From 5da3f34b3e138524e9226af3ecc9f673664d407c Mon Sep 17 00:00:00 2001
From: David Pedersen <david.pdrsn@gmail.com>
Date: Thu, 11 Nov 2021 17:33:33 +0100
Subject: [PATCH] Clean up axum-debug crate (#498)

* Clean up axum-debug crate

Mostly just brings the crate more in line with the rest of the crates in
the workspace.

I've also removed the axum-debug-macros crate since axum-debug only
contained one re-export from axum-debug-macros. So we didn't need two
crates. Can always bring the "backend" crate back if we need things in
axum-debug that aren't proc-macros.

* Just testing: This should make CI fail

* Misc CI clean up

* fix intentional breakage

* fix changelog

* Remove rustfmt config for now as it gives warnings on stable

* Fix paths
---
 .github/workflows/CI.yml             |  15 +-
 .rustfmt.toml                        |   2 -
 Cargo.toml                           |   1 -
 axum-debug-macros/CHANGELOG.md       |  13 --
 axum-debug-macros/Cargo.toml         |  20 --
 axum-debug-macros/LICENSE            |   7 -
 axum-debug-macros/README.md          |  23 --
 axum-debug-macros/src/lib.rs         | 305 -------------------------
 axum-debug/CHANGELOG.md              |   1 +
 axum-debug/Cargo.toml                |   9 +-
 axum-debug/README.md                 |  73 +++---
 axum-debug/src/lib.rs                | 321 ++++++++++++++++++++++++++-
 axum-handle-error-extract/src/lib.rs |   1 -
 axum/src/lib.rs                      |   1 -
 14 files changed, 354 insertions(+), 438 deletions(-)
 delete mode 100644 .rustfmt.toml
 delete mode 100644 axum-debug-macros/CHANGELOG.md
 delete mode 100644 axum-debug-macros/Cargo.toml
 delete mode 100644 axum-debug-macros/LICENSE
 delete mode 100644 axum-debug-macros/README.md
 delete mode 100644 axum-debug-macros/src/lib.rs

diff --git a/.github/workflows/CI.yml b/.github/workflows/CI.yml
index a1923ea0..c0eec713 100644
--- a/.github/workflows/CI.yml
+++ b/.github/workflows/CI.yml
@@ -41,9 +41,8 @@ jobs:
         profile: minimal
     - uses: Swatinem/rust-cache@v1
     - name: cargo doc
-      working-directory: ${{ matrix.subcrate }}
       env:
-          RUSTDOCFLAGS: "-D broken-intra-doc-links"
+        RUSTDOCFLAGS: "-D broken-intra-doc-links"
       run: cargo doc --all-features --no-deps
 
   cargo-hack:
@@ -60,7 +59,6 @@ jobs:
       run: |
         curl -LsSf https://github.com/taiki-e/cargo-hack/releases/latest/download/cargo-hack-x86_64-unknown-linux-gnu.tar.gz | tar xzf - -C ~/.cargo/bin
     - name: cargo hack check
-      working-directory: ${{ matrix.subcrate }}
       run: cargo hack check --each-feature --no-dev-deps --all
 
   test-versions:
@@ -88,14 +86,11 @@ jobs:
   test-msrv:
     needs: check
     runs-on: ubuntu-latest
-    strategy:
-      matrix:
-        rust: [1.54]
     steps:
     - uses: actions/checkout@master
     - uses: actions-rs/toolchain@v1
       with:
-        toolchain: ${{ matrix.rust }}
+        toolchain: 1.54
         override: true
         profile: minimal
     - uses: Swatinem/rust-cache@v1
@@ -103,7 +98,11 @@ jobs:
       uses: actions-rs/cargo@v1
       with:
         command: test
-        args: -p axum --all-features --all-targets
+        args: >
+          -p axum
+          -p axum-debug 
+          -p axum-handle-error-extract
+          --all-features --all-targets
 
