fix: keep selected list item always visible when scrolling

PesterExplorer/Private/Get-ListPanel.ps1

@@ -30,7 +30,9 @@ function Get-ListPanel {
         $List,
         [string]
         $SelectedItem,
-        [string]$SelectedPane = "list"
+        [string]$SelectedPane = "list",
+        [int]$ScrollOffset = 0,
+        [int]$ListHeight = 0
     )
     $paneColor = if($SelectedPane -ne "list") {
         # If the selected pane is not preview, return an empty panel
@@ -44,7 +46,19 @@ function Get-ListPanel {
         StemColor      = [Spectre.Console.Color]::Grey
         LeafColor      = [Spectre.Console.Color]::White
     }
-    $results = $List | ForEach-Object {
+    # Calculate the visible window. Panel borders and potential ellipsis rows consume 4 rows.
+    $visibleCount = if ($ListHeight -gt 4) { $ListHeight - 4 } else { $List.Count }
+    $startIndex = [Math]::Max(0, [Math]::Min($ScrollOffset, $List.Count - 1))
+    $endIndex = [Math]::Min($startIndex + $visibleCount - 1, $List.Count - 1)
+    $showEllipsisTop = $startIndex -gt 0
+    $showEllipsisBottom = $endIndex -lt ($List.Count - 1)
+    $visibleList = if ($List.Count -gt 0) { @($List[$startIndex..$endIndex]) } else { @() }
+
+    $results = @()
+    if ($showEllipsisTop) {
+        $results += Write-SpectreHost "[grey]...[/]" -PassThru | Format-SpectrePadded -Padding 0
+    }
+    $results += $visibleList | ForEach-Object {
         $name = $_
         if($name -eq '..') {
             # This is a parent item, so we show it as a folder
@@ -87,6 +101,9 @@ function Get-ListPanel {
             }
         }
     }
+    if ($showEllipsisBottom) {
+        $results += Write-SpectreHost "[grey]...[/]" -PassThru | Format-SpectrePadded -Padding 0
+    }
     $results |
         Format-SpectreRows |
         Format-SpectrePanel -Header "[white]List[/]" -Expand -Color $paneColor

PesterExplorer/Public/Show-PesterResult.ps1

@@ -79,13 +79,15 @@ function Show-PesterResult {
         $object = $PesterResult
         $selectedPane = 'list'
         $scrollPosition = 0
+        $listScrollOffset = 0
         #endregion Initial State
 
         while ($true) {
             # Check the layout sizes
             $sizes = $layout | Get-SpectreLayoutSizes
             $previewHeight = $sizes["preview"].Height
             $previewWidth = $sizes["preview"].Width
+            $listHeight = $sizes["list"].Height
             Write-Debug "Preview size: $previewWidth x $previewHeight"
 
             # Handle input
@@ -106,7 +108,7 @@ function Show-PesterResult {
                         $scrollPosition = 0
                     } elseif ($lastKeyPressed.Key -eq "PageUp") {
                         $currentIndex = $list.IndexOf($selectedItem)
-                        $newIndex = [Math]::Max($currentIndex - 10, $list.Count - 1)
+                        $newIndex = [Math]::Max($currentIndex - 10, 0)
                         $selectedItem = $list[$newIndex]
                         $scrollPosition = 0
                     } elseif ($lastKeyPressed.Key -eq "Home") {
@@ -135,6 +137,7 @@ function Show-PesterResult {
                         $list = [array]$items.Keys
                         $selectedItem = $list[0]
                         $scrollPosition = 0
+                        $listScrollOffset = 0
                     } elseif ($lastKeyPressed.Key -eq "Escape") {
                         # Move up via Esc key
                         if($stack.Count -eq 0) {
@@ -146,7 +149,17 @@ function Show-PesterResult {
                         $list = [array]$items.Keys
                         $selectedItem = $list[0]
                         $scrollPosition = 0
+                        $listScrollOffset = 0
                     }
+                    # Ensure the selected item is always within the visible viewport
+                    $selectedIndex = $list.IndexOf($selectedItem)
+                    $visibleCount = if ($listHeight -gt 4) { $listHeight - 4 } else { $list.Count }
+                    if ($selectedIndex -lt $listScrollOffset) {
+                        $listScrollOffset = $selectedIndex
+                    } elseif ($selectedIndex -ge ($listScrollOffset + $visibleCount)) {
+                        $listScrollOffset = $selectedIndex - $visibleCount + 1
+                    }
+                    if ($listScrollOffset -lt 0) { $listScrollOffset = 0 }
                 }
                 else {
                     #region Preview Navigation
@@ -175,6 +188,8 @@ function Show-PesterResult {
                 List = $list
                 SelectedItem = $selectedItem
                 SelectedPane = $selectedPane
+                ScrollOffset = $listScrollOffset
+                ListHeight = $listHeight
             }
             $listPanel = Get-ListPanel @getListPanelSplat
 

