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Fix PSUseDeclaredVarsMoreThanAssignments to not give false positives when using += operator #935

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Merged
merged 5 commits into from
Mar 30, 2018
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Fix PSUseDeclaredVarsMoreThanAssignments to not give false positives when using += operator #935

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c9f97de
fix false positives such as '$a=@(); $b | foreach-object { $a+=$c}' b…
bergmeister Mar 14, 2018
7daf5a4
add test (it turns out a regression happened for 'flags strongly type…
bergmeister Mar 14, 2018
bc1c007
fix regression for strongly typed variables by being more selective a…
bergmeister Mar 14, 2018
077d035
add additional test case for unassigned variable
bergmeister Mar 16, 2018
647efe7
Merge branch 'development' of https://github.com/PowerShell/PSScriptA…
bergmeister Mar 16, 2018
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14 changes: 12 additions & 2 deletions Rules/UseDeclaredVarsMoreThanAssignments.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -180,9 +180,19 @@ private IEnumerable<DiagnosticRecord> AnalyzeScriptBlockAst(ScriptBlockAst scrip
// Try casting to AssignmentStatementAst to be able to catch case where a variable is assigned more than once (https://github.com/PowerShell/PSScriptAnalyzer/issues/833)
var varInAssignmentAsStatementAst = varInAssignment.Parent as AssignmentStatementAst;
var varAstAsAssignmentStatementAst = varAst.Parent as AssignmentStatementAst;
if (varInAssignmentAsStatementAst != null && varAstAsAssignmentStatementAst != null)
if (varAstAsAssignmentStatementAst != null)
{
inAssignment = varInAssignmentAsStatementAst.Left.Extent.Text.Equals(varAstAsAssignmentStatementAst.Left.Extent.Text, StringComparison.OrdinalIgnoreCase);
if (varAstAsAssignmentStatementAst.Operator == TokenKind.Equals)
{
if (varInAssignmentAsStatementAst != null)
{
inAssignment = varInAssignmentAsStatementAst.Left.Extent.Text.Equals(varAstAsAssignmentStatementAst.Left.Extent.Text, StringComparison.OrdinalIgnoreCase);
}
else
{
inAssignment = varInAssignment.Equals(varAst);
}
}
}
else
{
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5 changes: 5 additions & 0 deletions Tests/Rules/UseDeclaredVarsMoreThanAssignments.tests.ps1
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Expand Up @@ -73,5 +73,10 @@ function MyFunc2() {
It "returns no violations" {
$noViolations.Count | Should -Be 0
}

It "Does not flag += operator" {
$results = Invoke-ScriptAnalyzer -ScriptDefinition '$array=@(); $list | ForEach-Object { $array += $c }' | Where-Object { $_.RuleName -eq $violationName }
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what about the case where $a is not initialized? Does that fall into this rule or a different one?

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@bergmeister bergmeister Mar 16, 2018 •
edited
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This is already covered because the way the algorithm works is that it first adds variable assignments to a list and then removes variables from this list when they are being used and at the end the left-over variables are basically the unused variables. In this case, += was not seen as a usage and therefore not being removed from this list. As a result, not initialising the variable does not affect the analysis because it already only looks for variable usages that are not in the list of assigned variables.
Using the += operator on an uninitialised variable might seem to be dangerous at first but it makes no problem in PowerShell at all therefore I do not think we should warn when doing that. It would only be a problem when using Set-StrictMode using version 1 or higher.
I added your test case though because it is always good to have more test cases moving forward.

$results.Count | Should -Be 0
}
}
}