends its own /api/v1/crates/... below that.
+
+const maxCratePublish = 64 << 20
+
+func (h *ProxyHandler) localCargoRemote(r *http.Request) (*models.Remote, bool) {
+	remote, err := h.db.GetRemote(r.Context(), chi.URLParam(r, "localName"))
+	if err != nil {
+		return nil, false
+	}
+	return remote, remote.RepoType == models.RepoTypeLocal && remote.PackageType == models.PackageCargo
+}
+
+func cargoError(w http.ResponseWriter, status int, format string, args ...any) {
+	w.Header().Set("Content-Type", "application/json")
+	w.WriteHeader(status)
+	_ = json.NewEncoder(w).Encode(map[string]any{
+		"errors": []map[string]string{{"detail": fmt.Sprintf(format, args...)}},
+	})
+}
+
+func cargoOK(w http.ResponseWriter, v any) {
+	w.Header().Set("Content-Type", "application/json")
+	w.WriteHeader(http.StatusOK)
+	_ = json.NewEncoder(w).Encode(v)
+}
+
+func (h *ProxyHandler) cargoPublish(w http.ResponseWriter, r *http.Request) {
+	remote, ok := h.localCargoRemote(r)
+	if !ok {
+		cargoError(w, http.StatusNotFound, "no local cargo registry %q", chi.URLParam(r, "localName"))
+		return
+	}
+	ctx := r.Context()
+
+	body, err := io.ReadAll(io.LimitReader(r.Body, maxCratePublish+1))
+	if err != nil {
+		cargoError(w, http.StatusBadRequest, "read body: %v", err)
+		return
+	}
+	if len(body) > maxCratePublish {
+		cargoError(w, http.StatusRequestEntityTooLarge, "publish body exceeds %d bytes", maxCratePublish)
+		return
+	}
+	meta, crate, err := cargo.ParsePublish(body)
+	if err != nil {
+		cargoError(w, http.StatusBadRequest, "%v", err)
+		return
+	}
+	line, err := cargo.NewIndexLine(meta, crate)
+	if err != nil {
+		cargoError(w, http.StatusBadRequest, "%v", err)
+		return
+	}
+
+	existing, err := h.db.ListCargoIndexEntries(ctx, remote.Name, meta.Name)
+	if err != nil {
+		cargoError(w, http.StatusInternalServerError, "%v", err)
+		return
+	}
+	for _, e := range existing {
+		if e.Name != meta.Name {
+			cargoError(w, http.StatusBadRequest, "crate %q already exists as %q", meta.Name, e.Name)
+			return
+		}
+		if e.Version == meta.Vers {
+			cargoError(w, http.StatusConflict, "crate version `%s@%s` already exists", meta.Name, meta.Vers)
+			return
+		}
+	}
+
+	lineJSON, err := json.Marshal(line)
+	if err != nil {
+		cargoError(w, http.StatusInternalServerError, "%v", err)
+		return
+	}
+
+	path := cargo.CratePath(meta.Name, meta.Vers)
+	result, err := h.cas.Store(ctx, bytes.NewReader(crate), "application/gzip")
+	if err != nil {
+		cargoError(w, http.StatusInternalServerError, "store failed: %v", err)
+		return
+	}
+	if err := h.db.UpsertBlob(ctx, result.ContentHash, result.S3Key, result.SizeBytes, "application/gzip"); err != nil {
+		cargoError(w, http.StatusInternalServerError, "record blob: %v", err)
+		return
+	}
+	if err := h.db.CreateLocalFile(ctx, remote.Name, path, result.ContentHash); err != nil {
+		if errors.Is(err, database.ErrAlreadyExists) {
+			cargoError(w, http.StatusConflict, "crate version `%s@%s` already exists", meta.Name, meta.Vers)
+			return
+		}
+		cargoError(w, http.StatusInternalServerError, "record file: %v", err)
+		return
+	}
+	entry := &provider.CargoIndexEntry{RepoName: remote.Name, FilePath: path, Name: meta.Name, Version: meta.Vers, Line: string(lineJSON)}
+	if err := h.db.InsertCargoIndexEntry(ctx, entry); err != nil {
+		// Drop the file so a retry is not rejected as a duplicate.
