Crate pretend[−][src]

Expand description

pretend HTTP client

pretend is a modular, Feign-inspired, HTTP client based on macros. It’s goal is to decouple the definition of a REST API from it’s implementation.

Some features:

Declarative
Support Asynchronous and blocking requests
HTTP client agnostic
JSON support thanks to serde

Getting started

A REST API is described by annotating a trait:

use pretend::{pretend, request, Result};

#[pretend]
trait HttpBin {
    #[request(method = "POST", path = "/anything")]
    async fn post_anything(&self, body: &'static str) -> Result<String>;
}

Under the hood, pretend will implement this trait for Pretend. An instance of this struct can be constructed by passing a client implementation, and the REST API’s base url. In the following example, we are using the reqwest based client.

use pretend::{Pretend, Url};
use pretend_reqwest::Client;

let client = Client::default();
let url = Url::parse("https://httpbin.org").unwrap();
let pretend = Pretend::for_client(client).with_url(url);
let response = pretend.post_anything("hello").await.unwrap();
assert!(response.contains("hello"));

Sending headers, query parameters and bodies

Headers are provided as attributes using header.

use pretend::{header, pretend, request, Result};

#[pretend]
trait HttpBin {
    #[request(method = "GET", path = "/get")]
    #[header(name = "X-Test-Header-1", value = "abc")]
    #[header(name = "X-Test-Header-2", value = "other")]
    async fn get_with_headers(&self, value: i32, custom: &str) -> Result<()>;
}

Query parameters and bodies are provided as method parameters. Body type is guessed based on the parameter name:

Parameter body will be sent as raw bytes.
Parameter form will be serialized as form-encoded using serde.
Parameter json will be serialized as JSON using serde.

Query parameter is passed with the query parameter. It is also serialized using serde.

use pretend::{pretend, request, Json, Result};
use serde::Serialize;

#[derive(Serialize)]
struct Data {
    value: i32,
}

#[pretend]
trait HttpBin {
    #[request(method = "POST", path = "/anything")]
    async fn post_bytes(&self, body: Vec<u8>) -> Result<()>;

    #[request(method = "POST", path = "/anything")]
    async fn post_string(&self, body: &'static str) -> Result<()>;

    #[request(method = "POST", path = "/anything")]
    async fn post_with_query_params(&self, query: &Data) -> Result<()>;

    #[request(method = "POST", path = "/anything")]
    async fn post_json(&self, json: &Data) -> Result<()>;
}

Handling responses

pretend support a wide range of response types, based on the return type of the method. The body can be returned as a Vec<u8>, a string or as JSON by using the Json wrapper type. The unit type () can also be used if the body should be discarded.

JsonResult is also offered as a convenience type. It will deserialize into a value type or an error type depending on the HTTP status code.

When retrieving body alone, an HTTP error will cause the method to return an error. It is possible to prevent the method to fail and access the HTTP status code by wrapping these types inside a Response. This also allows accessing response headers.

use pretend::{pretend, request, Json, JsonResult, Response, Result};
use serde::Deserialize;

#[derive(Deserialize)]
struct Data {
    value: i32,
}

#[derive(Deserialize)]
struct Error {
    error: String,
}

#[pretend]
trait HttpBin {
    #[request(method = "POST", path = "/anything")]
    async fn read_bytes(&self) -> Result<Vec<u8>>;

    #[request(method = "POST", path = "/anything")]
    async fn read_string(&self) -> Result<String>;

    #[request(method = "POST", path = "/anything")]
    async fn read_json(&self) -> Result<Json<Data>>;

    #[request(method = "POST", path = "/anything")]
    async fn read_json_result(&self) -> Result<JsonResult<Data, Error>>;

    #[request(method = "POST", path = "/anything")]
    async fn read_status(&self) -> Result<Response<()>>;
}

Templating

Request paths and headers support templating. A value between braces will be replaced by a parameter with the same name. The replacement is done with format!, meaning that any type that implement Display is supported.

use pretend::{header, pretend, request, Json, Pretend, Result};
use pretend_reqwest::Client;
use serde::Deserialize;
use std::collections::HashMap;

#[derive(Deserialize)]
struct Data {
    url: String,
    headers: HashMap<String, String>,
}

#[pretend]
trait HttpBin {
    #[request(method = "POST", path = "/{path}")]
    #[header(name = "X-{header}", value = "{value}$")]
    async fn read(&self, path: &str, header: &str, value: i32) -> Result<Json<Data>>;
}

let client = Client::default();
let url = Url::parse("https://httpbin.org").unwrap();
let pretend = Pretend::for_client(client).with_url(url);
let response = pretend.read("anything", "My-Header", 123).await.unwrap();
let data = response.value();
assert_eq!(data.url, "https://httpbin.org/anything");
assert_eq!(*data.headers.get("X-My-Header").unwrap(), "123$".to_string());

Blocking requests

When all methods in the pretend-annotated trait are async, pretend will generate an async implementation. To generate a blocking implementation, simply remove the async.

Blocking implementations will need a blocking client implementation.

use pretend::{pretend, request, Pretend, Result, Url};
use pretend_reqwest::BlockingClient;

#[pretend]
trait HttpBin {
    #[request(method = "POST", path = "/anything")]
    fn post_anything(&self, body: &'static str) -> Result<String>;
}

let client = BlockingClient::default();
let url = Url::parse("https://httpbin.org").unwrap();
let pretend = Pretend::for_client(client).with_url(url);
let response = pretend.post_anything("hello").unwrap();
assert!(response.contains("hello"));

Non-Send implementation

Today, Rust do not support futures in traits. pretend uses async_trait to workaround that limitation. By default, async_trait adds the Send bound to futures. This implies that Pretend itself is Send and Sync, and implies that the client implementation it uses is also Send and Sync.

However, some clients are not thread-safe, and cannot be shared between threads. To use these clients with Pretend, you have toopt-out from the Send constraint on returned futures by using #[pretend(?Send)]. This is similar to what is done in async_trait.

Clients implementations that are not thread-safe are usually called “local clients”.

Available client implementations

pretend can be used with the following HTTP clients

reqwest (async and blocking)
isahc (async)

Implementing a `pretend` HTTP client

pretend clients wraps HTTP clients from other crates. They allow Pretend to execute HTTP requests. See the client module level documentation for more information about how to implement a client.

URL resolvers

pretend uses URL resolvers to resolve a full URL from the path in request. By default the URL resolver will simply append the path to a base URL. More advanced resolvers can be implemented with the resolver module.

Examples

More examples are available in the examples folder.

MSRV

MSRV for the pretend ecosystem is Rust 1.44.

The future

Here is a quick roadmap

Introduce more attributes to mark method parameters (body, json, params)
Introduce interceptors

Re-exports

`pub use http;`
`pub use serde;`
`pub use url;`

Modules

client	Client traits
resolver	URL resolver

Structs

HeaderMap	A set of HTTP headers
Json	JSON body
Pretend	The pretend HTTP client
Response	Response type
StatusCode	An HTTP status code (`status-code` in RFC 7230 et al.).
Url	A parsed URL record.

Enums

Error	Pretend errors
JsonResult	JSON result

Type Definitions

Result

Pretend Result type

Attribute Macros

header
pretend
request