Fix network system error reporting (#1156)

Author: Ndpnt

CHANGELOG.md

@@ -2,6 +2,14 @@
 
 All changes that impact users of this module are documented in this file, in the [Common Changelog](https://common-changelog.org) format with some additional specifications defined in the CONTRIBUTING file. This codebase adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## Unreleased [patch]
+
+> Development of this release was supported by the [French Ministry for Foreign Affairs](https://www.diplomatie.gouv.fr/fr/politique-etrangere-de-la-france/diplomatie-numerique/) through its ministerial [State Startups incubator](https://beta.gouv.fr/startups/open-terms-archive.html) under the aegis of the Ambassador for Digital Affairs.
+
+### Fixed
+
+- Fix network system error reporting
+
 ## 5.4.0 - 2025-05-21
 
 _Full changeset and discussions: [#1155](https://github.com/OpenTermsArchive/engine/pull/1155)._

src/archivist/fetcher/htmlOnlyFetcher.js

@@ -49,6 +49,10 @@ export default async function fetch(url, config) {
       content,
     };
   } catch (error) {
+    if (error.type == 'system') { // Node-fetch wraps system-level errors (ENOTFOUND, ECONNREFUSED, ECONNRESET, etc.) with type 'system' and includes the original error code
+      throw new Error(`Network system error ${error.code} occurred when trying to fetch '${url}'`);
+    }
+
     if (error instanceof AbortError) {
       throw new Error(`Timed out after ${config.navigationTimeout / 1000} seconds when trying to fetch '${url}'`);
     }