Fix tonic conversion clippy warnings

CHANGELOG.md

@@ -3,6 +3,17 @@ All notable changes to this project will be documented in this file.
 
 ## [Unreleased]
 
+## [0.20.5] - 2025-10-05
+
+### Fixed
+- Promoted the gRPC converter to an infallible `From<Error>` implementation
+  while retaining the `TryFrom` API via the new documented
+  `StatusConversionError`, satisfying Clippy's infallible conversion lint.
+- Collapsed nested metadata guards in the Tonic adapter and reused borrowed
+  booleans to silence Clippy without regressing runtime behaviour.
+- Simplified the `AppResult` alias test to avoid large `Err` variant warnings
+  from Clippy's `result_large_err` lint.
+
 ## [0.20.4] - 2025-10-04
 
 ### Added

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "masterror"
-version = "0.20.4"
+version = "0.20.5"
 rust-version = "1.90"
 edition = "2024"
 license = "MIT OR Apache-2.0"

README.md

@@ -38,9 +38,9 @@ guides, comparisons with `thiserror`/`anyhow`, and troubleshooting recipes.
 
 ~~~toml
 [dependencies]
-masterror = { version = "0.20.4", default-features = false }
+masterror = { version = "0.20.5", default-features = false }
 # or with features:
-# masterror = { version = "0.20.4", features = [
+# masterror = { version = "0.20.5", features = [
 #   "axum", "actix", "openapi", "serde_json",
 #   "tracing", "metrics", "backtrace", "sqlx",
 #   "sqlx-migrate", "reqwest", "redis", "validator",
@@ -78,10 +78,10 @@ masterror = { version = "0.20.4", default-features = false }
 ~~~toml
 [dependencies]
 # lean core
-masterror = { version = "0.20.4", default-features = false }
+masterror = { version = "0.20.5", default-features = false }
 
 # with Axum/Actix + JSON + integrations
-# masterror = { version = "0.20.4", features = [
+# masterror = { version = "0.20.5", features = [
 #   "axum", "actix", "openapi", "serde_json",
 #   "tracing", "metrics", "backtrace", "sqlx",
 #   "sqlx-migrate", "reqwest", "redis", "validator",
@@ -720,13 +720,13 @@ assert_eq!(problem.grpc.expect("grpc").name, "UNAUTHENTICATED");
 Minimal core:
 
 ~~~toml
-masterror = { version = "0.20.4", default-features = false }
+masterror = { version = "0.20.5", default-features = false }
 ~~~
 
 API (Axum + JSON + deps):
 
 ~~~toml
-masterror = { version = "0.20.4", features = [
+masterror = { version = "0.20.5", features = [
   "axum", "serde_json", "openapi",
   "sqlx", "reqwest", "redis", "validator", "config", "tokio"
 ] }
@@ -735,7 +735,7 @@ masterror = { version = "0.20.4", features = [
 API (Actix + JSON + deps):
 
 ~~~toml
-masterror = { version = "0.20.4", features = [
+masterror = { version = "0.20.5", features = [
   "actix", "serde_json", "openapi",
   "sqlx", "reqwest", "redis", "validator", "config", "tokio"
 ] }

src/app_error/tests.rs

@@ -537,14 +537,9 @@ fn metrics_counter_is_incremented_once() {
 
 #[test]
 fn result_alias_is_generic() {
-    fn app() -> super::AppResult<u8> {
-        Ok(1)
-    }
-
-    fn other() -> super::AppResult<u8, &'static str> {
-        Ok(2)
-    }
+    let default_result: super::AppResult<u8> = Ok(1);
+    let custom_result: super::AppResult<u8, &'static str> = Ok(2);
 
-    assert_eq!(app().unwrap(), 1);
-    assert_eq!(other().unwrap(), 2);
+    assert_eq!(default_result.unwrap(), 1);
+    assert_eq!(custom_result.unwrap(), 2);
 }

src/convert/tonic.rs

@@ -14,11 +14,11 @@
 //! ```rust,ignore
 //! use masterror::{AppError, AppErrorKind};
 //!
-//! let status = tonic::Status::try_from(AppError::not_found("missing"))?;
+//! let status = tonic::Status::from(AppError::not_found("missing"));
 //! assert_eq!(status.code(), tonic::Code::NotFound);
 //! ```
 
-use std::{borrow::Cow, convert::Infallible};
+use std::{borrow::Cow, fmt};
 
 use tonic::{
     Code, Status,
@@ -32,11 +32,49 @@ use crate::{
     mapping_for_code
 };
 
+/// Error returned when converting [`Error`] into [`Status`] fails.
+///
+/// This type is never constructed in practice because the conversion is
+/// guaranteed to succeed. It exists solely to preserve the `TryFrom` API in
+/// addition to the infallible [`From`] conversion.
+///
+/// # Examples
+/// ```rust,ignore
+/// use masterror::{AppError, StatusConversionError};
+/// use tonic::{Code, Status};
+///
+/// fn convert() -> Result<Status, StatusConversionError> {
+///     Status::try_from(AppError::not_found("missing"))
+/// }
+///
+/// # fn main() -> Result<(), StatusConversionError> {
+/// let status = convert()?;
+/// assert_eq!(status.code(), Code::NotFound);
+/// # Ok(())
+/// # }
+/// ```
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub struct StatusConversionError;
+
+impl fmt::Display for StatusConversionError {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.write_str("conversion to tonic::Status cannot fail")
+    }
+}
+
+impl std::error::Error for StatusConversionError {}
+
+impl From<Error> for Status {
+    fn from(error: Error) -> Self {
+        status_from_error(&error)
+    }
+}
+
 impl TryFrom<Error> for Status {
-    type Error = Infallible;
+    type Error = StatusConversionError;
 
     fn try_from(error: Error) -> Result<Self, Self::Error> {
-        Ok(status_from_error(&error))
+        Ok(Status::from(error))
     }
 }
 
@@ -59,10 +97,10 @@ fn status_from_error(error: &Error) -> Status {
     if let Some(advice) = error.retry {
         insert_retry(&mut meta, advice);
     }
-    if let Some(challenge) = error.www_authenticate.as_deref() {
-        if is_ascii_metadata_value(challenge) {
-            insert_ascii(&mut meta, "www-authenticate", challenge);
-        }
+    if let Some(challenge) = error.www_authenticate.as_deref()
+        && is_ascii_metadata_value(challenge)
+    {
+        insert_ascii(&mut meta, "www-authenticate", challenge);
     }
 
     if !matches!(error.edit_policy, MessageEditPolicy::Redact) {
@@ -123,9 +161,7 @@ fn metadata_value_to_ascii(value: &FieldValue) -> Option<Cow<'_, str>> {
         }
         FieldValue::I64(value) => Some(Cow::Owned(value.to_string())),
         FieldValue::U64(value) => Some(Cow::Owned(value.to_string())),
-        FieldValue::Bool(value) => Some(Cow::Owned(
-            if *value { "true" } else { "false" }.to_string()
-        )),
+        FieldValue::Bool(value) => Some(Cow::Borrowed(if *value { "true" } else { "false" })),
         FieldValue::Uuid(value) => Some(Cow::Owned(value.to_string()))
     }
 }

src/lib.rs

@@ -363,3 +363,7 @@ pub use response::{
     }
 };
 pub use result_ext::ResultExt;
+
+#[cfg(feature = "tonic")]
+#[cfg_attr(docsrs, doc(cfg(feature = "tonic")))]
+pub use crate::convert::tonic::StatusConversionError;