use cow instead of &'static to better support testing use cases

core/template/rust/src/lib.rs

@@ -4,4 +4,5 @@ pub mod model;
 pub mod request;
 pub use httpclient::{Error, Result, InMemoryResponseExt};
 use std::sync::{Arc, OnceLock};
+use std::borrow::Cow;
 use crate::model::*;

libninja/src/rust.rs

@@ -253,8 +253,8 @@ fn static_shared_http_client(spec: &HirSpec, opt: &PackageConfig) -> TokenStream
             let _ = SHARED_HTTPCLIENT.set(init);
         }
 
-        fn shared_http_client() -> &'static httpclient::Client {
-            SHARED_HTTPCLIENT.get_or_init(default_http_client)
+        fn shared_http_client() -> Cow<'static, httpclient::Client> {
+            Cow::Borrowed(SHARED_HTTPCLIENT.get_or_init(default_http_client))
         }
     }
 }

libninja/src/rust/client.rs

@@ -83,7 +83,7 @@ fn build_Client_new_with(spec: &HirSpec, opt: &PackageConfig) -> Function<TokenS
     let auth_struct = opt.authenticator_name().to_rust_struct();
     let body = quote! {
         Self {
-            client,
+            client: Cow::Owned(client),
             authentication,
         }
     };
@@ -94,7 +94,7 @@ fn build_Client_new_with(spec: &HirSpec, opt: &PackageConfig) -> Function<TokenS
         body,
         args: vec![FnArg {
             name: ArgIdent::Ident("client".to_string()),
-            ty: quote!(&'static httpclient::Client),
+            ty: quote!(httpclient::Client),
             default: None,
             treatment: None,
         }, FnArg {
@@ -113,7 +113,7 @@ pub fn struct_Client(spec: &HirSpec, opt: &PackageConfig) -> Class<TokenStream>
     let mut instance_fields = vec![
         Field {
             name: "client".to_string(),
-            ty: quote!(&'static httpclient::Client),
+            ty: quote!(Cow<'static, httpclient::Client>),
             ..Field::default()
         }
     ];