feat(context): add Context-Type types to c.header

[nakasyou]

I added a Content-Type type helper to c.header.
I'm sure you can type mime-types easily than before.

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 96.25%. Comparing base (7cd0248) to head (e74beae).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3255      +/-   ##
==========================================
+ Coverage   96.23%   96.25%   +0.01%     
==========================================
  Files         151      151              
  Lines       15197    15261      +64     
  Branches     2643     2668      +25     
==========================================
+ Hits        14625    14689      +64     
  Misses        572      572              

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[yusukebe]

@nakasyou

Great feature! I'll review this later.

[yusukebe]

Hi @nakasyou

I propose the following changes.

diff --git a/src/context.ts b/src/context.ts
index 2a03cebb..9e1345e4 100644
--- a/src/context.ts
+++ b/src/context.ts
@@ -20,7 +20,10 @@ import type {
 } from './utils/types'
 import type { BaseMime } from './utils/mime'

-type HeaderRecord = Record<ResponseHeader, string | string[]> | Record<string, string | string[]>
+type HeaderRecord =
+  | Record<ResponseHeader, string | string[]>
+  | Record<'Content-Type', BaseMime>
+  | Record<string, string | string[]>

 /**
  * Data type can be a string, ArrayBuffer, or ReadableStream.
@@ -314,6 +317,7 @@ type ResponseHeadersInit =
   | [string, string][]
   | Record<string, string>
   | Record<ResponseHeader, string>
+  | Record<'Content-Type', BaseMime>
   | Headers

 interface ResponseInit {
diff --git a/src/utils/mime.ts b/src/utils/mime.ts
index d9a54cc4..f6df4853 100644
--- a/src/utils/mime.ts
+++ b/src/utils/mime.ts
@@ -79,7 +79,6 @@ export type BaseMime =
   | 'video/3gpp2'
   | 'model/gltf+json'
   | 'model/gltf-binary'
-  | (string & {})

 const baseMimes: Record<string, BaseMime> = {
   aac: 'audio/aac',

With this PR, it can infer other patterns, not only the c.header() pattern. And the last line | (string & {}) in utils/mime.ts diff is not necessary, I think. It should be strict.

[nakasyou]

@yusukebe OK, I changed it.

[yusukebe]

LGTM!

[yusukebe]

@nakasyou

Good! I'll release the new patch version that includes this feature. Thank you for your great idea!