Add optional warnings for windows-bindgen to improve diagnostics

crates/libs/bindgen/src/lib.rs

@@ -22,6 +22,7 @@ mod type_name;
 mod type_tree;
 mod types;
 mod value;
+mod warnings;
 mod winmd;
 mod writer;
 
@@ -44,6 +45,7 @@ use type_name::*;
 use type_tree::*;
 use types::*;
 use value::*;
+pub use warnings::*;
 use winmd::*;
 use writer::*;
 mod method_names;
@@ -64,11 +66,12 @@ struct Config {
     pub implement: bool,
     pub derive: Derive,
     pub link: String,
+    pub warnings: WarningBuilder,
 }
 
 /// The Windows code generator.
 #[track_caller]
-pub fn bindgen<I, S>(args: I)
+pub fn bindgen<I, S>(args: I) -> Warnings
 where
     I: IntoIterator<Item = S>,
     S: AsRef<str>,
@@ -201,6 +204,7 @@ where
         sys,
         implement,
         link,
+        warnings: WarningBuilder::default(),
     };
 
     let tree = TypeTree::new(&config.types);
@@ -210,7 +214,8 @@ where
         namespace: "",
     };
 
-    writer.write(tree)
+    writer.write(tree);
+    config.warnings.build()
 }
 
 enum ArgKind {

crates/libs/bindgen/src/types/cpp_interface.rs

@@ -38,6 +38,11 @@ impl CppInterface {
                 if method.dependencies.included(writer.config) {
                     CppMethodOrName::Method(method)
                 } else {
+                    writer.config.warnings.skip_method(
+                        method.def,
+                        &method.dependencies,
+                        writer.config,
+                    );
                     CppMethodOrName::Name(method.def)
                 }
             })

crates/libs/bindgen/src/types/interface.rs

@@ -61,6 +61,11 @@ impl Interface {
                 if method.dependencies.included(writer.config) {
                     MethodOrName::Method(method)
                 } else {
+                    writer.config.warnings.skip_method(
+                        method.def,
+                        &method.dependencies,
+                        writer.config,
+                    );
                     MethodOrName::Name(method.def)
                 }
             })

crates/libs/bindgen/src/warnings.rs

@@ -0,0 +1,65 @@
+use super::*;
+use std::sync::RwLock;
+
+#[derive(Default)]
+pub(crate) struct WarningBuilder(RwLock<Vec<String>>);
+
+impl WarningBuilder {
+    pub fn build(self) -> Warnings {
+        Warnings(self.0.write().unwrap().split_off(0))
+    }
+
+    pub fn add(&self, message: String) {
+        self.0.write().unwrap().push(message);
+    }
+
+    pub fn skip_method(&self, method: MethodDef, dependencies: &TypeMap, config: &Config) {
+        let mut message = String::new();
+        writeln!(
+            &mut message,
+            "skipping `{}.{}` due to missing dependencies:",
+            method.parent().type_name(),
+            method.name()
+        )
+        .unwrap();
+
+        for tn in dependencies.keys() {
+            if !config.types.contains_key(tn) && config.references.contains(*tn).is_none() {
+                writeln!(&mut message, "  {tn}").unwrap();
+            }
+        }
+
+        self.add(message);
+    }
+}
+
+/// Contains warnings collected during code generation.
+#[derive(Debug)]
+pub struct Warnings(Vec<String>);
+
+impl Warnings {
+    /// Panics if any warnings are present.
+    #[track_caller]
+    pub fn unwrap(&self) {
+        if !self.is_empty() {
+            panic!("{self}");
+        }
+    }
+}
+
+impl std::fmt::Display for Warnings {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        for message in &self.0 {
+            write!(f, "{message}")?;
+        }
+        Ok(())
+    }
+}
+
+impl std::ops::Deref for Warnings {
+    type Target = Vec<String>;
+
+    fn deref(&self) -> &Self::Target {
+        &self.0
+    }
+}

crates/libs/bindgen/src/winmd/codes.rs

@@ -84,6 +84,13 @@ code! { MemberRefParent(3)
 }
 
 impl MemberRefParent {
+    pub fn type_name(&self) -> TypeName {
+        match self {
+            Self::TypeDef(row) => row.type_name(),
+            Self::TypeRef(row) => row.type_name(),
+        }
+    }
+
     pub fn name(&self) -> &'static str {
         match self {
             Self::TypeDef(row) => row.name(),

crates/tests/bindgen/tests/panic.rs

@@ -1,6 +1,6 @@
 #[track_caller]
-fn bindgen(args: &str) {
-    windows_bindgen::bindgen(args.split_whitespace());
+fn bindgen(args: &str) -> windows_bindgen::Warnings {
+    windows_bindgen::bindgen(args.split_whitespace())
 }
 
