Add ability to cancel Intellisense engine results
Right now, if an exception occurs in the argument completer, then it immediately returns, and "falls back" to the built-in filesystem / item-based auto-completion. If an exception occurs in my custom argument completers, I'd rather be able to cancel auto-completion altogether, rather than have a bunch of useless results be thrown at the user.
Trevor Sullivan commented
If you're writing custom auto-completion / Intellisense results for your PowerShell module, and a problem occurs in the auto-completion code, then the PowerShell Engine "falls back" to providing auto-completion results from the local filesystem. Unfortunately, many PowerShell modules want to auto-complete parameters that have nothing to do with the filesystem, which makes this fallback behavior undesirable. What we're looking for, is to have some kind of mechanism that enables PowerShell module developers to catch exceptions in their custom auto-completion code, and return some kind of custom error state, or simply cancel the Intellisense Engine altogether, so it doesn't return useless results to the module's users.