   test-docs:
     needs: check
diff --git a/.rustfmt.toml b/.rustfmt.toml
deleted file mode 100644
index 946fb445..00000000
--- a/.rustfmt.toml
+++ /dev/null
@@ -1,2 +0,0 @@
-# Merge multiple `use`s from the same crate
-imports_granularity = "Crate"
diff --git a/Cargo.toml b/Cargo.toml
index 9e90f95d..1787db59 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -2,7 +2,6 @@
 members = [
     "axum",
     "axum-debug",
-    "axum-debug-macros",
     "axum-handle-error-extract",
     "examples/*",
 ]
diff --git a/axum-debug-macros/CHANGELOG.md b/axum-debug-macros/CHANGELOG.md
deleted file mode 100644
index 2b9586bb..00000000
--- a/axum-debug-macros/CHANGELOG.md
+++ /dev/null
@@ -1,13 +0,0 @@
-# Changelog
-All notable changes to this project will be documented in this file.
-
-The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
-and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
-
-# Unreleased
-
-- **breaking:** Removed `debug_router` macro.
-
-# 0.1.0 (6. October 2021)
-
-- Initial release.
diff --git a/axum-debug-macros/Cargo.toml b/axum-debug-macros/Cargo.toml
deleted file mode 100644
index 90f38275..00000000
--- a/axum-debug-macros/Cargo.toml
+++ /dev/null
@@ -1,20 +0,0 @@
-[package]
-authors = ["Programatik <programatik29@gmail.com>"]
-categories = ["development-tools::debugging"]
-description = "Macros for axum-debug crate."
-edition = "2018"
-homepage = "https://github.com/tokio-rs/axum"
-keywords = ["axum", "debugging", "debug"]
-license = "MIT"
-name = "axum-debug-macros"
-readme = "README.md"
-repository = "https://github.com/tokio-rs/axum"
-version = "0.1.0"
-
-[lib]
-proc-macro = true
-
-[dependencies]
-proc-macro2 = "1"
-quote = "1"
-syn = { version = "1", features = ["full"] }
diff --git a/axum-debug-macros/LICENSE b/axum-debug-macros/LICENSE
deleted file mode 100644
index d8b49ec9..00000000
--- a/axum-debug-macros/LICENSE
+++ /dev/null
@@ -1,7 +0,0 @@
-Copyright 2021 Axum Debug Contributors
-
-Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
-
-The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
-
-THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
diff --git a/axum-debug-macros/README.md b/axum-debug-macros/README.md
deleted file mode 100644
index 52886f56..00000000
--- a/axum-debug-macros/README.md
+++ /dev/null
@@ -1,23 +0,0 @@
-[![License](https://img.shields.io/crates/l/axum-debug-macros)](https://choosealicense.com/licenses/mit/)
-[![Crates.io](https://img.shields.io/crates/v/axum-debug-macros)](https://crates.io/crates/axum-debug-macros)
-[![Docs - Stable](https://img.shields.io/crates/v/axum-debug-macros?color=blue&label=docs)](https://docs.rs/axum-debug-macros/)
-
-# axum-debug-macros
-
-Procedural macros for [`axum-debug`] crate.
-
-## Safety
-
-This crate uses `#![forbid(unsafe_code)]` to ensure everything is implemented
-in 100% safe Rust.
-
-## Performance
-
-This crate have no effect when using release profile. (eg. `cargo build
---release`)
-
-## License
-
-This project is licensed under the [MIT license](LICENSE).
-
-[`axum-debug`]: https://crates.io/crates/axum-debug
diff --git a/axum-debug-macros/src/lib.rs b/axum-debug-macros/src/lib.rs
deleted file mode 100644
index 3c5ed531..00000000
--- a/axum-debug-macros/src/lib.rs
+++ /dev/null
@@ -1,305 +0,0 @@
-//! Procedural macros for [`axum-debug`] crate.
-//!
-//! [`axum-debug`]: https://crates.io/crates/axum-debug
-
-#![warn(
-    clippy::all,
-    clippy::dbg_macro,
-    clippy::todo,
-    clippy::mem_forget,
-    rust_2018_idioms,
-    future_incompatible,
-    nonstandard_style,
-    missing_debug_implementations,
-    missing_docs
-)]
-#![deny(unreachable_pub, private_in_public)]
-#![forbid(unsafe_code)]
-
-use proc_macro::TokenStream;
-
-/// Generates better error messages when applied to a handler function.
-///
-/// # Examples
-///
-/// Function is not async:
-///
-/// ```rust,ignore
-/// #[debug_handler]
-/// fn handler() -> &'static str {
-///     "Hello, world"
-/// }
-/// ```
-///
-/// ```text
-/// error: handlers must be async functions
-///   --> main.rs:xx:1
-///    |
-/// xx | fn handler() -> &'static str {
-///    | ^^
-/// ```
-///
-/// Wrong return type:
-///
-/// ```rust,ignore
-/// #[debug_handler]
-/// async fn handler() -> bool {
-///     false
-/// }
-/// ```
-///
-/// ```text
-/// error[E0277]: the trait bound `bool: IntoResponse` is not satisfied
-///   --> main.rs:xx:23
-///    |
-/// xx | async fn handler() -> bool {
-///    |                       ^^^^
-///    |                       |
-///    |                       the trait `IntoResponse` is not implemented for `bool`
-/// ```
-///
-/// Wrong extractor:
-///
-/// ```rust,ignore
-/// #[debug_handler]
-/// async fn handler(a: bool) -> String {
-///     format!("Can I extract a bool? {}", a)
-/// }
-/// ```
-///
-/// ```text
-/// error[E0277]: the trait bound `bool: FromRequest` is not satisfied
-///   --> main.rs:xx:21
-///    |
-/// xx | async fn handler(a: bool) -> String {
-///    |                     ^^^^
-///    |                     |
-///    |                     the trait `FromRequest` is not implemented for `bool`
-/// ```
-///
-/// Too many extractors:
-///
-/// ```rust,ignore
-/// #[debug_handler]
-/// async fn handler(
-///     a: String,
-///     b: String,
-///     c: String,
-///     d: String,
-///     e: String,
-///     f: String,
-///     g: String,
-///     h: String,
-///     i: String,
-///     j: String,
-///     k: String,
-///     l: String,
-///     m: String,
-///     n: String,
-///     o: String,
-///     p: String,
-///     q: String,
-/// ) {}
-/// ```
-///
-/// ```text
-/// error: too many extractors. 16 extractors are allowed
-/// note: you can nest extractors like "a: (Extractor, Extractor), b: (Extractor, Extractor)"
-///   --> main.rs:xx:5
-///    |
-/// xx | /     a: String,
-/// xx | |     b: String,
-/// xx | |     c: String,
-/// xx | |     d: String,
-/// ...  |
-/// xx | |     p: String,
-/// xx | |     q: String,
