[Bug Fix] - PoP token flow crash with nil pointer in cache.Replace when running non-root

[vineeth-thumma]

Fix bug - > PoP token support crashes with nil pointer in cache.Replace when running non-root

#734

kubelogin v0.2.14 panics with a nil pointer dereference in cache.(*Cache).Replace when PoP tokens are enabled and cache creation fails (typically non-root users or container environments without keyring access).

Root Cause
A Go nil-interface semantics bug. When NewCache() fails, a typed nil *popcache.Cache was stored in Options and later returned by GetPoPTokenCache(). When this typed nil was passed to an interface-typed parameter cache.ExportReplace, Go wrapped it into a non-nil interface (it carries type info). The downstream nil guard if cache != nil passed, MSAL received the nil-wrapping cache, and called Replace() on a nil receiver → panic.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 66.66667% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 57.31%. Comparing base (15edb67) to head (7fe0c8f).
⚠️ Report is 70 commits behind head on main.

Files with missing lines	Patch %	Lines
pkg/internal/token/execCredentialPlugin.go	33.33%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #736      +/-   ##
==========================================
- Coverage   63.43%   57.31%   -6.13%     
==========================================
  Files          37       47      +10     
  Lines        2210     2448     +238     
==========================================
+ Hits         1402     1403       +1     
- Misses        733      880     +147     
- Partials       75      165      +90     

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