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use proc_macro::TokenStream;
use proc_macro2::Span;
use quote::{quote, TokenStreamExt};
use syn::fold::{self, Fold};
use syn::token::Comma;
use syn::{
parse_macro_input, parse_quote, Attribute, Expr, ExprMatch, FieldValue, Fields, Ident, Item,
ItemFn, ItemStruct, LitStr, ReturnType, Type, Variant,
};
/// Struct to handle the folding of the ItemFn.
/// Holds the return type and message for use by the fold functions.
struct ContextMsg {
m: LitStr,
rettype: Box<Type>,
has_ok: bool,
}
impl ContextMsg {
fn new(m: LitStr, rettype: Box<Type>) -> Self {
ContextMsg {
m,
rettype,
has_ok: false,
}
}
}
// The Fold trait is used to inject the error handling into the the source code.
// The Fold will change this function...
// #[context("context message")]
// fn basic_exampleerror() -> Result<(), ExampleError> {
// if io_error()? {
// return example_error().map_err(|e| e.msg("msgs are great"));
// }
// example_error()
// }
//
// into...
// fn basic_exampleerror() -> Result<(), ExampleError> {
// if hb_error::ConvertInto::Result<(), ExampleError>::convert(io_error()).map_err(|er| er.make_inner().msg("context message")? {
// return hb_error::ConvertInto::Result<(), ExampleError>::convert(example_error().map_err(|e| e.msg("msgs are great"))).map_err(|er| er.make_inner().msg("context message");
// }
// example_error()
// }
impl Fold for ContextMsg {
fn fold_expr(&mut self, e: Expr) -> Expr {
match e {
Expr::Return(mut rexpr) => {
match rexpr.expr {
Some(ex) => {
let m = &self.m;
let rettype = &self.rettype;
if m.value().contains('{') {
let mut msg_args = syn::punctuated::Punctuated::<Expr, Comma>::new();
let str = m.value();
let mut brace_contents: Vec<String> = vec![];
let mut in_brace = false;
let mut buf = String::new();
let mut out_str = String::new();
for c in str.chars() {
if c == '{' {
in_brace = true;
out_str.push(c);
} else if c == '}' {
if buf.len() > 0 {
brace_contents.push(buf);
buf = String::new();
}
in_brace = false;
out_str.push(c);
} else if in_brace {
buf.push(c);
} else {
out_str.push(c);
}
}
for content in brace_contents {
msg_args.push(
syn::parse_str::<Expr>(&content).expect(
format!("cannot convert {} into an expression.", content)
.as_str(),
),
);
}
msg_args.insert(0, parse_quote!(#out_str));
rexpr.expr = Some(
parse_quote!(hb_error::ConvertInto::<#rettype>::convert(#ex).map_err(|er| er.make_inner().msg(format!(#msg_args)))),
);
} else {
rexpr.expr = Some(
parse_quote!(hb_error::ConvertInto::<#rettype>::convert(#ex).map_err(|er| er.make_inner().msg(#m))),
);
}
}
None => (),
}
fold::fold_expr(self, Expr::Return(rexpr))
}
Expr::Try(mut texpr) => {
let ex = texpr.expr;
let m = &self.m;
texpr.expr = parse_quote!(#ex.make_inner().msg(#m));
Expr::Try(texpr)
}
Expr::Path(mut exprpath) => match exprpath.path.is_ident("Ok") {
true => {
exprpath
.path
.segments
.insert(0, parse_quote!(HbErrorContextType));
self.has_ok = true;
Expr::Path(exprpath)
}
false => Expr::Path(exprpath),
},
_ => fold::fold_expr(self, e),
}
}
}
/// Converts Errors returned by the function into the correct type for the
/// function as well adding a context message provided. There are many different situations that
/// need to be handled. The context message can also have a special format to use variables
/// in the context message.
/// # The context message format
/// The context message is treated as string, but it also allows the use of curly braces to inject
/// variables into the message. In the example below the msg parameter to the function is injected
/// into the context message.
/// ```
/// #[context("could not find message {msg}")]
/// fn find_msg(msg: String) -> Result<bool, FindError> {...}
/// ```
/// # Return expressions and Fall Through values`
/// Return expressions are modified to convert the returned result into the type expected by the
/// function using the hb_error::ConvertInto function. In addition, the error is also given the provided context message.
/// ```
/// return example_error();
/// ```
/// into...