-///    | |______________^
-/// ```
-///
-/// Future is not [`Send`]:
-///
-/// ```rust,ignore
-/// #[debug_handler]
-/// async fn handler() {
-///     let not_send = std::rc::Rc::new(());
-///
-///     async{}.await;
-/// }
-/// ```
-///
-/// ```text
-/// error: future cannot be sent between threads safely
-///   --> main.rs:xx:10
-///    |
-/// xx | async fn handler() {
-///    |          ^^^^^^^
-///    |          |
-///    |          future returned by `handler` is not `Send`
-/// ```
-///
-/// [`Send`]: Send
-#[proc_macro_attribute]
-pub fn debug_handler(_attr: TokenStream, input: TokenStream) -> TokenStream {
-    #[cfg(not(debug_assertions))]
-    return input;
-
-    #[cfg(debug_assertions)]
-    return debug::apply_debug_handler(input);
-}
-
-#[cfg(debug_assertions)]
-mod debug {
-    use proc_macro::TokenStream;
-    use proc_macro2::Span;
-    use quote::quote_spanned;
-    use syn::{parse_macro_input, FnArg, Ident, ItemFn, ReturnType, Signature};
-
-    pub(crate) fn apply_debug_handler(input: TokenStream) -> TokenStream {
-        let function = parse_macro_input!(input as ItemFn);
-
-        let vis = &function.vis;
-        let sig = &function.sig;
-        let ident = &sig.ident;
-        let span = ident.span();
-        let len = sig.inputs.len();
-        let generics = create_generics(len);
-        let params = sig.inputs.iter().map(|fn_arg| {
-            if let FnArg::Typed(pat_type) = fn_arg {
-                &pat_type.pat
-            } else {
-                panic!("not a handler function");
-            }
-        });
-        let block = &function.block;
-
-        if let Err(error) = async_check(sig) {
-            return error;
-        }
-
-        if let Err(error) = param_limit_check(sig) {
-            return error;
-        }
-
-        let check_trait = check_trait_code(sig, &generics);
-        let check_return = check_return_code(sig, &generics);
-        let check_params = check_params_code(sig, &generics);
-
-        let expanded = quote_spanned! {span=>
-            #vis #sig {
-                #check_trait
-                #check_return
-                #(#check_params)*
-
-                #sig #block
-
-                #ident(#(#params),*).await
-            }
-        };
-
-        expanded.into()
-    }
-
-    fn create_generics(len: usize) -> Vec<Ident> {
-        let mut vec = Vec::new();
-        for i in 1..=len {
-            vec.push(Ident::new(&format!("T{}", i), Span::call_site()));
-        }
-        vec
-    }
-
-    fn async_check(sig: &Signature) -> Result<(), TokenStream> {
-        if sig.asyncness.is_none() {
-            let error = syn::Error::new_spanned(sig.fn_token, "handlers must be async functions")
-                .to_compile_error()
-                .into();
-
-            return Err(error);
-        }
-
-        Ok(())
-    }
-
-    fn param_limit_check(sig: &Signature) -> Result<(), TokenStream> {
-        if sig.inputs.len() > 16 {
-            let msg = "too many extractors. 16 extractors are allowed\n\
-                       note: you can nest extractors like \"a: (Extractor, Extractor), b: (Extractor, Extractor)\"";
-
-            let error = syn::Error::new_spanned(&sig.inputs, msg)
-                .to_compile_error()
-                .into();
-
-            return Err(error);
-        }
-
-        Ok(())
-    }
-
-    fn check_trait_code(sig: &Signature, generics: &[Ident]) -> proc_macro2::TokenStream {
-        let ident = &sig.ident;
-        let span = ident.span();
-
-        quote_spanned! {span=>
-            {
-                debug_handler(#ident);
-
-                fn debug_handler<F, Fut, #(#generics),*>(_f: F)
-                where
-                    F: ::std::ops::FnOnce(#(#generics),*) -> Fut + Clone + Send + Sync + 'static,
-                    Fut: ::std::future::Future + Send,
-                {}
-            }
-        }
-    }
-
-    fn check_return_code(sig: &Signature, generics: &[Ident]) -> proc_macro2::TokenStream {
-        let span = match &sig.output {
-            ReturnType::Default => syn::Error::new_spanned(&sig.output, "").span(),
-            ReturnType::Type(_, t) => syn::Error::new_spanned(t, "").span(),
-        };
-        let ident = &sig.ident;
-
-        quote_spanned! {span=>
-            {
-                debug_handler(#ident);
-
-                fn debug_handler<F, Fut, Res, #(#generics),*>(_f: F)
-                where
-                    F: ::std::ops::FnOnce(#(#generics),*) -> Fut,
-                    Fut: ::std::future::Future<Output = Res>,
-                    Res: ::axum_debug::axum::response::IntoResponse,
-                {}
-            }
-        }
-    }
-
-    fn check_params_code(sig: &Signature, generics: &[Ident]) -> Vec<proc_macro2::TokenStream> {
-        let mut vec = Vec::new();
-
-        let ident = &sig.ident;
-
-        for (i, generic) in generics.iter().enumerate() {
-            let span = match &sig.inputs[i] {
-                FnArg::Typed(pat_type) => syn::Error::new_spanned(&pat_type.ty, "").span(),
-                _ => panic!("not a handler"),
-            };
-
-            let token_stream = quote_spanned! {span=>
-                {
-                    debug_handler(#ident);
-
-                    fn debug_handler<F, Fut, #(#generics),*>(_f: F)
-                    where
-                        F: ::std::ops::FnOnce(#(#generics),*) -> Fut,
-                        Fut: ::std::future::Future,
-                        #generic: ::axum_debug::axum::extract::FromRequest + Send,
-                    {}
-                }
-            };
-
-            vec.push(token_stream);
-        }
-
-        vec
-    }
-}
diff --git a/axum-debug/CHANGELOG.md b/axum-debug/CHANGELOG.md
index 48cd86fc..9e227c8a 100644
--- a/axum-debug/CHANGELOG.md
+++ b/axum-debug/CHANGELOG.md
@@ -1,4 +1,5 @@
 # Changelog
+
 All notable changes to this project will be documented in this file.
 
