Add Deno multipart support (#6725)

Author: tim-smart

.changeset/add-deno-multipart.md

@@ -0,0 +1,5 @@
+---
+"@effect/platform-deno": patch
+---
+
+Add web-standard multipart request parsing helpers for Deno.

packages/platform-deno/src/DenoMultipart.ts

@@ -0,0 +1,53 @@
+/**
+ * Web-standard helpers for parsing HTTP `multipart/form-data` request bodies.
+ *
+ * This module mirrors `BunMultipart`, adapting a web `Request` body and headers
+ * into the shared `Multipart` model. `stream` returns multipart parts as a
+ * `Stream`, while `persisted` collects the form and writes file parts to scoped
+ * temporary files through the current `FileSystem`, `Path`, and `Scope`
+ * services.
+ *
+ * @since 4.0.0
+ */
+import type * as Effect from "effect/Effect"
+import type { FileSystem } from "effect/FileSystem"
+import type { Path } from "effect/Path"
+import type * as Scope from "effect/Scope"
+import * as Stream from "effect/Stream"
+import * as Multipart from "effect/unstable/http/Multipart"
+
+/**
+ * Parses a web `Request` body as multipart data and returns a stream of multipart parts.
+ *
+ * @category constructors
+ * @since 4.0.0
+ */
+export const stream = (source: Request): Stream.Stream<Multipart.Part, Multipart.MultipartError> =>
+  Stream.fromReadableStream({
+    evaluate: () =>
+      source.body ?? new ReadableStream({
+        start(controller) {
+          controller.enqueue(new Uint8Array())
+          controller.close()
+        }
+      }),
+    onError: (cause) => Multipart.MultipartError.fromReason("InternalError", cause)
+  }).pipe(
+    Stream.pipeThroughChannel(Multipart.makeChannel(Object.fromEntries(source.headers)))
+  )
+
+/**
+ * Parses and persists multipart data from a web `Request`, requiring file-system, path, and scope services.
+ *
+ * @category constructors
+ * @since 4.0.0
+ */
+export const persisted = (
+  source: Request
+): Effect.Effect<
+  Multipart.Persisted,
+  Multipart.MultipartError,
+  | FileSystem
+  | Path
+  | Scope.Scope
+> => Multipart.toPersisted(stream(source))

packages/platform-deno/src/index.ts

@@ -34,6 +34,11 @@ export * as DenoHttpPlatform from "./DenoHttpPlatform.ts"
  */
 export * as DenoKeyValueStore from "./DenoKeyValueStore.ts"
 
+/**
+ * @since 4.0.0
+ */
+export * as DenoMultipart from "./DenoMultipart.ts"
+
 /**
  * @since 4.0.0
  */