refactor(context): remove unnecessary initialization add add tests for Context

[yusukebe]

This refactoring removed unnecessary initialization in c.get() and c.set(). And added tests for improving coverage.

The author should do the following, if applicable

• Add tests
• Run tests
• bun run format:fix && bun run lint:fix to format the code
• Add TSDoc/JSDoc to document the code

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 94.55%. Comparing base (0a974ff) to head (9770d45).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2949      +/-   ##
==========================================
+ Coverage   94.44%   94.55%   +0.11%     
==========================================
  Files         136      136              
  Lines       13349    13346       -3     
  Branches     2284     2357      +73     
==========================================
+ Hits        12607    12619      +12     
+ Misses        742      727      -15     

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[yusukebe]

It throws a type error that points to the possibility of undefined. But it has been initialized above. So ignore it.

[yusukebe]

@usualoma Sorry for calling you again and again. Please review this!

[usualoma]

Hi @yusukebe

Some time ago, in applications that did not use app.set() or app.get(), this was done to avoid the cost of initialising the private this._var. It is this PR that this._var is now always initialised.

#1406
https://github.com/honojs/hono/pull/1406/files#diff-1c6b79733c620b41d7f8b63deb644f09e5fda79664918394b443c2a348731605L102

It is quite questionable whether this optimisation is still valid today, but if we were to reproduce the aims of that time, the following change would be appropriate.

diff --git a/src/context.ts b/src/context.ts
index e5eaa581..d067b048 100644
--- a/src/context.ts
+++ b/src/context.ts
@@ -237,7 +237,7 @@ export class Context<
    * ```
    */
   env: E['Bindings'] = {}
-  private _var: E['Variables'] = {}
+  private _var: E['Variables'] | undefined
   finalized: boolean = false
   /**
    * `.error` can get the error object from the middleware if the Handler throws an error.

If there is no need to reproduce previous aims, this is a good change as this PR change makes "context.ts" very simple.

[yusukebe]

Hi @usualoma

You are right! No need to initialize it. I've fixed it with your patch and will merge this now. Thanks!