Consolidate HTTP client errors and flatten exports

This change replaces the per-HTTP-client error types with a single
generic `HttpClientError` type shared by all the built-in clients.
This allows us to remove the public `reqwest`, `curl`, and `ureq`
modules and directly re-export those crates from the root, which
allows imports such as `oauth2::reqwest` instead of
`oauth2::reqwest::reqwest`.

BREAKING CHANGES:
 - Removed `reqwest`, `curl`, and `ureq` modules. The corresponding
   crates are now re-exported from the root of this crate.
 - `CurlHttpClient` is now exported from the root of this crate when
   the `curl` feature is enabled.
 - Per-client error enums (e.g., `oauth2::reqwest::Error`) have been
   replaced with a generic `HttpClientError` type (e.g.,
   `oauth2::HttpClientError<reqwest::Error>`).

Author: ramosbugs

.github/workflows/main.yml

@@ -58,6 +58,7 @@ jobs:
       - name: Doc tests
         run: |
           cargo test --doc
+          cargo test --doc --no-default-features
           cargo test --doc --all-features
       - name: Test with all features enabled
         run: cargo test --all-features

examples/github.rs

@@ -14,7 +14,7 @@
 //!
 
 use oauth2::basic::BasicClient;
-use oauth2::reqwest::reqwest;
+use oauth2::reqwest;
 use oauth2::{
     AuthUrl, AuthorizationCode, ClientId, ClientSecret, CsrfToken, RedirectUrl, Scope,
     TokenResponse, TokenUrl,

examples/github_async.rs

@@ -14,7 +14,7 @@
 //!
 
 use oauth2::basic::BasicClient;
-use oauth2::reqwest::reqwest;
+use oauth2::reqwest;
 use oauth2::{
     AuthUrl, AuthorizationCode, ClientId, ClientSecret, CsrfToken, RedirectUrl, Scope,
     TokenResponse, TokenUrl,

examples/google.rs

@@ -13,7 +13,7 @@
 //! ...and follow the instructions.
 //!
 
-use oauth2::reqwest::reqwest;
+use oauth2::reqwest;
 use oauth2::{basic::BasicClient, StandardRevocableToken, TokenResponse};
 use oauth2::{
     AuthUrl, AuthorizationCode, ClientId, ClientSecret, CsrfToken, PkceCodeChallenge, RedirectUrl,

examples/google_devicecode.rs

@@ -14,7 +14,7 @@
 //!
 
 use oauth2::basic::BasicClient;
-use oauth2::reqwest::reqwest;
+use oauth2::reqwest;
 use oauth2::{
     AuthType, AuthUrl, ClientId, ClientSecret, DeviceAuthorizationResponse, DeviceAuthorizationUrl,
     ExtraDeviceAuthorizationFields, Scope, TokenUrl,

examples/microsoft_devicecode_tenant_user.rs

@@ -1,5 +1,5 @@
 use oauth2::basic::BasicClient;
-use oauth2::reqwest::reqwest;
+use oauth2::reqwest;
 use oauth2::StandardDeviceAuthorizationResponse;
 use oauth2::{AuthUrl, ClientId, DeviceAuthorizationUrl, Scope, TokenUrl};
 

examples/msgraph.rs

@@ -21,7 +21,7 @@
 //!
 
 use oauth2::basic::BasicClient;
-use oauth2::reqwest::reqwest;
+use oauth2::reqwest;
 use oauth2::{
     AuthType, AuthUrl, AuthorizationCode, ClientId, ClientSecret, CsrfToken, PkceCodeChallenge,
     RedirectUrl, Scope, TokenUrl,

examples/wunderlist.rs

@@ -18,7 +18,7 @@ use oauth2::basic::{
     BasicErrorResponse, BasicRevocationErrorResponse, BasicTokenIntrospectionResponse,
     BasicTokenType,
 };
-use oauth2::reqwest::reqwest;
+use oauth2::reqwest;
 use oauth2::{
     AccessToken, AuthUrl, AuthorizationCode, Client, ClientId, ClientSecret, CsrfToken,
     EmptyExtraTokenFields, EndpointNotSet, ExtraTokenFields, RedirectUrl, RefreshToken, Scope,

src/curl.rs

@@ -0,0 +1,80 @@
+use crate::{HttpClientError, HttpRequest, HttpResponse, SyncHttpClient};
+
+use curl::easy::Easy;
+use http::header::{HeaderValue, CONTENT_TYPE};
+use http::method::Method;
+use http::status::StatusCode;
+
+use std::io::Read;
+
+/// A synchronous HTTP client using [`curl`].
+pub struct CurlHttpClient;
+impl SyncHttpClient for CurlHttpClient {
+    type Error = HttpClientError<curl::Error>;
+
+    fn call(&self, request: HttpRequest) -> Result<HttpResponse, Self::Error> {
+        let mut easy = Easy::new();
+        easy.url(&request.uri().to_string()[..]).map_err(Box::new)?;
+
+        let mut headers = curl::easy::List::new();
+        for (name, value) in request.headers() {
+            headers
+                .append(&format!(
+                    "{}: {}",
+                    name,
+                    // TODO: Unnecessary fallibility, curl uses a CString under the hood
+                    value.to_str().map_err(|_| HttpClientError::Other(format!(
+                        "invalid `{name}` header value {:?}",
+                        value.as_bytes()
+                    )))?
+                ))
+                .map_err(Box::new)?
+        }
+
+        easy.http_headers(headers).map_err(Box::new)?;
+
+        if let Method::POST = *request.method() {
+            easy.post(true).map_err(Box::new)?;
+            easy.post_field_size(request.body().len() as u64)
+                .map_err(Box::new)?;
+        } else {
+            assert_eq!(*request.method(), Method::GET);
+        }
+
+        let mut form_slice = &request.body()[..];
+        let mut data = Vec::new();
+        {
+            let mut transfer = easy.transfer();
+
+            transfer
+                .read_function(|buf| Ok(form_slice.read(buf).unwrap_or(0)))
+                .map_err(Box::new)?;
+
+            transfer
+                .write_function(|new_data| {
+                    data.extend_from_slice(new_data);
+                    Ok(new_data.len())
+                })
+                .map_err(Box::new)?;
+
+            transfer.perform().map_err(Box::new)?;
+        }
+
+        let mut builder = http::Response::builder().status(
+            StatusCode::from_u16(easy.response_code().map_err(Box::new)? as u16)
+                .map_err(http::Error::from)?,
+        );
+
+        if let Some(content_type) = easy
+            .content_type()
+            .map_err(Box::new)?
+            .map(HeaderValue::from_str)
+            .transpose()
+            .map_err(http::Error::from)?
+        {
+            builder = builder.header(CONTENT_TYPE, content_type);
+        }
+
+        builder.body(data).map_err(HttpClientError::Http)
+    }
+}