@cacheable/net - fix: send FormData/Blob correctly using the runtime's own fetch

[jaredwray]

Summary

@cacheable/net@2.0.7 silently coerced FormData to its toString() value ("[object FormData]") and sent it with Content-Type: text/plain;charset=UTF-8. Native fetch handles the same input correctly with multipart/form-data; boundary=….

Root cause

fetch.ts imported fetch from the standalone undici@^7 package. Node 18+ ships its own bundled undici (6.x in our test env) that produces globalThis.FormData, globalThis.Blob, globalThis.File, globalThis.ReadableStream. The standalone undici@7's fetch checks value instanceof <its own FormData>. The user-constructed new FormData() is from Node's bundled realm, so that check fails and the body falls through to a string coercion — "[object FormData]" — with text/plain.

Fix

Use globalThis.fetch internally. Now the fetch implementation and the body classes (FormData, Blob, File, URLSearchParams, ReadableStream) come from the same realm, and every BodyInit shape is recognized correctly:

Body	Before	After
FormData	text/plain + "[object FormData]"	multipart/form-data; boundary=… + real multipart
FormData (with File)	text/plain + "[object FormData]"	multipart/form-data with filename="…"
URLSearchParams	(worked)	application/x-www-form-urlencoded;charset=UTF-8
Blob	(worked)	declared type preserved
string, JSON object	(worked)	unchanged

undici's RequestInit and Response types are still imported as type-only so the public API surface is unchanged.

Test plan

• Local-server regression tests assert the wire-level Content-Type and body for FormData, FormData containing File, URLSearchParams, Blob, and a JSON object across post, patch, del
• All 7 new tests pass; type-check clean; pnpm build clean (CJS + ESM + DTS)
• No regressions in the existing FormData/URLSearchParams/Blob coverage
• CI: full test suite against the mockhttp service

https://claude.ai/code/session_01XVcwdY82D89NiYwinHSBvA

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Generated by Claude Code

[gemini-code-assist]

Code Review

This pull request switches from using a standalone undici fetch to the runtime's global fetch to ensure compatibility with global body classes like FormData, preventing incorrect coercion to strings. It also adds a suite of regression tests using a local HTTP server to verify correct body and header handling for various data types. Feedback suggests binding the captured fetch to globalThis for improved context safety and expanding the input type to support URL objects.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (e61e79a) to head (da0b404).

Additional details and impacted files

@@            Coverage Diff            @@
##              main     #1636   +/-   ##
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  Coverage   100.00%   100.00%           
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  Files           26        26           
  Lines         2496      2497    +1     
  Branches       554       555    +1     
=========================================
+ Hits          2496      2497    +1     

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