Public api test

Cargo.toml

@@ -157,6 +157,10 @@ tokio = { version = "1.24.1", features = ["rt", "macros"] }
 axum = { version = "0.7.4", features = ["macros"] }
 async-trait = "0.1"
 actix-web = "4.2.1"
+rustup-toolchain = "0.1.6"
+rustdoc-json = "0.9.0"
+public-api = "0.33.1"
+expect-test = "1.5.0"
 
 # MSRV PINS
 #

tests/public_api.rs

@@ -0,0 +1,29 @@
+#[test]
+fn public_api() {
+    // Install a compatible nightly toolchain if it is missing
+    rustup_toolchain::install(public_api::MINIMUM_NIGHTLY_RUST_VERSION).unwrap();
+
+    // Build rustdoc JSON
+    let rustdoc_json = rustdoc_json::Builder::default()
+        .toolchain(public_api::MINIMUM_NIGHTLY_RUST_VERSION)
+        .features(["runtime-tokio-hyper"])
+        .build()
+        .unwrap();
+
+    // Derive the public API from the rustdoc JSON
+    let public_api = public_api::Builder::from_rustdoc_json(rustdoc_json)
+        .omit_auto_derived_impls(true)
+        .omit_blanket_impls(true)
+        .build()
+        .unwrap();
+
+    // Assert that the public API looks correct
+    let content = expect_test::expect_file!["public-api.txt"].data();
+    // We do not use assert_eq here since it prints waaaay too much
+    if &content != &public_api.to_string() {
+        panic!(r#"Error: The API changed.
+
+        Use the following command if you want to commit these changes:
+        UPDATE_EXPECT=1 cargo test --features runtime-tokio-hyper"#);
+    }
+}