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Add #[thiserror(crate = "...")] attribute for re-export scenarios #450

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32934ea
Support #[thiserror(crate = "...")] to override crate path
suchyj-btlnet Apr 22, 2026
f81eec4
self-cr
suchyj-btlnet Apr 22, 2026
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32 changes: 31 additions & 1 deletion impl/src/attr.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -5,7 +5,7 @@ use syn::parse::discouraged::Speculative;
use syn::parse::{End, ParseStream};
use syn::{
braced, bracketed, parenthesized, token, Attribute, Error, ExprPath, Ident, Index, LitFloat,
LitInt, LitStr, Meta, Result, Token,
LitInt, LitStr, Meta, Path, Result, Token,
};

pub struct Attrs<'a> {
Expand All @@ -15,6 +15,7 @@ pub struct Attrs<'a> {
pub from: Option<From<'a>>,
pub transparent: Option<Transparent<'a>>,
pub fmt: Option<Fmt<'a>>,
pub crate_path: Option<Path>,
}

#[derive(Clone)]
Expand Down Expand Up @@ -74,6 +75,7 @@ pub fn get(input: &[Attribute]) -> Result<Attrs> {
from: None,
transparent: None,
fmt: None,
crate_path: None,
};

for attr in input {
Expand Down Expand Up @@ -115,12 +117,40 @@ pub fn get(input: &[Attribute]) -> Result<Attrs> {
original: attr,
span,
});
} else if attr.path().is_ident("thiserror") {
attr.parse_nested_meta(|meta| {
if !meta.path.is_ident("crate") {
let path_str = meta.path.to_token_stream().to_string().replace(' ', "");
return Err(
meta.error(format_args!("unknown thiserror attribute `{path_str}`"))
);
}
let crate_path_lit: LitStr = meta.value()?.parse()?;
let path = crate_path_lit
.parse::<Path>()
.map_err(|e| Error::new(crate_path_lit.span(), e))?;
if attrs.crate_path.is_some() {
return Err(Error::new_spanned(
attr,
"duplicate #[thiserror(crate)] attribute",
));
}
attrs.crate_path = Some(path);
Ok(())
})?;
}
}

Ok(attrs)
}

pub fn crate_path(attrs: &[Attribute]) -> syn::Path {
get(attrs)
.ok()
.and_then(|a| a.crate_path)
.unwrap_or_else(|| syn::parse_quote!(::thiserror))
}

fn parse_error_attribute<'a>(attrs: &mut Attrs<'a>, attr: &'a Attribute) -> Result<()> {
mod kw {
syn::custom_keyword!(transparent);
Expand Down
75 changes: 43 additions & 32 deletions impl/src/expand.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -7,7 +7,7 @@ use crate::unraw::MemberUnraw;
use proc_macro2::{Ident, Span, TokenStream};
use quote::{format_ident, quote, quote_spanned, ToTokens};
use std::collections::BTreeSet as Set;
use syn::{DeriveInput, GenericArgument, PathArguments, Result, Token, Type};
use syn::{DeriveInput, GenericArgument, Path, PathArguments, Result, Token, Type};

pub fn derive(input: &DeriveInput) -> TokenStream {
match try_expand(input) {
Expand All @@ -32,21 +32,26 @@ fn impl_struct(input: Struct) -> TokenStream {
let ty = call_site_ident(&input.ident);
let (impl_generics, ty_generics, where_clause) = input.generics.split_for_impl();
let mut error_inferred_bounds = InferredBounds::new();
let krate: Path = input
.attrs
.crate_path
.clone()
.unwrap_or_else(|| syn::parse_quote!(::thiserror));

