Use header constants across the handler package

internal/handler/cargo.go

@@ -80,7 +80,7 @@ func (h *CargoHandler) handleConfig(w http.ResponseWriter, r *http.Request) {
 		DL: h.proxyURL + "/cargo/crates/{crate}/{version}/download",
 	}
 
-	w.Header().Set("Content-Type", "application/json")
+	w.Header().Set(headerContentType, "application/json")
 	_ = json.NewEncoder(w).Encode(config)
 }
 
@@ -112,7 +112,7 @@ func (h *CargoHandler) handleIndex(w http.ResponseWriter, r *http.Request) {
 		contentType = "text/plain; charset=utf-8"
 	}
 
-	w.Header().Set("Content-Type", contentType)
+	w.Header().Set(headerContentType, contentType)
 	w.WriteHeader(http.StatusOK)
 	h.applyCooldownFiltering(w, body)
 }

internal/handler/composer.go

@@ -77,7 +77,7 @@ func (h *ComposerHandler) handleServiceIndex(w http.ResponseWriter, r *http.Requ
 		"providers-lazy-url": h.proxyURL + "/composer/p2/%package%.json",
 	}
 
-	w.Header().Set("Content-Type", "application/json")
+	w.Header().Set(headerContentType, "application/json")
 	_ = json.NewEncoder(w).Encode(index)
 }
 
@@ -113,12 +113,12 @@ func (h *ComposerHandler) handlePackageMetadata(w http.ResponseWriter, r *http.R
 	rewritten, err := h.rewriteMetadata(body)
 	if err != nil {
 		h.proxy.Logger.Warn("failed to rewrite metadata, proxying original", "error", err)
-		w.Header().Set("Content-Type", "application/json")
+		w.Header().Set(headerContentType, "application/json")
 		_, _ = w.Write(body)
 		return
 	}
 
-	w.Header().Set("Content-Type", "application/json")
+	w.Header().Set(headerContentType, "application/json")
 	_, _ = w.Write(rewritten)
 }
 

internal/handler/conda.go

@@ -174,12 +174,12 @@ func (h *CondaHandler) handleRepodata(w http.ResponseWriter, r *http.Request) {
 	filtered, err := h.applyCooldownFiltering(body)
 	if err != nil {
 		h.proxy.Logger.Warn("failed to filter repodata, proxying original", "error", err)
-		w.Header().Set("Content-Type", "application/json")
+		w.Header().Set(headerContentType, "application/json")
 		_, _ = w.Write(body)
 		return
 	}
 
-	w.Header().Set("Content-Type", "application/json")
+	w.Header().Set(headerContentType, "application/json")
 	_, _ = w.Write(filtered)
 }
 

internal/handler/container.go

@@ -126,9 +126,9 @@ func (h *ContainerHandler) handleBlobDownload(w http.ResponseWriter, r *http.Req
 	if cached != nil {
 		w.Header().Set("Docker-Content-Digest", digest)
 		if cached.ContentType != "" {
-			w.Header().Set("Content-Type", cached.ContentType)
+			w.Header().Set(headerContentType, cached.ContentType)
 		} else {
-			w.Header().Set("Content-Type", "application/octet-stream")
+			w.Header().Set(headerContentType, "application/octet-stream")
 		}
 		serveArtifact(w, r.Method, cached)
 		return
@@ -162,9 +162,9 @@ func (h *ContainerHandler) handleBlobDownload(w http.ResponseWriter, r *http.Req
 
 	w.Header().Set("Docker-Content-Digest", digest)
 	if result.ContentType != "" {
-		w.Header().Set("Content-Type", result.ContentType)
+		w.Header().Set(headerContentType, result.ContentType)
 	} else {
-		w.Header().Set("Content-Type", "application/octet-stream")
+		w.Header().Set(headerContentType, "application/octet-stream")
 	}
 	ServeArtifact(w, result)
 }
@@ -232,7 +232,7 @@ func (h *ContainerHandler) proxyBlobHead(w http.ResponseWriter, r *http.Request,
 	}
 	defer func() { _ = resp.Body.Close() }()
 
