SqlToolsService crashes with StackOverFlow exception

[kburtram]

• MSSQL Extension Version: 0.1.5
• VSCode Version: 1.7+
• OS Version: All

Steps to Reproduce:

1. Open SQL file with certain contents to trigger SqlParser stack overflow (I'll attach repro script once issue isolated)

Expected: Parser doesn't cause stackover flow

Workaround: Turning off diagnostics should avoid this stack overflow crash using this user setting "mssql.intelliSense.enableErrorChecking": false

[kburtram]

The issue here is if there is a lot of non-SQL content in a SQL file (such as 1000s of lines of XML or CSV) then the parser will build a long parse chain for this content. Since the content doesn't contain a terminating token the parse tree will grow very deep. The error recovery algorithm recursively descends this tree and about 10000 or 15000 levels deep the process crashes.

I think in SSMS we mitigate this using a larger stack size. I'll see if it's possible to do the same in .Net Core, otherwise, we need to add some upper limit on how deep the algorithm will traverse the tree.