gracefully handle cycles in crate graph

rust-lang/rust has absolutely weird setup with rustc-workspace-shim,
which leads to real cycles.

1 files changed, 21 insertions, 4 deletions

diff --git a/crates/ra_lsp_server/src/server_world.rs b/crates/ra_lsp_server/src/server_world.rs
index 4f3c231d3..d5dbf999f 100644
--- a/crates/ra_lsp_server/src/server_world.rs
+++ b/crates/ra_lsp_server/src/server_world.rs
@@ -73,7 +73,9 @@ impl ServerWorldState {
                     if let (Some(&from), Some(&to)) =
                         (sysroot_crates.get(&from), sysroot_crates.get(&to))
                     {
-                        crate_graph.add_dep(from, name.clone(), to);
+                        if let Err(_) = crate_graph.add_dep(from, name.clone(), to) {
+                            log::error!("cyclic dependency between sysroot crates")
+                        }
                     }
                 }
             }
@@ -108,11 +110,20 @@ impl ServerWorldState {
                 for &from in pkg_crates.get(&pkg).into_iter().flatten() {
                     if let Some(to) = lib_tgt {
                         if to != from {
-                            crate_graph.add_dep(from, pkg.name(&ws.cargo).into(), to);
+                            if let Err(_) =
+                                crate_graph.add_dep(from, pkg.name(&ws.cargo).into(), to)
+                            {
+                                log::error!(
+                                    "cyclic dependency between targets of {}",
+                                    pkg.name(&ws.cargo)
+                                )
+                            }
                         }
                     }
                     if let Some(std) = libstd {
-                        crate_graph.add_dep(from, "std".into(), std);
+                        if let Err(_) = crate_graph.add_dep(from, "std".into(), std) {
+                            log::error!("cyclic dependency on std for {}", pkg.name(&ws.cargo))
+                        }
                     }
                 }
             }
@@ -123,7 +134,13 @@ impl ServerWorldState {
                 for dep in pkg.dependencies(&ws.cargo) {
                     if let Some(&to) = pkg_to_lib_crate.get(&dep.pkg) {
                         for &from in pkg_crates.get(&pkg).into_iter().flatten() {
-                            crate_graph.add_dep(from, dep.name.clone(), to);
+                            if let Err(_) = crate_graph.add_dep(from, dep.name.clone(), to) {
+                                log::error!(
+                                    "cyclic dependency {} -> {}",
+                                    pkg.name(&ws.cargo),
+                                    dep.pkg.name(&ws.cargo)
+                                )
+                            }
                         }
                     }
                 }