-	for _, header := range []string{"Content-Type", "Content-Length", "Docker-Content-Digest"} {
+	for _, header := range []string{headerContentType, headerContentLength, "Docker-Content-Digest"} {
 		if v := resp.Header.Get(header); v != "" {
 			w.Header().Set(header, v)
 		}
@@ -261,7 +261,7 @@ func (h *ContainerHandler) registryForName(name string) (registryURL, upstreamNa
 
 // containerError writes an OCI-compliant error response.
 func (h *ContainerHandler) containerError(w http.ResponseWriter, status int, code, message string) {
-	w.Header().Set("Content-Type", "application/json")
+	w.Header().Set(headerContentType, "application/json")
 	w.WriteHeader(status)
 	_ = json.NewEncoder(w).Encode(map[string]any{
 		"errors": []map[string]string{

internal/handler/container_manifest.go

@@ -95,7 +95,7 @@ func (h *ContainerHandler) serveManifest(w http.ResponseWriter, r *http.Request,
 	}
 	manifest := &cachedContainerManifest{
 		body:          body,
-		contentType:   resp.Header.Get("Content-Type"),
+		contentType:   resp.Header.Get(headerContentType),
 		contentDigest: resp.Header.Get("Docker-Content-Digest"),
 		etag:          resp.Header.Get("ETag"),
 		size:          int64(len(body)),
@@ -228,9 +228,9 @@ func (h *ContainerHandler) storeContainerManifest(ctx context.Context, cacheKey
 
 func writeContainerManifest(w http.ResponseWriter, method string, manifest *cachedContainerManifest, stale bool) {
 	if manifest.contentType != "" {
-		w.Header().Set("Content-Type", manifest.contentType)
+		w.Header().Set(headerContentType, manifest.contentType)
 	}
-	w.Header().Set("Content-Length", strconv.FormatInt(manifest.size, 10))
+	w.Header().Set(headerContentLength, strconv.FormatInt(manifest.size, 10))
 	if manifest.contentDigest != "" {
 		w.Header().Set("Docker-Content-Digest", manifest.contentDigest)
 	}
@@ -383,7 +383,7 @@ func containerAcceptQuality(params map[string]string) float64 {
 }
 
 func copyContainerManifestHeaders(destination, source http.Header) {
-	for _, header := range []string{"Content-Type", "Content-Length", "Docker-Content-Digest", "ETag", "WWW-Authenticate"} {
+	for _, header := range []string{headerContentType, headerContentLength, "Docker-Content-Digest", "ETag", "WWW-Authenticate"} {
 		if value := source.Get(header); value != "" {
 			destination.Set(header, value)
 		}

internal/handler/container_tags.go

@@ -86,7 +86,7 @@ func (h *ContainerHandler) serveTagsList(w http.ResponseWriter, r *http.Request,
 	}
 	tags := &cachedContainerTags{
 		body:        body,
-		contentType: resp.Header.Get("Content-Type"),
+		contentType: resp.Header.Get(headerContentType),
 		etag:        resp.Header.Get("ETag"),
 		link:        h.rewriteContainerTagsLink(strings.Join(resp.Header.Values("Link"), ", "), registryURL, r.URL.Path),
 		size:        int64(len(body)),
@@ -169,8 +169,8 @@ func (h *ContainerHandler) storeContainerTags(ctx context.Context, cacheKey stri
 }
 
 func writeContainerTags(w http.ResponseWriter, tags *cachedContainerTags, stale bool) {
-	w.Header().Set("Content-Type", tags.contentType)
-	w.Header().Set("Content-Length", strconv.FormatInt(tags.size, 10))
+	w.Header().Set(headerContentType, tags.contentType)
+	w.Header().Set(headerContentLength, strconv.FormatInt(tags.size, 10))
 	if tags.etag != "" {
 		w.Header().Set("ETag", tags.etag)
 	}
@@ -185,7 +185,7 @@ func writeContainerTags(w http.ResponseWriter, tags *cachedContainerTags, stale
 }
 
 func copyContainerTagsHeaders(destination, source http.Header) {
-	for _, header := range []string{"Content-Type", "Content-Length", "ETag", "Link", "WWW-Authenticate"} {
+	for _, header := range []string{headerContentType, headerContentLength, "ETag", "Link", "WWW-Authenticate"} {
 		if value := source.Get(header); value != "" {
 			destination.Set(header, value)
 		}

internal/handler/debian.go

@@ -88,7 +88,7 @@ func (h *DebianHandler) handlePackageDownload(w http.ResponseWriter, r *http.Req
 		return
 	}
 