let source_body = if let Some(transparent_attr) = &input.attrs.transparent {
let only_field = &input.fields[0];
if only_field.contains_generic {
error_inferred_bounds.insert(only_field.ty, quote!(::thiserror::#private::Error));
error_inferred_bounds.insert(only_field.ty, quote!(#krate::#private::Error));
}
let member = &only_field.member;
Some(quote_spanned! {transparent_attr.span=>
::thiserror::#private::Error::source(self.#member.as_dyn_error())
#krate::#private::Error::source(self.#member.as_dyn_error())
})
} else if let Some(source_field) = input.source_field() {
let source = &source_field.member;
if source_field.contains_generic {
let ty = unoptional_type(source_field.ty);
error_inferred_bounds.insert(ty, quote!(::thiserror::#private::Error + 'static));
error_inferred_bounds.insert(ty, quote!(#krate::#private::Error + 'static));
}
let asref = if type_is_option(source_field.ty) {
Some(quote_spanned!(source.span()=> .as_ref()?))
Expand All @@ -64,8 +69,8 @@ fn impl_struct(input: Struct) -> TokenStream {
};
let source_method = source_body.map(|body| {
quote! {
fn source(&self) -> ::core::option::Option<&(dyn ::thiserror::#private::Error + 'static)> {
use ::thiserror::#private::AsDynError as _;
fn source(&self) -> ::core::option::Option<&(dyn #krate::#private::Error + 'static)> {
use #krate::#private::AsDynError as _;
#body
}
}
Expand All @@ -92,28 +97,28 @@ fn impl_struct(input: Struct) -> TokenStream {
} else if type_is_option(backtrace_field.ty) {
Some(quote! {
if let ::core::option::Option::Some(backtrace) = &self.#backtrace {
#request.provide_ref::<::thiserror::#private::Backtrace>(backtrace);
#request.provide_ref::<#krate::#private::Backtrace>(backtrace);
}
})
} else {
Some(quote! {
#request.provide_ref::<::thiserror::#private::Backtrace>(&self.#backtrace);
#request.provide_ref::<#krate::#private::Backtrace>(&self.#backtrace);
})
};
quote! {
use ::thiserror::#private::ThiserrorProvide as _;
use #krate::#private::ThiserrorProvide as _;
#source_provide
#self_provide
}
} else if type_is_option(backtrace_field.ty) {
quote! {
if let ::core::option::Option::Some(backtrace) = &self.#backtrace {
#request.provide_ref::<::thiserror::#private::Backtrace>(backtrace);
#request.provide_ref::<#krate::#private::Backtrace>(backtrace);
}
}
} else {
quote! {
#request.provide_ref::<::thiserror::#private::Backtrace>(&self.#backtrace);
#request.provide_ref::<#krate::#private::Backtrace>(&self.#backtrace);
}
};
quote! {
Expand All @@ -132,7 +137,7 @@ fn impl_struct(input: Struct) -> TokenStream {
})
} else if let Some(display) = &input.attrs.display {
display_implied_bounds.clone_from(&display.implied_bounds);
let use_as_display = use_as_display(display.has_bonus_display);
let use_as_display = use_as_display(display.has_bonus_display, &krate);
let pat = fields_pat(&input.fields);
Some(quote! {
#use_as_display
Expand Down Expand Up @@ -169,7 +174,7 @@ fn impl_struct(input: Struct) -> TokenStream {
let backtrace_field = input.distinct_backtrace_field();
let from = unoptional_type(from_field.ty);
let source_var = Ident::new("source", span);
let body = from_initializer(from_field, backtrace_field, &source_var);
let body = from_initializer(from_field, backtrace_field, &source_var, &krate);
let from_function = quote! {
fn from(#source_var: #from) -> Self {
#ty #body
Expand Down Expand Up @@ -209,7 +214,7 @@ fn impl_struct(input: Struct) -> TokenStream {
quote! {
#[allow(unused_qualifications)]
#[automatically_derived]
impl #impl_generics ::thiserror::#private::Error for #ty #ty_generics #error_where_clause {
impl #impl_generics #krate::#private::Error for #ty #ty_generics #error_where_clause {
#source_method
#provide_method
}
Expand All @@ -222,18 +227,23 @@ fn impl_enum(input: Enum) -> TokenStream {
let ty = call_site_ident(&input.ident);
let (impl_generics, ty_generics, where_clause) = input.generics.split_for_impl();
let mut error_inferred_bounds = InferredBounds::new();
let krate: Path = input
.attrs
.crate_path
.clone()
.unwrap_or_else(|| syn::parse_quote!(::thiserror));