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
diff --git a/axum-debug/Cargo.toml b/axum-debug/Cargo.toml
index ff9291b0..78d5ff5c 100644
--- a/axum-debug/Cargo.toml
+++ b/axum-debug/Cargo.toml
@@ -11,6 +11,11 @@ readme = "README.md"
 repository = "https://github.com/tokio-rs/axum"
 version = "0.1.0"
 
+[lib]
+proc-macro = true
+
 [dependencies]
-axum = { path = "../axum" }
-axum-debug-macros = { path = "../axum-debug-macros" }
+proc-macro2 = "1.0"
+quote = "1.0"
+syn = { version = "1.0", features = ["full"] }
+axum = { path = "../axum", version = "0.3" }
diff --git a/axum-debug/README.md b/axum-debug/README.md
index dd41a991..756b5862 100644
--- a/axum-debug/README.md
+++ b/axum-debug/README.md
@@ -1,63 +1,42 @@
-[![License](https://img.shields.io/crates/l/axum-debug)](https://choosealicense.com/licenses/mit/)
-[![Crates.io](https://img.shields.io/crates/v/axum-debug)](https://crates.io/crates/axum-debug)
-[![Docs - Stable](https://img.shields.io/crates/v/axum-debug?color=blue&label=docs)](https://docs.rs/axum-debug/)
-
 # axum-debug
 