+		_ = h.db.DeleteLocalFile(ctx, remote.Name, path)
+		cargoError(w, http.StatusInternalServerError, "record index: %v", err)
+		return
+	}
+
+	slog.Info("cargo: published", "repo", remote.Name, "crate", meta.Name, "version", meta.Vers)
+	cargoOK(w, map[string]any{"warnings": map[string][]string{"invalid_categories": {}, "invalid_badges": {}, "other": {}}})
+}
+
+func (h *ProxyHandler) cargoYank(yanked bool) http.HandlerFunc {
+	return func(w http.ResponseWriter, r *http.Request) {
+		remote, ok := h.localCargoRemote(r)
+		if !ok {
+			cargoError(w, http.StatusNotFound, "no local cargo registry %q", chi.URLParam(r, "localName"))
+			return
+		}
+		name, version := chi.URLParam(r, "crate"), chi.URLParam(r, "version")
+		found, err := h.db.SetCargoYanked(r.Context(), remote.Name, name, version, yanked)
+		if err != nil {
+			cargoError(w, http.StatusInternalServerError, "%v", err)
+			return
+		}
+		if !found {
+			cargoError(w, http.StatusNotFound, "crate version `%s@%s` not found", name, version)
+			return
+		}
+		slog.Info("cargo: yank updated", "repo", remote.Name, "crate", name, "version", version, "yanked", yanked)
+		cargoOK(w, map[string]bool{"ok": true})
+	}
+}

internal/api/v1/proxy.go

@@ -41,6 +41,9 @@ func (h *ProxyHandler) Routes() chi.Router {
 	r := chi.NewRouter()
 	r.Get("/remote/{remoteName}/*", h.handleProxy)
 	r.Get("/local/{localName}/*", h.handleLocal)
+	r.Put("/local/{localName}/api/v1/crates/new", h.cargoPublish)
+	r.Delete("/local/{localName}/api/v1/crates/{crate}/{version}/yank", h.cargoYank(true))
+	r.Put("/local/{localName}/api/v1/crates/{crate}/{version}/unyank", h.cargoYank(false))
 	r.Get("/virtual/{virtualName}/*", h.handleVirtual)
 	return r
 }

internal/database/cargo_index.go

@@ -0,0 +1,56 @@
+package database
+
+import (
+	"context"
+	"strings"
+
+	"git.unkin.net/unkin/artifactapi/internal/provider"
+)
+
+func (db *DB) InsertCargoIndexEntry(ctx context.Context, e *provider.CargoIndexEntry) error {
+	_, err := db.Pool.Exec(ctx, `
+		INSERT INTO cargo_index (repo_name, file_path, name, version, line, yanked)
+		VALUES ($1, $2, $3, $4, $5, $6)
+	`, e.RepoName, e.FilePath, e.Name, e.Version, e.Line, e.Yanked)
+	return err
+}
+
+func (db *DB) ListCargoIndexEntries(ctx context.Context, repoName, name string) ([]provider.CargoIndexEntry, error) {
+	rows, err := db.Pool.Query(ctx, `
+		SELECT repo_name, file_path, name, version, line, yanked
+		FROM cargo_index
+		WHERE repo_name = $1 AND lower(name) = $2
+		ORDER BY id
+	`, repoName, strings.ToLower(name))
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+
+	var result []provider.CargoIndexEntry
+	for rows.Next() {
+		var e provider.CargoIndexEntry
+		if err := rows.Scan(&e.RepoName, &e.FilePath, &e.Name, &e.Version, &e.Line, &e.Yanked); err != nil {
+			return nil, err
+		}
+		result = append(result, e)
+	}
+	return result, rows.Err()
+}
+
+// SetCargoYanked reports false when no such crate version exists.
