feat(tree): Add --depth public behind -Zunstable-options (#15243)

### What does this PR try to resolve?

I was investigating some issues around public dependency lints and
wanted to see the structure of the public dependencies and had the idea
to add this with us having added `--depth workspace`.

See
https://github.com/rust-lang/rust/issues/119428#issuecomment-2686384070
for some example output (comparing `cargo tree` with `cargo tree --depth
public`)

### How should we test and review this PR?

### Additional information

src/cargo/ops/tree/graph.rs

@@ -78,6 +78,7 @@ impl Node {
 pub struct Edge {
     kind: EdgeKind,
     node: NodeId,
+    public: bool,
 }
 
 impl Edge {
@@ -88,6 +89,10 @@ impl Edge {
     pub fn node(&self) -> NodeId {
         self.node
     }
+
+    pub fn public(&self) -> bool {
+        self.public
+    }
 }
 
 /// The kind of edge, for separating dependencies into different sections.
@@ -105,7 +110,7 @@ pub enum EdgeKind {
 ///
 /// The value is a `Vec` because each edge kind can have multiple outgoing
 /// edges. For example, package "foo" can have multiple normal dependencies.
-#[derive(Clone)]
+#[derive(Clone, Debug)]
 struct Edges(HashMap<EdgeKind, Vec<Edge>>);
 
 impl Edges {
@@ -135,6 +140,7 @@ impl Edges {
 }
 
 /// A graph of dependencies.
+#[derive(Debug)]
 pub struct Graph<'a> {
     nodes: Vec<Node>,
     /// The indexes of `edges` correspond to the `nodes`. That is, `edges[0]`
@@ -268,6 +274,7 @@ impl<'a> Graph<'a> {
                 let new_edge = Edge {
                     kind: edge.kind(),
                     node: new_to_index,
+                    public: edge.public(),
                 };
                 new_graph.edges_mut(new_from).add_edge(new_edge);
             }
@@ -290,6 +297,7 @@ impl<'a> Graph<'a> {
                 let new_edge = Edge {
                     kind: edge.kind(),
                     node: NodeId::new(from_idx, self.nodes[from_idx].name()),
+                    public: edge.public(),
                 };
                 new_edges[edge.node().index].add_edge(new_edge);
             }
@@ -514,6 +522,7 @@ fn add_pkg(
             let new_edge = Edge {
                 kind: EdgeKind::Dep(dep.kind()),
                 node: dep_index,
+                public: dep.is_public(),
             };
             if opts.graph_features {
                 // Add the dependency node with feature nodes in-between.
@@ -577,12 +586,14 @@ fn add_feature(
         let from_edge = Edge {
             kind: to.kind(),
             node: node_index,
+            public: to.public(),
         };
         graph.edges_mut(from).add_edge(from_edge);
     }
     let to_edge = Edge {
         kind: EdgeKind::Feature,
         node: to.node(),
+        public: true,
     };
     graph.edges_mut(node_index).add_edge(to_edge);
     (missing, node_index)
@@ -620,6 +631,7 @@ fn add_cli_features(
                 let feature_edge = Edge {
                     kind: EdgeKind::Feature,
                     node: package_index,
+                    public: true,
                 };
                 let index = add_feature(graph, feature, None, feature_edge).1;
                 graph.cli_features.insert(index);
@@ -654,6 +666,7 @@ fn add_cli_features(
                         let feature_edge = Edge {
                             kind: EdgeKind::Feature,
                             node: package_index,
+                            public: true,
                         };
                         let index = add_feature(graph, dep_name, None, feature_edge).1;
                         graph.cli_features.insert(index);
@@ -661,6 +674,7 @@ fn add_cli_features(
                     let dep_edge = Edge {
                         kind: EdgeKind::Feature,
                         node: dep_index,
+                        public: true,
                     };
                     let index = add_feature(graph, dep_feature, None, dep_edge).1;
                     graph.cli_features.insert(index);
@@ -721,6 +735,7 @@ fn add_feature_rec(
                 let feature_edge = Edge {
                     kind: EdgeKind::Feature,
                     node: package_index,
+                    public: true,
                 };
                 let (missing, feat_index) = add_feature(graph, *dep_name, Some(from), feature_edge);
                 // Don't recursive if the edge already exists to deal with cycles.
@@ -771,12 +786,14 @@ fn add_feature_rec(
                         let feature_edge = Edge {
                             kind: EdgeKind::Feature,
                             node: package_index,
+                            public: true,
                         };
                         add_feature(graph, *dep_name, Some(from), feature_edge);
                     }
                     let dep_edge = Edge {
                         kind: EdgeKind::Feature,
                         node: dep_index,
+                        public: true,
                     };
                     let (missing, feat_index) =
                         add_feature(graph, *dep_feature, Some(from), dep_edge);

