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update errorhandlers migration guide
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Rob Ede
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@ -3,8 +3,7 @@
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This guide walks you through the process of migrating from v3.x.y to v4.x.y.
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If you are migrating to v4.x.y from an older version of Actix Web (v2.x.y or earlier), check out the other historical migration notes in this folder.
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This document is not designed to be exhaustive - it focuses on the most significant changes coming in v4.
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You can find an exhaustive changelog in [CHANGES.md](./CHANGES.md), complete of PR links. If you think that some of the changes that we omitted deserve to be called out in this document, please open an issue or submit a PR.
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This document is not designed to be exhaustive—it focuses on the most significant changes coming in v4. You can find an exhaustive changelog in [CHANGES.md](./CHANGES.md), complete of PR links. If you think that some of the changes that we omitted deserve to be called out in this document, please open an issue or submit a PR.
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Headings marked with :warning: are **breaking behavioral changes**. They will probably not surface as compile-time errors though automated tests _might_ detect their effects on your app.
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@ -39,8 +38,9 @@ The MSRV of Actix Web has been raised from 1.42 to 1.54.
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## Tokio v1 Ecosystem
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Actix Web v4 is now underpinned by `tokio`'s v1 ecosystem.
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`cargo` supports having multiple versions of the same crate within the same dependency tree, but `tokio` v1 does not interoperate transparently with its previous versions (v0.2, v0.1). Some of your dependencies might rely on `tokio`, either directly or indirectly - if they are using an older version of `tokio`, check if an update is available.
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Actix Web v4 is now underpinned by `tokio`'s v1 ecosystem.
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`cargo` supports having multiple versions of the same crate within the same dependency tree, but `tokio` v1 does not interoperate transparently with its previous versions (v0.2, v0.1). Some of your dependencies might rely on `tokio`, either directly or indirectly—if they are using an older version of `tokio`, check if an update is available.
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The following command can help you to identify these dependencies:
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```sh
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@ -59,8 +59,8 @@ Lots of modules have been re-organized in this release. If a compile error refer
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## `NormalizePath` Middleware :warning:
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The default `NormalizePath` behavior now strips trailing slashes by default.
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This was the _documented_ behaviour in Actix Web v3, but the _actual_ behaviour differed - the discrepancy has now been fixed.
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The default `NormalizePath` behavior now strips trailing slashes by default. This was the _documented_ behaviour in Actix Web v3, but the _actual_ behaviour differed. The discrepancy has now been resolved.
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As a consequence of this change, routes defined with trailing slashes will become inaccessible when using `NormalizePath::default()`. Calling `NormalizePath::default()` will log a warning. We suggest to use `new` or `trim`.
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```diff
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@ -103,8 +103,7 @@ The `compress` feature flag has been split into more granular feature flags, one
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## `web::Path`
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The inner field for `web::Path` is now private.
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It was causing too many issues when used with inner tuple types due to its `Deref` implementation.
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The inner field for `web::Path` is now private. It was causing ambiguity when trying to use tuple indexing due to its `Deref` implementation.
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```diff
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- async fn handler(web::Path((foo, bar)): web::Path<(String, String)>) {
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@ -118,7 +117,7 @@ Actix Web now depends on version 0.20 of `rustls`. As a result, the server confi
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## Removed `awc` Client Re-export
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Actix Web's sister crate `awc` is no longer re-exported through the `client` module. This allows `awc` to have its own release cadence - its breaking changes are no longer blocked by Actix Web's (more conservative) release schedule.
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Actix Web's sister crate `awc` is no longer re-exported through the `client` module. This allows `awc` to have its own release cadence—its breaking changes are no longer blocked by Actix Web's (more conservative) release schedule.
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```diff
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- use actix_web::client::Client;
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@ -134,11 +133,11 @@ Actix Web's sister crate `awc` is no longer re-exported through the `client` mod
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+ use use actix_test::start;
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```
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`TestServer` previously lived in `actix_web::test`, but it depends on `awc` which is no longer part of Actix Web's public API (see above).
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`TestServer` previously lived in `actix_web::test`, but it depends on `awc` which is no longer part of Actix Web's public API (see above).
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## Header APIs
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Header related APIs have been standardized across all `actix-*` crates. The terminology now better matches the underlying `HeaderMap` naming conventions.
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Header related APIs have been standardized across all `actix-*` crates. The terminology now better matches the underlying `HeaderMap` naming conventions.
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In short, "insert" always indicates that any existing headers with the same name are overridden, while "append" is used for adding with no removal (e.g. multi-valued headers).
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@ -155,7 +154,7 @@ For request and response builder APIs, the new methods provide a unified interfa
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+ .insert_header(ContentType::json())
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```
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We chose to deprecate most of the old methods instead of removing them immediately - the warning notes will guide you on how to update.
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We chose to deprecate most of the old methods instead of removing them immediately—the warning notes will guide you on how to update.
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## Response Body Types
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@ -178,16 +177,65 @@ We have boosted the quality and completeness of the documentation for all items
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### `BoxBody`
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`BoxBody` is a new type-erased body type. It's used for all error response bodies.
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Creating a boxed body is best done by calling [`.boxed()`](https://docs.rs/actix-web/4/actix_web/body/trait.MessageBody.html#method.boxed) on a `MessageBody` type.
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`BoxBody` is a new type-erased body type.
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It can be useful when writing handlers, responders, and middleware when you want to trade a (very) small amount of performance for a simpler type.
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Creating a boxed body is done most efficiently by calling [`.boxed()`](https://docs.rs/actix-web/4/actix_web/body/trait.MessageBody.html#method.boxed) on a `MessageBody` type.
