Handle empty-string and null-value results returned from custom argument completer more properly (#27398)

2026-06-08 12:12:50 +00:00 · 2026-05-11 11:59:37 -07:00
parent 7164700777
commit c9ac205fda
4 changed files with 188 additions and 12 deletions
@@ -42,7 +42,7 @@
    <PackageReference Include="Microsoft.Management.Infrastructure" Version="3.0.0" />
    <PackageReference Include="Microsoft.PowerShell.Native" Version="700.0.0" />
    <!-- Signing APIs -->
-  <PackageReference Include="Microsoft.Security.Extensions" Version="1.4.0" />
+    <PackageReference Include="Microsoft.Security.Extensions" Version="1.4.0" />
  </ItemGroup>

  <PropertyGroup>
@@ -601,7 +601,10 @@ namespace System.Management.Automation
                    completionContext.ExecutionContext.LanguageMode = PSLanguageMode.ConstrainedLanguage;
                }

-                return GetResultHelper(completionContext, out replacementIndex, out replacementLength);
+                List<CompletionResult> results = GetResultHelper(completionContext, out replacementIndex, out replacementLength);
+                CompletionCompleters.RemoveLastNullCompletionResult(results);
+
+                return results;
            }
            finally
            {
@@ -2675,14 +2675,17 @@ namespace System.Management.Automation
                scriptBlock,
                new object[] { commandName, parameterName, wordToComplete, commandAst, GetBoundArgumentsAsHashtable(context) },
                resultList);
-            if (result)
-            {
-                resultList.Add(CompletionResult.Null);
-            }

            return result;
        }

+        /// <summary>
+        /// Invoke the custom argument completer and process its return values.
+        /// If we consider the completion successful, we add a null instance of the type 'CompletionResult'
+        /// to the end of the 'result' list to indicate that the argument completion has been processed, so we
+        /// will not go through the default argument completion even if the 'result' list is still empty.
+        /// </summary>
+        /// <returns>'true' if the argument completion was successful. 'false' otherwise.</returns>
        private static bool InvokeScriptArgumentCompleter(
            ScriptBlock scriptBlock,
            object[] argumentsToCompleter,
@@ -2702,20 +2705,44 @@ namespace System.Management.Automation
                return false;
            }

+            if (customResults.Count is 1 && customResults[0] is { BaseObject: "" } or null)
+            {
+                // If the script block returns a single empty string or a null value, we will treat it as if it has
+                // completed successfully but has no results to return.
+                // This allows a custom completer to suppress the default completions that we may fall back otherwise.
+                result.Add(CompletionResult.Null);
+                return true;
+            }
+
+            int initialCount = result.Count;
+
            foreach (var customResult in customResults)
            {
-                var resultAsCompletion = customResult.BaseObject as CompletionResult;
-                if (resultAsCompletion != null)
+                if (customResult is null)
+                {
+                    continue;
+                }
+
+                if (customResult.BaseObject is CompletionResult resultAsCompletion)
                {
                    result.Add(resultAsCompletion);
                    continue;
                }

                var resultAsString = customResult.ToString();
-                result.Add(new CompletionResult(resultAsString));
+                if (!string.IsNullOrEmpty(resultAsString))
+                {
+                    result.Add(new CompletionResult(resultAsString));
+                }
            }

-            return true;
+            bool success = result.Count > initialCount;
+            if (success)
+            {
+                result.Add(CompletionResult.Null);
+            }
+
+            return success;
        }

        // All the methods for native command argument completion will add a null instance of the type CompletionResult to the end of the
@@ -2723,9 +2750,9 @@ namespace System.Management.Automation
        // and has been processed already. So if the "result" list is still empty afterward, we will not go through the default argument completion anymore.
        #region Native Command Argument Completion

