Revert the PR #17856 (Do not preserve temporary results when no need to do so) by daxian-dbw · Pull Request #21368 · PowerShell/PowerShell

Dongbo Wang (daxian-dbw) · 2024-03-24T16:26:58Z

PR Summary

Fix #20739 by reverting the PR that caused this regression: #17856

#17856 causes the return value from a ReturnStatement to not be preserved too, which breaks an expected behavior.

This is the difference compared with the same code section from v7.3. After this change, the only difference is the updated comments.

Here is the relevant code section in v7.3:

PowerShell/src/System.Management.Automation/engine/parser/Compiler.cs

Lines 2278 to 2310 in d68aa89

    
           switch (context) 
        
           { 
        
               case CaptureAstContext.AssignmentWithResultPreservation: 
        
               case CaptureAstContext.AssignmentWithoutResultPreservation: 
        
                   result = Expression.Call(CachedReflectionInfo.PipelineOps_PipelineResult, resultList); 
        
                   // Clear the temporary pipe in case of exception, if we are not required to preserve the results 
        
                   if (context == CaptureAstContext.AssignmentWithoutResultPreservation) 
        
                   { 
        
                       var catchExprs = new List<Expression> 
        
                                        { 
        
                                            Expression.Call(CachedReflectionInfo.PipelineOps_ClearPipe, resultList), 
        
                                            Expression.Rethrow(), 
        
                                            Expression.Constant(null, typeof(object)) 
        
                                        }; 
        
                       catches.Add(Expression.Catch(typeof(RuntimeException), Expression.Block(typeof(object), catchExprs))); 
        
                   } 
        
                   // PipelineResult might get skipped in some circumstances due to a FlowControlException thrown out, in which case 
        
                   // we write to the oldPipe. This can happen in cases like: 
        
                   //     $(1;2;return 3) 
        
                   finallyExprs.Add(Expression.Call(CachedReflectionInfo.PipelineOps_FlushPipe, oldPipe, resultList)); 
        
                   break; 
        
               case CaptureAstContext.Condition: 
        
                   result = DynamicExpression.Dynamic(PSPipelineResultToBoolBinder.Get(), typeof(bool), resultList); 
        
                   break; 
        
               case CaptureAstContext.Enumerable: 
        
                   result = resultList; 
        
                   break; 
        
               default: 
        
                   throw new ArgumentOutOfRangeException(nameof(context)); 
        
           }

PR Checklist

…n no need to do so)

pull-request-quantifier-deprecated · 2024-03-24T16:27:04Z

This PR has 28 quantified lines of changes. In general, a change size of upto 200 lines is ideal for the best PR experience!

Quantification details

Label      : Extra Small
Size       : +7 -21
Percentile : 11.2%

Total files changed: 2

Change summary by file extension:
.cs : +7 -8
.ps1 : +0 -13

Change counts above are quantified counts, based on the PullRequestQuantifier customizations.

Why proper sizing of changes matters

Optimal pull request sizes drive a better predictable PR flow as they strike a
balance between between PR complexity and PR review overhead. PRs within the
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Fast and predictable releases to production:
- Optimal size changes are more likely to be reviewed faster with fewer
  iterations.
- Similarity in low PR complexity drives similar review times.
Review quality is likely higher as complexity is lower:
- Bugs are more likely to be detected.
- Code inconsistencies are more likely to be detected.
Knowledge sharing is improved within the participants:
- Small portions can be assimilated better.
Better engineering practices are exercised:
- Solving big problems by dividing them in well contained, smaller problems.
- Exercising separation of concerns within the code changes.

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How to interpret the change counts in git diff output

One line was added: +1 -0
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James Truher (JamesWTruher) · 2024-03-25T16:50:23Z

not only should we do the revert, but we need to improve validation so we don't get caught by this again. I quickly saw the added validation, but couldn't see how we didn't catch this.

pull-request-quantifier-deprecated · 2024-03-25T17:55:39Z

This PR has 42 quantified lines of changes. In general, a change size of upto 200 lines is ideal for the best PR experience!

