From 10d991be9dc2fbecdb910f44b8fd2efb9373100f Mon Sep 17 00:00:00 2001
From: Taiki Ono <taiki@finatext.com>
Date: Mon, 1 Jul 2024 19:43:38 +0900
Subject: [PATCH 1/2] Add "error handling with anyhow" example

Signed-off-by: Taiki Ono <taiki@finatext.com>
---
 examples/basic-error-anyhow/.gitignore  |  1 +
 examples/basic-error-anyhow/Cargo.toml  | 10 ++++++++++
 examples/basic-error-anyhow/README.md   | 13 +++++++++++++
 examples/basic-error-anyhow/src/main.rs | 21 +++++++++++++++++++++
 4 files changed, 45 insertions(+)
 create mode 100644 examples/basic-error-anyhow/.gitignore
 create mode 100644 examples/basic-error-anyhow/Cargo.toml
 create mode 100644 examples/basic-error-anyhow/README.md
 create mode 100644 examples/basic-error-anyhow/src/main.rs

diff --git a/examples/basic-error-anyhow/.gitignore b/examples/basic-error-anyhow/.gitignore
new file mode 100644
index 00000000..ea8c4bf7
--- /dev/null
+++ b/examples/basic-error-anyhow/.gitignore
@@ -0,0 +1 @@
+/target
diff --git a/examples/basic-error-anyhow/Cargo.toml b/examples/basic-error-anyhow/Cargo.toml
new file mode 100644
index 00000000..a0ff62db
--- /dev/null
+++ b/examples/basic-error-anyhow/Cargo.toml
@@ -0,0 +1,10 @@
+[package]
+name = "basic-error-anyhow"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]
+anyhow = "1"
+lambda_runtime = { path = "../../lambda-runtime" }
+serde = "1"
+tokio = { version = "1", features = ["macros"] }
diff --git a/examples/basic-error-anyhow/README.md b/examples/basic-error-anyhow/README.md
new file mode 100644
index 00000000..b659c283
--- /dev/null
+++ b/examples/basic-error-anyhow/README.md
@@ -0,0 +1,13 @@
+# AWS Lambda Function Error Handling With `anyhow` Crate Example
+
+This example shows how to use external error types like `anyhow::Error`.
+
+## Build & Deploy
+
+1. Install [cargo-lambda](https://github.com/cargo-lambda/cargo-lambda#installation)
+2. Build the function with `cargo lambda build --release`
+3. Deploy the function to AWS Lambda with `cargo lambda deploy --iam-role YOUR_ROLE`
+
+## Build for ARM 64
+
+Build the function with `cargo lambda build --release --arm64`
diff --git a/examples/basic-error-anyhow/src/main.rs b/examples/basic-error-anyhow/src/main.rs
new file mode 100644
index 00000000..cbca84fd
--- /dev/null
+++ b/examples/basic-error-anyhow/src/main.rs
@@ -0,0 +1,21 @@
+use anyhow::bail;
+use lambda_runtime::{service_fn, Error, LambdaEvent};
+use serde::Deserialize;
+
+#[derive(Deserialize)]
+struct Request {}
+
+/// Return anyhow::Result in the main body for the Lambda function.
+async fn function_handler(_event: LambdaEvent<Request>) -> anyhow::Result<()> {
+    bail!("This is an error message");
+}
+
+#[tokio::main]
+async fn main() -> Result<(), Error> {
+    lambda_runtime::run(service_fn(|event: LambdaEvent<Request>| async move {
+        function_handler(event)
+            .await
+            .map_err(Into::<Box<dyn std::error::Error>>::into)
+    }))
+    .await
+}

From 0f71e927835ca5b3eed2b84345bb8b66fddb0b2f Mon Sep 17 00:00:00 2001
From: Taiki Ono <taiki@finatext.com>
Date: Mon, 1 Jul 2024 20:00:22 +0900
Subject: [PATCH 2/2] More doc for users who use external error types

Signed-off-by: Taiki Ono <taiki@finatext.com>
---
 lambda-runtime/src/diagnostic.rs | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/lambda-runtime/src/diagnostic.rs b/lambda-runtime/src/diagnostic.rs
index bc9ba623..9a7230a7 100644
--- a/lambda-runtime/src/diagnostic.rs
+++ b/lambda-runtime/src/diagnostic.rs
@@ -7,6 +7,9 @@ use crate::{deserializer::DeserializeError, Error};
 ///
 /// `Diagnostic` is automatically derived for some common types,
 /// like boxed types that implement [`Error`][std::error::Error].
+/// If you use an error type which comes from a external crate like anyhow,
+/// you need convert it to common types like `Box<dyn std::error::Error>`.
+/// See the examples for more details.
 ///
 /// [`error_type`][`Diagnostic::error_type`] is derived from the type name of
 /// the original error with [`std::any::type_name`] as a fallback, which may