fix(idl): avoid quoted string constant values

lang/syn/src/idl/constant.rs

@@ -22,6 +22,12 @@ pub fn gen_idl_print_fn_constant(item: &syn::ItemConst) -> TokenStream {
         _ => quote! { vec![] },
     };
 
+    let value = if is_string_type(&item.ty) {
+        quote! { #expr.to_string() }
+    } else {
+        quote! { format!("{:?}", #expr) }
+    };
+
     let fn_body = match gen_idl_type(&item.ty, &[]) {
         Ok((ty, _)) => gen_print_section(
             "const",
@@ -30,7 +36,7 @@ pub fn gen_idl_print_fn_constant(item: &syn::ItemConst) -> TokenStream {
                     name: #name.into(),
                     docs: #docs,
                     ty: #ty,
-                    value: format!("{:?}", #expr),
+                    value: #value,
                 }
             },
         ),
@@ -44,3 +50,17 @@ pub fn gen_idl_print_fn_constant(item: &syn::ItemConst) -> TokenStream {
         }
     }
 }
+
+fn is_string_type(ty: &syn::Type) -> bool {
+    match ty {
+        syn::Type::Path(path) => {
+            path.path.segments.len() == 1
+                && matches!(
+                    path.path.segments.first().map(|segment| &segment.ident),
+                    Some(ident) if ident == "String" || ident == "str"
+                )
+        }
+        syn::Type::Reference(reference) => is_string_type(&reference.elem),
+        _ => false,
+    }
+}

tests/idl/idls/idl.json

@@ -1660,6 +1660,11 @@
       "type": "i128",
       "value": "1000000"
     },
+    {
+      "name": "SEED_PREFIX",
+      "type": "string",
+      "value": "favor"
+    },
     {
       "name": "TEST_CONVERT_MODULE_PATHS",
       "docs": [

tests/idl/programs/idl/src/lib.rs

@@ -15,6 +15,9 @@ pub const BYTE_STR: u8 = b't';
 #[constant]
 pub const BYTES_STR: &[u8] = b"test";
 
+#[constant]
+pub const SEED_PREFIX: &str = "favor";
+
 pub const NO_IDL: u16 = 55;
 
 #[program]

tests/idl/tests/idl.ts

@@ -606,6 +606,12 @@ describe("IDL", () => {
           c.type === "bytes" &&
           c.value === "[116, 101, 115, 116]"
       );
+      checkDefined(
+        (c) =>
+          c.name === "seedPrefix" &&
+          c.type === "string" &&
+          c.value === "favor"
+      );
     });
 
     it("Does not include constants that are not marked with `#[constant]`", () => {