Quantification details

Label      : Extra Small
Size       : +21 -21
Percentile : 16.8%

Total files changed: 2

Change summary by file extension:
.cs : +7 -8
.ps1 : +14 -13

Change counts above are quantified counts, based on the PullRequestQuantifier customizations.

Why proper sizing of changes matters

Optimal pull request sizes drive a better predictable PR flow as they strike a
balance between between PR complexity and PR review overhead. PRs within the
optimal size (typical small, or medium sized PRs) mean:

Fast and predictable releases to production:
- Optimal size changes are more likely to be reviewed faster with fewer
  iterations.
- Similarity in low PR complexity drives similar review times.
Review quality is likely higher as complexity is lower:
- Bugs are more likely to be detected.
- Code inconsistencies are more likely to be detected.
Knowledge sharing is improved within the participants:
- Small portions can be assimilated better.
Better engineering practices are exercised:
- Solving big problems by dividing them in well contained, smaller problems.
- Exercising separation of concerns within the code changes.

What can I do to optimize my changes

Use the PullRequestQuantifier to quantify your PR accurately
- Create a context profile for your repo using the context generator
- Exclude files that are not necessary to be reviewed or do not increase the review complexity. Example: Autogenerated code, docs, project IDE setting files, binaries, etc. Check out the Excluded section from your prquantifier.yaml context profile.
- Understand your typical change complexity, drive towards the desired complexity by adjusting the label mapping in your prquantifier.yaml context profile.
- Only use the labels that matter to you, see context specification to customize your prquantifier.yaml context profile.
Change your engineering behaviors
- For PRs that fall outside of the desired spectrum, review the details and check if:
  - Your PR could be split in smaller, self-contained PRs instead
  - Your PR only solves one particular issue. (For example, don't refactor and code new features in the same PR).

How to interpret the change counts in git diff output

One line was added: +1 -0
One line was deleted: +0 -1
One line was modified: +1 -1 (git diff doesn't know about modified, it will
interpret that line like one addition plus one deletion)
Change percentiles: Change characteristics (addition, deletion, modification)
of this PR in relation to all other PRs within the repository.

Was this comment helpful? 👍 :ok_hand: :thumbsdown: (Email)
Customize PullRequestQuantifier for this repository.

James Truher (JamesWTruher) · 2024-03-25T19:47:55Z

+    It 'Return statement on the right side of an assignment should write the retrun value to outer pipe' {
+        function TestFunc1 {
+            ## The return value are not assigned to the variable but should be written to the outer pipe.
+            $Global:mylhsvar = if ($true) { return "one" }


It might be worth adding a few more tests here as using return changes the behavior significantly

James Truher (JamesWTruher)

we should add more validation eventually

…n no need to do so) (PowerShell#21368)

…lts when no need to do so) (#21368) (#21425)

…n no need to do so) (PowerShell#21368)

Revert the PR PowerShell#17856 (Do not preserve temporary results whe…

dcbd75b

…n no need to do so)

pull-request-quantifier-deprecated Bot added the Extra Small label Mar 24, 2024

Dongbo Wang (daxian-dbw) added Backport-7.4.x-Consider CL-Engine Indicates that a PR should be marked as an engine change in the Change Log labels Mar 24, 2024

Dongbo Wang (daxian-dbw) mentioned this pull request Mar 24, 2024

If a block inside a function contains return, all output is written to the pipeline, even if assigned to a variable #17836

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Dongbo Wang (daxian-dbw) requested review from James Truher (JamesWTruher), Patrick Meinecke (SeeminglyScience) and Steve Lee (SteveL-MSFT) March 24, 2024 16:41

Dongbo Wang (daxian-dbw) self-assigned this Mar 24, 2024

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Dongbo Wang (daxian-dbw) closed this Mar 25, 2024