let source_method = if input.has_source() {
let arms = input.variants.iter().map(|variant| {
let ident = &variant.ident;
if let Some(transparent_attr) = &variant.attrs.transparent {
let only_field = &variant.fields[0];
if only_field.contains_generic {
error_inferred_bounds.insert(only_field.ty, quote!(::thiserror::#private::Error));
error_inferred_bounds.insert(only_field.ty, quote!(#krate::#private::Error));
}
let member = &only_field.member;
let source = quote_spanned! {transparent_attr.span=>
::thiserror::#private::Error::source(transparent.as_dyn_error())
#krate::#private::Error::source(transparent.as_dyn_error())
};
quote! {
#ty::#ident {#member: transparent} => #source,
Expand All @@ -242,7 +252,7 @@ fn impl_enum(input: Enum) -> TokenStream {
let source = &source_field.member;
if source_field.contains_generic {
let ty = unoptional_type(source_field.ty);
error_inferred_bounds.insert(ty, quote!(::thiserror::#private::Error + 'static));
error_inferred_bounds.insert(ty, quote!(#krate::#private::Error + 'static));
}
let asref = if type_is_option(source_field.ty) {
Some(quote_spanned!(source.span()=> .as_ref()?))
Expand All @@ -263,8 +273,8 @@ fn impl_enum(input: Enum) -> TokenStream {
}
});
Some(quote! {
fn source(&self) -> ::core::option::Option<&(dyn ::thiserror::#private::Error + 'static)> {
use ::thiserror::#private::AsDynError as _;
fn source(&self) -> ::core::option::Option<&(dyn #krate::#private::Error + 'static)> {
use #krate::#private::AsDynError as _;
#[allow(deprecated)]
match self {
#(#arms)*
Expand Down Expand Up @@ -300,12 +310,12 @@ fn impl_enum(input: Enum) -> TokenStream {
let self_provide = if type_is_option(backtrace_field.ty) {
quote! {
if let ::core::option::Option::Some(backtrace) = backtrace {
#request.provide_ref::<::thiserror::#private::Backtrace>(backtrace);
#request.provide_ref::<#krate::#private::Backtrace>(backtrace);
}
}
} else {
quote! {
#request.provide_ref::<::thiserror::#private::Backtrace>(backtrace);
#request.provide_ref::<#krate::#private::Backtrace>(backtrace);
}
};
quote! {
Expand All @@ -314,7 +324,7 @@ fn impl_enum(input: Enum) -> TokenStream {
#source: #varsource,
..
} => {
use ::thiserror::#private::ThiserrorProvide as _;
use #krate::#private::ThiserrorProvide as _;
#source_provide
#self_provide
}
Expand All @@ -338,7 +348,7 @@ fn impl_enum(input: Enum) -> TokenStream {
};
quote! {
#ty::#ident {#backtrace: #varsource, ..} => {
use ::thiserror::#private::ThiserrorProvide as _;
use #krate::#private::ThiserrorProvide as _;
#source_provide
}
}
Expand All @@ -348,12 +358,12 @@ fn impl_enum(input: Enum) -> TokenStream {
let body = if type_is_option(backtrace_field.ty) {
quote! {
if let ::core::option::Option::Some(backtrace) = backtrace {
#request.provide_ref::<::thiserror::#private::Backtrace>(backtrace);
#request.provide_ref::<#krate::#private::Backtrace>(backtrace);
}
}
} else {
quote! {
#request.provide_ref::<::thiserror::#private::Backtrace>(backtrace);
#request.provide_ref::<#krate::#private::Backtrace>(backtrace);
}
};
quote! {
Expand Down Expand Up @@ -387,7 +397,7 @@ fn impl_enum(input: Enum) -> TokenStream {
.as_ref()
.is_some_and(|display| display.has_bonus_display)
});
let use_as_display = use_as_display(has_bonus_display);
let use_as_display = use_as_display(has_bonus_display, &krate);
let void_deref = if input.variants.is_empty() {
Some(quote!(*))
} else {
Expand Down Expand Up @@ -451,7 +461,7 @@ fn impl_enum(input: Enum) -> TokenStream {
let variant = &variant.ident;
let from = unoptional_type(from_field.ty);
let source_var = Ident::new("source", span);
let body = from_initializer(from_field, backtrace_field, &source_var);
let body = from_initializer(from_field, backtrace_field, &source_var, &krate);
let from_function = quote! {
fn from(#source_var: #from) -> Self {
#ty::#variant #body
Expand Down Expand Up @@ -491,7 +501,7 @@ fn impl_enum(input: Enum) -> TokenStream {
quote! {
#[allow(unused_qualifications)]
#[automatically_derived]
impl #impl_generics ::thiserror::#private::Error for #ty #ty_generics #error_where_clause {
impl #impl_generics #krate::#private::Error for #ty #ty_generics #error_where_clause {
#source_method
#provide_method
}
Expand Down Expand Up @@ -523,10 +533,10 @@ fn fields_pat(fields: &[Field]) -> TokenStream {
}
}