/// ```
/// return hb_error::ConvertInto::<Result<(), ExampleError>>::convert(example_error()).map_err(|e| e.msg("some context message"));
/// ```
/// Similarly fall through values are handled similarly but with extra scaffolding around it so that
/// the compiler knows what type is expected in the block of the function and can show appropriate
/// error messages.
/// ```
/// fn something() -> Result<(), ExampleError> {
/// example_error
/// }
/// ```
/// into...
/// ```
/// fn something() -> Result<(), ExampleError> {
/// #[allow(unreachable_code)]
/// let ret: Result<(), ExampleError> = {
/// #[warn(unreachable_code)]
/// example_error
/// };
/// #[allow(unreachable_code)]
/// ret.map_err(|er| er.make_inner().msg("Some context message."))
/// }
/// ```
/// # Try expressions (? operator)
/// Try expressions are modified to convert the returned result into the type expected by the
/// function using the hb_error::ConvertInto function. In addition, the error is also given the provided context message.
/// ```
/// let a = example_error()?;
/// ```
/// into...
/// ```
/// let a = example_error().make_inner().msg("some context message")?;
/// ```
/// # Special Handling for Ok
/// The Ok return type needs special handling because the compiler cannot infer the return type with
/// the extra scaffolding that has been put around the main block of the function. To compensate for
/// this the Ok value is given a full path qualifier. As the path syntax changes based on how it is
/// used, a alias is defined at the begining of the function (HbErrorContextType).
/// ```
/// Ok(())
/// ```
/// into...
/// ```
/// type HbErrorContextType = Result<(), ExampleError>;
/// HbErrorContextType::Ok(())
/// ```
#[proc_macro_attribute]
pub fn context(args: TokenStream, input: TokenStream) -> TokenStream {
// convert the input TokenStream into a ItemFn syntax object
let input = parse_macro_input!(input as ItemFn);
let mut message;
// Extract the return type from the function signature
let gen = input.sig.generics.clone();
if let ReturnType::Type(_, r) = &input.sig.output {
// Read the args provided as a LitStr ie contents of the () after context in the attibute
// Then create a ContextMsg object
message = ContextMsg::new(parse_macro_input!(args as LitStr), r.clone());
} else {
// If the return type is the default return type () then skip processing
return TokenStream::from(quote! {#input});
}
// Handle Return and ? by folding the ItemFn syntax tree with the ContextMsg object
let mut output = message.fold_item_fn(input);
// Wrap the context of the function to grab the fall through Result then add the context
// onto the any errors with map_err
let rettype = message.rettype.clone();
let mut block = output.block.clone();
if message.has_ok {
block
.stmts
.insert(0, parse_quote! { type HbErrorContextType #gen = #rettype; });
}
let msg = message.m.clone();
output.block = parse_quote! {
{
#[allow(unreachable_code)]
let ret: #rettype = {
#[warn(unreachable_code)]
#block
};
#[allow(unreachable_code)]
ret.map_err(|er| er.make_inner().msg(#msg))
}
};
// Convert the SyntaxTree back into a TokenTree
TokenStream::from(quote! {#output})
}
#[proc_macro_attribute]
pub fn context_doc(_: TokenStream, input: TokenStream) -> TokenStream {
// convert the input TokenStream into a ItemFn syntax object
let input = parse_macro_input!(input as ItemFn);
let gen = input.sig.generics.clone();
let mut message;
let doc_comments: Vec<Attribute> = input
.attrs
.iter()
.filter(|a| a.path.is_ident("doc"))
.map(|a| a.clone())
.collect();
if doc_comments.len() == 0 || doc_comments.len() > 1 {
panic!("context_doc only works with single line doc comments.")
