Add Krates::direct_dependents (#43)

.gitignore

@@ -1,3 +1,4 @@
 **/target/
 **/*.rs.bk
-Cargo.lock
+Cargo.lock
+*.snap.new

src/lib.rs

@@ -270,6 +270,34 @@ impl<N, E> Krates<N, E> {
             })
     }
 
+    /// Gets the crates that have a direct dependency on the specified node
+    #[inline]
+    pub fn direct_dependents(&self, nid: NodeId) -> Vec<&N> {
+        let graph = self.graph();
+        let mut direct_dependencies = Vec::new();
+        let mut stack = vec![nid];
+        let mut visited = std::collections::BTreeSet::new();
+
+        while let Some(nid) = stack.pop() {
+            for edge in graph.edges_directed(nid, Direction::Incoming) {
+                match &self.graph[edge.source()] {
+                    Node::Krate { krate, .. } => {
+                        if visited.insert(edge.source()) {
+                            direct_dependencies.push(krate);
+                        }
+                    }
+                    Node::Feature { krate_index, .. } => {
+                        if *krate_index == nid {
+                            stack.push(edge.source());
+                        }
+                    }
+                }
+            }
+        }
+
+        direct_dependencies
+    }
+
     /// Get the node identifier for the specified crate identifier
     #[inline]
     pub fn nid_for_kid(&self, kid: &Kid) -> Option<NodeId> {

tests/direct/Cargo.toml

@@ -0,0 +1,9 @@
+[package]
+name = "direct"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]
+google-cloud-pubsub = { version = "0.8", default_features = false, features = ["rustls-tls"] }
+google-cloud-gax = { version = "0.9",  default_features = false, features = ["rustls-tls"] }
+google-cloud-googleapis = "0.6"

tests/direct/src/lib.rs

@@ -0,0 +1 @@
+

tests/misc.rs

@@ -1,3 +1,5 @@
+mod util;
+
 #[test]
 fn iter_names() {
     let contents = std::fs::read_to_string("tests/all-features.json")
@@ -123,3 +125,35 @@ fn iter_matches() {
         assert!(iter.next().is_none());
     }
 }
+
+#[test]
+fn direct_dependents() {
+    let mut kb = krates::Builder::new();
+    kb.include_targets(std::iter::once((
+        krates::cfg_expr::targets::get_builtin_target_by_triple("x86_64-unknown-linux-gnu")
+            .unwrap()
+            .triple
+            .clone(),
+        vec![],
+    )));
+
+    let grafs = util::build("direct.json", kb).unwrap();
+
+    let id = grafs
+        .actual
+        .krates()
+        .find(|k| k.0.repr.starts_with("reqwest"))
+        .unwrap();
+
+    let dd = grafs
+        .actual
+        .direct_dependents(grafs.actual.nid_for_kid(&id.0).unwrap())
+        .into_iter()
+        .fold(String::new(), |mut acc, jid| {
+            acc.push_str(&jid.0.repr);
+            acc.push('\n');
+            acc
+        });
+
+    insta::assert_snapshot!(dd);
+}

tests/snapshots/misc__direct_dependents.snap

@@ -0,0 +1,7 @@
+---
+source: tests/misc.rs
+expression: dd
+---
+google-cloud-metadata 0.3.1 (registry+https://github.com/rust-lang/crates.io-index)
+google-cloud-auth 0.5.0 (registry+https://github.com/rust-lang/crates.io-index)
+

tests/util.rs

@@ -2,7 +2,7 @@
 
 use std::{fmt, path::Path};
 
-pub struct JustId(krates::Kid);
+pub struct JustId(pub krates::Kid);
 
 pub type Graph = krates::Krates<JustId>;