Add underscore as a completion trigger character

This allows editors to request completions easier when a end-user
inputs "_" inside a resource type label for example,
(e.g `resource "aws_`)

This improves the completion experience along with
opentofu/hcl-lang#2 to allow users to get
improved completion when writing resources

Signed-off-by: James Humphries <james@james-humphries.co.uk>

Author: Yantrio

internal/langserver/handlers/handlers_test.go

@@ -41,7 +41,7 @@ func initializeResponse(t *testing.T, commandPrefix string) string {
 					"save": {}
 				},
 				"completionProvider": {
-					"triggerCharacters": [".", "["],
+					"triggerCharacters": [".", "[", "_"],
 					"resolveProvider": true
 				},
 				"hoverProvider": true,

internal/langserver/handlers/initialize.go

@@ -177,7 +177,7 @@ func initializeResult(ctx context.Context) lsp.InitializeResult {
 			},
 			CompletionProvider: lsp.CompletionOptions{
 				ResolveProvider:   true,
-				TriggerCharacters: []string{".", "["},
+				TriggerCharacters: []string{".", "[", "_"},
 			},
 			CodeActionProvider: lsp.CodeActionOptions{
 				CodeActionKinds: ilsp.SupportedCodeActions.AsSlice(),