src/cargo/ops/tree/mod.rs

@@ -91,6 +91,7 @@ impl FromStr for Prefix {
 #[derive(Clone, Copy)]
 pub enum DisplayDepth {
     MaxDisplayDepth(u32),
+    Public,
     Workspace,
 }
 
@@ -100,6 +101,7 @@ impl FromStr for DisplayDepth {
     fn from_str(s: &str) -> Result<Self, Self::Err> {
         match s {
             "workspace" => Ok(Self::Workspace),
+            "public" => Ok(Self::Public),
             s => s.parse().map(Self::MaxDisplayDepth).map_err(|_| {
                 clap::Error::raw(
                     clap::error::ErrorKind::ValueValidation,
@@ -282,7 +284,7 @@ fn print(
             &mut visited_deps,
             &mut levels_continue,
             &mut print_stack,
-        );
+        )?;
     }
 
     Ok(())
@@ -302,7 +304,7 @@ fn print_node<'a>(
     visited_deps: &mut HashSet<NodeId>,
     levels_continue: &mut Vec<(anstyle::Style, bool)>,
     print_stack: &mut Vec<NodeId>,
-) {
+) -> CargoResult<()> {
     let new = no_dedupe || visited_deps.insert(node_index);
 
     match prefix {
@@ -343,7 +345,7 @@ fn print_node<'a>(
     drop_println!(ws.gctx(), "{}{}", format.display(graph, node_index), star);
 
     if !new || in_cycle {
-        return;
+        return Ok(());
     }
     print_stack.push(node_index);
 
@@ -367,9 +369,11 @@ fn print_node<'a>(
             levels_continue,
             print_stack,
             kind,
-        );
+        )?;
     }
     print_stack.pop();
+
+    Ok(())
 }
 
 /// Prints all the dependencies of a package for the given dependency kind.
@@ -387,10 +391,10 @@ fn print_dependencies<'a>(
     levels_continue: &mut Vec<(anstyle::Style, bool)>,
     print_stack: &mut Vec<NodeId>,
     kind: &EdgeKind,
-) {
+) -> CargoResult<()> {
     let deps = graph.edges_of_kind(node_index, kind);
     if deps.is_empty() {
-        return;
+        return Ok(());
     }
 
     let name = match kind {
@@ -415,14 +419,20 @@ fn print_dependencies<'a>(
         }
     }
 
-    let (max_display_depth, filter_non_workspace_member) = match display_depth {
-        DisplayDepth::MaxDisplayDepth(max) => (max, false),
-        DisplayDepth::Workspace => (u32::MAX, true),
+    let (max_display_depth, filter_non_workspace_member, filter_private) = match display_depth {
+        DisplayDepth::MaxDisplayDepth(max) => (max, false, false),
+        DisplayDepth::Workspace => (u32::MAX, true, false),
+        DisplayDepth::Public => {
+            if !ws.gctx().cli_unstable().unstable_options {
+                anyhow::bail!("`--depth public` requires `-Zunstable-options`")
+            }
+            (u32::MAX, false, true)
+        }
     };
 
