Fix code completion panic in an empty Compose file

CHANGELOG.md

@@ -23,6 +23,9 @@ All notable changes to the Docker Language Server will be documented in this fil
 
 ### Fixed
 
+- Compose
+  - textDocument/completion
+    - fix panic in code completion in an empty file ([#196](https://github.com/docker/docker-language-server/issues/196))
 - Bake
   - textDocument/publishDiagnostics
     - stop flagging `BUILDKIT_SYNTAX` as an unrecognized `ARG` ([#187](https://github.com/docker/docker-language-server/issues/187))

internal/compose/completion.go

@@ -108,42 +108,58 @@ func array(line string, character int) bool {
 	return isArray
 }
 
+func createTopLevelItems() []protocol.CompletionItem {
+	items := []protocol.CompletionItem{}
+	for attributeName, schema := range schemaProperties() {
+		item := protocol.CompletionItem{Label: attributeName}
+		if schema.Description != "" {
+			item.Documentation = schema.Description
+		}
+		items = append(items, item)
+	}
+	slices.SortFunc(items, func(a, b protocol.CompletionItem) int {
+		return strings.Compare(a.Label, b.Label)
+	})
+	return items
+}
+
+func calculateTopLevelNodeOffset(file *ast.File) int {
+	if len(file.Docs) == 1 {
+		if m, ok := file.Docs[0].Body.(*ast.MappingNode); ok {
+			return m.Values[0].Key.GetToken().Position.Column - 1
+		}
+	}
+	return -1
+}
+
 func Completion(ctx context.Context, params *protocol.CompletionParams, manager *document.Manager, doc document.ComposeDocument) (*protocol.CompletionList, error) {
 	u, err := url.Parse(params.TextDocument.URI)
 	if err != nil {
 		return nil, fmt.Errorf("LSP client sent invalid URI: %v", params.TextDocument.URI)
 	}
 
-	if params.Position.Character == 0 {
-		items := []protocol.CompletionItem{}
-		for attributeName, schema := range schemaProperties() {
-			item := protocol.CompletionItem{Label: attributeName}
-			if schema.Description != "" {
-				item.Documentation = schema.Description
-			}
-			items = append(items, item)
-		}
-		slices.SortFunc(items, func(a, b protocol.CompletionItem) int {
-			return strings.Compare(a.Label, b.Label)
-		})
-		return &protocol.CompletionList{Items: items}, nil
+	file := doc.File()
+	if file == nil || len(file.Docs) == 0 {
+		return nil, nil
 	}
 
-	lines := strings.Split(string(doc.Input()), "\n")
 	lspLine := int(params.Position.Line)
-	if strings.HasPrefix(strings.TrimSpace(lines[lspLine]), "#") {
-		return nil, nil
+	topLevelNodeOffset := calculateTopLevelNodeOffset(file)
+	if topLevelNodeOffset != -1 && params.Position.Character == uint32(topLevelNodeOffset) {
+		return &protocol.CompletionList{Items: createTopLevelItems()}, nil
 	}
 
-	file := doc.File()
-	if file == nil || len(file.Docs) == 0 {
+	lines := strings.Split(string(doc.Input()), "\n")
+	if strings.HasPrefix(strings.TrimSpace(lines[lspLine]), "#") {
 		return nil, nil
 	}
 
 	line := int(lspLine) + 1
 	character := int(params.Position.Character) + 1
 	path := constructCompletionNodePath(file, line)
-	if len(path) == 1 {
+	if len(path) == 0 {
+		return &protocol.CompletionList{Items: createTopLevelItems()}, nil
+	} else if len(path) == 1 {
 		return nil, nil
 	} else if path[1].Key.GetToken().Position.Column >= character {
 		return nil, nil
@@ -452,9 +468,19 @@ func namedDependencyCompletionItems(file *ast.File, path []*ast.MappingValueNode
 }
 
 func constructCompletionNodePath(file *ast.File, line int) []*ast.MappingValueNode {
-	for _, documentNode := range file.Docs {
-		if mappingNode, ok := documentNode.Body.(*ast.MappingNode); ok {
-			return NodeStructure(line, mappingNode.Values)
+	for i := range len(file.Docs) {
+		if i+1 == len(file.Docs) {
+			if mappingNode, ok := file.Docs[i].Body.(*ast.MappingNode); ok {
+				return NodeStructure(line, mappingNode.Values)
+			}
+		}
+
+		if m, ok := file.Docs[i].Body.(*ast.MappingNode); ok {
+			if n, ok := file.Docs[i+1].Body.(*ast.MappingNode); ok {
+				if m.Values[0].Key.GetToken().Position.Line <= line && line <= n.Values[0].Key.GetToken().Position.Line {
+					return NodeStructure(line, m.Values)
+				}
+			}
 		}
 	}
 	return nil

internal/compose/completion_test.go

@@ -15,6 +15,41 @@ import (
 	"go.lsp.dev/uri"
 )
 
