fix: conditional clippy lint allows for lifetime generics

Cargo.toml

@@ -4,7 +4,7 @@
 
 [package]
 name = "masterror"
-version = "0.27.1"
+version = "0.27.2"
 rust-version = "1.92"
 edition = "2024"
 license = "MIT"
@@ -13,7 +13,7 @@ readme = "README.md"
 description = "Application error types and response mapping"
 documentation = "https://docs.rs/masterror"
 build = "build.rs"
-categories = ["rust-patterns", "web-programming"]
+categories = ["rust-patterns", "web-programming", "no-std"]
 keywords = ["error", "api", "framework"]
 include = [
   "Cargo.toml",

README.md

@@ -159,9 +159,9 @@ The build script keeps the full feature snippet below in sync with
 
 ~~~toml
 [dependencies]
-masterror = { version = "0.27.1", default-features = false }
+masterror = { version = "0.27.2", default-features = false }
 # or with features:
-# masterror = { version = "0.27.1", features = [
+# masterror = { version = "0.27.2", features = [
 #   "std", "axum", "actix", "openapi",
 #   "serde_json", "tracing", "metrics", "backtrace",
 #   "colored", "sqlx", "sqlx-migrate", "reqwest",
@@ -640,7 +640,7 @@ Enable the `colored` feature for enhanced terminal output in local mode:
 