     // Current level exceeds maximum display depth. Skip.
     if levels_continue.len() + 1 > max_display_depth as usize {
-        return;
+        return Ok(());
     }
 
     let mut it = deps
@@ -434,9 +444,17 @@ fn print_dependencies<'a>(
                     if filter_non_workspace_member && !ws.is_member_id(*package_id) {
                         return false;
                     }
+                    if filter_private && !dep.public() {
+                        return false;
+                    }
                     !pkgs_to_prune.iter().any(|spec| spec.matches(*package_id))
                 }
-                _ => true,
+                Node::Feature { .. } => {
+                    if filter_private && !dep.public() {
+                        return false;
+                    }
+                    true
+                }
             }
         })
         .peekable();
@@ -457,9 +475,11 @@ fn print_dependencies<'a>(
             visited_deps,
             levels_continue,
             print_stack,
-        );
+        )?;
         levels_continue.pop();
     }
+
+    Ok(())
 }
 
 fn edge_line_color(kind: EdgeKind) -> anstyle::Style {

tests/testsuite/cargo_tree/deps.rs

@@ -1901,6 +1901,138 @@ c v0.1.0 ([ROOT]/foo/c) (*)
         .run();
 }
 
+#[cargo_test(nightly, reason = "exported_private_dependencies lint is unstable")]
+fn depth_public() {
+    let p = project()
+        .file(
+            "Cargo.toml",
+            r#"
+            [workspace]
+            members = ["diamond", "left-pub", "right-priv", "dep"]
+            "#,
+        )
+        .file(
+            "diamond/Cargo.toml",
+            r#"
+            cargo-features = ["public-dependency"]
+
+            [package]
+            name = "diamond"
+            version = "0.1.0"
+
+            [dependencies]
+            left-pub = { path = "../left-pub", public = true }
+            right-priv = { path = "../right-priv", public = true }
+            "#,
+        )
+        .file("diamond/src/lib.rs", "")
+        .file(
+            "left-pub/Cargo.toml",
+            r#"
+            cargo-features = ["public-dependency"]
+
+            [package]
+            name = "left-pub"
+            version = "0.1.0"
+
+            [dependencies]
+            dep = { path = "../dep", public = true }
+            "#,
+        )
+        .file("left-pub/src/lib.rs", "")
+        .file(
+            "right-priv/Cargo.toml",
+            r#"
+            [package]
+            name = "right-priv"
+            version = "0.1.0"
+
+            [dependencies]
+            dep = { path = "../dep" }
+            "#,
+        )
+        .file("right-priv/src/lib.rs", "")
+        .file(
+            "dep/Cargo.toml",
+            r#"
+            [package]
+            name = "dep"
+            version = "0.1.0"
+            "#,
+        )
+        .file("dep/src/lib.rs", "")
+        .build();
+
+    p.cargo("tree --depth public")
+        .masquerade_as_nightly_cargo(&["public-dependency", "depth-public"])
+        .with_status(101)
+        .with_stderr_data(str![[r#"
+[ERROR] `--depth public` requires `-Zunstable-options`
+
+"#]])
+        .run();
+
+    p.cargo("tree --depth public -p left-pub")
+        .arg("-Zunstable-options")
+        .masquerade_as_nightly_cargo(&["public-dependency", "depth-public"])
+        .with_stdout_data(str![[r#"
+left-pub v0.1.0 ([ROOT]/foo/left-pub)
+└── dep v0.1.0 ([ROOT]/foo/dep)
+
+"#]])
+        .run();
+
+    p.cargo("tree --depth public -p right-priv")
+        .arg("-Zunstable-options")
+        .masquerade_as_nightly_cargo(&["public-dependency", "depth-public"])
+        .with_stdout_data(str![[r#"
+right-priv v0.1.0 ([ROOT]/foo/right-priv)
+
+"#]])
+        .run();
+
+    p.cargo("tree --depth public -p diamond")
+        .arg("-Zunstable-options")
+        .masquerade_as_nightly_cargo(&["public-dependency", "depth-public"])
+        .with_stdout_data(str![[r#"
+diamond v0.1.0 ([ROOT]/foo/diamond)
+├── left-pub v0.1.0 ([ROOT]/foo/left-pub)
+│   └── dep v0.1.0 ([ROOT]/foo/dep)
+└── right-priv v0.1.0 ([ROOT]/foo/right-priv)
+
+"#]])
+        .run();
+
+    p.cargo("tree --depth public")
+        .arg("-Zunstable-options")
+        .masquerade_as_nightly_cargo(&["public-dependency", "depth-public"])
+        .with_stdout_data(str![[r#"
+dep v0.1.0 ([ROOT]/foo/dep)
+
+diamond v0.1.0 ([ROOT]/foo/diamond)
+├── left-pub v0.1.0 ([ROOT]/foo/left-pub)
+│   └── dep v0.1.0 ([ROOT]/foo/dep)
+└── right-priv v0.1.0 ([ROOT]/foo/right-priv)
+
+left-pub v0.1.0 ([ROOT]/foo/left-pub) (*)
+
+right-priv v0.1.0 ([ROOT]/foo/right-priv) (*)
+
+"#]])
+        .run();
+
+    p.cargo("tree --depth public --invert dep")
+        .arg("-Zunstable-options")
+        .masquerade_as_nightly_cargo(&["public-dependency", "depth-public"])
+        .with_stdout_data(str![[r#"
+dep v0.1.0 ([ROOT]/foo/dep)
+└── left-pub v0.1.0 ([ROOT]/foo/left-pub)
+    └── diamond v0.1.0 ([ROOT]/foo/diamond)
+
+"#]])
+        .run();
+}
+
 #[cargo_test]
 fn prune() {
     let p = make_simple_proj();