+[![Build status](https://github.com/tokio-rs/axum-debug/actions/workflows/CI.yml/badge.svg?branch=main)](https://github.com/tokio-rs/axum-debug/actions/workflows/CI.yml)
+[![Crates.io](https://img.shields.io/crates/v/axum-debug)](https://crates.io/crates/axum-debug)
+[![Documentation](https://docs.rs/axum-debug/badge.svg)](https://docs.rs/axum-debug)
+
 This is a debugging crate that provides better error messages for [`axum`]
 framework.
 
-[`axum`] is a great framework for developing web applications. But when you
-make a mistake, error messages can be really complex and long. It can take a
-long time for you to figure out what is wrong in your code. This crate provides
-utilities to generate better error messages in case you make a mistake.
-
-## Usage Example
-
-Will fail with a better error message:
-
-```rust
-use axum::{routing::get, Router};
-use axum_debug::debug_handler;
-
-#[tokio::main]
-async fn main() {
-    let app = Router::new().route("/", get(handler));
-
-    axum::Server::bind(&"0.0.0.0:3000".parse().unwrap())
-        .serve(app.into_make_service())
-        .await
-        .unwrap();
-}
-
-#[debug_handler]
-async fn handler() -> bool {
-    false
-}
-```
-
-Error message:
-
-```
-error[E0277]: the trait bound `bool: IntoResponse` is not satisfied
-  --> main.rs:xx:23
-   |
-xx | async fn handler() -> bool {
-   |                       ^^^^
-   |                       |
-   |                       the trait `IntoResponse` is not implemented for `bool`
-```
+More information about this crate can be found in the [crate documentation][docs].
 
 ## Safety
 
 This crate uses `#![forbid(unsafe_code)]` to ensure everything is implemented in 100% safe Rust.
 
-## Performance
+## Minimum supported Rust version
 
-Macros in this crate have no effect when using release profile. (eg. `cargo build --release`)
+axum-handle-error-extract's MSRV is 1.54.
+
+## Getting Help
+
+You're also welcome to ask in the [Discord channel][chat] or open an [issue]
+with your question.
+
+## Contributing
+
+:balloon: Thanks for your help improving the project! We are so happy to have
+you! We have a [contributing guide][contributing] to help you get involved in the
+`axum` project.
 
