Generate features index for windows and sys crates (#2859)

crates/libs/bindgen/Cargo.toml

@@ -31,3 +31,10 @@ features = ["full", "extra-traits"]
 [dependencies.proc-macro2]
 version = "1.0"
 features = ["span-locations"]
+
+[dependencies.serde]
+version = "1.0.196"
+features = ["derive"]
+
+[dependencies.serde_json]
+version = "1.0.113"

crates/libs/bindgen/src/rust/index.rs

@@ -0,0 +1,69 @@
+use super::*;
+use rust::cfg::*;
+use serde::Serialize;
+use std::collections::BTreeMap;
+use windows_metadata::Item;
+
+#[derive(Default, Serialize)]
+struct Index {
+    namespace_map: Vec<String>,
+    feature_map: Vec<String>,
+    namespaces: BTreeMap<usize, Vec<IndexItem>>,
+}
+
+#[derive(Default, Serialize)]
+struct IndexItem {
+    name: String,
+    features: Vec<usize>,
+}
+
+pub fn gen_index(writer: &Writer) -> String {
+    let mut feature_index = Index { ..Default::default() };
+
+    for namespace in writer.reader.namespaces() {
+        let namespace_idx = match feature_index.namespace_map.iter().position(|ns| ns == namespace) {
+            Some(idx) => idx,
+            None => {
+                feature_index.namespace_map.push(namespace.to_string());
+                feature_index.namespace_map.len() - 1
+            }
+        };
+
+        for item in writer.reader.namespace_items(namespace) {
+            let mut index_item = IndexItem { ..Default::default() };
+            let mut cfg = Cfg::default();
+            cfg.add_feature(namespace);
+
+            cfg = match item {
+                Item::Type(def) => {
+                    index_item.name = def.name().to_string();
+                    cfg.union(&type_def_cfg(writer, def, &[]))
+                }
+                Item::Const(field) => {
+                    index_item.name = field.name().to_string();
+                    cfg.union(&field_cfg(writer, field))
+                }
+                Item::Fn(method, _) => {
+                    index_item.name = method.name().to_string();
+                    cfg.union(&signature_cfg(writer, method))
+                }
+            };
+
+            let cfg_features = cfg_features(&cfg);
+            index_item.features = cfg_features
+                .iter()
+                .map(|feature| match feature_index.feature_map.iter().position(|f| f == feature) {
+                    Some(idx) => idx,
+                    None => {
+                        feature_index.feature_map.push(feature.to_string());
+                        feature_index.feature_map.len() - 1
+                    }
+                })
+                .collect();
+
+            feature_index.namespaces.entry(namespace_idx).or_default().push(index_item);
+        }
+    }
+
+    serde_json::to_string(&feature_index).unwrap()
+}

crates/libs/bindgen/src/rust/mod.rs

@@ -8,6 +8,7 @@ mod extensions;
 mod functions;
 mod handles;
 mod implements;
+mod index;
 mod interfaces;
 mod iterators;
 mod method_names;
@@ -16,8 +17,11 @@ mod structs;
 mod try_format;
 mod winrt_methods;
 mod writer;
+
 use super::*;
+use index::*;
 use rayon::prelude::*;
+use writer::*;
 
 pub fn from_reader(reader: &'static metadata::Reader, mut config: std::collections::BTreeMap<&str, &str>, output: &str) -> Result<()> {
     let mut writer = Writer::new(reader, output);
@@ -101,7 +105,8 @@ fn gen_package(writer: &Writer) -> Result<()> {
         Ok::<(), Error>(())
     })?;
 
-    let cargo_toml = format!("{}/Cargo.toml", super::directory(directory));
+    let package_root = super::directory(directory);
+    let cargo_toml = format!("{package_root}/Cargo.toml");
     let mut toml = String::new();
 
     for line in read_file_lines(&cargo_toml)? {
@@ -129,14 +134,14 @@ fn gen_package(writer: &Writer) -> Result<()> {
         }
     }
 
-    write_to_file(&cargo_toml, toml)
+    write_to_file(&cargo_toml, toml)?;
+    write_to_file(&format!("{package_root}/features.json"), gen_index(writer))
 }
 
 use method_names::*;
 use std::fmt::Write;
 use tokens::*;
 use try_format::*;
-use writer::*;
 
 fn namespace(writer: &Writer, tree: &Tree) -> String {
     let writer = &mut writer.clone();

crates/libs/bindgen/src/rust/writer.rs

@@ -1185,6 +1185,22 @@ fn const_ptrs(pointers: usize) -> TokenStream {
     "*const ".repeat(pointers).into()
 }
 
+pub fn cfg_features(cfg: &cfg::Cfg) -> Vec<String> {
+    let mut compact = Vec::<&'static str>::new();
+    for feature in cfg.types.keys() {
+        if !feature.is_empty() {
+            for pos in 0..compact.len() {
+                if starts_with(feature, unsafe { compact.get_unchecked(pos) }) {
+                    compact.remove(pos);
+                    break;
+                }
+            }
+            compact.push(feature);
+        }
+    }
+    compact.into_iter().map(to_feature).collect()
+}
+
 fn to_feature(name: &str) -> String {
     let mut feature = String::new();
 

crates/libs/sys/Cargo.toml

@@ -9,6 +9,7 @@ description = "Rust for Windows"
 repository = "https://github.com/microsoft/windows-rs"
 readme = "readme.md"
 categories = ["os::windows-apis"]
+exclude = ["features.json"]
 
 [lints]
 workspace = true

crates/libs/windows/Cargo.toml

@@ -11,6 +11,7 @@ repository = "https://github.com/microsoft/windows-rs"
 documentation = "https://microsoft.github.io/windows-docs-rs/"
 readme = "readme.md"
 categories = ["os::windows-apis"]
+exclude = ["features.json"]
 
 [lints]
 workspace = true