tests/testsuite/cargo_tree/features.rs

@@ -350,3 +350,164 @@ foo v0.1.0 ([ROOT]/foo)
 "#]])
         .run();
 }
+
+#[cargo_test(nightly, reason = "exported_private_dependencies lint is unstable")]
+fn depth_public_no_features() {
+    Package::new("pub-defaultdep", "1.0.0").publish();
+    Package::new("priv-defaultdep", "1.0.0").publish();
+
+    let p = project()
+        .file(
+            "Cargo.toml",
+            r#"
+            cargo-features = ["public-dependency"]
+
+            [package]
+            name = "foo"
+            version = "0.1.0"
+
+            [dependencies]
+            pub-defaultdep = { version = "1.0.0", public = true }
+            priv-defaultdep = "1.0.0"
+            "#,
+        )
+        .file("src/lib.rs", "")
+        .build();
+
+    p.cargo("tree -e features --depth public")
+        .arg("-Zunstable-options")
+        .masquerade_as_nightly_cargo(&["public-dependency", "depth-public"])
+        .with_stdout_data(str![[r#"
+foo v0.1.0 ([ROOT]/foo)
+└── pub-defaultdep feature "default"
+    └── pub-defaultdep v1.0.0
+
+"#]])
+        .run();
+}
+
+#[cargo_test(nightly, reason = "exported_private_dependencies lint is unstable")]
+fn depth_public_transitive_features() {
+    Package::new("pub-defaultdep", "1.0.0")
+        .feature("default", &["f1"])
+        .feature("f1", &["f2"])
+        .feature("f2", &["optdep"])
+        .add_dep(Dependency::new("optdep", "1.0").optional(true).public(true))
+        .publish();
+    Package::new("priv-defaultdep", "1.0.0")
+        .feature("default", &["f1"])
+        .feature("f1", &["f2"])
+        .feature("f2", &["optdep"])
+        .add_dep(Dependency::new("optdep", "1.0").optional(true))
+        .publish();
+    Package::new("optdep", "1.0.0")
+        .feature("default", &["f"])
+        .feature("f", &[])
+        .publish();
+
+    let p = project()
+        .file(
+            "Cargo.toml",
+            r#"
+            cargo-features = ["public-dependency"]
+
+            [package]
+            name = "foo"
+            version = "0.1.0"
+
+            [dependencies]
+            pub-defaultdep = { version = "1.0.0", public = true }
+            priv-defaultdep = { version = "1.0.0", public = true }
+            "#,
+        )
+        .file("src/lib.rs", "")
+        .build();
+
+    p.cargo("tree -e features --depth public")
+        .arg("-Zunstable-options")
+        .masquerade_as_nightly_cargo(&["public-dependency", "depth-public"])
+        .with_stdout_data(str![[r#"
+foo v0.1.0 ([ROOT]/foo)