tests/Get-ListPanel.tests.ps1

@@ -0,0 +1,113 @@
+Describe 'Get-ListPanel' {
+    BeforeAll {
+        . (Join-Path $PSScriptRoot 'Helpers.ps1')
+        $manifest = Import-PowerShellDataFile -Path $env:BHPSModuleManifest
+        $outputDir = Join-Path -Path $env:BHProjectPath -ChildPath 'Output'
+        $outputModDir = Join-Path -Path $outputDir -ChildPath $env:BHProjectName
+        $outputModVerDir = Join-Path -Path $outputModDir -ChildPath $manifest.ModuleVersion
+        $outputModVerManifest = Join-Path -Path $outputModVerDir -ChildPath "$($env:BHProjectName).psd1"
+
+        # Remove all versions of the module from the session. Pester can't handle multiple versions.
+        Get-Module $env:BHProjectName | Remove-Module -Force -ErrorAction Ignore
+        Import-Module -Name $outputModVerManifest -Verbose:$false -ErrorAction Stop
+
+        InModuleScope $env:BHProjectName {
+            $script:tenItems = @('a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j')
+
+            # Viewport scrolling panel: ScrollOffset=2, ListHeight=8
+            # visibleCount = 8-4 = 4; items c,d,e,f visible; top and bottom ellipsis shown
+            $script:scrolledPanel = Get-ListPanel `
+                -List $script:tenItems `
+                -SelectedItem 'c' `
+                -ScrollOffset 2 `
+                -ListHeight 8
+            $script:scrolledText = global:Get-RenderedText -Panel $script:scrolledPanel
+
+            # Bottom-of-list panel: ScrollOffset=6, ListHeight=20
+            # visibleCount = 16; items g,h,i,j visible; top ellipsis only
+            $script:bottomPanel = Get-ListPanel `
+                -List $script:tenItems `
+                -SelectedItem 'j' `
+                -ScrollOffset 6 `
+                -ListHeight 20
+            $script:bottomText = global:Get-RenderedText -Panel $script:bottomPanel
+        }
+    }
+
+    It 'should return a Spectre.Console.Panel object' {
+        InModuleScope $env:BHProjectName {
+            $panel = Get-ListPanel -List @('item1', 'item2') -SelectedItem 'item1'
+            $panel.GetType().ToString() | Should -BeExactly 'Spectre.Console.Panel'
+        }
+    }
+
+    It 'should show all items when list fits within available height' {
+        InModuleScope $env:BHProjectName {
+            $panel = Get-ListPanel -List $script:tenItems -SelectedItem 'a' -ListHeight 20
+            $rendered = global:Get-RenderedText -Panel $panel
+            foreach ($item in $script:tenItems) {
+                $rendered | Should -BeLike "*$item*"
+            }
+        }
+    }
+
+    It 'should show all items when ListHeight is 0 (default, no constraint)' {
+        InModuleScope $env:BHProjectName {
+            $panel = Get-ListPanel -List $script:tenItems -SelectedItem 'a'
+            $rendered = global:Get-RenderedText -Panel $panel
+            foreach ($item in $script:tenItems) {
+                $rendered | Should -BeLike "*$item*"
+            }
+        }
+    }
+
+    It 'should show only items within the visible window when scrolled' {
+        InModuleScope $env:BHProjectName {
+            $script:scrolledText | Should -BeLike '*c*'
+            $script:scrolledText | Should -BeLike '*d*'
+            $script:scrolledText | Should -BeLike '*e*'
+            $script:scrolledText | Should -BeLike '*f*'
+        }
+    }
+
+    It 'should show top ellipsis when items are scrolled above the window' {
+        InModuleScope $env:BHProjectName {
+            $script:scrolledText | Should -BeLike '*...*'
+        }
+    }
+
+    It 'should show bottom ellipsis when items are below the window' {
+        InModuleScope $env:BHProjectName {
+            # Both top and bottom ellipsis are present since items a-b are above and g-j below
+            $script:scrolledText | Should -BeLike '*...*'
+        }
+    }
+
+    It 'should show visible items when scrolled to the bottom' {
+        InModuleScope $env:BHProjectName {
+            $script:bottomText | Should -BeLike '*g*'
+            $script:bottomText | Should -BeLike '*j*'
+        }
+    }
+
+    It 'should show top ellipsis when scrolled to the bottom' {
+        InModuleScope $env:BHProjectName {
+            $script:bottomText | Should -BeLike '*...*'
+        }
+    }
+
+    It 'should highlight the selected item in the rendered output' {
+        InModuleScope $env:BHProjectName {
+            $panel = Get-ListPanel -List @('alpha', 'beta', 'gamma') -SelectedItem 'beta'
+            $rendered = global:Get-RenderedText -Panel $panel
+            $rendered | Should -BeLike '*beta*'
+        }
+    }
+
+    It 'should return a Panel when list pane is not selected' {
+        InModuleScope $env:BHProjectName {
+            $panel = Get-ListPanel -List @('item1') -SelectedItem 'item1' -SelectedPane 'preview'
+            $panel.GetType().ToString() | Should -BeExactly 'Spectre.Console.Panel'
+        }
+    }
+}

tests/Help.tests.ps1

@@ -1,4 +1,4 @@
 # Taken with love from @juneb_get_help (https://raw.githubusercontent.com/juneb/PesterTDD/master/Module.Help.Tests.ps1)
 
 BeforeDiscovery {
 
@@ -9,7 +9,7 @@
         $params | Where-Object { $_.Name -notin $commonParameters } | Sort-Object -Property Name -Unique
     }
 
     $manifest = Import-PowerShellDataFile -Path $env:BHPSModuleManifest
     $outputDir = Join-Path -Path $env:BHProjectPath -ChildPath 'Output'
     $outputModDir = Join-Path -Path $outputDir -ChildPath $env:BHProjectName
     $outputModVerDir = Join-Path -Path $outputModDir -ChildPath $manifest.ModuleVersion
@@ -108,7 +108,7 @@
 
         # Shouldn't find extra parameters in help.
         It "finds help parameter in code: <_>" {
-            $_ -in $parameterNames | Should -Be $true
+            $_ -in $commandParameterNames | Should -Be $true
         }
     }
 }