Completion within parentheses

* Enables completion when typing inside parentheses
  (e.g. in-line arguments of a function call)
* Also fixes some edge-case bugs causing the server to crash
  (e.g. initiating auto-complete on an empty line)

Author: JacksonWrath

pkg/server/completion.go

@@ -44,6 +44,18 @@ func (s *Server) Completion(_ context.Context, params *protocol.CompletionParams
 
 	vm := s.getVM(doc.Item.URI.SpanURI().Filename())
 
+	// Inside parentheses, search for completions as if the content was on a separate line
+	// e.g., this enables completion in function arguments
+	if strings.LastIndex(line, "(") > strings.LastIndex(line, ")") {
+		argsPart := line[strings.LastIndex(line, "(")+1:]
+		// Only consider the last argument for completion
+		arguments := strings.Split(argsPart, ",")
+		lastArg := arguments[len(arguments)-1]
+		lastArg = strings.TrimSpace(lastArg)
+		lastArg = strings.TrimLeft(lastArg, "{[") // Ignore leading array or object tokens
+		line = lastArg
+	}
+
 	items := s.completionFromStack(line, searchStack, vm, params.Position)
 	return &protocol.CompletionList{IsIncomplete: false, Items: items}, nil
 }
@@ -62,6 +74,7 @@ func (s *Server) completionFromStack(line string, stack *nodestack.NodeStack, vm
 	lineWords := splitWords(line)
 	lastWord := lineWords[len(lineWords)-1]
 	lastWord = strings.TrimRight(lastWord, ",;") // Ignore trailing commas and semicolons, they can present when someone is modifying an existing line
+	lastWord = strings.TrimSpace(lastWord)
 
 	indexes := strings.Split(lastWord, ".")
 
@@ -289,5 +302,9 @@ func splitWords(input string) []string {
 		words = append(words, "")
 	}
 
+	if len(words) == 0 {
+		words = append(words, "")
+	}
+
 	return words
 }

pkg/server/completion_test.go

@@ -692,6 +692,44 @@ func TestCompletion(t *testing.T) {
 				},
 			},
 		},
+		{
+			name:            "completion in function arguments",
+			filename:        "testdata/goto-functions.libsonnet",
+			replaceString:   "test: myfunc(arg1, arg2)",
+			replaceByString: "test: myfunc(arg1, self.",
+			expected: protocol.CompletionList{
+				IsIncomplete: false,
+				Items: []protocol.CompletionItem{
+					{
+						Label:      "a",
+						Kind:       protocol.FieldCompletion,
+						Detail:     "self.a",
+						InsertText: "a",
+						LabelDetails: protocol.CompletionItemLabelDetails{
+							Description: "variable",
+						},
+					},
+					{
+						Label:      "b",
+						Kind:       protocol.FieldCompletion,
+						Detail:     "self.b",
+						InsertText: "b",
+						LabelDetails: protocol.CompletionItemLabelDetails{
+							Description: "variable",
+						},
+					},
+					{
+						Label:      "c",
+						Kind:       protocol.FieldCompletion,
+						Detail:     "self.c",
+						InsertText: "c",
+						LabelDetails: protocol.CompletionItemLabelDetails{
+							Description: "string",
+						},
+					},
+				},
+			},
+		},
 	}
 	for _, tc := range testCases {
 		t.Run(tc.name, func(t *testing.T) {