2 files changed, 119 insertions, 0 deletions
diff --git a/third_party/rust/error-support-macros/src/argument.rs b/third_party/rust/error-support-macros/src/argument.rs
new file mode 100644
index 0000000000..ad7bf87a6e
--- /dev/null
+++ b/third_party/rust/error-support-macros/src/argument.rs
@@ -0,0 +1,21 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+use syn::spanned::Spanned;
+
+const ERR_MSG: &str = "Expected #[handle_error(path::to::Error)]";
+
+/// Returns the path to the type of the "internal" error.
+pub(crate) fn validate(arguments: &syn::AttributeArgs) -> syn::Result<&syn::Path> {
+    if arguments.len() != 1 {
+        return Err(syn::Error::new(proc_macro2::Span::call_site(), ERR_MSG));
+    }
+
+    let nested_meta = arguments.iter().next().unwrap();
+    if let syn::NestedMeta::Meta(syn::Meta::Path(path)) = nested_meta {
+        Ok(path)
+    } else {
+        Err(syn::Error::new(nested_meta.span(), ERR_MSG))
+    }
+}
diff --git a/third_party/rust/error-support-macros/src/lib.rs b/third_party/rust/error-support-macros/src/lib.rs
new file mode 100644
index 0000000000..22686b466b
--- /dev/null
+++ b/third_party/rust/error-support-macros/src/lib.rs
@@ -0,0 +1,98 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+use proc_macro::TokenStream;
+use quote::quote;
+use syn::{parse_quote, spanned::Spanned};
+
+mod argument;
+
+/// A procedural macro that exposes internal errors to external errors the
+/// consuming applications should handle. It requires that the internal error
+/// implements [`error_support::ErrorHandling`].
+///
+/// Additionally, this procedural macro has side effects, including:
+/// * It would log the error based on a pre-defined log level. The log level is defined
+///  in the [`error_support::ErrorHandling`] implementation.
+/// * It would report some errors using an external error reporter, in practice, this
+///   is implemented using Sentry in the app.
+///
+/// # Example
+/// ```ignore
+/// use error_support::{handle_error, GetErrorHandling, ErrorHandling};
+/// use std::fmt::Display
+///#[derive(Debug, thiserror::Error)]
+/// struct Error {}
+/// type Result<T, E = Error> = std::result::Result<T, E>;
+
+/// impl Display for Error {
+///     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+///         write!(f, "Internal Error!")
+///     }
+/// }
+///
+/// #[derive(Debug, thiserror::Error)]
+/// struct ExternalError {}
+///
+/// impl Display for ExternalError {
+///     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+///         write!(f, "External Error!")
+///     }
+/// }
+///
+/// impl GetErrorHandling for Error {
+///    type ExternalError = ExternalError;
+///
+///    fn get_error_handling(&self) -> ErrorHandling<Self::ExternalError> {
+///        ErrorHandling::convert(ExternalError {})
+///    }
+/// }
+///
+/// // The `handle_error` macro maps from the error supplied in the mandatory argument
+/// // (ie, `Error` in this example) to the error returned by the function (`ExternalError`
+/// // in this example)
+/// #[handle_error(Error)]
+/// fn do_something() -> std::result::Result<String, ExternalError> {
+///    Err(Error{})
+/// }
+///
+/// // The error here is an `ExternalError`
+/// let _: ExternalError = do_something().unwrap_err();
+/// ```
+#[proc_macro_attribute]
+pub fn handle_error(args: TokenStream, input: TokenStream) -> TokenStream {
+    let args = syn::parse_macro_input!(args as syn::AttributeArgs);
+    let parsed = syn::parse_macro_input!(input as syn::Item);
+    TokenStream::from(match impl_handle_error(&parsed, &args) {
+        Ok(res) => res,
+        Err(e) => e.to_compile_error(),
+    })
+}
+
+fn impl_handle_error(
+    input: &syn::Item,
+    arguments: &syn::AttributeArgs,
+) -> syn::Result<proc_macro2::TokenStream> {
+    if let syn::Item::Fn(item_fn) = input {
+        let err_path = argument::validate(arguments)?;
+        let original_body = &item_fn.block;
+
+        let mut new_fn = item_fn.clone();
+        new_fn.block = parse_quote! {
+            {
+                (|| -> ::std::result::Result<_, #err_path> {
+                    #original_body
+                })().map_err(::error_support::convert_log_report_error)
+            }
+        };
+
+        Ok(quote! {
+            #new_fn
+        })
+    } else {
+        Err(syn::Error::new(
+            input.span(),
+            "#[handle_error(..)] can only be used on functions",
+        ))
+    }
+}