 ## License
 
-This project is licensed under the [MIT license](LICENSE).
+This project is licensed under the [MIT license][license].
+
+### Contribution
+
+Unless you explicitly state otherwise, any contribution intentionally submitted
+for inclusion in `axum` by you, shall be licensed as MIT, without any
+additional terms or conditions.
 
 [`axum`]: https://crates.io/crates/axum
+[docs]: https://docs.rs/axum-debug
diff --git a/axum-debug/src/lib.rs b/axum-debug/src/lib.rs
index f4e28ace..5c7bf467 100644
--- a/axum-debug/src/lib.rs
+++ b/axum-debug/src/lib.rs
@@ -1,10 +1,5 @@
 //! This is a debugging crate that provides better error messages for [`axum`] framework.
 //!
-//! [`axum`] is a great framework for developing web applications. But when you make a mistake,
-//! error messages can be really complex and long. It can take a long time for you to figure out
-//! what is wrong in your code. This crate provides utilities to generate better error messages in
-//! case you make a mistake.
-//!
 //! While using [`axum`], you can get long error messages for simple mistakes. For example:
 //!
 //! ```rust,compile_fail
@@ -84,13 +79,36 @@
 //!
 //! [`axum`]: axum
 //! [`Handler`]: axum::handler::Handler
-//! [`debug_handler`]: debug_handler
+//! [`debug_handler`]: macro@debug_handler
 
 #![warn(
     clippy::all,
     clippy::dbg_macro,
     clippy::todo,
+    clippy::empty_enum,
+    clippy::enum_glob_use,
     clippy::mem_forget,
+    clippy::unused_self,
+    clippy::filter_map_next,
+    clippy::needless_continue,
+    clippy::needless_borrow,
+    clippy::match_wildcard_for_single_variants,
+    clippy::if_let_mutex,
+    clippy::mismatched_target_os,
+    clippy::await_holding_lock,
+    clippy::match_on_vec_items,
+    clippy::imprecise_flops,
+    clippy::suboptimal_flops,
+    clippy::lossy_float_literal,
+    clippy::rest_pat_in_fully_bound_structs,
+    clippy::fn_params_excessive_bools,
+    clippy::exit,
+    clippy::inefficient_to_string,
+    clippy::linkedlist,
+    clippy::macro_use_imports,
+    clippy::option_option,
+    clippy::verbose_file_reads,
+    clippy::unnested_or_patterns,
     rust_2018_idioms,
     future_incompatible,
     nonstandard_style,
@@ -98,7 +116,294 @@
     missing_docs
 )]
 #![deny(unreachable_pub, private_in_public)]
+#![allow(elided_lifetimes_in_paths, clippy::type_complexity)]
 #![forbid(unsafe_code)]
+#![cfg_attr(docsrs, feature(doc_cfg))]
+#![cfg_attr(test, allow(clippy::float_cmp))]
 
