Fix line breakpoints for `return` statements without a value #17179

SeeminglyScience · Apr 22, 2022

PR Summary

Adds an explicit call to UpdatePosition when a return statement does not include a pipeline.

Codegen before change:

// Generated with:
// { return } | Get-ScriptBlockDisassembly -IgnoreStartupAndTeardown
// ScriptBlock.EndBlock
funcContext._currentSequencePointIndex = 0;
try
{
    return ;
}
catch (FlowControlException)
{
    throw;
}
catch (Exception exception)
{
    ExceptionHandlingOps.CheckActionPreference(funcContext, exception);
}
funcContext._currentSequencePointIndex = 1;

if (context._debuggingMode > 0)
{
    context._debugger.OnSequencePointHit(funcContext);
}

Codegen after change:

// Generated with:
// { return } | Get-ScriptBlockDisassembly -IgnoreStartupAndTeardown
// ScriptBlock.EndBlock
funcContext._currentSequencePointIndex = 0;
try
{
    funcContext._currentSequencePointIndex = 1;

    if (context._debuggingMode > 0)
    {
        context._debugger.OnSequencePointHit(funcContext);
    }
    return ;
}
catch (FlowControlException)
{
    throw;
}
catch (Exception exception)
{
    ExceptionHandlingOps.CheckActionPreference(funcContext, exception);
}
funcContext._currentSequencePointIndex = 2;

if (context._debuggingMode > 0)
{
    context._debugger.OnSequencePointHit(funcContext);
}

Trap compilation (click to expand)

Turns out there wasn't an easy way to view disassembly of a trap with ScriptBlockDisassembler. So that took a minute to figure out how to do easily:

Code to generate (click to expand)

#requires -Modules ImpliedReflection, ScriptBlockDisassembler

Enable-ImpliedReflection -YesIKnowIShouldNotDoThis

$sb = {
    trap { return }
    throw
}

$trap = $sb.Ast.EndBlock.Traps[0]
$main = [System.Management.Automation.Language.Compiler]::new()
$main.Compile($sb.ScriptBlockData, $true)
$secondary = [System.Management.Automation.Language.Compiler]::new(
    $main._sequencePoints,
    $main._sequencePointIndexMap)

$secondary._compilingTrap = $true
$funcName = $main._currentFunctionName + '<trap>'
if ($null -ne $trap.TrapType) {
    $funcName += '<' + $trap.TrapType.TypeName.Name + '>'
}

$tuple = [Management.Automation.Language.VariableAnalysis]::AnalyzeTrap($trap)
$secondary.LocalVariablesTupleType = $tuple.Item1
$secondary.LocalVariablesParameter = [Linq.Expressions.Expression]::Variable(
    $secondary.LocalVariablesTupleType,
    'locals')

$lambda = $secondary.CompileSingleLambda(
    $trap.Body.Statements,
    $trap.Body.Traps,
    $funcName,
    <# entryExtent: #> $null,
    <# exitExtent: #> $null,
    <# rootForDefiningTypesAndUsings: #> $null)

$lambda | Format-ExpressionTree | bat -l cs

Codegen before:

(FunctionContext funcContext) =>
{
    try
    {
        ExecutionContext context = funcContext._executionContext;
        MutableTuple<object, object[], object, object, PSScriptCmdlet, PSBoundParametersDictionary, InvocationInfo, string, string, LanguagePrimitives.Null, LanguagePrimitives.Null, LanguagePrimitives.Null, LanguagePrimitives.Null, LanguagePrimitives.Null, LanguagePrimitives.Null, LanguagePrimitives.Null> locals = (MutableTuple<object, object[], object, object, PSScriptCmdlet, PSBoundParametersDictionary, InvocationInfo, string, string, LanguagePrimitives.Null, LanguagePrimitives.Null, LanguagePrimitives.Null, LanguagePrimitives.Null, LanguagePrimitives.Null, LanguagePrimitives.Null, LanguagePrimitives.Null>)funcContext._localsTuple;
        funcContext._functionName = "<ScriptBlock><trap>";
        context._debugger.EnterScriptFunction(funcContext);
        try
        {
            throw new ReturnException(AutomationNull.Value);
        }
        catch (FlowControlException)
        {
            throw;
        }
        catch (Exception exception)
        {
            ExceptionHandlingOps.CheckActionPreference(funcContext, exception);
        }
    }
    finally
    {
        context._debugger.ExitScriptFunction();
    }
}

Codegen after:

