Provide process id to before middleware

[devpaul]

Enhancement

I created a middleware that automatically updates the store to indicate that the process is in progress using an object literal mapping in the store. Its easy to update the related state in the after middleware because it gets the process id. Unfortunately the before middleware does not. It'd be great if it did! :)

Package Version: Dojo 5

Code

Here's the example middleware. It needs to be created via a function to provide the id to before.

const setComplete = createProcess('request-complete', [
	commandFactory(({ path, payload: { id } }) => {
		return [
			replace(path('request', id), {
				isLoading: false
			})
		];
	})
]);

const setStarting = createProcess('request-sent', [
	commandFactory(({ path, payload: { id } }) => {
		return [
			replace(path('request', id), {
				isLoading: true
			})
		];
	})
]);

const setError = createProcess('set-error', [
	({ path, payload: { id, error } }) => {
		return [replace(path('request', id), { isLoading: false, message: error.message, error })];
	}
]);

export function createRequestMiddleware(id: string): ProcessCallback<State> {
	return () => ({
		before(payload, store) {
			setStarting(store)({ id });
		},
		after(errorState, result) {
			if (errorState) {
				const { error } = errorState;
				if (error) {
					result.executor(setError, { id, error });
				}
			} else {
				result.executor(setComplete, { id });
			}
		}
	});
}

It's currently used like this

export const login = appProcess('login', [loginCommand, getSelfCommand], createRequestMiddleware('login'));

The Login container uses state created by this middleware to get error messages automatically and know when the process is loading and disable the login button.

Expected behavior:

If the process id was provided to before I could create a generic requestMiddleware and use it as such:

export const login = appProcess('login', [loginCommand, getSelfCommand], [requestMiddleware]);

this would eliminate accidentally passing the wrong id when creating the middleware and obviate the need for the middleware factory, not to mention it should be an easy PR to add id here https://github.com/dojo/framework/blob/master/src/stores/process.ts#L178