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### `EitherBody`
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`EitherBody` is a new "either" type that is particularly useful in middlewares that can bail early, returning their own response plus body type.
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`EitherBody` is a new "either" type that implements `MessageBody`
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It is particularly useful in middleware that can bail early, returning their own response plus body type. By default the "right" variant is `BoxBody` (i.e., `EitherBody<B>` === `EitherBody<B, BoxBody>`) but it can be anything that implements `MessageBody`.
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For example, it will be common among middleware which value performance of the hot path to use:
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```rust
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type Response = Result<ServiceResponse<EitherBody<B>>, Error>
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```
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This can be read (ignoring the `Result`) as "resolves with a `ServiceResponse` that is either the inner service's `B` body type or a boxed body type from elsewhere, likely constructed within the middleware itself". Of course, if your middleware contains only simple string other/error responses, it's possible to use them without boxes at the cost of a less simple implementation:
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```rust
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type Response = Result<ServiceResponse<EitherBody<B, String>>, Error>
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```
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### Error Handlers
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TODO In particular, folks seem to be struggling with the `ErrorHandlers` middleware because of this change and the obscured nature of `EitherBody` within its types.
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`ErrorHandlers` is a commonly used middleware that has changed in design slightly due to the other body type changes.
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In particular, an implicit `EitherBody` is used in the `ErrorHandlerResponse<B>` type. An `ErrorHandlerResponse<B>` now expects a `ServiceResponse<EitherBody<B>>` to be returned within response variants. The following is a migration for an error handler that **only modifies** the response argument (left body).
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```diff
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fn add_error_header<B>(mut res: ServiceResponse<B>) -> Result<ErrorHandlerResponse<B>, Error> {
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res.response_mut().headers_mut().insert(
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header::CONTENT_TYPE,
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header::HeaderValue::from_static("Error"),
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);
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- Ok(ErrorHandlerResponse::Response(res))
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+ Ok(ErrorHandlerResponse::Response(res.map_into_left_body()))
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}
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```
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The following is a migration for an error handler that creates a new response instead (right body).
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```diff
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fn error_handler<B>(res: ServiceResponse<B>) -> Result<ErrorHandlerResponse<B>, Error> {
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- let req = res.request().clone();
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+ let (req, _res) = res.into_parts();
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let res = actix_files::NamedFile::open("./templates/404.html")?
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.set_status_code(StatusCode::NOT_FOUND)
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- .into_response(&req)?
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- .into_body();
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+ .into_response(&req);
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- let res = ServiceResponse::new(req, res);
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+ let res = ServiceResponse::new(req, res).map_into_right_body();
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Ok(ErrorHandlerResponse::Response(res))
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}
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```
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## Middleware Trait APIs
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@ -251,7 +299,7 @@ You may need to review the [guidance on shared mutable state](https://docs.rs/ac
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Improvements to module management and re-exports have resulted in not needing direct dependencies on these underlying crates for the vast majority of cases. In particular:
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- all traits necessary for creating middlewares are now re-exported through the `dev` modules;
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- `#[actix_web::test]` now exists for async test definitions.
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- `#[actix_web::test]` now exists for async test definitions.
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Relying on these re-exports will ease the transition to future versions of Actix Web.
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@ -185,11 +185,13 @@ mod tests {
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use super::*;
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use crate::{
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body,
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http::{
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header::{HeaderValue, CONTENT_TYPE},
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StatusCode,
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},
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test::{self, TestRequest},
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ResponseError,
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};
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#[actix_rt::test]
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@ -245,9 +247,7 @@ mod tests {
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#[actix_rt::test]
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async fn changes_body_type() {
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#[allow(clippy::unnecessary_wraps)]
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fn error_handler<B: 'static>(
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res: ServiceResponse<B>,
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) -> Result<ErrorHandlerResponse<B>> {
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fn error_handler<B>(res: ServiceResponse<B>) -> Result<ErrorHandlerResponse<B>> {
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let (req, res) = res.into_parts();
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let res = res.set_body(Bytes::from("sorry, that's no bueno"));
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@ -270,5 +270,33 @@ mod tests {
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assert_eq!(test::read_body(res).await, "sorry, that's no bueno");
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}
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// TODO: test where error is thrown
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#[actix_rt::test]
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async fn error_thrown() {
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#[allow(clippy::unnecessary_wraps)]
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fn error_handler<B>(_res: ServiceResponse<B>) -> Result<ErrorHandlerResponse<B>> {
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Err(crate::error::ErrorInternalServerError(
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"error in error handler",
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))
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}
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let srv = test::simple_service(StatusCode::BAD_REQUEST);
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let mw = ErrorHandlers::new()
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.handler(StatusCode::BAD_REQUEST, error_handler)
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.new_transform(srv.into_service())
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.await
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.unwrap();
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let err = mw
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.call(TestRequest::default().to_srv_request())
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.await
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.unwrap_err();
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let res = err.error_response();
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assert_eq!(res.status(), StatusCode::INTERNAL_SERVER_ERROR);
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assert_eq!(
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body::to_bytes(res.into_body()).await.unwrap(),
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"error in error handler"
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);
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}
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}
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@ -89,7 +89,7 @@ where
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/// ```
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///
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/// # Panics
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/// Panics if service call returns error.
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/// Panics if service call returns error. To handle errors use `app.call(req)`.
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pub async fn call_service<S, R, B, E>(app: &S, req: R) -> S::Response
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where
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S: Service<R, Response = ServiceResponse<B>, Error = E>,
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