+func (db *DB) SetCargoYanked(ctx context.Context, repoName, name, version string, yanked bool) (bool, error) {
+	tag, err := db.Pool.Exec(ctx, `
+		UPDATE cargo_index SET yanked = $4
+		WHERE repo_name = $1 AND lower(name) = $2 AND version = $3
+	`, repoName, strings.ToLower(name), version, yanked)
+	if err != nil {
+		return false, err
+	}
+	return tag.RowsAffected() > 0, nil
+}
+
+func (db *DB) DeleteCargoIndexEntry(ctx context.Context, repoName, filePath string) error {
+	_, err := db.Pool.Exec(ctx, `DELETE FROM cargo_index WHERE repo_name = $1 AND file_path = $2`, repoName, filePath)
+	return err
+}

internal/database/database_test.go

@@ -425,3 +425,38 @@ func TestRPMMetadata(t *testing.T) {
 		t.Fatalf("list rpm rows: %v %v", len(rows), err)
 	}
 }
+
+func TestCargoIndex(t *testing.T) {
+	requireDB(t)
+	for _, v := range []string{"0.1.0", "0.2.0"} {
+		if err := testDB.InsertCargoIndexEntry(ctx(), &provider.CargoIndexEntry{
+			RepoName: "cargo-db", FilePath: "crates/Unkin-Hello/Unkin-Hello-" + v + ".crate",
+			Name: "Unkin-Hello", Version: v, Line: `{"vers":"` + v + `"}`,
+		}); err != nil {
+			t.Fatal(err)
+		}
+	}
+
+	found, err := testDB.SetCargoYanked(ctx(), "cargo-db", "unkin-hello", "0.1.0", true)
+	if err != nil || !found {
+		t.Fatalf("yank: found=%v err=%v", found, err)
+	}
+	if found, _ := testDB.SetCargoYanked(ctx(), "cargo-db", "unkin-hello", "9.9.9", true); found {
+		t.Error("yank of a missing version reported found")
+	}
+
+	entries, err := testDB.ListCargoIndexEntries(ctx(), "cargo-db", "unkin-hello")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(entries) != 2 || entries[0].Version != "0.1.0" || !entries[0].Yanked || entries[1].Yanked {
+		t.Fatalf("entries = %+v", entries)
+	}
+
+	if err := testDB.DeleteCargoIndexEntry(ctx(), "cargo-db", entries[0].FilePath); err != nil {
+		t.Fatal(err)
+	}
+	if entries, _ = testDB.ListCargoIndexEntries(ctx(), "cargo-db", "UNKIN-HELLO"); len(entries) != 1 {
+		t.Fatalf("after delete: %+v", entries)
+	}
+}

internal/provider/cargo/local.go

@@ -0,0 +1,303 @@
+package cargo
+
+import (
+	"context"
+	"crypto/sha256"
+	"encoding/binary"
+	"encoding/hex"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"log/slog"
+	"net/http"
+	"strings"
+
+	"git.unkin.net/unkin/artifactapi/internal/provider"
+)
+
+// publishDep is a dependency as cargo sends it in the publish metadata.
+type publishDep struct {
+	Name               string   `json:"name"`
+	VersionReq         string   `json:"version_req"`
+	Features           []string `json:"features"`
+	Optional           bool     `json:"optional"`
+	DefaultFeatures    bool     `json:"default_features"`
+	Target             *string  `json:"target"`
+	Kind               string   `json:"kind"`
+	Registry           *string  `json:"registry"`
+	ExplicitNameInToml *string  `json:"explicit_name_in_toml"`
+}
+
+// PublishMeta is the JSON half of a `PUT /api/v1/crates/new` body; fields the
+// index does not carry are ignored.
+type PublishMeta struct {
+	Name        string              `json:"name"`
+	Vers        string              `json:"vers"`
+	Deps        []publishDep        `json:"deps"`
+	Features    map[string][]string `json:"features"`
+	Links       *string             `json:"links"`
+	RustVersion *string             `json:"rust_version"`
+}
+
+type indexDep struct {
+	Name            string   `json:"name"`
+	Req             string   `json:"req"`
+	Features        []string `json:"features"`
+	Optional        bool     `json:"optional"`
+	DefaultFeatures bool     `json:"default_features"`
+	Target          *string  `json:"target"`
+	Kind            string   `json:"kind"`
+	Registry        *string  `json:"registry,omitempty"`
+	Package         *string  `json:"package,omitempty"`
+}
+
+// IndexLine is one line of a sparse index file.
