From 65b47996e35b98287499f3a407baf6e3469ace88 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Max=20K=C3=A4nner?= <max.kaenner@gmail.com>
Date: Mon, 15 Apr 2024 21:40:32 +0200
Subject: [PATCH] remove unwraps and panics

---
 src/lib.rs | 49 +++++++++++++++++++++++++++++++++----------------
 1 file changed, 33 insertions(+), 16 deletions(-)

diff --git a/src/lib.rs b/src/lib.rs
index 64d25da..4b1b696 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -3,7 +3,7 @@ use std::iter::once;
 use convert_case::{Case, Casing};
 use proc_macro::TokenStream;
 use proc_macro2::{Span as Span2, TokenStream as TokenStream2};
-use quote::{format_ident, quote};
+use quote::{format_ident, quote, ToTokens};
 use syn::{
     parse_macro_input, parse_quote, Attribute, DataStruct, DeriveInput, Expr, ExprLit, Field,
     Ident, Lit, Type, Visibility,
@@ -12,10 +12,6 @@ use syn::{
 /// Creates structs for the values to extend them with extra metadata.
 ///
 /// supported metadata is `min`, `max` and `default`. Doc comments are parsed as `description`
-///
-/// # Panics
-///
-/// Panics if it is unable to generate a config struct from the input
 #[proc_macro_attribute]
 pub fn config(_attr: TokenStream, item: TokenStream) -> TokenStream {
     let mut input = parse_macro_input!(item as DeriveInput);
@@ -33,8 +29,12 @@ pub fn config(_attr: TokenStream, item: TokenStream) -> TokenStream {
                 }
             }
         }
-        syn::Data::Enum(_) => panic!("Enums are not supported"),
-        syn::Data::Union(_) => panic!("Unions are not supported"),
+        syn::Data::Enum(_) => {
+            return quote! {compile_error!("Enums are not supported")}.into();
+        }
+        syn::Data::Union(_) => {
+            return quote! {compile_error!("Unions are not supported")}.into();
+        }
     }
 
     quote! {
@@ -145,9 +145,12 @@ fn parse_min(
     let const_ident = Ident::new(KEY.to_case(Case::Upper).as_str(), Span2::mixed_site());
     let (value, new_check) = attr.meta.require_path_only().map_or_else(
         |_| {
-            let value = &attr.meta.require_name_value().unwrap().value;
+            let value = match &attr.meta.require_name_value() {
+                Ok(meta) => &meta.value,
+                Err(e) => return (e.to_owned().into_compile_error(), None),
+            };
             (
-                quote!(#value),
+                value.to_token_stream(),
                 Some(quote! {
                     if (value < Self::#const_ident.0) {
                         return None;
@@ -177,9 +180,12 @@ fn parse_max(
     let const_ident = Ident::new(KEY.to_case(Case::Upper).as_str(), Span2::mixed_site());
     let (value, new_check) = attr.meta.require_path_only().map_or_else(
         |_| {
-            let value = &attr.meta.require_name_value().unwrap().value;
+            let value = match &attr.meta.require_name_value() {
+                Ok(meta) => &meta.value,
+                Err(e) => return (e.to_owned().into_compile_error(), None),
+            };
             (
-                quote!(#value),
+                value.to_token_stream(),
                 Some(quote! {
                     if (value > Self::#const_ident.0) {
                         return None;
@@ -208,9 +214,9 @@ fn parse_default(
     }
     let const_ident = Ident::new(KEY.to_case(Case::Upper).as_str(), Span2::mixed_site());
     let value = attr.meta.require_path_only().map_or_else(
-        |_| {
-            let value = &attr.meta.require_name_value().unwrap().value;
-            quote!(#value)
+        |_| match &attr.meta.require_name_value() {
+            Ok(meta) => meta.value.to_token_stream(),
+            Err(e) => e.to_owned().into_compile_error(),
         },
         |_| quote!(#ty::#const_ident),
     );
@@ -237,13 +243,24 @@ fn parse_description(
         return None;
     }
     let const_ident = Ident::new(KEY.to_case(Case::Upper).as_str(), Span2::mixed_site());
-    let value = &attr.meta.require_name_value().ok()?.value;
+    let value = match attr.meta.require_name_value() {
+        Ok(meta) => &meta.value,
+        Err(e) => {
+            return Some((e.into_compile_error(), const_ident, KEY));
+        }
+    };
     let value = match value {
         Expr::Lit(ExprLit {
             attrs: _,
             lit: Lit::Str(ref string),
         }) => string.value(),
-        _ => panic!("doc comment must be a string"),
+        _ => {
+            return Some((
+                quote!(compile_error!("doc comment must be a string")),
+                const_ident,
+                KEY,
+            ))
+        }
     };
     let trimmed_value = value.trim();
     let impl_quote = quote! {