feat(stageleft_tool)!: use features to gate test-mode staged code (#37)

Previously, we would generate either the `__staged` module with
`#[cfg(test)]` APIs included or not based on a boolean flag. This makes
it harder to share the generated staged code across separate
deployments, since some may be in test mode or not. With this PR, we
instead take in a string which is the feature under which test APIs
should be included. This allows us to generate the `__staged` module
once and share it across several targets.

Author: shadaj

stageleft_tool/src/lib.rs

@@ -122,7 +122,7 @@ impl VisitMut for InlineTopLevelMod {
 struct GenFinalPubVistor {
     current_mod: Option<syn::Path>,
     all_macros: Vec<syn::Ident>,
-    test_mode: bool,
+    test_mode_feature: Option<String>,
 }
 
 fn get_cfg_attrs(attrs: &[syn::Attribute]) -> impl Iterator<Item = &syn::Attribute> + '_ {
@@ -228,8 +228,10 @@ impl VisitMut for GenFinalPubVistor {
             i.attrs
                 .retain(|a| a.to_token_stream().to_string() != "# [cfg (test)]");
 
-            if !self.test_mode {
-                // if test mode is not true, there are no quoted snippets behind #[cfg(test)],
+            if let Some(feature) = &self.test_mode_feature {
+                i.attrs.insert(0, parse_quote!(#[cfg(feature = #feature)]));
+            } else {
+                // if test mode is not enabled, there are no quoted snippets behind #[cfg(test)],
                 // so no #[cfg(test)] modules will ever be reachable
                 i.attrs.insert(
                     0,
@@ -468,15 +470,19 @@ fn gen_deps_module(stageleft_name: syn::Ident, manifest_path: &Path) -> syn::Ite
 
 /// Generates the contents of `mod __staged`, which contains a copy of the crate's code but with
 /// all APIs made public so they can be resolved when quoted code is spliced.
-fn gen_staged_mod(lib_path: &Path, orig_crate_ident: syn::Path, test_mode: bool) -> syn::File {
+fn gen_staged_mod(
+    lib_path: &Path,
+    orig_crate_ident: syn::Path,
+    test_mode_feature: Option<String>,
+) -> syn::File {
     let mut orig_flow_lib = syn_inline_mod::parse_and_inline_modules(lib_path);
     InlineTopLevelMod {}.visit_file_mut(&mut orig_flow_lib);
 
     let mut flow_lib_pub = syn_inline_mod::parse_and_inline_modules(lib_path);
 
     let mut final_pub_visitor = GenFinalPubVistor {
         current_mod: Some(parse_quote!(#orig_crate_ident)),
-        test_mode,
+        test_mode_feature,
         all_macros: vec![],
     };
     final_pub_visitor.visit_file_mut(&mut flow_lib_pub);
@@ -500,10 +506,10 @@ pub fn gen_staged_trybuild(
     lib_path: &Path,
     manifest_path: &Path,
     orig_crate_name: String,
-    test_mode: bool,
+    test_mode_feature: Option<String>,
 ) -> syn::File {
     let crate_name = syn::Ident::new(&orig_crate_name, Span::call_site());
-    let flow_lib_pub = gen_staged_mod(lib_path, parse_quote!(#crate_name), test_mode);
+    let flow_lib_pub = gen_staged_mod(lib_path, parse_quote!(#crate_name), test_mode_feature);
 
     let deps_mod = gen_deps_module(parse_quote!(stageleft), manifest_path);
 
@@ -517,7 +523,7 @@ pub fn gen_staged_trybuild(
 pub fn gen_staged_pub() {
     let out_dir = env::var_os("OUT_DIR").unwrap();
 
-    let flow_lib_pub = gen_staged_mod(Path::new("src/lib.rs"), parse_quote!(crate), false);
+    let flow_lib_pub = gen_staged_mod(Path::new("src/lib.rs"), parse_quote!(crate), None);
 
     fs::write(
         Path::new(&out_dir).join("lib_pub.rs"),