+type IndexLine struct {
+	Name        string              `json:"name"`
+	Vers        string              `json:"vers"`
+	Deps        []indexDep          `json:"deps"`
+	Cksum       string              `json:"cksum"`
+	Features    map[string][]string `json:"features"`
+	Features2   map[string][]string `json:"features2,omitempty"`
+	Yanked      bool                `json:"yanked"`
+	Links       *string             `json:"links,omitempty"`
+	V           int                 `json:"v,omitempty"`
+	RustVersion *string             `json:"rust_version,omitempty"`
+}
+
+// ParsePublish splits a publish body: u32le JSON length, JSON, u32le crate length, crate.
+func ParsePublish(body []byte) (PublishMeta, []byte, error) {
+	var meta PublishMeta
+	jsonBytes, rest, err := lengthPrefixed(body)
+	if err != nil {
+		return meta, nil, fmt.Errorf("metadata: %w", err)
+	}
+	crate, rest, err := lengthPrefixed(rest)
+	if err != nil {
+		return meta, nil, fmt.Errorf("crate: %w", err)
+	}
+	if len(rest) != 0 {
+		return meta, nil, errors.New("trailing bytes after crate")
+	}
+	if err := json.Unmarshal(jsonBytes, &meta); err != nil {
+		return meta, nil, fmt.Errorf("metadata: %w", err)
+	}
+	return meta, crate, nil
+}
+
+func lengthPrefixed(b []byte) ([]byte, []byte, error) {
+	if len(b) < 4 {
+		return nil, nil, errors.New("truncated length")
+	}
+	n := binary.LittleEndian.Uint32(b)
+	b = b[4:]
+	if uint64(n) > uint64(len(b)) {
+		return nil, nil, errors.New("truncated body")
+	}
+	return b[:n], b[n:], nil
+}
+
+// NewIndexLine validates the metadata and translates it into index form.
+func NewIndexLine(meta PublishMeta, crate []byte) (IndexLine, error) {
+	if !validName(meta.Name) {
+		return IndexLine{}, fmt.Errorf("invalid crate name %q", meta.Name)
+	}
+	if !validVersion(meta.Vers) {
+		return IndexLine{}, fmt.Errorf("invalid version %q", meta.Vers)
+	}
+	sum := sha256.Sum256(crate)
+	line := IndexLine{
+		Name:        meta.Name,
+		Vers:        meta.Vers,
+		Deps:        make([]indexDep, 0, len(meta.Deps)),
+		Cksum:       hex.EncodeToString(sum[:]),
+		Features:    map[string][]string{},
+		Links:       meta.Links,
+		RustVersion: meta.RustVersion,
+	}
+	for _, d := range meta.Deps {
+		dep := indexDep{
+			Name:            d.Name,
+			Req:             d.VersionReq,
+			Features:        d.Features,
+			Optional:        d.Optional,
+			DefaultFeatures: d.DefaultFeatures,
+			Target:          d.Target,
+			Kind:            d.Kind,
+			Registry:        d.Registry,
+		}
+		if dep.Features == nil {
+			dep.Features = []string{}
+		}
+		if dep.Kind == "" {
+			dep.Kind = "normal"
+		}
+		if d.ExplicitNameInToml != nil && *d.ExplicitNameInToml != "" {
+			pkg := d.Name
+			dep.Name, dep.Package = *d.ExplicitNameInToml, &pkg
+		}
+		line.Deps = append(line.Deps, dep)
+	}
+	// Older cargo cannot parse dep:/?/ feature syntax, so those features live in
+	// features2 behind v:2, as on crates.io.
