From 1d12a7fa7dac3c3dec660540ced0999c4c05acda Mon Sep 17 00:00:00 2001
From: Marley Powell <marley.powell@exclaimer.com>
Date: Thu, 17 Aug 2023 11:59:01 +0100
Subject: [PATCH] fix: :bug: updated `detectCircularDependency` in
 `DependencyGraph` to return circular dependencies starting from the first
 node

Signed-off-by: Marley Powell <marley.powell@exclaimer.com>
---
 .../src/lib/DependencyGraph.test.ts                | 13 ++++++++++++-
 .../backend-app-api/src/lib/DependencyGraph.ts     | 14 +++++++-------
 2 files changed, 19 insertions(+), 8 deletions(-)

diff --git a/packages/backend-app-api/src/lib/DependencyGraph.test.ts b/packages/backend-app-api/src/lib/DependencyGraph.test.ts
index 65efac0252..0ac993484b 100644
--- a/packages/backend-app-api/src/lib/DependencyGraph.test.ts
+++ b/packages/backend-app-api/src/lib/DependencyGraph.test.ts
@@ -66,6 +66,17 @@ describe('DependencyGraph', () => {
       ).toEqual(['1', '2', '1']);
     });
 
+    it('should detect a circular dep starting from the first node', async () => {
+      expect(
+        DependencyGraph.fromMap({
+          1: { provides: ['a'], consumes: ['b'] },
+          2: { provides: ['b'], consumes: ['c'] },
+          3: { provides: ['c'], consumes: ['d'] },
+          4: { provides: ['d'], consumes: ['a'] },
+        }).detectCircularDependency(),
+      ).toEqual(['1', '2', '3', '4', '1']);
+    });
+
     it('should detect a larger distant circular dep', async () => {
       expect(
         DependencyGraph.fromMap({
@@ -74,7 +85,7 @@ describe('DependencyGraph', () => {
           3: { provides: ['c'], consumes: ['b'] },
           4: { provides: ['d', 'e'], consumes: ['c', 'a'] },
         }).detectCircularDependency(),
-      ).toEqual(['2', '3', '4', '2']);
+      ).toEqual(['2', '4', '3', '2']);
     });
   });
 
diff --git a/packages/backend-app-api/src/lib/DependencyGraph.ts b/packages/backend-app-api/src/lib/DependencyGraph.ts
index 8fd679f555..3e7618a096 100644
--- a/packages/backend-app-api/src/lib/DependencyGraph.ts
+++ b/packages/backend-app-api/src/lib/DependencyGraph.ts
@@ -108,16 +108,16 @@ export class DependencyGraph<T> {
           continue;
         }
         visited.add(node);
-        for (const produced of node.provides) {
-          const consumerNodes = this.#nodes.filter(other =>
-            other.consumes.has(produced),
+        for (const consumed of node.consumes) {
+          const providerNodes = this.#nodes.filter(other =>
+            other.provides.has(consumed),
           );
-          for (const consumer of consumerNodes) {
-            if (consumer === startNode) {
+          for (const provider of providerNodes) {
+            if (provider === startNode) {
               return [...path, startNode.value];
             }
-            if (!visited.has(consumer)) {
-              stack.push([consumer, [...path, consumer.value]]);
+            if (!visited.has(provider)) {
+              stack.push([provider, [...path, provider.value]]);
             }
           }
         }