}
let tokens = doc_comments.first().unwrap().tokens.clone();
let mut msg = format!("{}", tokens);
msg = msg[3..msg.len() - 1].trim().to_owned();
msg = msg.replace("\\'", "'");
msg = msg.replace("[", "'{");
msg = msg.replace("]", "}'");
// Extract the return type from the function signature
if let ReturnType::Type(_, r) = &input.sig.output {
// Read the args provided as a LitStr ie contents of the () after context in the attibute
// Then create a ContextMsg object
message = ContextMsg::new(LitStr::new(&msg, Span::mixed_site()), r.clone());
//message = ContextMsg::new(parse_macro_input!(tokens as LitStr), r.clone());
} else {
// If the return type is the default return type () then skip processing
return TokenStream::from(quote! {#input});
}
// Handle Return and ? by folding the ItemFn syntax tree with the ContextMsg object
let mut output = message.fold_item_fn(input);
// Wrap the context of the function to grab the fall through Result then add the context
// onto the any errors with map_err
let rettype = message.rettype.clone();
let mut block = output.block.clone();
if message.has_ok {
block
.stmts
.insert(0, parse_quote! { type HbErrorContextType #gen = #rettype; });
}
let msg = message.m.clone();
output.block = parse_quote! {
{
#[allow(unreachable_code)]
let ret: #rettype = {
#[warn(unreachable_code)]
#block
};
#[allow(unreachable_code)]
ret.map_err(|er| er.make_inner().msg(#msg))
}
};
// Convert the SyntaxTree back into a TokenTree
TokenStream::from(quote! {#output})
}
/// Struct to handle the folding of the ItemFn.
struct Converter {
rettype: Box<Type>,
}
// The Fold trait is used to inject the error handling into the the source code.
// The Fold will change this function...
// #[convert_error]
// fn basic_exampleerror() -> Result<(), ExampleError> {
// if io_error()? {
// return example_error().map_err(|e| e.msg("msgs are great"));
// }
// example_error()
// }
//
// into...
// fn basic_exampleerror() -> Result<(), ExampleError> {
// if hb_error::ConvertInto::Result<(), ExampleError>::convert(io_error())? {
// return hb_error::ConvertInto::Result<(), ExampleError>::convert(example_error().map_err(|e| e.msg("msgs are great")));
// }
// example_error()
// }
impl Fold for Converter {
fn fold_expr(&mut self, e: Expr) -> Expr {
match e {
Expr::Return(mut rexpr) => {
match rexpr.expr {
Some(ex) => {
let rettype = &self.rettype;
rexpr.expr =
Some(parse_quote!(hb_error::ConvertInto::<#rettype>::convert(#ex)));
}
None => (),
}
fold::fold_expr(self, Expr::Return(rexpr))
}
Expr::Try(mut texpr) => {
let ex = texpr.expr;
let rettype = &self.rettype;
texpr.expr = parse_quote!(hb_error::ConvertInto::<#rettype>::convert(#ex));
Expr::Try(texpr)
}
_ => fold::fold_expr(self, e),
}
}
}
/// Converts Errors returned by the function into the correct type for the
/// function as well adding a context message provided.
/// This macro will change the following function...
/// ```
/// #[convert_error]
/// fn basic_exampleerror() -> Result<(), ExampleError> {
/// if io_error()? {
/// return example_error().map_err(|e| e.msg("msgs are great"));
/// }
/// example_error()
/// }
/// ```
///
/// into...
/// ```
/// fn basic_exampleerror() -> Result<(), ExampleError> {
/// #[allow(unreachable_code)]
/// let ret: Result<(), ExampleError> = {
/// #[warn(unreachable_code)]
/// if hb_error::ConvertInto::Result<(), ExampleError>::convert(io_error())? {
/// return hb_error::ConvertInto::Result<(), ExampleError>::convert(example_error());
/// }
/// example_error()
/// };
/// #[allow(unreachable_code)]
/// ret
/// }
/// ```
#[proc_macro_attribute]
pub fn convert_error(_args: TokenStream, input: TokenStream) -> TokenStream {
// convert the input TokenStream into a ItemFn syntax object
let input = parse_macro_input!(input as ItemFn);
let mut message;
// Extract the return type from the function signature
if let ReturnType::Type(_, r) = &input.sig.output {
// Read the args provided as a LitStr ie contents of the () after context in the attibute
// Then create a ContextMsg object
message = Converter { rettype: r.clone() };
} else {
// If the return type is the default return type () then skip processing
return TokenStream::from(quote! {#input});
}
// Handle Return and ? by folding the ItemFn syntax tree with the ContextMsg object
let output = message.fold_item_fn(input);
// Convert the SyntaxTree back into a TokenTree
TokenStream::from(quote! {#output})
}
/// This macro is used to generate all of the boiler plate code for error types so that they all
/// have the same format.
/// # Overview
/// This macro is applied to structs like this one.
/// ```
/// #[hberror]
/// struct ExampleError {
/// }
/// ```
/// This macro will modify the struct to add in the msg and inner_msgs fields as well as doing the impls for new, ErrorContext, Display and Debug.
