PowerShell · adityapatwardhan · Aug 9, 2022 · Jul 26, 2022 · Jul 28, 2022 · Jul 28, 2022
diff --git a/src/System.Management.Automation/engine/Utils.cs b/src/System.Management.Automation/engine/Utils.cs
@@ -1573,6 +1573,7 @@ public static class InternalTestHooks
         internal static bool UseDebugAmsiImplementation;
         internal static bool BypassAppLockerPolicyCaching;
         internal static bool BypassOnlineHelpRetrieval;
+        internal static bool ThrowHelpCultureNotSupported;
         internal static bool ForcePromptForChoiceDefaultOption;
         internal static bool NoPromptForPassword;
         internal static bool ForceFormatListFixedLabelWidth;

@@ -509,6 +509,7 @@ private void ProcessModule(UpdatableHelpModuleInfo module)
             // Win8: 572882 When the system locale is English and the UI is JPN,
             // running "update-help" still downs English help content.
             var cultures = _language ?? _helpSystem.GetCurrentUICulture();
+            UpdatableHelpSystemException implicitCultureNotSupported = null;
 
             foreach (string culture in cultures)
             {
@@ -558,6 +559,12 @@ private void ProcessModule(UpdatableHelpModuleInfo module)
                             // Display the error message only if we are not using the fallback chain
                             ProcessException(module.ModuleName, culture, e);
                         }
+                        else
+                        {
+                            // Hold first exception, it will be displayed if fallback chain fails
+                            WriteVerbose(StringUtil.Format(HelpDisplayStrings.HelpCultureNotSupportedFallback, e.Message));
+                            implicitCultureNotSupported ??= e;
+                        }
                     }
                     else
                     {
@@ -581,13 +588,19 @@ private void ProcessModule(UpdatableHelpModuleInfo module)
                     }
                 }
 
-                // If -Language is not specified, we only install
+                // If -UICulture is not specified, we only install
                 // one culture from the fallback chain
                 if (_language == null && installed)
                 {
-                    break;
+                    return;
                 }
             }
+
+            // If the exception is not null and did not return early, then all of the fallback chain failed
+            if (implicitCultureNotSupported != null)
+            {
+                ProcessException(module.ModuleName, cultures.First(), implicitCultureNotSupported);
+            }
         }
 
         /// <summary>

@@ -214,6 +214,14 @@ protected override void ProcessRecord()
         /// <returns>True if the module has been processed, false if not.</returns>
         internal override bool ProcessModuleWithCulture(UpdatableHelpModuleInfo module, string culture)
         {
+            // Simulate culture not found
+            if (InternalTestHooks.ThrowHelpCultureNotSupported)
+            {
+                throw new UpdatableHelpSystemException("HelpCultureNotSupported",
+                    StringUtil.Format(HelpDisplayStrings.HelpCultureNotSupported, culture, "en-US"),
+                    ErrorCategory.InvalidOperation, null, null);
+            }
+
             UpdatableHelpInfo currentHelpInfo = null;
             UpdatableHelpInfo newHelpInfo = null;
             string helpInfoUri = null;

diff --git a/src/System.Management.Automation/resources/HelpDisplayStrings.resx b/src/System.Management.Automation/resources/HelpDisplayStrings.resx
@@ -306,6 +306,10 @@
   <data name="HelpCultureNotSupported" xml:space="preserve">
     <value>The specified culture is not supported: {0}. Specify a culture from the following list: {{{1}}}.</value>
   </data>
+  <data name="HelpCultureNotSupportedFallback" xml:space="preserve">
+    <value>Postponing error and trying fallback cultures, will show as error if none of fallbacks are supported:
+{0}</value>
+  </data>
   <data name="ModuleBaseMustExist" xml:space="preserve">
     <value>The ModuleBase directory cannot be found. Verify the directory and try again.</value>
   </data>

diff --git a/test/powershell/engine/Help/HelpSystem.Tests.ps1 b/test/powershell/engine/Help/HelpSystem.Tests.ps1
@@ -30,7 +30,8 @@ function UpdateHelpFromLocalContentPath {
         throw "Unable to find help content at '$helpContentPath'"
     }
 
-    Update-Help -Module $ModuleName -SourcePath $helpContentPath -Force -ErrorAction Stop -Scope $Scope
+    # Test files are 'en-US', set explicit culture so test does not help on non-US systems
+    Update-Help -Module $ModuleName -SourcePath $helpContentPath -UICulture 'en-US' -Force -ErrorAction Stop -Scope $Scope
 }
 
 function GetCurrentUserHelpRoot {

diff --git a/test/powershell/engine/Help/UpdatableHelpSystem.Tests.ps1 b/test/powershell/engine/Help/UpdatableHelpSystem.Tests.ps1
@@ -434,6 +434,34 @@ Describe "Validate Update-Help -SourcePath for all PowerShell modules for user s
     RunUpdateHelpTests -Tag "Feature" -useSourcePath -Scope 'CurrentUser'
 }
 
+Describe "Validate 'Update-Help' shows 'HelpCultureNotSupported' when thrown" -Tags @('Feature') {
+    BeforeAll {
+        [System.Management.Automation.Internal.InternalTestHooks]::SetTestHook('ThrowHelpCultureNotSupported', $true)
+    }
+    AfterAll {
+        [System.Management.Automation.Internal.InternalTestHooks]::SetTestHook('ThrowHelpCultureNotSupported', $false)
+    }
+
+    It 'Shows error if help culture does not match: <name>' -TestCases @(
+        @{ 'name' = 'implicit culture'; 'culture' = $null }
+        @{ 'name' = 'explicit culture en-GB'; 'culture' = 'en-GB' }
+        @{ 'name' = 'explicit culture de-DE'; 'culture' = 'de-DE' }
+    ) {
+        param ($name, $culture)
+        # Cannot pass null, have to splat to skip argument entirely
+        $cultureArg = $culture ? @{ 'UICulture' = $culture } : @{}
+        $cultureUsed = $culture ?? (Get-Culture)
+
+        $ErrorVariable = $null
+        $VerboseOutput = New-TemporaryFile
+        Update-Help @cultureArg -ErrorVariable ErrorVariable -ErrorAction SilentlyContinue -Verbose 4>$VerboseOutput
+        $ErrorVariable | Should -Match "No UI culture was found that matches the following pattern: ${cultureUsed}"
+        if (-not $culture) {
+            Get-Content -Raw $VerboseOutput | Should -Match 'Postponing error and trying fallback cultures'
+        }
+    }
+}
+
 Describe "Validate 'Save-Help -DestinationPath for one PowerShell modules." -Tags @('CI', 'RequireAdminOnWindows') {
     BeforeAll {
         $SavedProgressPreference = $ProgressPreference