Fix cyclic features

examples/graph.rs

@@ -5,7 +5,7 @@ use std::fmt;
 #[derive(Parser, Debug)]
 struct Args {
     #[arg(short, long)]
-    manifest_path: String,
+    manifest_path: Option<String>,
     #[arg(long)]
     features: Vec<String>,
     #[arg(long)]
@@ -14,6 +14,8 @@ struct Args {
     no_default_features: bool,
     #[arg(long)]
     no_dev: bool,
+    #[arg(long, conflicts_with = "manifest_path")]
+    json: Option<String>,
 }
 
 pub struct Simple {
@@ -41,27 +43,42 @@ impl fmt::Display for Simple {
 fn main() {
     let args = Args::parse();
 
-    let cmd = {
-        let mut cmd = krates::Cmd::new();
-        if args.all_features {
-            cmd.all_features();
-        }
-        if args.no_default_features {
-            cmd.no_default_features();
+    let graph: Graph = if let Some(manifest_path) = args.manifest_path {
+        let cmd = {
+            let mut cmd = krates::Cmd::new();
+            if args.all_features {
+                cmd.all_features();
+            }
+            if args.no_default_features {
+                cmd.no_default_features();
+            }
+            if !args.features.is_empty() {
+                cmd.features(args.features);
+            }
+            cmd.manifest_path(manifest_path);
+            cmd
+        };
+
+        let mut builder = krates::Builder::new();
+        if args.no_dev {
+            builder.ignore_kind(krates::DepKind::Dev, krates::Scope::All);
         }
-        if !args.features.is_empty() {
-            cmd.features(args.features);
+
+        builder.build(cmd, krates::NoneFilter).unwrap()
+    } else if let Some(json) = args.json {
+        let mut builder = krates::Builder::new();
+        if args.no_dev {
+            builder.ignore_kind(krates::DepKind::Dev, krates::Scope::All);
         }
-        cmd.manifest_path(args.manifest_path);
-        cmd
-    };
 
-    let mut builder = krates::Builder::new();
-    if args.no_dev {
-        builder.ignore_kind(krates::DepKind::Dev, krates::Scope::All);
-    }
+        let json = std::fs::read(json).expect("failed to read json");
+        let md: krates::cm::Metadata =
+            serde_json::from_slice(&json).expect("failed to deserialize metadata from json");
 
-    let graph: Graph = builder.build(cmd, krates::NoneFilter).unwrap();
+        builder.build_with_metadata(md, krates::NoneFilter).unwrap()
+    } else {
+        panic!("must specify either --manifest-path or --json");
+    };
 
     let dot = krates::petgraph::dot::Dot::new(graph.graph()).to_string();
 

src/builder.rs

@@ -1055,6 +1055,10 @@ impl Builder {
                     // enabled explicitly on each edge
                     let mut feature_stack: Vec<_> = rnode.features.iter().map(|s| s.as_str()).collect();
 
+                    // Apparently features can have cycles, so we need to ensure we don't enter an
+                    // infinite loop https://github.com/EmbarkStudios/krates/issues/48
+                    let mut simple_features = std::collections::BTreeSet::new();
+
                     let mut features: Vec<String> = Vec::new();
 
                     while let Some(feat) = feature_stack.pop() {
@@ -1073,7 +1077,9 @@ impl Builder {
 
                             let (krate, feature) = match pf.feat() {
                                 Feature::Simple(feat) => {
-                                    feature_stack.push(feat);
+                                    if simple_features.insert(feat) {
+                                        feature_stack.push(feat);
+                                    }
                                     continue;
                                 },
                                 Feature::Krate(_krate) => { continue; }

tests/features.rs

@@ -218,3 +218,18 @@ fn ensure_weak_features_dont_add_edges() {
         ]
     );
 }
+
+/// Ensures we handle cyclic features
+#[test]
+fn handles_cyclic_features() {
+    let mut cmd = krates::Cmd::new();
+    cmd.manifest_path("tests/features/Cargo.toml")
+        .no_default_features()
+        .features(feats!(["cycle"]));
+
+    let mut builder = krates::Builder::new();
+    builder.include_targets([("x86_64-unknown-linux-musl", vec![])]);
+    let md: krates::Krates = builder.build(cmd, krates::NoneFilter).unwrap();
+
+    assert_features!(md, "features-galore", ["cycle", "midi", "subfeatcycle"]);
+}

tests/features/Cargo.toml

@@ -35,3 +35,5 @@ stream = ["reqest?/stream"]
 tls = ["tls-no-reqwest", "reqest?/rustls-tls"]
 tls-no-reqwest = ["rustls"]
 zlib = ["git/zlib-ng-compat", "reqest?/deflate"]
+cycle = ["subfeatcycle", "midi"]
+subfeatcycle = ["cycle"]