Fix out of bounds context for short scripts (#58)

* Limit pre and post context by calculating number of lines available in either direction

Add test case coverage for issue

* Update CHANGELOG.md

Author: willhcr

CHANGELOG.md

@@ -5,6 +5,7 @@
 ### Fixes
 
 - StackTrace parsing on Windows Powershell 5.1 ([#50](https://github.com/getsentry/sentry-powershell/pull/50))
+- Fix out of bounds context for short scripts ([#58](https://github.com/getsentry/sentry-powershell/pull/58))
 
 ### Dependencies
 

modules/Sentry/private/StackTraceProcessor.ps1

@@ -291,15 +291,17 @@ class StackTraceProcessor : SentryEventProcessor
                 {
                     $sentryFrame.ContextLine = $lines[$sentryFrame.LineNumber - 1]
                 }
+                $preContextCount = [math]::Min(5, $sentryFrame.LineNumber - 1)
+                $postContextCount = [math]::Min(5, $lines.Count - $sentryFrame.LineNumber)
                 if ($sentryFrame.LineNumber -gt 6)
                 {
                     $lines = $lines | Select-Object -Skip ($sentryFrame.LineNumber - 6)
                 }
                 # Note: these are read-only in sentry-dotnet so we just update the underlying lists instead of replacing.
                 $sentryFrame.PreContext.Clear()
-                $lines | Select-Object -First 5 | ForEach-Object { $sentryFrame.PreContext.Add($_) }
+                $lines | Select-Object -First $preContextCount | ForEach-Object { $sentryFrame.PreContext.Add($_) }
                 $sentryFrame.PostContext.Clear()
-                $lines | Select-Object -Last 5  | ForEach-Object { $sentryFrame.PostContext.Add($_) }
+                $lines | Select-Object -Last $postContextCount  | ForEach-Object { $sentryFrame.PostContext.Add($_) }
             }
             catch
             {

tests/stacktrace.tests.ps1

@@ -1,6 +1,7 @@
 BeforeAll {
     . "$PSScriptRoot/utils.ps1"
     . "$PSScriptRoot/throwing.ps1"
+    . "$PSScriptRoot/throwingshort.ps1"
     $events = [System.Collections.Generic.List[Sentry.SentryEvent]]::new();
     $transport = [RecordingTransport]::new()
     StartSentryForEventTests ([ref] $events) ([ref] $transport)
@@ -77,6 +78,31 @@ BeforeAll {
         # A module-based frame should be in-app=false
         $frames | Where-Object -Property Module | Select-Object -First 1 -ExpandProperty 'InApp' | Should -Be $false
     }
+
+    $checkShortErrorRecord = {
+        $events.Count | Should -Be 1
+        [Sentry.SentryEvent]$event = $events.ToArray()[0]
+        $event.SentryExceptions.Count | Should -Be 2
+
+        $event.SentryExceptions[1].Type | Should -Be 'Short context test'
+        $event.SentryExceptions[1].Value | Should -Be 'Short context test'
+        $event.SentryExceptions[1].Module | Should -BeNullOrEmpty
+        [Sentry.SentryStackFrame[]] $frames = $event.SentryExceptions[1].Stacktrace.Frames
+        $frames.Count | Should -BeGreaterThan 1
+
+        $frame = GetListItem $frames -1
+
+        $frame.Function | Should -Be "funcC"
+        $frame.AbsolutePath | Should -Be (Join-Path $PSScriptRoot 'throwingshort.ps1')
+        $frame.LineNumber | Should -BeGreaterThan 0
+        $frame.InApp | Should -Be $true
+
+        $frame.PreContext | Should -Be @('function funcC {')
+        $frame.PreContext.Count | Should -Be 1
+        $frame.ContextLine | Should -Be '    throw "Short context test"'
+        $frame.PostContext | Should -Be @('}')
+        $frame.PostContext.Count | Should -Be 1
+    }
 }
 
 AfterAll {
@@ -119,6 +145,19 @@ Describe 'Out-Sentry' {
         @($null) | ForEach-Object $checkErrorRecord
     }
 
+    It 'captures short context' {
+        try
+        {
+            funcC
+        }
+        catch
+        {
+            $_ | Out-Sentry
+        }
+
+        @($null) | ForEach-Object $checkShortErrorRecord
+    }
+
     It 'captures exception' {
         try
         {

tests/throwingshort.ps1

@@ -0,0 +1,3 @@
+function funcC {
+    throw "Short context test"
+}