feat: improve macro error messages

1 files changed, 97 insertions, 38 deletions

diff --git a/macros/src/injectable/macro_args.rs b/macros/src/injectable/macro_args.rs
index d730e0d..6582cc6 100644
--- a/macros/src/injectable/macro_args.rs
+++ b/macros/src/injectable/macro_args.rs
@@ -1,8 +1,10 @@
+use proc_macro2::Span;
 use syn::parse::{Parse, ParseStream};
 use syn::punctuated::Punctuated;
-use syn::{Token, TypePath};
+use syn::{Ident, Token, TypePath};
 
 use crate::macro_flag::MacroFlag;
+use crate::util::error::diagnostic_error_enum;
 use crate::util::iterator_ext::IteratorExt;
 
 pub const INJECTABLE_MACRO_FLAGS: &[&str] =
@@ -14,9 +16,34 @@ pub struct InjectableMacroArgs
     pub flags: Punctuated<MacroFlag, Token![,]>,
 }
 
+impl InjectableMacroArgs
+{
+    pub fn check_flags(&self) -> Result<(), InjectableMacroArgsError>
+    {
+        for flag in &self.flags {
+            if !INJECTABLE_MACRO_FLAGS.contains(&flag.flag.to_string().as_str()) {
+                return Err(InjectableMacroArgsError::UnknownFlag {
+                    flag_ident: flag.flag.clone(),
+                });
+            }
+        }
+
+        if let Some((dupe_flag_first, dupe_flag_second)) =
+            self.flags.iter().find_duplicate()
+        {
+            return Err(InjectableMacroArgsError::DuplicateFlag {
+                first_flag_ident: dupe_flag_first.flag.clone(),
+                last_flag_span: dupe_flag_second.flag.span(),
+            });
+        }
+
+        Ok(())
+    }
+}
+
 impl Parse for InjectableMacroArgs
 {
-    fn parse(input: ParseStream) -> syn::Result<Self>
+    fn parse(input: ParseStream) -> Result<Self, syn::Error>
     {
         let input_fork = input.fork();
 
@@ -50,31 +77,33 @@ impl Parse for InjectableMacroArgs
 
         let flags = Punctuated::<MacroFlag, Token![,]>::parse_terminated(input)?;
 
-        for flag in &flags {
-            let flag_str = flag.flag.to_string();
-
-            if !INJECTABLE_MACRO_FLAGS.contains(&flag_str.as_str()) {
-                return Err(input.error(format!(
-                    "Unknown flag '{}'. Expected one of [ {} ]",
-                    flag_str,
-                    INJECTABLE_MACRO_FLAGS.join(",")
-                )));
-            }
-        }
-
-        let flag_names = flags
-            .iter()
-            .map(|flag| flag.flag.to_string())
-            .collect::<Vec<_>>();
-
-        if let Some(dupe_flag_name) = flag_names.iter().find_duplicate() {
-            return Err(input.error(format!("Duplicate flag '{dupe_flag_name}'")));
-        }
-
         Ok(Self { interface, flags })
     }
 }
 
+diagnostic_error_enum! {
+pub enum InjectableMacroArgsError
+{
+    #[error("Unknown flag '{flag_ident}'"), span = flag_ident.span()]
+    #[
+        help("Expected one of: {}", INJECTABLE_MACRO_FLAGS.join(", ")),
+        span = flag_ident.span()
+    ]
+    UnknownFlag
+    {
+        flag_ident: Ident
+    },
+
+    #[error("Duplicate flag '{first_flag_ident}'"), span = first_flag_ident.span()]
+    #[note("Previously mentioned here"), span = last_flag_span]
+    DuplicateFlag
+    {
+        first_flag_ident: Ident,
+        last_flag_span: Span
+    },
+}
+}
+
 #[cfg(test)]
 mod tests
 {
@@ -188,30 +217,60 @@ mod tests
     }
 
     #[test]
-    fn cannot_parse_with_invalid_flag()
+    fn can_parse_with_unknown_flag() -> Result<(), Box<dyn Error>>
     {
         let input_args = quote! {
             IFoo, haha = true, async = false
         };
 
-        assert!(matches!(parse2::<InjectableMacroArgs>(input_args), Err(_)));
+        assert!(parse2::<InjectableMacroArgs>(input_args).is_ok());
+
+        Ok(())
     }
 
     #[test]
-    fn cannot_parse_with_duplicate_flag()
+    fn can_parse_with_duplicate_flag()
     {
-        assert!(matches!(
-            parse2::<InjectableMacroArgs>(quote! {
-                IFoo, async = false, no_doc_hidden = true, async = false
-            }),
-            Err(_)
-        ));
+        assert!(parse2::<InjectableMacroArgs>(quote! {
+            IFoo, async = false, no_doc_hidden = true, async = false
+        })
+        .is_ok());
+
+        assert!(parse2::<InjectableMacroArgs>(quote! {
+            IFoo, async = true , no_doc_hidden = true, async = false
+        })
+        .is_ok());
+    }
 
-        assert!(matches!(
-            parse2::<InjectableMacroArgs>(quote! {
-                IFoo, async = true , no_doc_hidden = true, async = false
-            }),
-            Err(_)
-        ));
+    #[test]
+    fn check_flags_fail_with_unknown_flag() -> Result<(), Box<dyn Error>>
+    {
+        let input_args = quote! {
+            IFoo, haha = true, async = false
+        };
+
+        let injectable_macro_args = parse2::<InjectableMacroArgs>(input_args)?;
+
+        assert!(injectable_macro_args.check_flags().is_err());
+
+        Ok(())
+    }
+
+    #[test]
+    fn check_flags_fail_with_duplicate_flag() -> Result<(), Box<dyn Error>>
+    {
+        let macro_args = parse2::<InjectableMacroArgs>(quote! {
+            IFoo, async = false, no_doc_hidden = true, async = false
+        })?;
+
+        assert!(macro_args.check_flags().is_err());
+
+        let macro_args_two = parse2::<InjectableMacroArgs>(quote! {
+            IFoo, async = true , no_doc_hidden = true, async = false
+        })?;
+
+        assert!(macro_args_two.check_flags().is_err());
+
+        Ok(())
     }
 }