fix(router): fallback for method-shadowed routes

[pi0]

🔗 Linked issue

Resolves #460

❓ Type of change

• 📖 Documentation (updates to the documentation, readme, or JSdoc annotations)
• 🐞 Bug fix (a non-breaking change that fixes an issue)
• 👌 Enhancement (improving an existing functionality like performance)
• ✨ New feature (a non-breaking change that adds functionality)
• 🧹 Chore (updates to the build process or auxiliary tools and libraries)
• ⚠️ Breaking change (fix or feature that would cause existing functionality to change)

📚 Description

This PR resolves router issue with multiple routes matching shadowing their method by using a (lazy initialized) multi-matcher.

Performance note: While this adds small overhead, the prefix matcher is really fast specially for static routes (without params) which are usually the usecase for this feature for implementing renderer fallback routes. Regardless it is super fast and used for nitro route rules matcher as well (src).

Performance: After first resolution of method-shadowed match, we update main match with missing method. This means that, only once (in server lifecycle) the resolution will happen.

📝 Checklist

• I have linked an issue or discussion.
• I have updated the documentation accordingly.

[codecov]

Codecov Report

Merging #461 (0d49698) into main (8c73933) will increase coverage by 0.09%.
The diff coverage is 87.87%.

@@            Coverage Diff             @@
##             main     #461      +/-   ##
==========================================
+ Coverage   78.38%   78.47%   +0.09%     
==========================================
  Files          26       26              
  Lines        2803     2834      +31     
  Branches      408      414       +6     
==========================================
+ Hits         2197     2224      +27     
- Misses        606      610       +4     

Files Changed	Coverage Δ
src/router.ts	96.29% <87.87%> (-2.18%)	⬇️

[Hebilicious]

This looks great !
I was thinking if the name catchAll wouldn't be more fitting than shadow, but maybe there's a use case that doesn't involve ** that I'm not aware of ?

[pi0]

I was thinking if the name catchAll wouldn't be more fitting than shadow, but maybe there's a use case that doesn't involve ** that I'm not aware of ?

All nitro route rules use this feature to catch matching paths :)

---

Marking PR as draft since I'm not still sure if this is best approach for fixing the issue

[pi0]

Update: Spent couple of minutes trying different data structures and methods for radix3 and router implementations. There was to experiments:

1. Use methods in radix routes to directly match by method

This can cause side effects, especially for routes being registered with /**$ or /*$. We need to add another segment like {path}/?{method}.

2. Support filter function for radix3 lookup

It adds a function calling overhead per-request per-tree-node. Ideally this would be the best if radix3 natively supports methods.

Therefore i think we can move forward with this (dirty) workaround as fix until shipping native method matching for radix3 (unjs/rou3#58)