allow passing a callback to useFetch's run to modify init

README.md

@@ -191,6 +191,15 @@ const MyComponent = () => {
   const headers = { Accept: "application/json" }
   const { data, error, isLoading, run } = useFetch("/api/example", { headers }, options)
   // This will setup a promiseFn with a fetch request and JSON deserialization.
+
+  // you can later call `run` with an optional callback argument to 
+  // last-minute modify the `init` parameter that is passed to `fetch`
+  function clickHandler() {
+    run(init => ({
+      ...init, 
+      body: JSON.stringify(formValues)
+    }))
+  }
 }
 ```
 

packages/react-async/src/useAsync.js

@@ -126,8 +126,7 @@ const useAsync = (arg1, arg2) => {
 
 const parseResponse = (accept, json) => res => {
   if (!res.ok) return Promise.reject(res)
-  if (json === false) return res
-  if (json === true || accept === "application/json") return res.json()
+  if (json === true || (json !== false && accept === "application/json")) return res.json()
   return res
 }
 
@@ -136,13 +135,17 @@ const useAsyncFetch = (input, init, { defer, json, ...options } = {}) => {
   const headers = input.headers || (init && init.headers) || {}
   const accept = headers["Accept"] || headers["accept"] || (headers.get && headers.get("accept"))
   const doFetch = (input, init) => globalScope.fetch(input, init).then(parseResponse(accept, json))
-  const isDefer = defer === true || ~["POST", "PUT", "PATCH", "DELETE"].indexOf(method)
-  const fn = defer === false || !isDefer ? "promiseFn" : "deferFn"
+  const isDefer =
+    defer === true || (defer !== false && ~["POST", "PUT", "PATCH", "DELETE"].indexOf(method))
+  const fn = isDefer ? "deferFn" : "promiseFn"
   const state = useAsync({
     ...options,
     [fn]: useCallback(
-      (_, props, ctrl) => doFetch(input, { signal: ctrl ? ctrl.signal : props.signal, ...init }),
-      [JSON.stringify(input), JSON.stringify(init)]
+      isDefer
+        ? ([override], _, { signal }) =>
+            doFetch(input, { signal, ...(typeof override === "function" ? override(init) : init) })
+        : (_, { signal }) => doFetch(input, { signal, ...init }),
+      [(isDefer, JSON.stringify(input), JSON.stringify(init))]
     ),
   })
   useDebugValue(state, ({ counter, status }) => `[${counter}] ${status}`)

packages/react-async/src/useAsync.spec.js

@@ -161,4 +161,21 @@ describe("useFetch", () => {
     await Promise.resolve()
     expect(json).toHaveBeenCalled()
   })
+
+  test("calling `run` with an argument allows to override `init` parameters", () => {
+    const component = (
+      <Fetch input="/test" init={{ method: "POST" }}>
+        {({ run }) => (
+          <button onClick={() => run(init => ({ ...init, body: '{"name":"test"}' }))}>run</button>
+        )}
+      </Fetch>
+    )
+    const { getByText } = render(component)
+    expect(globalScope.fetch).not.toHaveBeenCalled()
+    fireEvent.click(getByText("run"))
+    expect(globalScope.fetch).toHaveBeenCalledWith(
+      "/test",
+      expect.objectContaining({ method: "POST", signal: abortCtrl.signal, body: '{"name":"test"}' })
+    )
+  })
 })