+var topLevelNodes = []protocol.CompletionItem{
+	{
+		Label:         "configs",
+		Documentation: "Configurations that are shared among multiple services.",
+	},
+	{
+		Label:         "include",
+		Documentation: "compose sub-projects to be included.",
+	},
+	{
+		Label:         "name",
+		Documentation: "define the Compose project name, until user defines one explicitly.",
+	},
+	{
+		Label:         "networks",
+		Documentation: "Networks that are shared among multiple services.",
+	},
+	{
+		Label:         "secrets",
+		Documentation: "Secrets that are shared among multiple services.",
+	},
+	{
+		Label:         "services",
+		Documentation: "The services that will be used by your application.",
+	},
+	{
+		Label:         "version",
+		Documentation: "declared for backward compatibility, ignored. Please remove it.",
+	},
+	{
+		Label:         "volumes",
+		Documentation: "Named volumes that are shared among multiple services.",
+	},
+}
+
 func serviceProperties(line, character, prefixLength protocol.UInteger) []protocol.CompletionItem {
 	return []protocol.CompletionItem{
 		{
@@ -934,40 +969,90 @@ configs:
 			line:      3,
 			character: 0,
 			list: &protocol.CompletionList{
-				Items: []protocol.CompletionItem{
-					{
-						Label:         "configs",
-						Documentation: "Configurations that are shared among multiple services.",
-					},
-					{
-						Label:         "include",
-						Documentation: "compose sub-projects to be included.",
-					},
-					{
-						Label:         "name",
-						Documentation: "define the Compose project name, until user defines one explicitly.",
-					},
-					{
-						Label:         "networks",
-						Documentation: "Networks that are shared among multiple services.",
-					},
-					{
-						Label:         "secrets",
-						Documentation: "Secrets that are shared among multiple services.",
-					},
-					{
-						Label:         "services",
-						Documentation: "The services that will be used by your application.",
-					},
-					{
-						Label:         "version",
-						Documentation: "declared for backward compatibility, ignored. Please remove it.",
-					},
-					{
-						Label:         "volumes",
-						Documentation: "Named volumes that are shared among multiple services.",
-					},
-				},
+				Items: topLevelNodes,
+			},
+		},
+		{
+			name:      "top level node suggestions with a space in the front",
+			content:   ` `,
+			line:      0,
+			character: 1,
+			list: &protocol.CompletionList{
+				Items: topLevelNodes,
+			},
+		},
+		{
+			name: "top level node suggestions with indented content but code completion is unindented",
+			content: `
+ configs:
+   test:
+`,
+			line:      3,
+			character: 0,
+			list:      nil,
+		},
+		{
+			name: "top level node suggestions with indented content and code completion is aligned correctly",
+			content: `
+ configs:
+   test:
+ `,
+			line:      3,
+			character: 1,
+			list: &protocol.CompletionList{
+				Items: topLevelNodes,
+			},
+		},
+		{
+			name: "alignment correct with multiple documents",
+			content: `
+---
+---
+ configs:
+   test:
+ `,
+			line:      5,
+			character: 1,
+			list: &protocol.CompletionList{
+				Items: topLevelNodes,
+			},
+		},
+		{
+			name: "alignment incorrect with multiple documents",
+			content: `
+---
+configs:
+  test:
+---
+ configs:
+   test2:
+`,
+			line:      7,
+			character: 0,
+			list:      nil,
+		},
+		{
+			name: "top level node suggestions with indented content and code completion is aligned correctly but in a comment",
+			content: `
+ configs:
+   test:
+#`,
+			line:      3,
+			character: 1,
+			list:      nil,
+		},
+		{
+			name: "top level node suggestions with multiple files",
+			content: `
+---
+ configs:
+   test:
+---
+`,
+			line:      5,
+			character: 0,
+			list: &protocol.CompletionList{
+				Items: topLevelNodes,
 			},
 		},
 		{