 #[test]
@@ -151,3 +151,32 @@ fn failed_to_write_file() {
 
     bindgen(&format!("--out {test_path} --in default --filter POINT",));
 }
+
+#[test]
+#[should_panic(
+    expected = "skipping `Windows.Win32.System.Com.IPersistFile.Load` due to missing dependencies:\n  Windows.Win32.System.Com.STGM"
+)]
+fn skip_cpp_method() {
+    let mut path = std::env::temp_dir();
+    path.push("skip_cpp_method");
+
+    windows_bindgen::bindgen(["--out", &path.to_string_lossy(), "--filter", "IPersistFile"])
+        .unwrap();
+}
+
+#[test]
+#[should_panic(
+    expected = "skipping `Windows.Foundation.IMemoryBuffer.CreateReference` due to missing dependencies:\n  Windows.Foundation.IMemoryBufferReference"
+)]
+fn skip_method() {
+    let mut path = std::env::temp_dir();
+    path.push("skip_method");
+
+    windows_bindgen::bindgen([
+        "--out",
+        &path.to_string_lossy(),
+        "--filter",
+        "IMemoryBuffer",
+    ])
+    .unwrap();
+}

crates/tools/bindings/src/main.rs

@@ -3,18 +3,19 @@ use windows_bindgen::*;
 fn main() {
     let time = std::time::Instant::now();
 
-    bindgen(["--etc", "crates/tools/bindings/src/async.txt"]);
-    bindgen(["--etc", "crates/tools/bindings/src/async_impl.txt"]);
-    bindgen(["--etc", "crates/tools/bindings/src/collections.txt"]);
-    bindgen(["--etc", "crates/tools/bindings/src/core_com.txt"]);
-    bindgen(["--etc", "crates/tools/bindings/src/core.txt"]);
-    bindgen(["--etc", "crates/tools/bindings/src/metadata.txt"]);
-    bindgen(["--etc", "crates/tools/bindings/src/numerics.txt"]);
-    bindgen(["--etc", "crates/tools/bindings/src/registry.txt"]);
-    bindgen(["--etc", "crates/tools/bindings/src/result.txt"]);
-    bindgen(["--etc", "crates/tools/bindings/src/strings.txt"]);
+    bindgen(["--etc", "crates/tools/bindings/src/async.txt"]).unwrap();
+    bindgen(["--etc", "crates/tools/bindings/src/async_impl.txt"]).unwrap();
+    bindgen(["--etc", "crates/tools/bindings/src/collections.txt"]).unwrap();
+    bindgen(["--etc", "crates/tools/bindings/src/core_com.txt"]).unwrap();
+    bindgen(["--etc", "crates/tools/bindings/src/core.txt"]).unwrap();
+    bindgen(["--etc", "crates/tools/bindings/src/metadata.txt"]).unwrap();
+    bindgen(["--etc", "crates/tools/bindings/src/numerics.txt"]).unwrap();
+    bindgen(["--etc", "crates/tools/bindings/src/registry.txt"]).unwrap();
+    bindgen(["--etc", "crates/tools/bindings/src/result.txt"]).unwrap();
+    bindgen(["--etc", "crates/tools/bindings/src/strings.txt"]).unwrap();
+    bindgen(["--etc", "crates/tools/bindings/src/version.txt"]).unwrap();
+
     bindgen(["--etc", "crates/tools/bindings/src/sys.txt"]);
-    bindgen(["--etc", "crates/tools/bindings/src/version.txt"]);
     bindgen(["--etc", "crates/tools/bindings/src/windows.txt"]);
 
     println!("Finished in {:.2}s", time.elapsed().as_secs_f32());