-        private static void RemoveLastNullCompletionResult(List<CompletionResult> result)
+        internal static void RemoveLastNullCompletionResult(List<CompletionResult> result)
        {
-            if (result.Count > 0 && result[result.Count - 1].Equals(CompletionResult.Null))
+            if (result?.Count > 0 && result[^1].Equals(CompletionResult.Null))
            {
                result.RemoveAt(result.Count - 1);
            }
@@ -149,4 +149,150 @@ Describe "Tab completion bug fix" -Tags "CI" {
            Pop-Location
        }
    }
+
+    Context 'Native CLI argument completion' {
+        BeforeAll {
+            $testDir = Join-Path $TestDrive "TempTestDir"
+            $file1 = Join-Path $testDir "abc.ps1"
+            $file2 = Join-Path $testDir "def.py"
+
+            New-Item -ItemType Directory -Path $testDir > $null
+            New-Item -ItemType File -Path $file1 > $null
+            New-Item -ItemType File -Path $file2 > $null
+
+            $dirSep = [System.IO.Path]::DirectorySeparatorChar
+            $relative_name_abc = ".${dirSep}abc.ps1"
+            $relative_name_def = ".${dirSep}def.py"
+        }
+
+        AfterAll {
+            ## Unregister the completer for 'ping' to avoid affecting other tests.
+            register-ArgumentCompleter -Native -CommandName ping -ScriptBlock $null
+        }
+
+        It 'Completer script block returning nothing should fall back to file name completion' {
+            register-ArgumentCompleter -Native -CommandName ping -ScriptBlock {
+                param($WordToComplete, $CommandAst, $CursorPosition)
+            }
+
+            try {
+                Push-Location -Path $testDir
+                $cmd = "ping "
+                $result = TabExpansion2 -inputScript $cmd -cursorColumn $cmd.Length
+                $result.CompletionMatches | Should -Not -BeNullOrEmpty
+                $result.CompletionMatches.Count | Should -Be 2
+                $result.CompletionMatches[0].CompletionText | Should -BeExactly $relative_name_abc
+                $result.CompletionMatches[1].CompletionText | Should -BeExactly $relative_name_def
+            } finally {
+                Pop-Location
+            }
+        }
+
+        It 'Completer script block returning $null should suppress default completion fallback' {
+            register-ArgumentCompleter -Native -CommandName ping -ScriptBlock {
+                param($WordToComplete, $CommandAst, $CursorPosition)
+                return $null
+            }
+
+            try {
+                Push-Location -Path $testDir
+                $cmd = "ping "
+                ## This call should not throw, and should suppress the default file name completion fallback, returning no results.
+                $result = TabExpansion2 -inputScript $cmd -cursorColumn $cmd.Length
+                $result.CompletionMatches.Count | Should -Be 0
+            } finally {
+                Pop-Location
+            }
+        }
+
+        It 'Completer script block returning empty string should suppress default completion fallback' {
+            register-ArgumentCompleter -Native -CommandName ping -ScriptBlock {
+                param($WordToComplete, $CommandAst, $CursorPosition)
+                return ''
+            }
+
+            try {
+                Push-Location -Path $testDir
+                $cmd = "ping "
+                ## This call should not throw, and should suppress the default file name completion fallback, returning no results.
+                $result = TabExpansion2 -inputScript $cmd -cursorColumn $cmd.Length
+                $result.CompletionMatches.Count | Should -Be 0
+            } finally {
+                Pop-Location
+            }
+        }
+
+        It 'Completer script block returning empty-string-only array should fall back to default completion' {
+            register-ArgumentCompleter -Native -CommandName ping -ScriptBlock {
+                param($WordToComplete, $CommandAst, $CursorPosition)
+                return '', ''
+            }
+
+            try {
+                Push-Location -Path $testDir
+                $cmd = "ping "
+                ## This call should not throw, and should fall back to the default completion.
+                $result = TabExpansion2 -inputScript $cmd -cursorColumn $cmd.Length
+                $result.CompletionMatches.Count | Should -Be 2
+                $result.CompletionMatches[0].CompletionText | Should -BeExactly $relative_name_abc
+                $result.CompletionMatches[1].CompletionText | Should -BeExactly $relative_name_def
+            } finally {
+                Pop-Location
+            }
+        }
+
+        It 'Completer script block returning null-value-only array should fall back to default completion' {
+            register-ArgumentCompleter -Native -CommandName ping -ScriptBlock {
+                param($WordToComplete, $CommandAst, $CursorPosition)
+                return $null, $null
+            }
+
+            try {
+                Push-Location -Path $testDir
+                $cmd = "ping "
+                ## This call should not throw, and should fall back to the default completion.
+                $result = TabExpansion2 -inputScript $cmd -cursorColumn $cmd.Length
+                $result.CompletionMatches.Count | Should -Be 2
+                $result.CompletionMatches[0].CompletionText | Should -BeExactly $relative_name_abc
+                $result.CompletionMatches[1].CompletionText | Should -BeExactly $relative_name_def
+            } finally {
+                Pop-Location
+            }
+        }
+
+        It 'Completer script block returning a single string works as expected' {
+            register-ArgumentCompleter -Native -CommandName ping -ScriptBlock {
+                param($WordToComplete, $CommandAst, $CursorPosition)
+                return 'hello'
+            }
+
+            try {
+                Push-Location -Path $testDir
+                $cmd = "ping "
+                $result = TabExpansion2 -inputScript $cmd -cursorColumn $cmd.Length
+                $result.CompletionMatches.Count | Should -Be 1
+                $result.CompletionMatches[0].CompletionText | Should -BeExactly "hello"
+            } finally {
+                Pop-Location
+            }
+        }
+
+        It 'Completer script block returning an array that contains non-empty-or-null strings works as expected' {
+            register-ArgumentCompleter -Native -CommandName ping -ScriptBlock {
+                param($WordToComplete, $CommandAst, $CursorPosition)
+                return '', 'hello', $null, 'world'
+            }
+
+            try {
+                Push-Location -Path $testDir
+                $cmd = "ping "
+                $result = TabExpansion2 -inputScript $cmd -cursorColumn $cmd.Length
+                $result.CompletionMatches.Count | Should -Be 2
+                $result.CompletionMatches[0].CompletionText | Should -BeExactly "hello"
+                $result.CompletionMatches[1].CompletionText | Should -BeExactly "world"
+            } finally {
+                Pop-Location
+            }
+        }
+    }
 }