Dongbo Wang (daxian-dbw) reopened this Mar 25, 2024

James Truher (JamesWTruher) approved these changes Mar 25, 2024

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Add a validation test

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Fix typo

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James Truher (JamesWTruher) reviewed Mar 25, 2024

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James Truher (JamesWTruher) approved these changes Mar 25, 2024

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Dongbo Wang (daxian-dbw) merged commit 171d9df into PowerShell:master Mar 25, 2024

Dongbo Wang (daxian-dbw) deleted the regression branch March 25, 2024 21:09

Dongbo Wang (daxian-dbw) added Backport-7.4.x-Approved and removed Backport-7.4.x-Consider labels Mar 25, 2024

Patrick Meinecke (SeeminglyScience) pushed a commit to SeeminglyScience/PowerShell that referenced this pull request Apr 4, 2024

Revert the PR PowerShell#17856 (Do not preserve temporary results whe…

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…n no need to do so) (PowerShell#21368)

Patrick Meinecke (SeeminglyScience) mentioned this pull request Apr 4, 2024

[release/v7.4.2] Revert the PR #17856 (Do not preserve temporary results when no need to do so) #21425

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Dongbo Wang (daxian-dbw) pushed a commit that referenced this pull request Apr 4, 2024

[release/v7.4.2] Revert the PR #17856 (Do not preserve temporary resu…

3dd4451

…lts when no need to do so) (#21368) (#21425)

Patrick Meinecke (SeeminglyScience) added Backport-7.4.x-Done and removed Backport-7.4.x-Approved labels Apr 5, 2024

Chris Dent (chrisdent-de) pushed a commit to chrisdent-de/PowerShell that referenced this pull request Sep 12, 2024

Revert the PR PowerShell#17856 (Do not preserve temporary results whe…

4a5f772

…n no need to do so) (PowerShell#21368)

Justin Chung (jshigetomi) mentioned this pull request Jan 21, 2025

Fix backport issues with release pipeline #24835

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Thatgfsj (Thatgfsj) pushed a commit to Thatgfsj-contribs/PowerShell that referenced this pull request Aug 6, 2026

Revert the PR PowerShell#17856 (Do not preserve temporary results whe…

14336d2

…n no need to do so) (PowerShell#21368)

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Revert the PR #17856 (Do not preserve temporary results when no need to do so) - #21368

Revert the PR #17856 (Do not preserve temporary results when no need to do so)#21368
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Dongbo Wang (daxian-dbw) commented Mar 24, 2024 •

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	switch (context)
	{
	case CaptureAstContext.AssignmentWithResultPreservation:
	case CaptureAstContext.AssignmentWithoutResultPreservation:
	result = Expression.Call(CachedReflectionInfo.PipelineOps_PipelineResult, resultList);

	// Clear the temporary pipe in case of exception, if we are not required to preserve the results
	if (context == CaptureAstContext.AssignmentWithoutResultPreservation)
	{
	var catchExprs = new List<Expression>
	{
	Expression.Call(CachedReflectionInfo.PipelineOps_ClearPipe, resultList),
	Expression.Rethrow(),
	Expression.Constant(null, typeof(object))
	};

	catches.Add(Expression.Catch(typeof(RuntimeException), Expression.Block(typeof(object), catchExprs)));
	}

	// PipelineResult might get skipped in some circumstances due to a FlowControlException thrown out, in which case
	// we write to the oldPipe. This can happen in cases like:
	// $(1;2;return 3)
	finallyExprs.Add(Expression.Call(CachedReflectionInfo.PipelineOps_FlushPipe, oldPipe, resultList));
	break;
	case CaptureAstContext.Condition:
	result = DynamicExpression.Dynamic(PSPipelineResultToBoolBinder.Get(), typeof(bool), resultList);
	break;
	case CaptureAstContext.Enumerable:
	result = resultList;
	break;
	default:
	throw new ArgumentOutOfRangeException(nameof(context));
	}

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Dongbo Wang (daxian-dbw) commented Mar 24, 2024 •

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