From 9c3ea82ba777924f8b78a6606504d3ca3eb00128 Mon Sep 17 00:00:00 2001
From: Remy Suen <remy.suen@docker.com>
Date: Thu, 12 Jun 2025 09:32:08 -0400
Subject: [PATCH] Check node types before casting when looking up references in
 other files

Signed-off-by: Remy Suen <remy.suen@docker.com>
---
 CHANGELOG.md                        |  2 ++
 internal/compose/definition.go      |  8 +++++---
 internal/compose/definition_test.go | 16 ++++++++++++++++
 3 files changed, 23 insertions(+), 3 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 4e64d63..87bea1c 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -18,6 +18,8 @@ All notable changes to the Docker Language Server will be documented in this fil
 - Compose
   - textDocument/completion
     - fix error case triggered by using code completion before the first node ([#314](https://github.com/docker/docker-language-server/issues/314))
+  - textDocument/definition
+    - check the type of a dependency node's value before assuming it is a map and recursing into it ([#324](https://github.com/docker/docker-language-server/issues/324))
   - textDocument/hover
     - protect the processing of included files if the node is not a proper array ([#322](https://github.com/docker/docker-language-server/issues/322))
 - Bake
diff --git a/internal/compose/definition.go b/internal/compose/definition.go
index 00e9402..03f7fb6 100644
--- a/internal/compose/definition.go
+++ b/internal/compose/definition.go
@@ -68,9 +68,11 @@ func dependencyLookup(doc document.ComposeDocument, dependencyType, name string)
 			if mappingNode, ok := doc.Body.(*ast.MappingNode); ok {
 				for _, node := range mappingNode.Values {
 					if s, ok := node.Key.(*ast.StringNode); ok && s.Value == dependencyType {
-						for _, service := range node.Value.(*ast.MappingNode).Values {
-							if s, ok := service.Key.(*ast.StringNode); ok && s.Value == name {
-								return service, u
+						if m, ok := node.Value.(*ast.MappingNode); ok {
+							for _, service := range m.Values {
+								if s, ok := service.Key.(*ast.StringNode); ok && s.Value == name {
+									return service, u
+								}
 							}
 						}
 					}
diff --git a/internal/compose/definition_test.go b/internal/compose/definition_test.go
index 85fd67c..b6cf3a5 100644
--- a/internal/compose/definition_test.go
+++ b/internal/compose/definition_test.go
@@ -443,6 +443,22 @@ services:
 				},
 			},
 		},
+		{
+			name: "dependent file is not defined properly",
+			content: `
+include:
+  - compose.other.yaml
+services:
+  test:
+    networks:
+      - other`,
+			otherContent: `
+networks: string`,
+			line:      6,
+			character: 11,
+			locations: nil,
+			links:     nil,
+		},
 	}
 
 	for _, tc := range testCases {