-	w.Header().Set("Content-Type", "application/vnd.debian.binary-package")
+	w.Header().Set(headerContentType, "application/vnd.debian.binary-package")
 	ServeArtifact(w, result)
 }
 

internal/handler/gem.go

@@ -182,7 +182,7 @@ func (h *GemHandler) fetchCompactIndex(r *http.Request, name string) (*http.Resp
 // writeFilteredIndex writes the compact index response with cooldown-filtered versions removed.
 func (h *GemHandler) writeFilteredIndex(w http.ResponseWriter, resp *http.Response, name string, filtered map[string]bool) {
 	for k, vv := range resp.Header {
-		if strings.EqualFold(k, "Content-Length") {
+		if strings.EqualFold(k, headerContentLength) {
 			continue // length will change after filtering
 		}
 		for _, v := range vv {

internal/handler/gradle.go

@@ -93,7 +93,7 @@ func (h *GradleBuildCacheHandler) cacheStoragePath(key string) string {
 
 func (h *GradleBuildCacheHandler) handleGetOrHead(w http.ResponseWriter, r *http.Request, key string) {
 	storagePath := h.cacheStoragePath(key)
-	w.Header().Set("Content-Type", gradleBuildCacheContentType)
+	w.Header().Set(headerContentType, gradleBuildCacheContentType)
 
 	if r.Method == http.MethodHead {
 		existsStart := time.Now()
@@ -118,7 +118,7 @@ func (h *GradleBuildCacheHandler) handleGetOrHead(w http.ResponseWriter, r *http
 		if err != nil {
 			metrics.RecordStorageError("read")
 		} else if size >= 0 {
-			w.Header().Set("Content-Length", strconv.FormatInt(size, 10))
+			w.Header().Set(headerContentLength, strconv.FormatInt(size, 10))
 		}
 
 		w.WriteHeader(http.StatusOK)
@@ -171,7 +171,7 @@ func (h *GradleBuildCacheHandler) handlePut(w http.ResponseWriter, r *http.Reque
 		return
 	}
 
-	w.Header().Set("Content-Length", "0")
+	w.Header().Set(headerContentLength, "0")
 	w.Header().Set("ETag", `"`+hash+`"`)
 
 	w.WriteHeader(http.StatusCreated)

internal/handler/handler.go

@@ -91,7 +91,11 @@ func packagePURLStrings(ecosystem, name, version string) (string, string, error)
 
 const contentTypeJSON = "application/json"
 
-const headerAcceptEncoding = "Accept-Encoding"
+const (
+	headerAcceptEncoding = "Accept-Encoding"
+	headerContentType    = "Content-Type"
+	headerContentLength  = "Content-Length"
+)
 
 // defaultMetadataMaxSize is used when Proxy.MetadataMaxSize is unset.
 const defaultMetadataMaxSize = 100 << 20
@@ -453,10 +457,10 @@ func serveArtifact(w http.ResponseWriter, method string, result *CacheResult) {
 	}
 
 	if result.ContentType != "" {
-		w.Header().Set("Content-Type", result.ContentType)
+		w.Header().Set(headerContentType, result.ContentType)
 	}
 	if result.Size > 0 || (method == http.MethodHead && result.Size == 0) {
-		w.Header().Set("Content-Length", strconv.FormatInt(result.Size, 10))
+		w.Header().Set(headerContentLength, strconv.FormatInt(result.Size, 10))
 	}
 	if result.Hash != "" {
 		w.Header().Set("ETag", `"`+result.Hash+`"`)
@@ -537,7 +541,7 @@ func (p *Proxy) ProxyFile(w http.ResponseWriter, r *http.Request, upstreamURL st
 