/// This will generate the following code:
///
/// ```
///
/// pub struct ExampleError {
/// msg: String,
/// inner_msgs: Vec<String>,
/// }
///
/// impl ExampleError {
/// pub fn new() -> ExampleError {
/// ExampleError {
/// msg: default::Default(),
/// inner_msgs: default::Default(),
/// }
/// }
/// }
///
/// impl ErrorContext for ExampleError {
/// fn make_inner(mut self) -> ExampleError {
/// self.inner_msgs.push(self.msg);
/// self.msg = String::new();
/// self
/// }
///
/// fn msg<T: Into<String>>(mut self, msg: T) -> ExampleError {
/// self.msg = msg.into();
/// self
/// }
/// }
///
/// impl std::fmt::Display for ExampleError {
/// fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::result::Result<(), std::fmt::Error> {
/// write!(f,"{}{}", self.msg, self.inner_msgs.join("\n...because..."))
/// }
/// }
///
/// impl std::fmt::Debug for ExampleError {
/// fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::result::Result<(), std::fmt::Error> {
/// write!(f,"{}{}", self.msg, self.inner_msgs.join("\n...because..."))
/// }
/// }
/// ```
/// # Custom fields and messages
/// This macro also has the capability of dealing with custom fields and custom messages.
/// Using the Default attribute on these custom fields will tell the macro to use the val provided
/// in the new function rather than default::Default().
///
/// ```
/// #[hberror("{self.custom_field}:{self.msg}{self.inner_msgs.join(\"\n...due to...\")}")]
/// struct ExampleError {
/// #[Default(10)]
/// custom_field: i32,
/// }
/// ```
/// This becomes
/// ```
/// pub struct ExampleError {
/// msg: String,
/// inner_msgs: Vec<String>,
/// custom_field: i32
/// }
///
/// impl ExampleError {
/// pub fn new() -> ExampleError {
/// ExampleError {
/// msg: default::Default(),
/// inner_msgs: default::Default(),
/// custom_field: 10
/// }
/// }
/// }
///
/// impl ErrorContext for ExampleError {
/// fn make_inner(mut self) -> ExampleError {
/// self.inner_msgs.push(self.msg);
/// self.msg = String::new();
/// self
/// }
///
/// fn msg<T: Into<String>>(mut self, msg: T) -> ExampleError {
/// self.msg = msg.into();
/// self
/// }
/// }
///
/// impl std::fmt::Display for ExampleError {
/// fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::result::Result<(), std::fmt::Error> {
/// write!(f,"{}:{}{}", self.custom_field, self.msg, self.inner_msgs.join("\n...due to..."))
/// }
/// }
///
/// impl std::fmt::Debug for ExampleError {
/// fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::result::Result<(), std::fmt::Error> {
/// write!(f,"{}:{}{}", self.custom_field, self.msg, self.inner_msgs.join("\n...due to..."))
/// }
/// }
/// ```
/// # Easy Conversion from other errors
/// You can also define errors that you want to convert from and store as a source variable which
/// will be printed after message. The Source attribute tell the macro which fields to process as
/// the source. A enum will be created using the identity of the sturct with Source at the end
/// (eg ExampleErrorSource). This enum will have variants for each field marked with a source
/// attribute as well as a None value. The variants for the sources are created using the field
/// identity as the enum variant identity and contains the error type provided.
///
/// This means that the context or convert_error macros can be used on this error type without any
/// additional work.
