Ability to configure custom JSON.parse reviver for the HttpClient

[bygrace1986]

I'm submitting a...

[x] Feature request

Current behavior

With the new HttpClient if the responseType is set to 'json' or if it is not set (defaulted to 'json') then the JSON is parsed before being returned to the consuming code. Here is the source-code where the JSON.parse occurs:

angular/packages/common/http/src/xhr.ts

Line 189 in 20e1cc0

body = body !== '' ? JSON.parse(body) : null;

Expected behavior

A reviver function can be configured that the HttpClient will use when parsing json. As far as the implementation, maybe an injection token can be exposed which developers can use to provide a reviver function.

What is the motivation / use case for changing the behavior?

Dates are deserialized as strings with JSON.parse. It is convenient to have dates serialized to Date objects globally via a centralized service using a reviver.

[Toxicable]

You just ask for the body as text rather than json then parse it yourself

[bygrace1986]

@Toxicable That is what I am already doing with an interceptor. So it isn't a major priority and with interceptors I am already better off than I was with pre 4.3. But it would be nice to have a hook rather than copying/pasting that section of code to match the XSSI prefix striping, error handling, and whatever else changes in the future. I would also like to be able to set the proper responseType rather than changing it as a way to opt-out.

[TobiDimmel]

+1. Same reason - for deserializing dates in a central place.
Maybe one provides even an option in HttpClient to turn date deserialization to Date objects on.

[bygrace1986]

@tade90 I'd say that the MVP is to allow a reviver to be specified. This will allow custom deserialization in general and not everyone will want to deserialize dates to the JavaScript Date object. People may want to deserialize to 3rd party representations (moment, js-joda, ...) that are better suited for their use-cases (handling timezones, date arithmetic, ...).

To what you said about "turn date deserialization to Date objects on" we would first have to define what a date is since the JSON standard does not seem to specify a format for dates. There are several but I think that ISO 8601 is what most people probably want. Maybe angular could provide a reviver function that you could configure or even a flag, but if ISO 8601 is the standard then you can easily setup a reviver using Date.parse. So it might be something that is better solved by an example in the documentation related to configuring custom revivers.

[TobiDimmel]

@bygrace1986

I'd say that the MVP is to allow a reviver to be specified.

Totally agree. Making the reviver able to be specified should be the base. Everthing from there would be sugar-coating. But it would be easier to use if there are pre-defined reviver functions for common use-cases like date serialization. This could be similar to the DatePipe where you have some pre-defined formats ('short', 'medium', ...) and you also can define custom formats ('M/d/yy, h:mm a').

There are several but I think that ISO 8601 is what most people probably want.

ISO 8601 would fulfill my needs.

[dholcombe]

I am also looking for a way to specify a custom reviver. My use case is also due to the need to handle dates. In this case ISO 8601 dates of the form "1999-02-28" which I want to revivify as Luxon DateTime objects.

[ezequielzacca]

its such a common case im amazed this hasnt been implemented yet

[hjb417]

There should be a dependency injected service (E.x.: JsonSerializationService with a serialize/deserialize method) responsible for serialization that's used through angular so we can easily swap in our own serializer. The out of the box implementation should just call JSON.parse and JSON.stringify. It would also be great if the HttpClient had a property to allow getting/setting the serializer it will use. It will default to the dependency injected JsonSerializationService but exposing this allows specifying the serializer for that specific instance of HttpClient.

This is all based on the premise that services can be replaced/overridden by reregistering them with 'providedIn: root'. If that's not possible, I'm hoping there are other means of doing so.