From 628f6e7dcc0c15c1afc4c0b7b1d27210725d90ad Mon Sep 17 00:00:00 2001
From: Ikey Doherty <ikey@serpentos.com>
Date: Thu, 28 Sep 2023 00:41:14 +0100
Subject: [PATCH] moss/registry/transaction: Avoid adding cyclical deps

This fixes the majority of *acceptable* cyclical dependencies
and allows installation to proceed!

Signed-off-by: Ikey Doherty <ikey@serpentos.com>
---
 dag/src/lib.rs                   |  1 +
 moss/src/registry/transaction.rs | 16 +++++++++++++---
 2 files changed, 14 insertions(+), 3 deletions(-)

diff --git a/dag/src/lib.rs b/dag/src/lib.rs
index 80fa653d..fd43480e 100644
--- a/dag/src/lib.rs
+++ b/dag/src/lib.rs
@@ -9,4 +9,5 @@ pub use self::reexport::*;
 pub mod reexport {
     pub use petgraph::algo::{toposort, Cycle};
     pub use petgraph::graph::DiGraph;
+    pub use petgraph::visit::Dfs;
 }
diff --git a/moss/src/registry/transaction.rs b/moss/src/registry/transaction.rs
index 138c356c..eed2c1a0 100644
--- a/moss/src/registry/transaction.rs
+++ b/moss/src/registry/transaction.rs
@@ -4,7 +4,7 @@
 
 use std::collections::HashSet;
 
-use dag::{toposort, DiGraph};
+use dag::{toposort, Dfs, DiGraph};
 use futures::{StreamExt, TryFutureExt};
 use itertools::Itertools;
 use serde::{Deserialize, Serialize};
@@ -116,8 +116,18 @@ impl<'a> Transaction<'a> {
                         next.push(search.clone());
                     }
 
-                    // Connect w/ edges
-                    graph.add_edge(check_node, dep_node, 1);
+                    // Connect w/ edges if non cyclical
+                    let mut dfs = Dfs::new(&graph, dep_node);
+                    let mut add_edge = true;
+                    while let Some(item) = dfs.next(&graph) {
+                        if item == dep_node {
+                            add_edge = false;
+                            break;
+                        }
+                    }
+                    if graph.find_edge_undirected(check_node, dep_node).is_none() && add_edge {
+                        graph.add_edge(check_node, dep_node, 1);
+                    }
                 }
             }
             items = next;