GeezerVison

At this point, the algorithm becomes O(n^2) in the number of parameters, which is undesirable.

Instead, it should be possible to do the following:

1. Create an empty case insensitive hashset of variable names
2. Collect all the variable names used in the begin, process and end blocks of the script block
3. Run through the parameters and warn for each one not found in the hashset

Rob Holt (@rjmholt) Forgive me, but I'm failing to see how that will reduce the complexity. Isn't the current code doing essentially what you've described?

It almost does, but currently:

• The variable lookup is O(n) in the number of variables. The more variables that occur in a script, the longer it will take to verify that parameter is used in that script. Worse, we must look through the whole list of variables for each parameter. With particularly large scripts, the latency of that will start to hit (visible particularly in the VSCode scenario). Instead, we should use an O(1) lookup data structure like a HashSet<string>
• Variable name comparison is currently case sensitive (done with .Where(variable => variable == parameterAst.Name.VariablePath.ToString())). Instead it should be case insensitive. This is easy to do with new HashSet<string>(StringComparer.OrdinalIgnoreCase).

Yeah, it's definitely case-sensitive at the moment. I'll take a look at implementing the hashset - I think I can come up with something. Thanks!

I would think of this as a violation. Since PowerShell has dynamic, rather than lexical, scope, Child's $Param1 reference is not guaranteed to be foo's $Param1 parameter.

I'd rather avoid violations that are going to be false positives in most cases in order to avoid similar problems to PSUseDeclaredVarsMoreThanAssignments

I think fair enough we want to not emit when at the boundary of our heuristic. Ideally we'd change this to an actual false case, but it's not that important.

Rob Holt (@rjmholt) Your recently added complex.psm1 test actually caught an edge case that happened when I first added StringComparer.OrdinalIgnoreCase only on .ToDictionary, which caused items of different cases (due to groupby originally being case sensitive) to to be added to the case insensitive dictionary, which then gave the error that the same item had already been added. Therefore I had to add it to GroupBy as well. Chapeau 👏

Makes me think that PowerShell and other PowerShell tools should have a few real-world test cases too