+	for name, vals := range meta.Features {
+		if vals == nil {
+			vals = []string{}
+		}
+		if usesNewFeatureSyntax(vals) {
+			if line.Features2 == nil {
+				line.Features2 = map[string][]string{}
+			}
+			line.Features2[name] = vals
+			continue
+		}
+		line.Features[name] = vals
+	}
+	if line.Features2 != nil {
+		line.V = 2
+	}
+	return line, nil
+}
+
+func usesNewFeatureSyntax(vals []string) bool {
+	for _, v := range vals {
+		if strings.HasPrefix(v, "dep:") || strings.Contains(v, "?/") {
+			return true
+		}
+	}
+	return false
+}
+
+func validName(name string) bool {
+	if name == "" || len(name) > 64 {
+		return false
+	}
+	for i, c := range name {
+		alpha := (c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z')
+		if i == 0 && !alpha {
+			return false
+		}
+		if !alpha && (c < '0' || c > '9') && c != '-' && c != '_' {
+			return false
+		}
+	}
+	return true
+}
+
+func validVersion(v string) bool {
+	if v == "" || len(v) > 128 || !strings.ContainsAny(v[:1], "0123456789") {
+		return false
+	}
+	return strings.Trim(v, "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789.-+") == ""
+}
+
+// IndexPath is the sparse-index file path for a crate name.
+func IndexPath(name string) string {
+	n := strings.ToLower(name)
+	switch len(n) {
+	case 0:
+		return ""
+	case 1:
+		return "1/" + n
+	case 2:
+		return "2/" + n
+	case 3:
+		return "3/" + n[:1] + "/" + n
+	}
+	return n[:2] + "/" + n[2:4] + "/" + n
+}
+
+// CratePath is where a published .crate is stored, matching config.json's dl.
+func CratePath(name, version string) string {
+	return crateDir + name + "/" + name + "-" + version + ".crate"
+}
+
+// RenderIndex joins stored lines into an index file with each yanked flag applied.
+func RenderIndex(entries []provider.CargoIndexEntry) ([]byte, error) {
+	var b strings.Builder
+	for _, e := range entries {
+		var line IndexLine
+		if err := json.Unmarshal([]byte(e.Line), &line); err != nil {
+			return nil, fmt.Errorf("%s %s: %w", e.Name, e.Version, err)
+		}
+		line.Yanked = e.Yanked
+		raw, err := json.Marshal(line)
+		if err != nil {
+			return nil, err
+		}
+		b.Write(raw)
+		b.WriteByte('\n')
+	}
+	return []byte(b.String()), nil
+}
+
+// LocalConfig is config.json for a local registry rooted at base.
+func LocalConfig(base string) map[string]string {
+	return map[string]string{
+		"dl":  base + "/" + crateDir + "{crate}/{crate}-{version}.crate",
+		"api": base,
+	}
+}
+
+func (p *Provider) ServeLocalIndex(w http.ResponseWriter, r *http.Request, files provider.FileStore, repoName, path string) bool {
+	path = strings.TrimLeft(path, "/")
+	if path == "config.json" {
+		w.Header().Set("Content-Type", "application/json")
+		_ = json.NewEncoder(w).Encode(LocalConfig(requestBase(r) + "/api/v1/local/" + repoName))
+		return true
+	}
+	name := path[strings.LastIndex(path, "/")+1:]
+	if name == "" || IndexPath(name) != path {
+		return false
+	}
+
+	reader, ok := files.(provider.CargoIndexReader)
+	if !ok {
+		http.Error(w, "cargo index not available", http.StatusInternalServerError)
+		return true
+	}
+	entries, err := reader.ListCargoIndexEntries(r.Context(), repoName, name)
+	if err != nil {
+		http.Error(w, err.Error(), http.StatusInternalServerError)