-pub use axum;
-pub use axum_debug_macros::debug_handler;
+use proc_macro::TokenStream;
+
+/// Generates better error messages when applied to a handler function.
+///
+/// # Examples
+///
+/// Function is not async:
+///
+/// ```rust,ignore
+/// #[debug_handler]
+/// fn handler() -> &'static str {
+///     "Hello, world"
+/// }
+/// ```
+///
+/// ```text
+/// error: handlers must be async functions
+///   --> main.rs:xx:1
+///    |
+/// xx | fn handler() -> &'static str {
+///    | ^^
+/// ```
+///
+/// Wrong return type:
+///
+/// ```rust,ignore
+/// #[debug_handler]
+/// async fn handler() -> bool {
+///     false
+/// }
+/// ```
+///
+/// ```text
+/// error[E0277]: the trait bound `bool: IntoResponse` is not satisfied
+///   --> main.rs:xx:23
+///    |
+/// xx | async fn handler() -> bool {
+///    |                       ^^^^
+///    |                       |
+///    |                       the trait `IntoResponse` is not implemented for `bool`
+/// ```
+///
+/// Wrong extractor:
+///
+/// ```rust,ignore
+/// #[debug_handler]
+/// async fn handler(a: bool) -> String {
+///     format!("Can I extract a bool? {}", a)
+/// }
+/// ```
+///
+/// ```text
+/// error[E0277]: the trait bound `bool: FromRequest` is not satisfied
+///   --> main.rs:xx:21
+///    |
+/// xx | async fn handler(a: bool) -> String {
+///    |                     ^^^^
+///    |                     |
+///    |                     the trait `FromRequest` is not implemented for `bool`
+/// ```
+///
+/// Too many extractors:
+///
+/// ```rust,ignore
+/// #[debug_handler]
+/// async fn handler(
+///     a: String,
+///     b: String,
+///     c: String,
+///     d: String,
+///     e: String,
+///     f: String,
+///     g: String,
+///     h: String,
+///     i: String,
+///     j: String,
+///     k: String,
+///     l: String,
+///     m: String,
+///     n: String,
+///     o: String,
+///     p: String,
+///     q: String,
+/// ) {}
+/// ```
+///
+/// ```text
+/// error: too many extractors. 16 extractors are allowed
+/// note: you can nest extractors like "a: (Extractor, Extractor), b: (Extractor, Extractor)"
+///   --> main.rs:xx:5
+///    |
+/// xx | /     a: String,
+/// xx | |     b: String,
+/// xx | |     c: String,
+/// xx | |     d: String,
+/// ...  |
+/// xx | |     p: String,
+/// xx | |     q: String,
+///    | |______________^
+/// ```
+///
+/// Future is not [`Send`]:
+///
+/// ```rust,ignore
+/// #[debug_handler]
+/// async fn handler() {
+///     let not_send = std::rc::Rc::new(());
+///
+///     async{}.await;
+/// }
+/// ```
+///
+/// ```text
+/// error: future cannot be sent between threads safely
+///   --> main.rs:xx:10
+///    |
+/// xx | async fn handler() {
+///    |          ^^^^^^^
+///    |          |
+///    |          future returned by `handler` is not `Send`
+/// ```
+#[proc_macro_attribute]
+pub fn debug_handler(_attr: TokenStream, input: TokenStream) -> TokenStream {
+    #[cfg(not(debug_assertions))]
+    return input;
+
+    #[cfg(debug_assertions)]
+    return debug::apply_debug_handler(input);
+}
+
+#[cfg(debug_assertions)]
+mod debug {
+    use proc_macro::TokenStream;
+    use proc_macro2::Span;
+    use quote::quote_spanned;
+    use syn::{parse_macro_input, FnArg, Ident, ItemFn, ReturnType, Signature};
+
+    pub(crate) fn apply_debug_handler(input: TokenStream) -> TokenStream {
+        let function = parse_macro_input!(input as ItemFn);
+
+        let vis = &function.vis;
+        let sig = &function.sig;
+        let ident = &sig.ident;
+        let span = ident.span();
+        let len = sig.inputs.len();
+        let generics = create_generics(len);
+        let params = sig.inputs.iter().map(|fn_arg| {
+            if let FnArg::Typed(pat_type) = fn_arg {
+                &pat_type.pat
+            } else {
+                panic!("not a handler function");
+            }
+        });
+        let block = &function.block;
+
+        if let Err(error) = async_check(sig) {
+            return error;
+        }
+
+        if let Err(error) = param_limit_check(sig) {
+            return error;
+        }
+
+        let check_trait = check_trait_code(sig, &generics);
+        let check_return = check_return_code(sig, &generics);
+        let check_params = check_params_code(sig, &generics);
+
+        let expanded = quote_spanned! {span=>
+            #vis #sig {
+                #check_trait
