http-error: add new http-error crate

Break out proxmox-router's HttpError into it's own crate so that it can
be used without pulling in proxmox-router.

This commit also implements `Serialize` for `HttpError` so that it can
be returned from perlmod bindings, allowing Perl code to access the
status code as well as the message.

Also add some smoke-tests to make sure that the `http_bail` and
`http_err` macros actually produce valid code.

Suggested-by: Wolfgang Bumiller <w.bumiller@proxmox.com>
Signed-off-by: Lukas Wagner <l.wagner@proxmox.com>

Cargo.toml

@@ -7,6 +7,7 @@ members = [
     "proxmox-borrow",
     "proxmox-compression",
     "proxmox-http",
+    "proxmox-http-error",
     "proxmox-human-byte",
     "proxmox-io",
     "proxmox-lang",
@@ -88,6 +89,7 @@ proxmox-api-macro = { version = "1.0.4", path = "proxmox-api-macro" }
 proxmox-async = { version = "0.4.1", path = "proxmox-async" }
 proxmox-compression = { version = "0.2.0", path = "proxmox-compression" }
 proxmox-http = { version = "0.9.0", path = "proxmox-http" }
+proxmox-http-error = { version = "0.1.0", path = "proxmox-http-error" }
 proxmox-human-byte = { version = "0.1.0", path = "proxmox-human-byte" }
 proxmox-io = { version = "1.0.0", path = "proxmox-io" }
 proxmox-lang = { version = "1.1", path = "proxmox-lang" }

proxmox-http-error/Cargo.toml

@@ -0,0 +1,16 @@
+[package]
+name = "proxmox-http-error"
+version = "0.1.0"
+
+edition.workspace = true
+authors.workspace = true
+license.workspace = true
+repository.workspace = true
+description = "Proxmox HTTP Error"
+
+exclude.workspace = true
+
+[dependencies]
+anyhow.workspace = true
+http.workspace = true
+serde.workspace = true

proxmox-http-error/src/lib.rs

@@ -0,0 +1,81 @@
+use serde::{ser::SerializeStruct, Serialize, Serializer};
+use std::fmt;
+
+#[doc(hidden)]
+pub use http::StatusCode;
+
+/// HTTP error including `StatusCode` and message.
+#[derive(Debug)]
+pub struct HttpError {
+    pub code: StatusCode,
+    pub message: String,
+}
+
+impl std::error::Error for HttpError {}
+
+impl HttpError {
+    pub fn new(code: StatusCode, message: String) -> Self {
+        HttpError { code, message }
+    }
+}
+
+impl fmt::Display for HttpError {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        write!(f, "{}", self.message)
+    }
+}
+
+impl Serialize for HttpError {
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+    where
+        S: Serializer,
+    {
+        let mut state = serializer.serialize_struct("HttpError", 2)?;
+        state.serialize_field("code", &self.code.as_u16())?;
+        state.serialize_field("message", &self.message)?;
+        state.end()
+    }
+}
+
+/// Macro to create a HttpError inside a anyhow::Error
+#[macro_export]
+macro_rules! http_err {
+    ($status:ident, $($fmt:tt)+) => {{
+        ::anyhow::Error::from($crate::HttpError::new(
+            $crate::StatusCode::$status,
+            format!($($fmt)+)
+        ))
+    }};
+}
+
+/// Bail with an error generated with the `http_err!` macro.
+#[macro_export]
+macro_rules! http_bail {
+    ($status:ident, $($fmt:tt)+) => {{
+        return Err($crate::http_err!($status, $($fmt)+));
+    }};
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_http_err() {
+        // Make sure the macro generates valid code.
+        http_err!(IM_A_TEAPOT, "Cannot brew coffee");
+    }
+
+    #[test]
+    fn test_http_bail() {
+        fn t() -> Result<(), anyhow::Error> {
+            // Make sure the macro generates valid code.
+            http_bail!(
+                UNAVAILABLE_FOR_LEGAL_REASONS,
+                "Nothing to see here, move along"
+            );
+        }
+
+        assert!(t().is_err());
+    }
+}