3 files changed, 97 insertions, 0 deletions

diff --git a/crates/ide/Cargo.toml b/crates/ide/Cargo.toml
index f04bcf531..88f3d09d3 100644
--- a/crates/ide/Cargo.toml
+++ b/crates/ide/Cargo.toml
@@ -20,6 +20,7 @@ oorandom = "11.1.2"
 pulldown-cmark-to-cmark = "6.0.0"
 pulldown-cmark = { version = "0.8.0", default-features = false }
 url = "2.1.1"
+dot = "0.1.4"
 
 stdx = { path = "../stdx", version = "0.0.0" }
 syntax = { path = "../syntax", version = "0.0.0" }
diff --git a/crates/ide/src/lib.rs b/crates/ide/src/lib.rs
index 8e5b72044..db08547d1 100644
--- a/crates/ide/src/lib.rs
+++ b/crates/ide/src/lib.rs
@@ -49,6 +49,7 @@ mod syntax_tree;
 mod typing;
 mod markdown_remove;
 mod doc_links;
+mod view_crate_graph;
 
 use std::sync::Arc;
 
@@ -287,6 +288,11 @@ impl Analysis {
         self.with_db(|db| view_hir::view_hir(&db, position))
     }
 
+    /// Renders the crate graph to GraphViz "dot" syntax.
+    pub fn view_crate_graph(&self) -> Cancelable<Result<String, String>> {
+        self.with_db(|db| view_crate_graph::view_crate_graph(&db))
+    }
+
     pub fn expand_macro(&self, position: FilePosition) -> Cancelable<Option<ExpandedMacro>> {
         self.with_db(|db| expand_macro::expand_macro(db, position))
     }
diff --git a/crates/ide/src/view_crate_graph.rs b/crates/ide/src/view_crate_graph.rs
new file mode 100644
index 000000000..df6cc8aed
--- /dev/null
+++ b/crates/ide/src/view_crate_graph.rs
@@ -0,0 +1,90 @@
+use std::sync::Arc;
+
+use dot::{Id, LabelText};
+use ide_db::{
+    base_db::{CrateGraph, CrateId, Dependency, SourceDatabase, SourceDatabaseExt},
+    RootDatabase,
+};
+use rustc_hash::FxHashSet;
+
+// Feature: View Crate Graph
+//
+// Renders the currently loaded crate graph as an SVG graphic. Requires the `dot` tool, which
+// is part of graphviz, to be installed.
+//
+// Only workspace crates are included, no crates.io dependencies or sysroot crates.
+//
+// |===
+// | Editor  | Action Name
+//
+// | VS Code | **Rust Analyzer: View Crate Graph**
+// |===
+pub(crate) fn view_crate_graph(db: &RootDatabase) -> Result<String, String> {
+    let crate_graph = db.crate_graph();
+    let crates_to_render = crate_graph
+        .iter()
+        .filter(|krate| {
+            // Only render workspace crates
+            let root_id = db.file_source_root(crate_graph[*krate].root_file_id);
+            !db.source_root(root_id).is_library
+        })
+        .collect();
+    let graph = DotCrateGraph { graph: crate_graph, crates_to_render };
+
+    let mut dot = Vec::new();
+    dot::render(&graph, &mut dot).unwrap();
+    Ok(String::from_utf8(dot).unwrap())
+}
+
+struct DotCrateGraph {
+    graph: Arc<CrateGraph>,
+    crates_to_render: FxHashSet<CrateId>,
+}
+
+type Edge<'a> = (CrateId, &'a Dependency);
+
+impl<'a> dot::GraphWalk<'a, CrateId, Edge<'a>> for DotCrateGraph {
+    fn nodes(&'a self) -> dot::Nodes<'a, CrateId> {
+        self.crates_to_render.iter().copied().collect()
+    }
+
+    fn edges(&'a self) -> dot::Edges<'a, Edge<'a>> {
+        self.crates_to_render
+            .iter()
+            .flat_map(|krate| {
+                self.graph[*krate]
+                    .dependencies
+                    .iter()
+                    .filter(|dep| self.crates_to_render.contains(&dep.crate_id))
+                    .map(move |dep| (*krate, dep))
+            })
+            .collect()
+    }
+
+    fn source(&'a self, edge: &Edge<'a>) -> CrateId {
+        edge.0
+    }
+
+    fn target(&'a self, edge: &Edge<'a>) -> CrateId {
+        edge.1.crate_id
+    }
+}
+
+impl<'a> dot::Labeller<'a, CrateId, Edge<'a>> for DotCrateGraph {
+    fn graph_id(&'a self) -> Id<'a> {
+        Id::new("rust_analyzer_crate_graph").unwrap()
+    }
+
+    fn node_id(&'a self, n: &CrateId) -> Id<'a> {
+        Id::new(format!("_{}", n.0)).unwrap()
+    }
+
+    fn node_shape(&'a self, _node: &CrateId) -> Option<LabelText<'a>> {
+        Some(LabelText::LabelStr("box".into()))
+    }
+
+    fn node_label(&'a self, n: &CrateId) -> LabelText<'a> {
+        let name = self.graph[*n].display_name.as_ref().map_or("(unnamed crate)", |name| &*name);
+        LabelText::LabelStr(name.into())
+    }
+}