fix: formdata post, wrong inference of json payload

[rubnogueira]

Allow usage of FormData payloads and URLSearchParams. Using Headers, case-sensitive header handling is also ensured.

Fix #32, #178

Summary by CodeRabbit

• New Features
  • Added support for multipart/form-data requests, including file uploads.
• Bug Fixes
  • Prevented accidental JSON serialization of FormData and URLSearchParams.
  • Improved Content-Type detection and handling to respect existing headers.
  • Automatically sets application/json when appropriate for JSON bodies without an explicit content type.
• Refactor
  • Centralized request header preparation for consistency across requests.
• Tests
  • Added end-to-end tests for multipart/form-data uploads, validating file name and size handling.

[coderabbitai]

Caution

Review failed

The pull request is closed.

Walkthrough

Centralizes header handling using the Headers API, adjusts content-type detection and setting, and conditionally JSON-serializes bodies only when appropriate. Adds test coverage for multipart/form-data via a new /form-data route and a client test posting FormData to verify correct file name and size handling.

Changes

Cohort / File(s)	Summary
Fetch header/body handling src/fetch/index.ts	Replaced object headers with Headers; normalized content-type access via headers.get/set; conditionally JSON.stringify only when body isn’t FormData/URLSearchParams and no explicit non-JSON content-type; set application/json when serializable and no content-type; preserved URL assembly and fetch call.
Form-data test and route test/fetch.test.ts	Added /form-data route with parse: 'formdata' and schema { file: t.File() }; imported form helper; added client test posting FormData and asserting returned file name and size.

Sequence Diagram(s)

sequenceDiagram
  autonumber
  participant C as Client Code
  participant EF as edenFetch()
  participant H as Headers
  participant F as fetch()
  participant S as Server

  C->>EF: call edenFetch(url, { body, headers })
  EF->>H: construct Headers from options
  alt Body is FormData or URLSearchParams
    EF-->>H: do not set Content-Type
    note over EF,H: Let browser set multipart/boundary
    EF->>F: fetch(url, { headers, body })
  else Body is other
    EF->>H: read content-type via headers.get()
    alt No content-type and JSON.stringify succeeds
      EF->>H: set content-type: application/json
      EF->>F: fetch(url, { headers, body: JSON.stringify(body) })
    else Explicit non-JSON content-type
      EF->>F: fetch(url, { headers, body })
    end
  end
  F->>S: HTTP request
  S-->>F: Response
  F-->>C: Response

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Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~25 minutes

Poem

I thump my paw at headers neat,
Let browsers spin their boundary sheet;
If JSON fits, we set it right,
If forms arrive, we don’t uptight.
A tiny hop, a tidy send—
Now files and bytes both comprehend.
Carrot-approve! ✅🥕

✨ Finishing touches

• 📝 Generate docstrings

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment

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📜 Recent review details

Configuration used: CodeRabbit UI

Review profile: CHILL

Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between 1e387cd and 02b0911.

📒 Files selected for processing (2)

• src/fetch/index.ts (1 hunks)
• test/fetch.test.ts (3 hunks)

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