/// ```
/// #[hberror]
/// struct ExampleError {
/// #[Source]
/// IOError: std::io::Error,
/// }
/// ```
/// This becomes:
/// ```
/// use std::default;
/// pub struct ExampleError {
/// msg: String,
/// inner_msgs: Vec<String>,
/// source: ExampleErrorSource,
/// }
///
/// impl ExampleError {
/// pub fn new() -> ExampleError {
/// ExampleError {
/// msg: default::Default(),
/// inner_msgs: default::Default(),
/// source: default::Default(),
/// }
/// }
///
/// pub fn source(mut self, s: ExampleErrorSource) -> ExampleError {
/// self.source = s;
/// self
/// }
/// }
///
/// impl ErrorContext for ExampleError {
/// fn make_inner(mut self) -> ExampleError {
/// self.inner_msgs.push(self.msg);
/// self.msg = String::new();
/// self
/// }
///
/// fn msg<T: Into<String>>(mut self, msg: T) -> ExampleError {
/// self.msg = msg.into();
/// self
/// }
/// }
///
/// impl std::fmt::Display for ExampleError {
/// fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::result::Result<(), std::fmt::Error> {
/// write!(f,"{}{}{}", self.msg, self.inner_msgs.join("\n...due to..."), self.source)
/// }
/// }
///
/// impl std::fmt::Debug for ExampleError {
/// fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::result::Result<(), std::fmt::Error> {
/// write!(f,"{}{}{}", self.msg, self.inner_msgs.join("\n...due to..."), self.source)
/// }
/// }
///
/// pub enum ExampleErrorSource {
/// None,
/// IOError(std::io::Error),
/// }
///
/// impl std::default::Default for ExampleErrorSource {
/// fn default() -> Self { ExampleErrorSource::None }
/// }
///
/// impl std::fmt::Display for ExampleErrorSource {
/// fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::result::Result<(), std::fmt::Error> {
/// match self {
/// ExampleErrorSource::None => Ok(()),
/// ExampleErrorSource::IOError(e) => write!("\n...Source Error...{}", e)
/// }
/// }
/// }
///
/// impl std::fmt::Debug for ExampleErrorSource {
/// fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::result::Result<(), std::fmt::Error> {
/// match self {
/// ExampleErrorSource::None => Ok(()),
/// ExampleErrorSource::IOError(e) => write!("\n...Source Error...{}", e)
/// }
/// }
/// }
///
/// ```
#[proc_macro_attribute]
pub fn hberror(args: TokenStream, input: TokenStream) -> TokenStream {
// parse the input as an ItemStruct, it should panic if anything other than a struct is annotated with this macro
let input = parse_macro_input!(input as ItemStruct);
// create a copy which we can edit easily
let mut output_struct = input.clone();
// get some details from the struct
// Struct Name
let ident = input.ident;
// Create the source enum's name from the structs name
let ident_source = Ident::new(&format!("{}Source", ident), Span::call_site());
// visibility of the struct - eg pub
let vis = input.vis;
// sort and process the provided fields
let mut has_source_enum = false;
let mut enum_variants = syn::punctuated::Punctuated::<Variant, Comma>::new();
let mut new_fields = syn::punctuated::Punctuated::<FieldValue, Comma>::new();
let mut enum_display_match = ExprMatch {
attrs: vec![],
match_token: Default::default(),
expr: Box::new(parse_quote!(self)),
brace_token: Default::default(),
arms: vec![],
};
let mut source_from_impl_items: Vec<Item> = vec![];
let mut custom_fields = vec![];
match &input.fields {
Fields::Named(namedfields) => {
namedfields.named.iter().for_each(|f| {
let mut handled = false;
for a in &f.attrs {
if a.path.is_ident("Source") {
let mut cleaned_field = f.clone();
let mut cleaned_attrs : Vec<Attribute> = vec![];
f.attrs
.iter()
.filter(|a| !a.path.is_ident("Source"))
.for_each(|a| cleaned_attrs.push(a.clone()));
cleaned_field.attrs = cleaned_attrs;
let ty = f.ty.clone();
let f_ident = f.ident.clone().unwrap();
enum_variants.push(Variant {
ident: f.ident.clone().unwrap(),
attrs: vec![],
fields: Fields::Unnamed(parse_quote!((#ty))),
discriminant: None,
});
enum_display_match
.arms
.push(parse_quote!(#ident_source::#f_ident(e) => write!(f, "\n...source error {}...{}",stringify!(#f_ident), e)));
source_from_impl_items.push(parse_quote!(impl From<#ty> for #ident {
fn from(e: #ty) -> #ident {
#ident::new().source(#ident_source::#f_ident(e))
}
}));
has_source_enum = true;
handled = true;
break;
} else if a.path.is_ident("Default") {
let mut cleaned_field = f.clone();
let mut cleaned_attrs : Vec<Attribute> = vec![];
f.attrs
.iter()
.filter(|a| !a.path.is_ident("Default"))
.for_each(|a| cleaned_attrs.push(a.clone()));
cleaned_field.attrs = cleaned_attrs;
custom_fields.push((cleaned_field, Some(a.tokens.clone())));
