feat(search): Nominatim as the last-resort geocoder (#573)

Supersedes #350 by @sendmebits, ported onto the current component layout with fixes from review.

Verified before merge: format, package boundaries, unit suite, build, and the browser tracking suite; a browser harness for the change where one applies; adversarial review applied.

Co-authored-by: sendmebits <[email protected]>

server/providers/regional/http.js

@@ -5,42 +5,52 @@ import {
 
 const REGIONAL_MAX_RESPONSE_BYTES = 2 * 1024 * 1024;
 
-async function fetchRegionalJson(
-  url,
-  {
+/**
+ * One bounded upstream read for the regional providers.
+ *
+ * The deadline covers the BODY, not just the headers. `return`ing the reader's
+ * promise from inside a try/finally leaves the try block the moment the promise
+ * exists, so the abort timer used to be cleared before a single byte of body had
+ * arrived — an upstream that answered its headers and then stalled had no
+ * deadline at all. Awaiting inside the try keeps the timer alive until the body
+ * is in hand, and the same signal is handed to the reader so an abort stops the
+ * read rather than just the connect.
+ *
+ * `redirect` is stated rather than inherited: feeds that legitimately redirect
+ * (news RSS) follow, and a fixed API endpoint can be given 'error' so a
+ * redirect cannot steer the proxy at a destination this code never named.
+ *
+ * @param {string} url
+ * @param {{headers?: object, timeoutMs?: number, maxBytes?: number, redirect?: 'follow'|'error'|'manual'}} [options]
+ */
+async function fetchRegional(url, read, options = {}) {
+  const {
     headers = {},
     timeoutMs = 9000,
     maxBytes = REGIONAL_MAX_RESPONSE_BYTES,
-  } = {},
-) {
+    redirect = 'follow',
+  } = options;
   const controller = new AbortController();
   const timeout = setTimeout(() => controller.abort(), timeoutMs);
   try {
-    const response = await fetch(url, { signal: controller.signal, headers });
+    const response = await fetch(url, {
+      signal: controller.signal,
+      headers,
+      redirect,
+    });
     if (!response.ok) throw new Error(`Upstream returned ${response.status}`);
-    return readResponseJsonCapped(response, maxBytes);
+    return await read(response, maxBytes, controller.signal);
   } finally {
     clearTimeout(timeout);
   }
 }
 
-async function fetchRegionalText(
-  url,
-  {
-    headers = {},
-    timeoutMs = 9000,
-    maxBytes = REGIONAL_MAX_RESPONSE_BYTES,
-  } = {},
-) {
-  const controller = new AbortController();
-  const timeout = setTimeout(() => controller.abort(), timeoutMs);
-  try {
-    const response = await fetch(url, { signal: controller.signal, headers });
-    if (!response.ok) throw new Error(`Upstream returned ${response.status}`);
-    return readResponseTextCapped(response, maxBytes);
-  } finally {
-    clearTimeout(timeout);
-  }
+function fetchRegionalJson(url, options = {}) {
+  return fetchRegional(url, readResponseJsonCapped, options);
+}
+
+function fetchRegionalText(url, options = {}) {
+  return fetchRegional(url, readResponseTextCapped, options);
 }
 
 export { fetchRegionalJson, fetchRegionalText };