Can I check header existense for HttpResponseBuilder inside external crate?

[ym-project]

Hi!

I'm trying to extend HttpResponse struct with my own functions.

use actix_web::{HttpResponse, HttpResponseBuilder};
use actix_web::error::Error;
use actix_web::http::header;

trait MyResponseBuilder {
    fn my_func<T>(&mut self, value: T) -> Result<HttpResponse, Error>;
}

impl MyResponseBuilder for HttpResponseBuilder {
    fn my_func<T>(&mut self, value: T) -> Result<HttpResponse, Error> {
        self.insert_header(header::ContentType("Some Content Type"));
    }
}

My goal - I want to check contentType existence.

if hasContentType {
    // do nothing
} else {
    self.insert_header(...)
}

But I don't know how to do this.

I looked for implementation of json and noticed what actix-web uses method self.inner() to implement the same condition

actix-web/actix-web/src/response/builder.rs

Lines 333 to 350 in d445742

	pub fn json(&mut self, value: impl Serialize) -> HttpResponse {
	match serde_json::to_string(&value) {
	Ok(body) => {
	let contains = if let Some(parts) = self.inner() {
	parts.headers.contains_key(header::CONTENT_TYPE)
	} else {
	true
	};
	if !contains {
	self.insert_header((header::CONTENT_TYPE, mime::APPLICATION_JSON));
	}
	self.body(body)
	}
	Err(err) => HttpResponse::from_error(JsonPayloadError::Serialize(err)),
	}
	}

But that method is private.
How can I do the same?