LSP: Symantic highlight (`textDocument/semanticTokens/full`) returned empty right after language-server start about sdk

[bwilkerson]

@DanTup

[hauserx]

Some quick debugging shows that there are no drivers in driversMap when empty data[] is returned, but there is driver when it starts to show up:

sdk/pkg/analysis_server/lib/src/analysis_server.dart

Line 520 in 20316bc

var drivers = driverMap.values.toList();

[DanTup]

Creating the analysis roots is async, so at the time the request is being handled they probably haven't been set up yet.

Probably the fix will be something like changing this direct call to server.getResolvedUnit():

sdk/pkg/analysis_server/lib/src/lsp/handlers/handler_semantic_tokens.dart

Line 35 in 43fa0e0

var result = await server.getResolvedUnit(path);

To instead use requireResolvedUnit which wraps it, but in the case where context roots are being set up, will wait for them to complete:

sdk/pkg/analysis_server/lib/src/lsp/handlers/handlers.dart

Lines 207 to 215 in 43fa0e0

	/// Attempts to get a [ResolvedUnitResult] for [path] or an error.
	///
	/// When [waitForInProgressContextRebuilds] is `true` and the file appears to
	/// not be analyzed but analysis roots are currently being discovered, will
	/// wait for discovery to complete and then try again (once) to get a result.
	Future<ErrorOr<ResolvedUnitResult>> requireResolvedUnit(
	String path, {
	bool waitForInProgressContextRebuilds = true,
	}) async {

That method treats errors slightly differently though so it might need a little tweaking to ensure requests for semantic tokens for non-Dart files or files that legitimately aren't analyzed are handled correctly.

[hauserx]

Indeed this dirty fix helped. Thanks! (not sure how to make it better so that it can be merged, so just leaving here for now).

diff --git a/pkg/analysis_server/lib/src/lsp/handlers/handler_semantic_tokens.dart b/pkg/analysis_server/lib/src/lsp/handlers/handler_semantic_tokens.dart
index 1a0e4da212d..740df9aaea5 100644
--- a/pkg/analysis_server/lib/src/lsp/handlers/handler_semantic_tokens.dart
+++ b/pkg/analysis_server/lib/src/lsp/handlers/handler_semantic_tokens.dart
@@ -32,8 +32,11 @@ abstract class AbstractSemanticTokensHandler<T>

   Future<List<SemanticTokenInfo>> getServerResult(
       String path, SourceRange? range) async {
-    var result = await server.getResolvedUnit(path);
-    var unit = result?.unit;
+    var result = await requireResolvedUnit(path);
+    if (result.isError) {
+        return [];
+    }
+    var unit = result.resultOrNull?.unit;
     if (unit != null) {
       var computer = DartUnitHighlightsComputer(unit, range: range);
       return computer.computeSemanticTokens();