Disable periadic diagnostic update on language-server on CI (#7445)

The "textDocument/publishDiagnostics" Notification in the official
Language Server Protocol, or LSP for short, is a notification that
the server sends to the client such as VSCode or Visual Studio
without the client having to ask for it. Its purpose is to provide
a list of errors, warnings, or other informational "squiggles" for
a specific file.

Because the notification is an asynchronous push notification, it
is receieved as an unexpected RPC message during the slang-test CI
tests. When a notificatoin is unexpectedly sent to slang-test, the
communication goes out-of-sync and the rest of language-server
based tests intermittently fails.

In order to address the problem, this PR adds a new command-line
argument to change the behavior of the notification and it will
be sent in a more deterministic manner where the notification can
be sent only in one of three cases: didOpen, didChange, and
didClose. Because these evets are only ways to cause a new
notification, we can still expect to get the same diagnostic
messages without missing any of them. For slang-test CI test,
this new option will be used to make the notification more
deterministic.

1 files changed, 2 insertions, 0 deletions

diff --git a/tools/slang-test/test-context.cpp b/tools/slang-test/test-context.cpp
index d1b809766..ede12d0d7 100644
--- a/tools/slang-test/test-context.cpp
+++ b/tools/slang-test/test-context.cpp
@@ -213,6 +213,8 @@ SlangResult TestContext::createLanguageServerJSONRPCConnection(RefPtr<JSONRPCCon
     {
         CommandLine cmdLine;
         cmdLine.setExecutableLocation(ExecutableLocation(exeDirectoryPath, "slangd"));
+        cmdLine.addArg("-periodic-diagnostic-update");
+        cmdLine.addArg("false");
         SLANG_RETURN_ON_FAIL(Process::create(cmdLine, Process::Flag::AttachDebugger, process));
     }