+		return true
+	}
+	if len(entries) == 0 {
+		http.Error(w, "not found", http.StatusNotFound)
+		return true
+	}
+	body, err := RenderIndex(entries)
+	if err != nil {
+		http.Error(w, err.Error(), http.StatusInternalServerError)
+		return true
+	}
+	w.Header().Set("Content-Type", "text/plain")
+	w.WriteHeader(http.StatusOK)
+	_, _ = w.Write(body)
+	return true
+}
+
+func (p *Provider) GenerateLocalIndex(ctx context.Context, files provider.FileStore, repoName, path string) ([]byte, error) {
+	return nil, fmt.Errorf("cargo local index generation for virtual repos not supported")
+}
+
+func (p *Provider) AfterDelete(ctx context.Context, repoName, storagePath string, db provider.MetadataDeleter) error {
+	deleter, ok := db.(provider.CargoIndexDeleter)
+	if !ok {
+		return nil
+	}
+	if err := deleter.DeleteCargoIndexEntry(ctx, repoName, storagePath); err != nil {
+		slog.Error("cargo index: delete failed", "repo", repoName, "path", storagePath, "error", err)
+		return err
+	}
+	return nil
+}
+
+func requestBase(r *http.Request) string {
+	scheme := "http"
+	if r.TLS != nil {
+		scheme = "https"
+	} else if fwd := r.Header.Get("X-Forwarded-Proto"); fwd != "" {
+		scheme = fwd
+	}
+	return scheme + "://" + r.Host
+}

internal/provider/cargo/local_test.go

@@ -0,0 +1,218 @@
+package cargo
+
+import (
+	"context"
+	"crypto/sha256"
+	"encoding/binary"
+	"encoding/hex"
+	"encoding/json"
+	"net/http/httptest"
+	"strings"
+	"testing"
+
+	"git.unkin.net/unkin/artifactapi/internal/provider"
+)
+
+func publishBody(meta string, crate []byte) []byte {
+	var b []byte
+	b = binary.LittleEndian.AppendUint32(b, uint32(len(meta)))
+	b = append(b, meta...)
+	b = binary.LittleEndian.AppendUint32(b, uint32(len(crate)))
+	return append(b, crate...)
+}
+
+const sampleMeta = `{
+  "name": "unkin-hello", "vers": "0.2.0",
+  "deps": [
+    {"name": "serde", "version_req": "^1", "features": ["derive"], "optional": false,
+     "default_features": true, "target": null, "kind": "normal",
+     "registry": "https://github.com/rust-lang/crates.io-index"},
+    {"name": "rand_core", "version_req": "^0.6", "features": null, "optional": true,
+     "default_features": false, "target": "cfg(unix)", "kind": "dev",
+     "explicit_name_in_toml": "rc"}
+  ],
+  "features": {"default": ["std"], "std": [], "extra": ["dep:rc"], "weak": ["serde?/std"]},
+  "links": null, "rust_version": "1.70", "description": "ignored"
+}`
+
+func TestParsePublishAndIndexLine(t *testing.T) {
+	crate := []byte("fake crate bytes")
+	meta, gotCrate, err := ParsePublish(publishBody(sampleMeta, crate))
+	if err != nil {
+		t.Fatal(err)
+	}
+	if string(gotCrate) != string(crate) {
+		t.Fatalf("crate = %q", gotCrate)
+	}
+	line, err := NewIndexLine(meta, crate)
+	if err != nil {
+		t.Fatal(err)
+	}
+	sum := sha256.Sum256(crate)
+	if line.Cksum != hex.EncodeToString(sum[:]) {
+		t.Errorf("cksum = %s", line.Cksum)
+	}
+
+	raw, _ := json.Marshal(line)
+	var got map[string]any
+	_ = json.Unmarshal(raw, &got)
+	if _, ok := got["version_req"]; ok {
+		t.Error("publish-only field leaked into index line")
+	}
+	if got["v"] != float64(2) {
+		t.Errorf("v = %v, want 2 with features2 present", got["v"])