 ~~~toml
 [dependencies]
-masterror = { version = "0.27.1", features = ["colored"] }
+masterror = { version = "0.27.2", features = ["colored"] }
 ~~~
 
 With `colored` enabled, errors display with syntax highlighting:

masterror-derive/Cargo.toml

@@ -5,7 +5,7 @@
 [package]
 name = "masterror-derive"
 rust-version = "1.92"
-version = "0.11.1"
+version = "0.11.2"
 edition = "2024"
 license = "MIT"
 repository = "https://github.com/RAprogramm/masterror"

masterror-derive/src/display/enum_impl.rs

@@ -24,6 +24,7 @@ use crate::{
     input::{
         DisplaySpec, ErrorInput, Field, Fields, FormatArgsSpec, VariantData, placeholder_error
     },
+    lint::lifetime_lint_allows,
     template_support::{DisplayTemplate, TemplateIdentifierSpec}
 };
 
@@ -47,7 +48,9 @@ pub fn expand_enum(input: &ErrorInput, variants: &[VariantData]) -> Result<Token
     }
     let ident = &input.ident;
     let (impl_generics, ty_generics, where_clause) = input.generics.split_for_impl();
+    let lint_allows = lifetime_lint_allows(&input.generics);
     Ok(quote! {
+        #lint_allows
         impl #impl_generics core::fmt::Display for #ident #ty_generics #where_clause {
             fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
                 match self {

masterror-derive/src/display/struct_impl.rs

@@ -21,6 +21,7 @@ use super::{
 };
 use crate::{
     input::{DisplaySpec, ErrorInput, Field, Fields, StructData, placeholder_error},
+    lint::lifetime_lint_allows,
     template_support::TemplateIdentifierSpec
 };
 
@@ -64,7 +65,9 @@ pub fn expand_struct(input: &ErrorInput, data: &StructData) -> Result<TokenStrea
     };
     let ident = &input.ident;
     let (impl_generics, ty_generics, where_clause) = input.generics.split_for_impl();
+    let lint_allows = lifetime_lint_allows(&input.generics);
     Ok(quote! {
+        #lint_allows
         impl #impl_generics core::fmt::Display for #ident #ty_generics #where_clause {
             fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
                 #body

masterror-derive/src/error_trait.rs

@@ -51,7 +51,10 @@ use proc_macro2::TokenStream;
 use quote::quote;
 use syn::Error;
 
-use crate::input::{ErrorData, ErrorInput, StructData, VariantData};
+use crate::{
+    input::{ErrorData, ErrorInput, StructData, VariantData},
+    lint::lifetime_lint_allows
+};
 
 pub mod backtrace;
 pub mod binding;
@@ -107,7 +110,9 @@ fn expand_struct(input: &ErrorInput, data: &StructData) -> Result<TokenStream, E
     let provide_method = provide_method.unwrap_or_default();
     let ident = &input.ident;
     let (impl_generics, ty_generics, where_clause) = input.generics.split_for_impl();
+    let lint_allows = lifetime_lint_allows(&input.generics);
     Ok(quote! {
+        #lint_allows
         impl #impl_generics std::error::Error for #ident #ty_generics #where_clause {
             fn source(&self) -> Option<&(dyn std::error::Error + 'static)> {
                 #body
@@ -142,7 +147,9 @@ fn expand_enum(input: &ErrorInput, variants: &[VariantData]) -> Result<TokenStre
     let provide_method = provide_method.unwrap_or_default();
     let ident = &input.ident;
     let (impl_generics, ty_generics, where_clause) = input.generics.split_for_impl();
+    let lint_allows = lifetime_lint_allows(&input.generics);
     Ok(quote! {
+        #lint_allows
         impl #impl_generics std::error::Error for #ident #ty_generics #where_clause {
             fn source(&self) -> Option<&(dyn std::error::Error + 'static)> {
                 match self {

masterror-derive/src/lib.rs

@@ -12,6 +12,7 @@ mod display;
 mod error_trait;
 mod from_impl;
 mod input;
+mod lint;
 mod masterror_impl;
 mod span;
 mod template_support;

masterror-derive/src/lint.rs

@@ -0,0 +1,83 @@
+// SPDX-FileCopyrightText: 2025 RAprogramm <andrey.rozanov.vl@gmail.com>
+//
+// SPDX-License-Identifier: MIT
+
+//! Clippy lint suppression for generated code.
+//!
+//! When generating trait implementations for types with lifetime parameters,
+//! clippy may emit `needless_lifetimes` or `elidable_lifetime_names` warnings.
+//! These warnings conflict with project-level `forbid` directives, so we
+//! conditionally suppress them only when the type actually has lifetimes.
+
+use proc_macro2::TokenStream;
+use quote::quote;
+use syn::Generics;
+
+/// Generates conditional clippy lint allows for lifetime-related warnings.
+///
+/// Returns `#[allow(...)]` attributes only when the generics contain lifetime
+/// parameters. This prevents conflicts with project-level `forbid` directives
+/// while still suppressing false positives in generated code.
+///
+/// # Arguments
+///
+/// * `generics` - The generics from the type definition
+///
+/// # Returns
+///
+/// Token stream with allow attributes if lifetimes present, empty otherwise
+pub fn lifetime_lint_allows(generics: &Generics) -> TokenStream {
+    if generics.lifetimes().next().is_some() {
+        quote! {
+            #[allow(clippy::elidable_lifetime_names, clippy::needless_lifetimes)]
+        }
+    } else {
+        TokenStream::new()
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use syn::parse_quote;
+
+    use super::*;
+
+    #[test]
+    fn test_no_lifetimes_returns_empty() {
+        let generics: Generics = parse_quote!();
+        let result = lifetime_lint_allows(&generics);
+        assert!(result.is_empty());
+    }
+
+    #[test]
+    fn test_type_params_only_returns_empty() {
+        let generics: Generics = parse_quote!(<T, U>);
+        let result = lifetime_lint_allows(&generics);
+        assert!(result.is_empty());
+    }
+
+    #[test]
+    fn test_with_lifetime_returns_allows() {
+        let generics: Generics = parse_quote!(<'a>);
+        let result = lifetime_lint_allows(&generics);
+        let output = result.to_string();
+        assert!(output.contains("allow"));
+        assert!(output.contains("elidable_lifetime_names"));
+        assert!(output.contains("needless_lifetimes"));
+    }
+
+    #[test]
+    fn test_mixed_params_with_lifetime_returns_allows() {
+        let generics: Generics = parse_quote!(<'a, T, 'b>);
+        let result = lifetime_lint_allows(&generics);
+        let output = result.to_string();
+        assert!(output.contains("allow"));
+    }
+
+    #[test]
+    fn test_const_generics_only_returns_empty() {
+        let generics: Generics = parse_quote!(<const N: usize>);
+        let result = lifetime_lint_allows(&generics);
+        assert!(result.is_empty());
+    }
+}

src/app_error.rs

@@ -69,6 +69,7 @@
 mod constructors;
 mod context;
 mod core;
+mod inline_vec;
 mod metadata;
 
 pub use core::{AppError, AppResult, DisplayMode, Error, ErrorChain, MessageEditPolicy};

src/app_error/core/error.rs

@@ -110,11 +110,8 @@ impl Display for Error {
                 let mut current: &dyn CoreError = source.as_ref();
                 let mut depth = 0;
                 while depth < 10 {
-                    writeln!(
-                        f,
-                        "{}",
-                        style::source_context(alloc::format!("Caused by: {}", current))
-                    )?;
+                    write!(f, "  {}: ", style::source_context("Caused by"))?;
+                    writeln!(f, "{}", style::source_context(current.to_string()))?;
                     if let Some(next) = current.source() {
                         current = next;
                         depth += 1;