@wildix/smithy-react-native

React Native runtime support for generated Wildix Smithy clients. Every @wildix/*-client depends on this and wires it in from its own runtimeConfig.native.ts, so applications do not import it directly.

What an app has to do

Install the two polyfills the AWS SDK also documents, as the first statements of the entry point:

npm install react-native-get-random-values react-native-url-polyfill

import "react-native-get-random-values";
import "react-native-url-polyfill/auto";

That is the whole contract. No metro.config.js resolver override, and no patches to @smithy/*.

What this package provides

| Export | Purpose | | --- | --- | | XhrHttpHandler | HttpHandler built on XMLHttpRequest, API-compatible with FetchHttpHandler. React Native's fetch never populates response.body, so the fetch handler buffers every response into a Blob — and React Native's Blob implements neither arrayBuffer() (nothing deserializes) nor stream() (streaming operations get no body). This one delivers a real ReadableStream, incrementally, which is what makes text/event-stream operations work. | | installReactNativeGlobals() | Installs TextDecoder, structuredClone and ReadableStream only when absent, and warns once naming the packages for the globals it deliberately will not fake. | | MinimalReadableStream, createPushStream | The stream implementation behind the handler, exported for tests and for anything building a body by hand. | | decodeUtf8, createUtf8DecoderState | Incremental UTF-8 decoding, including the mid-code-point chunk boundaries a streaming body produces. |

Why these and not others

The list was measured against the engine React Native ships (ios/Pods/hermes-engine/destroot/bin/hermes), not inferred:

TextEncoder = function      TextDecoder = undefined
structuredClone = undefined ReadableStream = undefined
URL = undefined             URLSearchParams = undefined
crypto = undefined          btoa / atob = function
Symbol.asyncIterator = undefined

Blob, FileReader, XMLHttpRequest and fetch come from React Native itself rather than the engine. Two consequences:

• TextEncoder is present and complete, encodeInto included, so fromUtf8 and calculateBodyLength from @smithy/core/serde need nothing from us. Only the decoder is missing, and it is installed as a global because its callers — @smithy/core/cbor at module-evaluation time, and sdkStreamMixin.transformToString — cannot be reached through client config.
• crypto.getRandomValues, URL and URLSearchParams are reported, never faked. A Math.random stand-in for a CSPRNG is a silent security downgrade, and a partial WHATWG URL parser corrupts request paths instead of failing. Both are on the AWS SDK's documented polyfill list for the same reason.

sdk-ts/docs/react_native.md records the full comparison against @aws-sdk/client-s3, the version numbers everything was checked at, and which upstream bugs this compensates for.

Development

pnpm run build   # dist-cjs + dist-es + dist-types
pnpm test        # jest

The transport is tested against a fake that mirrors React Native's own XMLHttpRequest semantics — cumulative responseText, incremental delivery only for the text response type — because a transport that passes against a well-behaved fake can still buffer the whole body on a device.