fix: handle FormData on the server

Author: sukovanej

Diff for: .changeset/honest-wombats-decide.md

@@ -0,0 +1,5 @@
+---
+"effect-http": patch
+---
+
+Handle `FormData` on the server.

Diff for: examples/form-data.ts

@@ -0,0 +1,43 @@
+import * as Schema from "@effect/schema/Schema";
+import { Effect, Predicate, pipe } from "effect";
+import * as Http from "effect-http";
+
+import { debugLogger } from "./_utils";
+
+const api = pipe(
+  Http.api(),
+  Http.post("upload", "/upload", {
+    request: {
+      body: Http.FormData,
+    },
+    response: Schema.string,
+  }),
+);
+
+const server = pipe(
+  Http.server(api),
+  Http.handle("upload", ({ body }) => {
+    const file = body.get("file");
+
+    if (file === null) {
+      return Effect.fail(Http.invalidBodyError('Expected "file"'));
+    }
+
+    if (Predicate.isString(file)) {
+      return Effect.fail(Http.invalidBodyError("Expected file"));
+    }
+
+    return pipe(
+      Effect.promise(() => file.text()),
+      Effect.map((content) => `Received file with content: ${content}`),
+    );
+  }),
+);
+
+const program = pipe(
+  server,
+  Http.listen({ port: 3000 }),
+  Effect.provideSomeLayer(debugLogger),
+);
+
+Effect.runPromise(program);

Diff for: src/Server.ts

@@ -119,6 +119,8 @@ const buildHandler =
             if (contentLength > 0) {
               if (contentTypeHeader?.startsWith("application/json")) {
                 return request.json();
+              } else if (contentTypeHeader?.startsWith("multipart/form-data")) {
+                return request.formData();
               } else {
                 return request.text();
               }