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Fix for #7128 Methods with return type [object] should return null for an empty result #7138

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Merged
daxian-dbw merged 2 commits into from
Jul 2, 2018
Merged

Fix for #7128 Methods with return type [object] should return null for an empty result #7138

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cde81d7
Fix for #7128 Methods with return type [object] should return null fo…
Jun 21, 2018
a1fb00a
added a comment and fixed a codeflow issue
Jun 22, 2018
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13 changes: 12 additions & 1 deletion src/System.Management.Automation/engine/lang/scriptblock.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -519,7 +519,18 @@ internal T InvokeAsMemberFunctionT<T>(object instance, object[] args)
invocationInfo: null,
propagateAllExceptionsToTop: true,
args: args);
Diagnostics.Assert(result.Count == 1, "Code generation ensures we return the correct type");

// This is needed only for the case where the
// method returns [object]. If the argument to 'return'
// is a pipeline that emits nothing then result.Count will
// be zero so we catch that and "convert" it to null. Note that
// the return statement is still required in the method, it
// just recieves nothing from it's argument.
if (result.Count == 0)
{
return default(T);
}

return (T)result[0];
}

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10 changes: 10 additions & 0 deletions test/powershell/Language/Classes/Scripting.Classes.BasicParsing.Tests.ps1
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Expand Up @@ -116,6 +116,16 @@ Describe 'Positive Parse Properties Tests' -Tags "CI" {
class C9b { [System.Collections.Generic.List[C9b]] f() { return [C9b]::new() } }
$c9b = [C9b]::new().f()
It "Expected a System.Collections.Generic.List[C9b] returned" { $c9b -is [System.Collections.Generic.List[C9b]] | Should -BeTrue }
It 'Methods returning object should return $null if no output was produced' {
class Foo {
[object] Bar1() { return & {} }
static [object] Bar2() { return & {} }
}
# Test instance method
[Foo]::new().Bar1() | Should -BeNullOrEmpty
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@iSazonov iSazonov Jun 22, 2018

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We could explicitly check result type. I believe it make sense to use testcase for two return types (object and int/string) to ensure that default(T) works as expected.

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@BrucePay BrucePay Jun 22, 2018

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The only time this code path is hit is if the method returns [object]. All of the other cases are already handled elsewhere. And the object returned is null. How do you propose checking it's type?

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@iSazonov iSazonov Jun 23, 2018 •
edited
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Sorry, it was my misunderstanding of default(T).

Should it be Should -BeNull?

# Test static method
[foo]::Bar2() | Should -BeNullOrEmpty
}
}

It 'Positive ParseProperty Attributes Test' {
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