fix: bump axios to ~1.15.2 and harden debug logging against non-stringifiable values

Author: Lucas Mathis

CHANGELOG.md

@@ -5,6 +5,11 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
 ## [Unreleased]
+### Fixed
+- The debug log helper no longer crashes when axios error fields return a non-primitive from `toString` or `Symbol.toPrimitive`.
+
+### Security
+- Bumped `axios` to `~1.15.2` to address 13 high-severity advisories.
 
 ## [1.27.0] - 2026-04-27
 ### Changed

package-lock.json

@@ -21,7 +21,7 @@
     "dependencies": {
         "@types/node": ">=12.0",
         "adm-zip": "^0.5.16",
-        "axios": "^1.7.4",
+        "axios": "~1.15.2",
         "form-data": "^3.0.4",
         "loglevel": ">=1.6.2"
     },

package.json

@@ -22,11 +22,28 @@ import {
 
 const logger = loglevel.getLogger('deepl');
 
+// Stringify a value safely for logging. Default `${value}` interpolation
+// throws "Cannot convert object to primitive value" on objects whose
+// `[Symbol.toPrimitive]`/`toString`/`valueOf` returns an object instead of a
+// primitive (some axios error fields fall into this category in certain
+// releases). Fall back to JSON.stringify, and finally to a sentinel string.
+function safeStringify(value: unknown): string {
+    try {
+        return String(value);
+    } catch {
+        try {
+            return JSON.stringify(value) ?? '<unprintable>';
+        } catch {
+            return '<unprintable>';
+        }
+    }
+}
+
 function concatLoggingArgs(args?: object): string {
     let detail = '';
     if (args) {
         for (const [key, value] of Object.entries(args)) {
-            detail += `, ${key} = ${value}`;
+            detail += `, ${key} = ${safeStringify(value)}`;
         }
     }
     return detail;