Redis ShortKey encoding is not reversible for keys containing literal percent-encoded sequences

[gfraiteur]

Description

The ShortKey encoding in PostSharp.Patterns.Caching.Backends.Redis is not reversible when user cache keys contain literal percent-encoded sequences like %7B, %7D, or %3A.

Root Cause

GetShortKeyFromUserKey escapes {, }, : to %7B, %7D, %3A respectively, but does not escape the % character itself. This means GetUserKeyFromShortKey cannot distinguish between an escaped { (which becomes %7B) and a literal %7B that was already in the original key.

Example:

• User key: key-with-%7B-literal
• After encoding: key-with-%7B-literal (unchanged, no {, }, or : present)
• After decoding: key-with-{-literal (incorrect — %7B was decoded even though it was literal)

Fix

Escape % to %25 before escaping the other characters in GetShortKeyFromUserKey, and unescape %25 back to % after unescaping the others in GetUserKeyFromShortKey.

Fixed in PR #35.

Related: metalama/Metalama#1427