+├── priv-defaultdep feature "default"
+│   ├── priv-defaultdep v1.0.0
+│   └── priv-defaultdep feature "f1"
+│       ├── priv-defaultdep v1.0.0 (*)
+│       └── priv-defaultdep feature "f2"
+│           ├── priv-defaultdep v1.0.0 (*)
+│           └── priv-defaultdep feature "optdep"
+│               └── priv-defaultdep v1.0.0 (*)
+└── pub-defaultdep feature "default"
+    ├── pub-defaultdep v1.0.0
+    │   └── optdep feature "default"
+    │       ├── optdep v1.0.0
+    │       └── optdep feature "f"
+    │           └── optdep v1.0.0
+    └── pub-defaultdep feature "f1"
+        ├── pub-defaultdep v1.0.0 (*)
+        └── pub-defaultdep feature "f2"
+            ├── pub-defaultdep v1.0.0 (*)
+            └── pub-defaultdep feature "optdep"
+                └── pub-defaultdep v1.0.0 (*)
+
+"#]])
+        .run();
+}
+
+#[cargo_test(nightly, reason = "exported_private_dependencies lint is unstable")]
+fn depth_public_cli() {
+    Package::new("priv", "1.0.0").feature("f", &[]).publish();
+    Package::new("pub", "1.0.0").feature("f", &[]).publish();
+
+    let p = project()
+        .file(
+            "Cargo.toml",
+            r#"
+            cargo-features = ["public-dependency"]
+
+            [package]
+            name = "foo"
+            version = "0.1.0"
+
+            [features]
+            priv-indirect = ["priv"]
+            priv = ["dep:priv", "priv?/f"]
+            pub-indirect = ["pub"]
+            pub = ["dep:pub", "priv?/f"]
+
+            [dependencies]
+            priv = { version = "1.0.0", optional = true }
+            pub = { version = "1.0.0", optional = true, public = true }
+            "#,
+        )
+        .file("src/lib.rs", "")
+        .build();
+
+    p.cargo("tree -e features --depth public")
+        .arg("-Zunstable-options")
+        .masquerade_as_nightly_cargo(&["public-dependency", "depth-public"])
+        .with_stdout_data(str![[r#"
+foo v0.1.0 ([ROOT]/foo)
+
+"#]])
+        .run();
+
+    p.cargo("tree -e features --depth public --features pub-indirect")
+        .arg("-Zunstable-options")
+        .masquerade_as_nightly_cargo(&["public-dependency", "depth-public"])
+        .with_stdout_data(str![[r#"
+foo v0.1.0 ([ROOT]/foo)
+└── pub feature "default"
+    └── pub v1.0.0
+
+"#]])
+        .run();
+
+    p.cargo("tree -e features --depth public --features priv-indirect")
+        .arg("-Zunstable-options")
+        .masquerade_as_nightly_cargo(&["public-dependency", "depth-public"])
+        .with_stdout_data(str![[r#"
+foo v0.1.0 ([ROOT]/foo)
+
+"#]])
+        .run();
+}