 // JSONError writes a JSON error response.
 func JSONError(w http.ResponseWriter, status int, message string) {
-	w.Header().Set("Content-Type", contentTypeJSON)
+	w.Header().Set(headerContentType, contentTypeJSON)
 	w.WriteHeader(status)
 	_, _ = fmt.Fprintf(w, `{"error":%q}`, message)
 }
@@ -711,7 +715,7 @@ func (p *Proxy) fetchUpstreamMetadata(ctx context.Context, upstreamURL string, e
 		return nil, "", "", zeroTime, fmt.Errorf("reading response: %w", err)
 	}
 
-	contentType := resp.Header.Get("Content-Type")
+	contentType := resp.Header.Get(headerContentType)
 	if contentType == "" {
 		contentType = contentTypeJSON
 	}
@@ -826,8 +830,8 @@ func (p *Proxy) writeMetadataCachedResponse(w http.ResponseWriter, r *http.Reque
 		}
 	}
 
-	w.Header().Set("Content-Type", contentType)
-	w.Header().Set("Content-Length", strconv.Itoa(len(body)))
+	w.Header().Set(headerContentType, contentType)
+	w.Header().Set(headerContentLength, strconv.Itoa(len(body)))
 	if cm.etag != "" {
 		w.Header().Set("ETag", cm.etag)
 	}
@@ -870,7 +874,7 @@ func (p *Proxy) proxyMetadataStream(w http.ResponseWriter, r *http.Request, upst
 	}
 	defer func() { _ = resp.Body.Close() }()
 
-	for _, header := range []string{"Content-Type", "Content-Length", "Last-Modified", "ETag"} {
+	for _, header := range []string{headerContentType, headerContentLength, "Last-Modified", "ETag"} {
 		if v := resp.Header.Get(header); v != "" {
 			w.Header().Set(header, v)
 		}

internal/handler/helm.go

@@ -136,7 +136,7 @@ func (h *HelmHandler) serveChart(w http.ResponseWriter, r *http.Request, reposit
 	}
 
 	if result.ContentType == "" {
-		w.Header().Set("Content-Type", "application/gzip")
+		w.Header().Set(headerContentType, "application/gzip")
 	}
 	ServeArtifact(w, result)
 }

internal/handler/hex.go

@@ -135,7 +135,7 @@ func (h *HexHandler) handlePackages(w http.ResponseWriter, r *http.Request) {
 
 	if len(filteredVersions) == 0 {
 		// No versions to filter or couldn't get timestamps, pass through
-		w.Header().Set("Content-Type", protoResp.Header.Get("Content-Type"))
+		w.Header().Set(headerContentType, protoResp.Header.Get(headerContentType))
 		w.Header().Set("Content-Encoding", "gzip")
 		_, _ = w.Write(body)
 		return
@@ -144,13 +144,13 @@ func (h *HexHandler) handlePackages(w http.ResponseWriter, r *http.Request) {
 	filtered, err := h.filterSignedPackage(body, filteredVersions)
 	if err != nil {
 		h.proxy.Logger.Warn("failed to filter hex package, proxying original", "error", err)
-		w.Header().Set("Content-Type", protoResp.Header.Get("Content-Type"))
+		w.Header().Set(headerContentType, protoResp.Header.Get(headerContentType))
 		w.Header().Set("Content-Encoding", "gzip")
 		_, _ = w.Write(body)
 		return
 	}
 
-	w.Header().Set("Content-Type", "application/octet-stream")
+	w.Header().Set(headerContentType, "application/octet-stream")
 	w.Header().Set("Content-Encoding", "gzip")
 	_, _ = w.Write(filtered)
 }

internal/handler/npm.go

@@ -98,13 +98,13 @@ func (h *NPMHandler) handlePackageMetadata(w http.ResponseWriter, r *http.Reques
 	if err != nil {
 		// If rewriting fails, just proxy the original
 		h.proxy.Logger.Warn("failed to rewrite metadata, proxying original", "error", err)
-		w.Header().Set("Content-Type", contentTypeJSON)
+		w.Header().Set(headerContentType, contentTypeJSON)
 		w.WriteHeader(http.StatusOK)
 		_, _ = w.Write(body)
 		return
 	}
 
