Restore ability to gen with windows as dep crate (#1551)

Author: riverar

crates/libs/bindgen/src/gen.rs

@@ -10,13 +10,15 @@ pub struct Gen<'a> {
     pub min_enum: bool,
     pub min_inherit: bool,
     pub min_xaml: bool,
+    pub windows_extern: bool,
 }
 
 impl Gen<'_> {
     pub(crate) fn namespace(&self, namespace: &str) -> TokenStream {
         if self.flatten || namespace == self.namespace {
             quote! {}
         } else {
+            let is_external = namespace.starts_with("Windows.") && !self.namespace.starts_with("Windows");
             let mut relative = self.namespace.split('.').peekable();
             let mut namespace = namespace.split('.').peekable();
 
@@ -30,8 +32,13 @@ impl Gen<'_> {
 
             let mut tokens = TokenStream::new();
 
-            for _ in 0..relative.count() {
-                tokens.push_str("super::");
+            if is_external {
+                tokens.push_str("::windows::");
+                namespace.next();
+            } else {
+                for _ in 0..relative.count() {
+                    tokens.push_str("super::");
+                }
             }
 
             for namespace in namespace {
@@ -49,7 +56,11 @@ impl Gen<'_> {
         } else {
             let mut tokens = format!("'{}'", to_feature(self.namespace));
 
-            for features in &cfg.features(self.namespace) {
+            let mut features = cfg.features(self.namespace);
+            if self.windows_extern {
+                features = features.into_iter().filter(|f| !f.starts_with("Windows.")).collect();
+            }
+            for features in features {
                 tokens.push_str(&format!(", '{}'", to_feature(features)));
             }
 
@@ -72,7 +83,11 @@ impl Gen<'_> {
                 }
             };
 
-            let features = &cfg.features(self.namespace);
+            let mut features = cfg.features(self.namespace);
+            if self.windows_extern {
+                features = features.into_iter().filter(|f| !f.starts_with("Windows.")).collect();
+            }
+
             let features = match features.len() {
                 0 => quote! {},
                 1 => {
@@ -90,10 +105,13 @@ impl Gen<'_> {
     }
 
     pub(crate) fn not_cfg(&self, cfg: &Cfg) -> TokenStream {
-        let features = &cfg.features(self.namespace);
+        let mut features = cfg.features(self.namespace);
         if !self.cfg || features.is_empty() {
             quote! {}
         } else {
+            if self.windows_extern {
+                features = features.into_iter().filter(|f| !f.starts_with("Windows.")).collect();
+            }
             match features.len() {
                 0 => quote! {},
                 1 => {