Error handling.

Cargo.lock

@@ -2,12 +2,42 @@
 # It is not intended for manual editing.
 version = 3
 
+[[package]]
+name = "addr2line"
+version = "0.19.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a76fd60b23679b7d19bd066031410fb7e458ccc5e958eb5c325888ce4baedc97"
+dependencies = [
+ "gimli",
+]
+
+[[package]]
+name = "adler"
+version = "1.0.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f26201604c87b1e01bd3d98f8d5d9a8fcbb815e8cedb41ffccbeb4bf593a35fe"
+
 [[package]]
 name = "autocfg"
 version = "1.1.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "d468802bab17cbc0cc575e9b053f41e72aa36bfa6b7f55e3529ffa43161b97fa"
 
+[[package]]
+name = "backtrace"
+version = "0.3.67"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "233d376d6d185f2a3093e58f283f60f880315b6c60075b01f36b3b85154564ca"
+dependencies = [
+ "addr2line",
+ "cc",
+ "cfg-if",
+ "libc",
+ "miniz_oxide",
+ "object",
+ "rustc-demangle",
+]
+
 [[package]]
 name = "base64"
 version = "0.21.0"
@@ -36,6 +66,7 @@ checksum = "89b2fd2a0dcf38d7971e2194b6b6eebab45ae01067456a7fd93d5547a61b70be"
 name = "catscii"
 version = "0.1.0"
 dependencies = [
+ "color-eyre",
  "reqwest",
  "serde",
  "tokio",
@@ -53,6 +84,33 @@ version = "1.0.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "baf1de4339761588bc0619e3cbc0120ee582ebb74b53b4efbf79117bd2da40fd"
 
+[[package]]
+name = "color-eyre"
+version = "0.6.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5a667583cca8c4f8436db8de46ea8233c42a7d9ae424a82d338f2e4675229204"
+dependencies = [
+ "backtrace",
+ "color-spantrace",
+ "eyre",
+ "indenter",
+ "once_cell",
+ "owo-colors",
+ "tracing-error",
+]
+
+[[package]]
+name = "color-spantrace"
+version = "0.2.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1ba75b3d9449ecdccb27ecbc479fdc0b87fa2dd43d2f8298f9bf0e59aacc8dce"
+dependencies = [
+ "once_cell",
+ "owo-colors",
+ "tracing-core",
+ "tracing-error",
+]
+
 [[package]]
 name = "core-foundation"
 version = "0.9.3"
@@ -99,6 +157,16 @@ dependencies = [
  "libc",
 ]
 
+[[package]]
+name = "eyre"
+version = "0.6.8"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "4c2b6b5a29c02cdc822728b7d7b8ae1bab3e3b05d44522770ddd49722eeac7eb"
+dependencies = [
+ "indenter",
+ "once_cell",
+]
+
 [[package]]
 name = "fastrand"
 version = "1.9.0"
@@ -177,6 +245,12 @@ dependencies = [
  "pin-utils",
 ]
 
+[[package]]
+name = "gimli"
+version = "0.27.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ad0a93d233ebf96623465aad4046a8d3aa4da22d4f4beba5388838c8a434bbb4"
+
 [[package]]
 name = "h2"
 version = "0.3.19"
@@ -298,6 +372,12 @@ dependencies = [
  "unicode-normalization",
 ]
 
+[[package]]
+name = "indenter"
+version = "0.3.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ce23b50ad8242c51a442f3ff322d56b02f08852c77e4c0b4d3fd684abc89c683"
+
 [[package]]
 name = "indexmap"
 version = "1.9.3"
@@ -386,12 +466,27 @@ dependencies = [
  "cfg-if",
 ]
 
+[[package]]
+name = "memchr"
+version = "2.5.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2dffe52ecf27772e601905b7522cb4ef790d2cc203488bbd0e2fe85fcb74566d"
+
 [[package]]
 name = "mime"
 version = "0.3.17"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "6877bb514081ee2a7ff5ef9de3281f14a4dd4bceac4c09388074a6b5df8a139a"
 
+[[package]]
+name = "miniz_oxide"
+version = "0.6.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b275950c28b37e794e8c55d88aeb5e139d0ce23fdbbeda68f8d7174abdf9e8fa"
+dependencies = [
+ "adler",
+]
+
 [[package]]
 name = "mio"
 version = "0.8.6"
@@ -432,6 +527,15 @@ dependencies = [
  "libc",
 ]
 
