Summary

This PR addresses issue #6670, where AxiosError.from() overwrote the original error’s stack trace. As a result, only the AxiosError internal stack appears in error logs (e.g. in Sentry), which obscures the root cause (DNS errors, timeouts, etc.)

Changes

• Captures the error.stack before calling AxiosError.call(...)
• After constructing the new AxiosError, appends the original stack (if present) as a Caused by: section
• Updated logic to use only syntax supported by current ESLint (no optional chaining)
• Added a unit test in test/specs/core/AxiosError.spec.js that asserts the new stack trace contains the original error message
• Verified that all existing Node tests pass (219/219)
• Browser tests are environment-dependent — local failures are acceptable if CI passes them

Example Before & After

Before :
AxiosError: Network Error
at AxiosError.from (AxiosError.js:…)

After :
AxiosError: Network Error
at AxiosError.from (AxiosError.js:…)
Caused by: Error: getaddrinfo ENOTFOUND example.com
at GetAddrInfoReqWrap.onlookupall (node:dns:…)

Impact & Backward Compatibility

No public API changes. This only enhances error diagnostics, so existing code consuming AxiosError continues to work.
This change helps debugging and observability (e.g. in error-tracking services) without altering behavior.

Testing & CI

• Node tests ran locally and passed
• ESLint fine after style fix
• Browser tests may require environment setup, but should be green in CI
• I welcome feedback or improvements if maintainers suggest adjustments

Thanks for reviewing this change and improving diagnostics for the community!

fixes #6670