+	}
+	if got["rust_version"] != "1.70" {
+		t.Errorf("rust_version = %v", got["rust_version"])
+	}
+	if _, ok := line.Features["extra"]; ok {
+		t.Error("dep: feature must move to features2")
+	}
+	if len(line.Features2) != 2 || len(line.Features) != 2 {
+		t.Errorf("features = %v features2 = %v", line.Features, line.Features2)
+	}
+
+	deps := got["deps"].([]any)
+	serde := deps[0].(map[string]any)
+	if serde["req"] != "^1" || serde["registry"] != "https://github.com/rust-lang/crates.io-index" || serde["target"] != nil {
+		t.Errorf("serde dep = %v", serde)
+	}
+	if _, ok := serde["package"]; ok {
+		t.Error("package set without a rename")
+	}
+	renamed := deps[1].(map[string]any)
+	if renamed["name"] != "rc" || renamed["package"] != "rand_core" || renamed["kind"] != "dev" {
+		t.Errorf("renamed dep = %v", renamed)
+	}
+	if f, ok := renamed["features"].([]any); !ok || len(f) != 0 {
+		t.Errorf("null features must render as [], got %v", renamed["features"])
+	}
+}
+
+func TestIndexLineNoNewFeaturesOmitsV(t *testing.T) {
+	line, err := NewIndexLine(PublishMeta{Name: "a", Vers: "1.0.0", Features: map[string][]string{"x": nil}}, nil)
+	if err != nil {
+		t.Fatal(err)
+	}
+	raw, _ := json.Marshal(line)
+	s := string(raw)
+	for _, bad := range []string{`"v":`, `"features2"`, `"links"`} {
+		if strings.Contains(s, bad) {
+			t.Errorf("%s present in %s", bad, s)
+		}
+	}
+	if !strings.Contains(s, `"deps":[]`) || !strings.Contains(s, `"features":{"x":[]}`) {
+		t.Errorf("deps/features must be non-null: %s", s)
+	}
+}
+
+func TestParsePublishRejectsMalformed(t *testing.T) {
+	good := publishBody(`{"name":"a","vers":"1.0.0"}`, []byte("c"))
+	for name, body := range map[string][]byte{
+		"empty":     nil,
+		"short":     good[:len(good)-1],
+		"trailing":  append(append([]byte{}, good...), 'x'),
+		"bad json":  publishBody(`{`, []byte("c")),
+		"no length": good[:6],
+	} {
+		if _, _, err := ParsePublish(body); err == nil {
+			t.Errorf("%s: expected error", name)
+		}
+	}
+}
+
+func TestNewIndexLineValidation(t *testing.T) {
+	for _, m := range []PublishMeta{
+		{Name: "", Vers: "1.0.0"},
+		{Name: "1abc", Vers: "1.0.0"},
+		{Name: "../x", Vers: "1.0.0"},
+		{Name: "ok", Vers: "1.0.0/../../x"},
+		{Name: "ok", Vers: ""},
+		{Name: strings.Repeat("a", 65), Vers: "1.0.0"},
+	} {
+		if _, err := NewIndexLine(m, nil); err == nil {
+			t.Errorf("%q@%q accepted", m.Name, m.Vers)
+		}
+	}
+	if _, err := NewIndexLine(PublishMeta{Name: "Foo_bar-2", Vers: "1.0.0-rc.1+build.5"}, nil); err != nil {
+		t.Error(err)
+	}
+}
+
+func TestIndexPath(t *testing.T) {
+	for name, want := range map[string]string{
+		"a": "1/a", "ab": "2/ab", "abc": "3/a/abc", "Serde": "se/rd/serde", "unkin-hello": "un/ki/unkin-hello",
+	} {
+		if got := IndexPath(name); got != want {
+			t.Errorf("IndexPath(%q) = %q, want %q", name, got, want)
+		}
+	}
+}
+
+type fakeIndex struct {
+	entries []provider.CargoIndexEntry
+	asked   string
+}
+
+func (f *fakeIndex) ListCargoIndexEntries(_ context.Context, _, name string) ([]provider.CargoIndexEntry, error) {
+	f.asked = name
+	return f.entries, nil
+}
+func (f *fakeIndex) ListFilesByPrefix(context.Context, string, string) ([]provider.FileEntry, error) {