+                #check_return
+                #(#check_params)*
+
+                #sig #block
+
+                #ident(#(#params),*).await
+            }
+        };
+
+        expanded.into()
+    }
+
+    fn create_generics(len: usize) -> Vec<Ident> {
+        let mut vec = Vec::new();
+        for i in 1..=len {
+            vec.push(Ident::new(&format!("T{}", i), Span::call_site()));
+        }
+        vec
+    }
+
+    fn async_check(sig: &Signature) -> Result<(), TokenStream> {
+        if sig.asyncness.is_none() {
+            let error = syn::Error::new_spanned(sig.fn_token, "handlers must be async functions")
+                .to_compile_error()
+                .into();
+
+            return Err(error);
+        }
+
+        Ok(())
+    }
+
+    fn param_limit_check(sig: &Signature) -> Result<(), TokenStream> {
+        if sig.inputs.len() > 16 {
+            let msg = "too many extractors. 16 extractors are allowed\n\
+                       note: you can nest extractors like \"a: (Extractor, Extractor), b: (Extractor, Extractor)\"";
+
+            let error = syn::Error::new_spanned(&sig.inputs, msg)
+                .to_compile_error()
+                .into();
+
+            return Err(error);
+        }
+
+        Ok(())
+    }
+
+    fn check_trait_code(sig: &Signature, generics: &[Ident]) -> proc_macro2::TokenStream {
+        let ident = &sig.ident;
+        let span = ident.span();
+
+        quote_spanned! {span=>
+            {
+                debug_handler(#ident);
+
+                fn debug_handler<F, Fut, #(#generics),*>(_f: F)
+                where
+                    F: ::std::ops::FnOnce(#(#generics),*) -> Fut + Clone + Send + Sync + 'static,
+                    Fut: ::std::future::Future + Send,
+                {}
+            }
+        }
+    }
+
+    fn check_return_code(sig: &Signature, generics: &[Ident]) -> proc_macro2::TokenStream {
+        let span = match &sig.output {
+            ReturnType::Default => syn::Error::new_spanned(&sig.output, "").span(),
+            ReturnType::Type(_, t) => syn::Error::new_spanned(t, "").span(),
+        };
+        let ident = &sig.ident;
+
+        quote_spanned! {span=>
+            {
+                debug_handler(#ident);
+
+                fn debug_handler<F, Fut, Res, #(#generics),*>(_f: F)
+                where
+                    F: ::std::ops::FnOnce(#(#generics),*) -> Fut,
+                    Fut: ::std::future::Future<Output = Res>,
+                    Res: ::axum::response::IntoResponse,
+                {}
+            }
+        }
+    }
+
+    fn check_params_code(sig: &Signature, generics: &[Ident]) -> Vec<proc_macro2::TokenStream> {
+        let mut vec = Vec::new();
+
+        let ident = &sig.ident;
+
+        for (i, generic) in generics.iter().enumerate() {
+            let span = if let FnArg::Typed(pat_type) = &sig.inputs[i] {
+                syn::Error::new_spanned(&pat_type.ty, "").span()
+            } else {
+                panic!("not a handler")
+            };
+
+            let token_stream = quote_spanned! {span=>
+                {
+                    debug_handler(#ident);
+
+                    fn debug_handler<F, Fut, #(#generics),*>(_f: F)
+                    where
+                        F: ::std::ops::FnOnce(#(#generics),*) -> Fut,
+                        Fut: ::std::future::Future,
+                        #generic: ::axum::extract::FromRequest + Send,
+                    {}
+                }
+            };
+
+            vec.push(token_stream);
+        }
+
+        vec
+    }
+}
diff --git a/axum-handle-error-extract/src/lib.rs b/axum-handle-error-extract/src/lib.rs
index a4550b5e..05db6165 100644
--- a/axum-handle-error-extract/src/lib.rs
+++ b/axum-handle-error-extract/src/lib.rs
@@ -125,7 +125,6 @@
     clippy::option_option,
     clippy::verbose_file_reads,
     clippy::unnested_or_patterns,
-    clippy::self_named_module_files,
     rust_2018_idioms,
     future_incompatible,
     nonstandard_style,
diff --git a/axum/src/lib.rs b/axum/src/lib.rs
index a424db6e..74eaf0be 100644
--- a/axum/src/lib.rs
+++ b/axum/src/lib.rs
@@ -295,7 +295,6 @@
     clippy::option_option,
     clippy::verbose_file_reads,
     clippy::unnested_or_patterns,
-    clippy::self_named_module_files,
     rust_2018_idioms,
     future_incompatible,
     nonstandard_style,