+[[package]]
+name = "object"
+version = "0.30.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ea86265d3d3dcb6a27fc51bd29a4bf387fae9d2986b823079d4986af253eb439"
+dependencies = [
+ "memchr",
+]
+
 [[package]]
 name = "once_cell"
 version = "1.17.1"
@@ -482,6 +586,12 @@ dependencies = [
  "vcpkg",
 ]
 
+[[package]]
+name = "owo-colors"
+version = "3.5.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c1b04fb49957986fdce4d6ee7a65027d55d4b6d2265e5848bbb507b58ccfdb6f"
+
 [[package]]
 name = "parking_lot"
 version = "0.12.1"
@@ -602,6 +712,12 @@ dependencies = [
  "winreg",
 ]
 
+[[package]]
+name = "rustc-demangle"
+version = "0.1.23"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d626bb9dae77e28219937af045c257c28bfd3f69333c512553507f5f9798cb76"
+
 [[package]]
 name = "rustix"
 version = "0.37.19"
@@ -703,6 +819,15 @@ dependencies = [
  "serde",
 ]
 
+[[package]]
+name = "sharded-slab"
+version = "0.1.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "900fba806f70c630b0a382d0d825e17a0f19fcd059a2ade1ff237bcddf446b31"
+dependencies = [
+ "lazy_static",
+]
+
 [[package]]
 name = "signal-hook-registry"
 version = "1.4.1"
@@ -761,6 +886,16 @@ dependencies = [
  "windows-sys 0.45.0",
 ]
 
+[[package]]
+name = "thread_local"
+version = "1.1.7"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "3fdd6f064ccff2d6567adcb3873ca630700f00b5ad3f060c25b5dcfd9a4ce152"
+dependencies = [
+ "cfg-if",
+ "once_cell",
+]
+
 [[package]]
 name = "tinyvec"
 version = "1.6.0"
@@ -854,6 +989,28 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "0955b8137a1df6f1a2e9a37d8a6656291ff0297c1a97c24e0d8425fe2312f79a"
 dependencies = [
  "once_cell",
+ "valuable",
+]
+
+[[package]]
+name = "tracing-error"
+version = "0.2.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d686ec1c0f384b1277f097b2f279a2ecc11afe8c133c1aabf036a27cb4cd206e"
+dependencies = [
+ "tracing",
+ "tracing-subscriber",
+]
+
+[[package]]
+name = "tracing-subscriber"
+version = "0.3.17"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "30a651bc37f915e81f087d86e62a18eec5f79550c7faff886f7090b4ea757c77"
+dependencies = [
+ "sharded-slab",
+ "thread_local",
+ "tracing-core",
 ]
 
 [[package]]
@@ -894,6 +1051,12 @@ dependencies = [
  "percent-encoding",
 ]
 
+[[package]]
+name = "valuable"
+version = "0.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "830b7e5d4d90034032940e4ace0d9a9a057e7a45cd94e6c007832e39edb82f6d"
+
 [[package]]
 name = "vcpkg"
 version = "0.2.15"

Cargo.toml

@@ -5,6 +5,7 @@ authors = ["Amos Wenger <amos@fasterthanli.me>"]
 edition = "2018"
 
 [dependencies]
+color-eyre = "0.6"
 reqwest = { version = "0.11", features = ["json"] }
 serde = { version = "1", features = ["derive"] }
 tokio = { version = "1", features = ["full"] }

src/main.rs

@@ -2,11 +2,18 @@ use serde::Deserialize;
 
 #[tokio::main]
 async fn main() {
-    let res = reqwest::get("https://api.thecatapi.com/v1/images/search")
+    let url = get_cat_image_url().await.unwrap();
-        .await
+    println!("The image is at {}", url);
-        .unwrap();
+}
+
+async fn get_cat_image_url() -> color_eyre::Result<String> {
+    let api_url = "https://api.thecatapi.com/v1/images/search";
+    let res = reqwest::get(api_url).await?;
     if !res.status().is_success() {
-        panic!("Request failed with HTTP {}", res.status());
+        return Err(color_eyre::eyre::eyre!(
+            "The Cat API returned HTTP {}",
+            res.status()
+        ));
     }
 
     #[derive(Deserialize)]
@@ -14,9 +21,10 @@ async fn main() {
         url: String,
     }
 
-    let images: Vec<CatImage> = res.json().await.unwrap();
+    let mut images: Vec<CatImage> = res.json().await?;
-    let image = images
+    if let Some(image) = images.pop() {
-        .first()
+        Ok(image.url)
-        .expect("the cat API should return at least one image");
+    } else {
-    println!("The image is at {}", image.url);
+        Err(color_eyre::eyre::eyre!("The Cat API returned no images"))
+    }
 }