-	w.Header().Set("Content-Type", contentTypeJSON)
+	w.Header().Set(headerContentType, contentTypeJSON)
 	w.WriteHeader(http.StatusOK)
 	_, _ = w.Write(rewritten)
 }

internal/handler/nuget.go

@@ -85,12 +85,12 @@ func (h *NuGetHandler) handleServiceIndex(w http.ResponseWriter, r *http.Request
 	rewritten, err := h.rewriteServiceIndex(body)
 	if err != nil {
 		h.proxy.Logger.Warn("failed to rewrite service index, proxying original", "error", err)
-		w.Header().Set("Content-Type", "application/json")
+		w.Header().Set(headerContentType, "application/json")
 		_, _ = w.Write(body)
 		return
 	}
 
-	w.Header().Set("Content-Type", "application/json")
+	w.Header().Set(headerContentType, "application/json")
 	_, _ = w.Write(rewritten)
 }
 
@@ -188,12 +188,12 @@ func (h *NuGetHandler) handleRegistration(w http.ResponseWriter, r *http.Request
 	filtered, err := h.applyCooldownFiltering(body)
 	if err != nil {
 		h.proxy.Logger.Warn("failed to filter registration, proxying original", "error", err)
-		w.Header().Set("Content-Type", "application/json")
+		w.Header().Set(headerContentType, "application/json")
 		_, _ = w.Write(body)
 		return
 	}
 
-	w.Header().Set("Content-Type", "application/json")
+	w.Header().Set(headerContentType, "application/json")
 	_, _ = w.Write(filtered)
 }
 

internal/handler/pub.go

@@ -110,13 +110,13 @@ func (h *PubHandler) handlePackageMetadata(w http.ResponseWriter, r *http.Reques
 	rewritten, err := h.rewriteMetadata(name, body)
 	if err != nil {
 		h.proxy.Logger.Warn("failed to rewrite metadata, proxying original", "error", err)
-		w.Header().Set("Content-Type", "application/json")
+		w.Header().Set(headerContentType, "application/json")
 		w.WriteHeader(http.StatusOK)
 		_, _ = w.Write(body)
 		return
 	}
 
-	w.Header().Set("Content-Type", "application/json")
+	w.Header().Set(headerContentType, "application/json")
 	w.WriteHeader(http.StatusOK)
 	_, _ = w.Write(rewritten)
 }

internal/handler/pypi.go

@@ -130,7 +130,7 @@ func (h *PyPIHandler) handleSimplePackage(w http.ResponseWriter, r *http.Request
 		rewritten = h.rewriteSimpleHTML(body, filteredVersions)
 	}
 
-	w.Header().Set("Content-Type", contentType)
+	w.Header().Set(headerContentType, contentType)
 	ensureVaryAccept(w.Header())
 	w.WriteHeader(http.StatusOK)
 	_, _ = w.Write(rewritten)
@@ -401,12 +401,12 @@ func (h *PyPIHandler) proxyAndRewriteJSON(w http.ResponseWriter, r *http.Request
 	rewritten, err := h.rewriteJSONMetadata(body)
 	if err != nil {
 		h.proxy.Logger.Warn("failed to rewrite metadata, proxying original", "error", err)
-		w.Header().Set("Content-Type", "application/json")
+		w.Header().Set(headerContentType, "application/json")
 		_, _ = w.Write(body)
 		return
 	}
 
-	w.Header().Set("Content-Type", "application/json")
+	w.Header().Set(headerContentType, "application/json")
 	_, _ = w.Write(rewritten)
 }
 

internal/handler/rpm.go

@@ -94,7 +94,7 @@ func (h *RPMHandler) handlePackageDownload(w http.ResponseWriter, r *http.Reques
 		return
 	}
 
-	w.Header().Set("Content-Type", "application/x-rpm")
+	w.Header().Set(headerContentType, "application/x-rpm")
 	ServeArtifact(w, result)
 }