Redo Cargo features

Using optional dependency features (`package?/feature`) in Cargo is not
too well supported, see:
rust-lang/cargo#10801

So instead we now always enable needed features of optional
dependencies. This fixes #656.

I thought this would be a harder trade-off (e.g. I thought that we'd
have to enable a bunch of sub-dependencies for each dependency, and that
wouldn't be nice since I'd prefer to have each crate as explicitly
imported as possible), but it actually turned out to not be too bad,
only a few crates actually enable sub-crates of their dependencies, and
then it's usually `objc2-core-foundation`.

Additionally, I've cleaned up a lot of our feature handling, which:
- Fixes dependent features.
- Removes unnecessary imports.
- Fixes the last part of #640.

There are still a few errors found by `check_framework_features` (esp.
regarding the `objc2` feature), but those can be fixed later.

crates/dispatch2/Cargo.toml

@@ -17,7 +17,7 @@ authors = ["Mads Marquart <[email protected]>", "Mary <[email protected]>"]
 workspace = true
 
 [dependencies]
-bitflags = { version = "2.5.0", default-features = false }
+bitflags = { version = "2.5.0", default-features = false, features = ["std"] }
 block2 = { path = "../block2", version = "0.5.1", default-features = false, optional = true, features = ["alloc"] }
 libc = { version = "0.2.80", default-features = false, optional = true }
 objc2 = { path = "../objc2", version = "0.5.2", default-features = false, optional = true, features = ["std"] }
@@ -40,7 +40,7 @@ targets = [
 
 [features]
 default = ["std"]
-std = ["alloc", "bitflags/std"]
+std = ["alloc"]
 alloc = []
 block2 = ["dep:block2"]
 libc = ["dep:libc"]

crates/header-translator/src/bin/check_framework_features.rs

@@ -132,10 +132,20 @@ fn main() -> Result<(), Box<dyn Error>> {
     for dir in workspace_dir.join("framework-crates").read_dir().unwrap() {
         let dir = dir.unwrap();
         if dir.file_type().unwrap().is_dir() {
+            let feature_sets = [vec!["all"]];
+            // println!("Testing all {dir:?} features");
+            // let features = get_features(&dir.path().join("Cargo.toml"))?;
+            // let feature_sets = features.iter().map(|feature| {
+            //     let mut set = vec![&**feature];
+            //     if features.contains(&"objc2".to_string()) {
+            //         set.push("objc2");
+            //     }
+            //     set
+            // });
             test_feature_sets(
                 &mut success,
                 workspace_dir,
-                [vec!["all"]],
+                feature_sets,
                 dir.file_name().to_str().unwrap(),
             )?;
         }

crates/header-translator/src/cfgs.rs

@@ -212,6 +212,38 @@ impl PlatformCfg {
     }
 }
 
+pub(crate) fn cfg_features_ln<'a, I, F>(feature_names: I) -> impl Display + 'a
+where
+    I: IntoIterator<Item = F> + Clone + 'a,
+    F: AsRef<str>,
+{
+    FormatterFn(move |f| {
+        let mut iter = feature_names.clone().into_iter().peekable();
+
+        if let Some(first) = iter.next() {
+            if iter.peek().is_none() {
+                // One feature.
+                writeln!(f, "#[cfg(feature = {:?})]", first.as_ref())?;
+            } else {
+                write!(f, "#[cfg(all(")?;
+
+                write!(f, "feature = {:?}", first.as_ref())?;
+
+                for feature in iter {
+                    write!(f, ", feature = {:?}", feature.as_ref())?;
+                }
+
+                write!(f, "))]")?;
+                writeln!(f)?;
+            }
+        } else {
+            // No features, no output.
+        }
+
+        Ok(())
+    })
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;

crates/header-translator/src/config.rs

@@ -48,15 +48,16 @@ impl Config {
     }
 
     pub fn library_from_crate(&self, krate: &str) -> &LibraryConfig {
-        self.libraries
-            .values()
-            .find(|lib| lib.krate == krate)
-            .unwrap_or_else(|| {
-                error!("tried to get library config from krate {krate:?}");
-                self.libraries
-                    .get("__builtin__")
-                    .expect("could not find builtin library")
-            })
+        self.try_library_from_crate(krate).unwrap_or_else(|| {
+            error!("tried to get library config from krate {krate:?}");
+            self.libraries
+                .get("__builtin__")
+                .expect("could not find builtin library")
+        })
+    }
+
+    pub fn try_library_from_crate(&self, krate: &str) -> Option<&LibraryConfig> {
+        self.libraries.values().find(|lib| lib.krate == krate)
     }
 
     pub fn replace_protocol_name(&self, id: ItemIdentifier) -> ItemIdentifier {

crates/header-translator/src/expr.rs

@@ -7,6 +7,7 @@ use clang::{Entity, EntityKind, EntityVisitResult, EvaluationResult};
 
 use crate::availability::Availability;
 use crate::context::MacroLocation;
+use crate::id::ItemTree;
 use crate::name_translation::enum_prefix;
 use crate::rust_type::Ty;
 use crate::unexposed_attr::UnexposedAttr;
@@ -274,7 +275,7 @@ impl Expr {
         }
     }
 
-    pub(crate) fn required_items(&self) -> Vec<ItemIdentifier> {
+    pub(crate) fn required_items(&self) -> impl Iterator<Item = ItemTree> {
         let mut items = Vec::new();
 
         match self {
@@ -283,18 +284,17 @@ impl Expr {
             Self::Float(_) => {}
             Self::MacroInvocation { evaluated, id } => {
                 if evaluated.is_none() {
-                    items.push(id.clone());
+                    items.push(ItemTree::from_id(id.clone()));
                 }
             }
             Self::Enum { id, .. } => {
-                items.push(id.clone());
+                items.push(ItemTree::from_id(id.clone()));
             }
             Self::Const(id) => {
-                items.push(id.clone());
+                items.push(ItemTree::from_id(id.clone()));
             }
             Self::Var { id, ty } => {
-                items.push(id.clone());
-                items.extend(ty.required_items());
+                items.push(ItemTree::new(id.clone(), ty.required_items()));
             }
             Self::Tokens(tokens) => {
                 for token in tokens {
@@ -309,7 +309,7 @@ impl Expr {
             }
         }
 
-        items
+        items.into_iter()
     }
 }