Adapt per review

packages/safe-chain/src/registryProxy/http-utils.js

@@ -16,9 +16,42 @@ export function getHeaderValueAsString(headers, headerName) {
   return header;
 }
 
+/**
+ * Returns a copy of headers without the provided header names, matched
+ * either exactly or case-insensitively.
+ *
+ * @param {NodeJS.Dict<string | string[]> | undefined} headers
+ * @param {string[]} headerNames
+ * @param {{ caseInsensitive?: boolean }} [options]
+ * @returns {NodeJS.Dict<string | string[]> | undefined}
+ */
+export function omitHeaders(headers, headerNames, options = {}) {
+  if (!headers) {
+    return headers;
+  }
+
+  const omittedHeaderNames = new Set(
+    options.caseInsensitive
+      ? headerNames.map((name) => name.toLowerCase())
+      : headerNames
+  );
+  /** @type {NodeJS.Dict<string | string[]>} */
+  const filteredHeaders = {};
+
+  for (const [headerName, value] of Object.entries(headers)) {
+    const comparableHeaderName = options.caseInsensitive
+      ? headerName.toLowerCase()
+      : headerName;
+    if (!omittedHeaderNames.has(comparableHeaderName)) {
+      filteredHeaders[headerName] = value;
+    }
+  }
+
+  return filteredHeaders;
+}
+
 /**
  * Remove headers that become stale when the response body is modified.
- * Mutates the provided headers object in place.
  *
  * @param {NodeJS.Dict<string | string[]> | undefined} headers
  * @returns {void}
@@ -28,8 +61,20 @@ export function clearCachingHeaders(headers) {
     return;
   }
 
-  delete headers["etag"];
+  const filteredHeaders = omitHeaders(headers, [
-  delete headers["last-modified"];
+    "etag",
-  delete headers["cache-control"];
+    "last-modified",
-  delete headers["content-length"];
+    "cache-control",
+    "content-length",
+  ]);
+
+  if (!filteredHeaders) {
+    return;
+  }
+
+  for (const key of Object.keys(headers)) {
+    delete headers[key];
+  }
+
+  Object.assign(headers, filteredHeaders);
 }

packages/safe-chain/src/registryProxy/interceptors/pip/pipMetadataVersionUtils.js

@@ -37,21 +37,27 @@ export function getAvailableVersionsFromJson(json, metadataUrl) {
     return Object.keys(json.releases);
   }
 
-  if (Array.isArray(json.files)) {
+  if (!Array.isArray(json.files)) {
-    return [
+    return [];
-      ...new Set(
-        json.files
-          .map((/** @type {any} */ file) =>
-            getPackageVersionFromMetadataFile(file, metadataUrl)
-          )
-          .filter((/** @type {string | undefined} */ version) =>
-            typeof version === "string"
-          )
-      ),
-    ];
   }
 
-  return [];
+  return [
+    ...new Set(
+      json.files
+        .map((/** @type {any} */ file) =>
+          getPackageVersionFromMetadataFile(file, metadataUrl)
+        )
+        .filter(isDefinedString)
+    ),
+  ];
+}
+
+/**
+ * @param {string | undefined} value
+ * @returns {value is string}
+ */
+function isDefinedString(value) {
+  return typeof value === "string";
 }
 
 /**

packages/safe-chain/src/registryProxy/mitmRequestHandler.js

@@ -3,6 +3,7 @@ import { generateCertForHost } from "./certUtils.js";
 import { HttpsProxyAgent } from "https-proxy-agent";
 import { ui } from "../environment/userInteraction.js";
 import { gunzipSync } from "zlib";
+import { omitHeaders } from "./http-utils.js";
 
 /**
  * @typedef {import("./interceptors/interceptorBuilder.js").Interceptor} Interceptor
@@ -107,28 +108,6 @@ function getRequestPathAndQuery(url) {
   return url;
 }
 
-/**
- * @param {NodeJS.Dict<string | string[]>} headers
- * @returns {NodeJS.Dict<string | string[]>}
- */
-function normalizeRewrittenResponseHeaders(headers) {
-  /** @type {NodeJS.Dict<string | string[]>} */
-  const normalizedHeaders = { ...headers };
-
-  for (const headerName of Object.keys(headers)) {
-    const lowerHeaderName = headerName.toLowerCase();
-    if (
-      lowerHeaderName === "content-length" ||
-      lowerHeaderName === "transfer-encoding" ||
-      lowerHeaderName === "content-encoding"
-    ) {
-      delete normalizedHeaders[headerName];
-    }
-  }
-
-  return normalizedHeaders;
-}
-
 /**
  * @param {import("http").IncomingMessage} req
  * @param {string} hostname
@@ -240,7 +219,11 @@ function createProxyRequest(hostname, port, req, res, requestHandler) {
         // For rewritten responses, send the final body uncompressed.
         // This avoids mismatches between upstream compression metadata and the
         // rewritten payload on the wire.
-        const rewrittenHeaders = normalizeRewrittenResponseHeaders(headers);
+        const rewrittenHeaders = omitHeaders(
+          headers,
+          ["content-length", "transfer-encoding", "content-encoding"],
+          { caseInsensitive: true }
+        ) || {};
         rewrittenHeaders["content-length"] = String(buffer.byteLength);
         res.writeHead(statusCode, rewrittenHeaders);
         res.end(buffer);