(FunctionContext funcContext) =>
{
    try
    {
        ExecutionContext context = funcContext._executionContext;
        MutableTuple<object, object[], object, object, PSScriptCmdlet, PSBoundParametersDictionary, InvocationInfo, string, string, LanguagePrimitives.Null, LanguagePrimitives.Null, LanguagePrimitives.Null, LanguagePrimitives.Null, LanguagePrimitives.Null, LanguagePrimitives.Null, LanguagePrimitives.Null> locals = (MutableTuple<object, object[], object, object, PSScriptCmdlet, PSBoundParametersDictionary, InvocationInfo, string, string, LanguagePrimitives.Null, LanguagePrimitives.Null, LanguagePrimitives.Null, LanguagePrimitives.Null, LanguagePrimitives.Null, LanguagePrimitives.Null, LanguagePrimitives.Null>)funcContext._localsTuple;
        funcContext._functionName = "<ScriptBlock><trap>";
        context._debugger.EnterScriptFunction(funcContext);
        try
        {
            funcContext._currentSequencePointIndex = 1;

            if (context._debuggingMode > 0)
            {
                context._debugger.OnSequencePointHit(funcContext);
            }
            throw new ReturnException(AutomationNull.Value);
        }
        catch (FlowControlException)
        {
            throw;
        }
        catch (Exception exception)
        {
            ExceptionHandlingOps.CheckActionPreference(funcContext, exception);
        }
    }
    finally
    {
        context._debugger.ExitScriptFunction();
    }
}

PR Context

PR Checklist

Fixes PowerShell#17081 Adds an explicit call to UpdatePosition when a return statement does not include a pipeline.

daxian-dbw

LGTM with a comment

daxian-dbw · Apr 28, 2022

test/powershell/Language/Scripting/Debugging/Debugging.Tests.ps1

+'@
+            $return_script_2 = @'
+return 10
+'@


Can you please add one more test case to cover return statement in a trap block?

Done! Also added disassembly for traps in the description.

Probably should have waited for the tests to pass before saying that. Looking into the failure

Okay it really does hit twice. Apparently when a trap is present that hits a breakpoint when it's registered. So even with this:

'something' trap { 'something else' return 'testing' } throw

If you put a breakpoint on every line and run it, line 4 hits a breakpoint first, then line 1, then 8, then 5. That seems like a bug but for another time. I've added another line before the return in the trap test so that doesn't interfere with the result.

Thanks for the additional fix. Will take a look today.

pull-request-quantifier-deprecated · Apr 29, 2022

This PR has 35 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       : +34 -1
Percentile : 14%

Total files changed: 2

Change summary by file extension:
.cs : +3 -1
.ps1 : +31 -0

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One line was added: +1 -0
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ghost · May 23, 2022

🎉v7.3.0-preview.4 has been released which incorporates this pull request.:tada:

Handy links:

Release Notes

Ensure UpdatePosition is called for return

5fb41db

Fixes PowerShell#17081 Adds an explicit call to UpdatePosition when a return statement does not include a pipeline.

SeeminglyScience requested a review from daxian-dbw as a code owner April 22, 2022 19:11

pull-request-quantifier-deprecated bot added the Extra Small label Apr 22, 2022

ghost assigned TravisEz13 Apr 22, 2022

Fix return statement test variable names

4941794

daxian-dbw reviewed Apr 28, 2022

View reviewed changes

SeeminglyScience added 2 commits April 29, 2022 11:56

Add test for return in a trap

7b40bb2

Fix trap return bp test

65d6cf6

daxian-dbw approved these changes May 4, 2022

View reviewed changes

daxian-dbw merged commit 99f3bb7 into PowerShell:master May 4, 2022

SeeminglyScience deleted the SeeminglyScience/issue17081 branch May 4, 2022 20:54

ghost mentioned this pull request May 23, 2022

Breakpoint set on return doesn't work properly #17081

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Fix line breakpoints for `return` statements without a value #17179

Fix line breakpoints for `return` statements without a value #17179

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SeeminglyScience commented Apr 22, 2022 •

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Fix line breakpoints for return statements without a value #17179

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SeeminglyScience commented Apr 22, 2022 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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PR Summary

Trap compilation (click to expand)

Code to generate (click to expand)

Codegen before:

Codegen after:

PR Context

PR Checklist

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Fix line breakpoints for `return` statements without a value #17179

Fix line breakpoints for `return` statements without a value #17179

SeeminglyScience commented Apr 22, 2022 •

edited

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