handled = true;
break;
}
}
if !handled {
custom_fields.push((f.clone(), None));
}
});
}
Fields::Unnamed(_) => (),
Fields::Unit => (),
};
if has_source_enum {
enum_variants.push(Variant {
ident: parse_quote!(None),
attrs: vec![],
fields: Fields::Unit,
discriminant: None,
});
enum_display_match
.arms
.push(parse_quote!(#ident_source::None => Ok(())))
}
new_fields.push(parse_quote!(msg: String::new()));
new_fields.push(parse_quote!(inner_msgs: vec![]));
let mut final_fields = Fields::Named(match has_source_enum {
true => {
new_fields.push(parse_quote!(source: #ident_source::None));
parse_quote! {
{
msg: String,
inner_msgs: Vec<String>,
source: #ident_source,
}
}
}
false => parse_quote! {
{
msg: String,
inner_msgs: Vec<String>,
}
},
});
match &mut final_fields {
Fields::Named(ref mut named_fields) => {
for (f, toks) in custom_fields {
let f_ident = f.ident.clone();
named_fields.named.push(f);
match toks {
Some(tok) => new_fields.push(parse_quote!(#f_ident: #tok)),
None => new_fields.push(parse_quote!(#f_ident: Default::default())),
}
}
}
_ => panic!("should not happen"),
}
let mut msg_args = syn::punctuated::Punctuated::<Expr, Comma>::new();
msg_args.push(parse_quote!(f));
match syn::parse::<LitStr>(args) {
Err(_) => {
if has_source_enum {
msg_args.push(parse_quote!("{}{}{}"));
msg_args.push(parse_quote!(self.msg));
msg_args.push(parse_quote!(self.inner_msgs.join("\n...because...")));
msg_args.push(parse_quote!(self.source));
} else {
msg_args.push(parse_quote!("{}{}"));
msg_args.push(parse_quote!(self.msg));
msg_args.push(parse_quote!(self.inner_msgs.join("\n...because...")));
}
}
Ok(litstr) => {
let str = litstr.value();
let mut brace_contents: Vec<String> = vec![];
let mut in_brace = false;
let mut buf = String::new();
let mut out_str = String::new();
for c in str.chars() {
if c == '{' {
in_brace = true;
out_str.push(c);
} else if c == '}' {
if buf.len() > 0 {
brace_contents.push(buf);
buf = String::new();
}
in_brace = false;
out_str.push(c);
} else if in_brace {
buf.push(c);
} else {
out_str.push(c);
}
}
for content in brace_contents {
msg_args
.push(syn::parse_str::<Expr>(&content).expect(
format!("cannot convert {} into an expression.", content).as_str(),
));
}
if has_source_enum {
msg_args.push(parse_quote!(self.source));
out_str.push_str("{}")
}
msg_args.insert(1, parse_quote!(#out_str));
}
}
output_struct.fields = final_fields;
//Build the output code
//Parts that don't matter if there is any source enum
let main_output = quote!(
#output_struct
impl ErrorContext for #ident {
fn make_inner(mut self) -> #ident {
self.inner_msgs.push(self.msg);
self.msg = String::new();
self
}
fn msg<T: Into<String>>(mut self, msg: T) -> #ident {
self.msg = msg.into();
self
}
}
impl std::fmt::Display for #ident {
fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::result::Result<(), std::fmt::Error> {
write!(#msg_args)
}
}
impl std::fmt::Debug for #ident {
fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::result::Result<(), std::fmt::Error> {
write!(#msg_args)
}
}
);
// Add source enum stuff if there is one
let final_output = match has_source_enum {
true => {
let mut out = quote!(
#main_output
impl #ident {
/// Create a new error with empty values.
#vis fn new() -> #ident {
#ident {
#new_fields
}
}
/// Set the source value of the error type with special enum. This function is
/// usually used by the From implementation between the source error type and
/// the final error type, where the source error is stored in the applicable
/// variant of the enum in the source field of the error.
#vis fn source(mut self, s: #ident_source) -> #ident {
self.source = s;
self
}
}
/// This enum represents all of the errors that can be a source for this Error.
/// The trait From has been implemented between all of these Error types and the
/// main error type where the source field is set to the applicable variant of this
/// enum.
#vis enum #ident_source {
#enum_variants
}
impl std::fmt::Display for #ident_source {
fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::result::Result<(), std::fmt::Error> {
#enum_display_match
}
}
impl std::fmt::Debug for #ident_source {
fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::result::Result<(), std::fmt::Error> {
#enum_display_match
}
}
impl std::default::Default for #ident_source {
fn default() -> Self { #ident_source::None }
}
);
out.append_all(source_from_impl_items);
out
}
false => {
parse_quote!(
#main_output
impl #ident {
#vis fn new() -> #ident {
#ident {
#new_fields
}
}
}
)
}
};
final_output.into()
}