Allow viewing the crate graph in a webview

crates/ide/src/view_crate_graph.rs

@@ -0,0 +1,81 @@
+use std::{
+    error::Error,
+    io::{Read, Write},
+    process::{Command, Stdio},
+    sync::Arc,
+};
+
+use dot::Id;
+use ide_db::{
+    base_db::{CrateGraph, CrateId, Dependency, SourceDatabase},
+    RootDatabase,
+};
+
+// Feature: View Crate Graph
+//
+// Renders the currently loaded crate graph as an SVG graphic. Requires the `dot` tool to be
+// installed.
+//
+// |===
+// | Editor  | Action Name
+//
+// | VS Code | **Rust Analyzer: View Crate Graph**
+// |===
+pub(crate) fn view_crate_graph(db: &RootDatabase) -> Result<String, String> {
+    let mut dot = Vec::new();
+    let graph = DotCrateGraph(db.crate_graph());
+    dot::render(&graph, &mut dot).unwrap();
+
+    render_svg(&dot).map_err(|e| e.to_string())
+}
+
+fn render_svg(dot: &[u8]) -> Result<String, Box<dyn Error>> {
+    // We shell out to `dot` to render to SVG, as there does not seem to be a pure-Rust renderer.
+    let child = Command::new("dot")
+        .arg("-Tsvg")
+        .stdin(Stdio::piped())
+        .stdout(Stdio::piped())
+        .spawn()
+        .map_err(|err| format!("failed to spawn `dot -Tsvg`: {}", err))?;
+    child.stdin.unwrap().write_all(&dot)?;
+
+    let mut svg = String::new();
+    child.stdout.unwrap().read_to_string(&mut svg)?;
+    Ok(svg)
+}
+
+struct DotCrateGraph(Arc<CrateGraph>);
+
+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.0.iter().collect()
+    }
+
+    fn edges(&'a self) -> dot::Edges<'a, Edge<'a>> {
+        self.0
+            .iter()
+            .flat_map(|krate| self.0[krate].dependencies.iter().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> {
+        let name = self.0[*n].display_name.as_ref().map_or("_missing_name_", |name| &*name);
+        Id::new(name).unwrap()
+    }
+}