fn use_as_display(needs_as_display: bool) -> Option<TokenStream> {
fn use_as_display(needs_as_display: bool, krate: &Path) -> Option<TokenStream> {
if needs_as_display {
Some(quote! {
use ::thiserror::#private::AsDisplay as _;
use #krate::#private::AsDisplay as _;
})
} else {
None
Expand All @@ -537,6 +547,7 @@ fn from_initializer(
from_field: &Field,
backtrace_field: Option<&Field>,
source_var: &Ident,
krate: &Path,
) -> TokenStream {
let from_member = &from_field.member;
let some_source = if type_is_option(from_field.ty) {
Expand All @@ -548,11 +559,11 @@ fn from_initializer(
let backtrace_member = &backtrace_field.member;
if type_is_option(backtrace_field.ty) {
quote! {
#backtrace_member: ::core::option::Option::Some(::thiserror::#private::Backtrace::capture()),
#backtrace_member: ::core::option::Option::Some(#krate::#private::Backtrace::capture()),
}
} else {
quote! {
#backtrace_member: ::core::convert::From::from(::thiserror::#private::Backtrace::capture()),
#backtrace_member: ::core::convert::From::from(#krate::#private::Backtrace::capture()),
}
}
});
Expand Down
3 changes: 2 additions & 1 deletion impl/src/fallback.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -7,6 +7,7 @@ use syn::DeriveInput;
pub(crate) fn expand(input: &DeriveInput, error: syn::Error) -> TokenStream {
let ty = call_site_ident(&input.ident);
let (impl_generics, ty_generics, where_clause) = input.generics.split_for_impl();
let krate = crate::attr::crate_path(&input.attrs);

let error = error.to_compile_error();

Expand All @@ -15,7 +16,7 @@ pub(crate) fn expand(input: &DeriveInput, error: syn::Error) -> TokenStream {

#[allow(unused_qualifications)]
#[automatically_derived]
impl #impl_generics ::thiserror::#private::Error for #ty #ty_generics #where_clause
impl #impl_generics #krate::#private::Error for #ty #ty_generics #where_clause
where
// Work around trivial bounds being unstable.
// https://github.com/rust-lang/rust/issues/48214
Expand Down
2 changes: 1 addition & 1 deletion impl/src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -36,7 +36,7 @@ use proc_macro2::{Ident, Span};
use quote::{ToTokens, TokenStreamExt as _};
use syn::{parse_macro_input, DeriveInput};

#[proc_macro_derive(Error, attributes(backtrace, error, from, source))]
#[proc_macro_derive(Error, attributes(backtrace, error, from, source, thiserror))]
pub fn derive_error(input: TokenStream) -> TokenStream {
let input = parse_macro_input!(input as DeriveInput);
expand::derive(&input).into()
Expand Down
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