+	return nil, nil
+}
+func (f *fakeIndex) ListPackages(context.Context, string) ([]string, error) { return nil, nil }
+
+func TestServeLocalIndex(t *testing.T) {
+	line, _ := NewIndexLine(PublishMeta{Name: "unkin-hello", Vers: "0.1.0"}, []byte("x"))
+	raw, _ := json.Marshal(line)
+	files := &fakeIndex{entries: []provider.CargoIndexEntry{
+		{Name: "unkin-hello", Version: "0.1.0", Line: string(raw), Yanked: true},
+		{Name: "unkin-hello", Version: "0.2.0", Line: strings.Replace(string(raw), "0.1.0", "0.2.0", 1)},
+	}}
+	p := &Provider{}
+
+	rec := httptest.NewRecorder()
+	if !p.ServeLocalIndex(rec, httptest.NewRequest("GET", "http://aa.example/x", nil), files, "crates-local", "un/ki/unkin-hello") {
+		t.Fatal("index path not served")
+	}
+	lines := strings.Split(strings.TrimSpace(rec.Body.String()), "\n")
+	if len(lines) != 2 || !strings.Contains(lines[0], `"yanked":true`) || !strings.Contains(lines[1], `"yanked":false`) {
+		t.Errorf("index body = %q", rec.Body.String())
+	}
+	if files.asked != "unkin-hello" {
+		t.Errorf("looked up %q", files.asked)
+	}
+
+	rec = httptest.NewRecorder()
+	req := httptest.NewRequest("GET", "http://aa.example/config.json", nil)
+	req.Header.Set("X-Forwarded-Proto", "https")
+	p.ServeLocalIndex(rec, req, files, "crates-local", "config.json")
+	var cfg map[string]string
+	_ = json.Unmarshal(rec.Body.Bytes(), &cfg)
+	if cfg["api"] != "https://aa.example/api/v1/local/crates-local" ||
+		cfg["dl"] != "https://aa.example/api/v1/local/crates-local/crates/{crate}/{crate}-{version}.crate" {
+		t.Errorf("config = %v", cfg)
+	}
+
+	for _, path := range []string{"crates/unkin-hello/unkin-hello-0.1.0.crate", "xx/ki/unkin-hello", ""} {
+		if p.ServeLocalIndex(httptest.NewRecorder(), httptest.NewRequest("GET", "/", nil), files, "r", path) {
+			t.Errorf("%q should fall through", path)
+		}
+	}
+
+	files.entries = nil
+	rec = httptest.NewRecorder()
+	p.ServeLocalIndex(rec, httptest.NewRequest("GET", "/", nil), files, "r", "3/a/abc")
+	if rec.Code != 404 {
+		t.Errorf("unknown crate code = %d", rec.Code)
+	}
+}
+
+func TestCratePathMatchesDL(t *testing.T) {
+	dl := LocalConfig("http://h/api/v1/local/r")["dl"]
+	want := strings.NewReplacer("{crate}", "unkin-hello", "{version}", "0.1.0").Replace(dl)
+	if got := "http://h/api/v1/local/r/" + CratePath("unkin-hello", "0.1.0"); got != want {
+		t.Errorf("CratePath = %q, dl expands to %q", got, want)
+	}
+}

internal/provider/cargo_index.go

@@ -0,0 +1,24 @@
+package provider
+
+import "context"
+
+// CargoIndexEntry is one published crate version in a local cargo registry.
+// Line is the sparse-index JSON line; Yanked is applied when it is served.
+type CargoIndexEntry struct {
+	RepoName string
+	FilePath string
+	Name     string
+	Version  string
+	Line     string
+	Yanked   bool
+}
+
+// CargoIndexReader lists every version of one crate (matched case-insensitively).
+// *database.DB satisfies it and CargoIndexDeleter.
+type CargoIndexReader interface {
+	ListCargoIndexEntries(ctx context.Context, repoName, name string) ([]CargoIndexEntry, error)
+}
+
+type CargoIndexDeleter interface {
+	DeleteCargoIndexEntry(ctx context.Context, repoName, filePath string) error
+}