From 2286c2b85a94f21ff2d5b27fe4f0d0beda702fb9 Mon Sep 17 00:00:00 2001
From: wcampbell <wcampbell1995@gmail.com>
Date: Wed, 3 Jan 2024 00:18:46 -0500
Subject: [PATCH] Fix unknown id Type for EnumExt::deku_id()

Remove unwrap causing the following error when the EnumExt tried to infer
what type is was to return. An attribute could be added in the future to aid this,
but for now we will just not emit the deku_id() for this type of enum.
I decided in other causes (which aren't tested), to also remove the error
and just not emit the function also.

 help: message: called `Result::unwrap()` on an `Err` value: Error("expected `,`")

See #397
---
 deku-derive/src/macros/deku_read.rs | 11 +++++-----
 deku-derive/src/macros/mod.rs       |  4 +++-
 tests/test_regression.rs            | 32 +++++++++++++++++++++++++++++
 3 files changed, 40 insertions(+), 7 deletions(-)

diff --git a/deku-derive/src/macros/deku_read.rs b/deku-derive/src/macros/deku_read.rs
index 9e7a788d..4d1c28fe 100644
--- a/deku-derive/src/macros/deku_read.rs
+++ b/deku-derive/src/macros/deku_read.rs
@@ -397,12 +397,11 @@ fn emit_enum(input: &DekuData) -> Result<TokenStream, syn::Error> {
     let deku_id_type = if let Some(id_type) = id_type {
         Some(quote! {#id_type})
     } else if let (Some(ctx), Some(id)) = (input.ctx.as_ref(), input.id.as_ref()) {
-        Some(gen_type_from_ctx_id(ctx, id).ok_or_else(|| {
-            syn::Error::new(
-                id.span(),
-                "DekuReader: cannot determine `id` type from `ctx`",
-            )
-        })?)
+        if let Some(r) = gen_type_from_ctx_id(ctx, id) {
+            Some(r)
+        } else {
+            None
+        }
     } else {
         None
     };
diff --git a/deku-derive/src/macros/mod.rs b/deku-derive/src/macros/mod.rs
index b24d0ba2..2fa865c3 100644
--- a/deku-derive/src/macros/mod.rs
+++ b/deku-derive/src/macros/mod.rs
@@ -199,7 +199,9 @@ fn gen_type_from_ctx_id(
     id: &crate::Id,
 ) -> Option<TokenStream> {
     let parser = Punctuated::<Ident, Comma>::parse_terminated;
-    let s = parser.parse(id.to_token_stream().into()).unwrap();
+    let Ok(s) = parser.parse(id.to_token_stream().into()) else {
+        return None;
+    };
     let mut matching_types = quote! {};
     for s in s {
         let id = syn::Ident::new(&s.to_string(), id.span());
diff --git a/tests/test_regression.rs b/tests/test_regression.rs
index c3afb70d..84ff9904 100644
--- a/tests/test_regression.rs
+++ b/tests/test_regression.rs
@@ -359,3 +359,35 @@ fn issue_310() {
     #[derive(DekuRead, DekuWrite)]
     struct Test {}
 }
+
+#[test]
+fn issue_397() {
+    use deku::prelude::*;
+
+    #[derive(Debug, Copy, Clone, PartialEq, DekuRead, DekuWrite)]
+    struct Header {
+        kind: PacketType,
+    }
+
+    #[derive(Debug, Copy, Clone, PartialEq, DekuRead, DekuWrite)]
+    #[deku(type = "u8", endian = "big")]
+    enum PacketType {
+        #[deku(id = 0)]
+        Zero,
+    }
+
+    #[derive(Debug, Copy, Clone, PartialEq, DekuRead, DekuWrite)]
+    struct Packet {
+        header: Header,
+        #[deku(ctx = "header")]
+        payload: Payload,
+    }
+
+    #[derive(Debug, Copy, Clone, PartialEq, DekuRead, DekuWrite)]
+    #[deku(ctx = "header: &Header", id = "header.kind")]
+    enum Payload {
+        #[deku(id = "PacketType::Zero")]
+        Zero(u8),
+    }
+    let _ = Packet::from_bytes((&[0x00, 0x01], 0));
+}