Fix: Fix PowerShell completion test for Register-ArgumentCompleter

.gitignore

@@ -51,3 +51,4 @@ tests/data/common_wheels/
 
 # Profiling related artifacts
 *.prof
+pip-dev-env/

news/12440.feature.rst

@@ -0,0 +1 @@
+Fix PowerShell completion by switching to Register-ArgumentCompleter (Closes #12440)

src/pip/_internal/commands/completion.py

@@ -53,24 +53,37 @@
         complete -fa "(__fish_complete_pip)" -c {prog}
     """,
     "powershell": """
-        if ((Test-Path Function:\\TabExpansion) -and -not `
-            (Test-Path Function:\\_pip_completeBackup)) {{
-            Rename-Item Function:\\TabExpansion _pip_completeBackup
-        }}
-        function TabExpansion($line, $lastWord) {{
-            $lastBlock = [regex]::Split($line, '[|;]')[-1].TrimStart()
-            if ($lastBlock.StartsWith("{prog} ")) {{
-                $Env:COMP_WORDS=$lastBlock
-                $Env:COMP_CWORD=$lastBlock.Split().Length - 1
-                $Env:PIP_AUTO_COMPLETE=1
-                (& {prog}).Split()
-                Remove-Item Env:COMP_WORDS
-                Remove-Item Env:COMP_CWORD
-                Remove-Item Env:PIP_AUTO_COMPLETE
-            }}
-            elseif (Test-Path Function:\\_pip_completeBackup) {{
-                # Fall back on existing tab expansion
-                _pip_completeBackup $line $lastWord
+        Register-ArgumentCompleter -Native -CommandName '{prog}' -ScriptBlock {{
+            param($commandName, $commandAst, $cursorPosition)
+            $commandElements = $commandAst.CommandElements
+            $command = @(
+                '{prog}'
+                for ($i = 1; $i -lt $commandElements.Count; $i++) {{
+                    $element = $commandElements[$i]
+                    if ($element -isnot [StringConstantExpressionAst] -or
+                        $element.StringConstantType -ne`
+                            [StringConstantType]::BareWord -or
+                        $element.Value.StartsWith('-')) {{
+                        break
+                    }}
+                    $element.Value
+                }}
+            ) -join ' '
+
+            $Env:COMP_WORDS = $command
+            $Env:COMP_CWORD = $commandElements.Count - 1
+            $Env:PIP_AUTO_COMPLETE = 1
+            $completions = & {prog} 2>$null
+            Remove-Item Env:COMP_WORDS
+            Remove-Item Env:COMP_CWORD
+            Remove-Item Env:PIP_AUTO_COMPLETE
+
+            if ($completions) {{
+                $completions.Split() | ForEach-Object {{
+                    [System.Management.Automation.CompletionResult]::new(
+                        $_, $_, 'ParameterValue', $_
+                    )
+                }}
             }}
         }}
     """,

tests/functional/test_completion.py

@@ -60,26 +60,42 @@
     (
         "powershell",
         """\
-if ((Test-Path Function:\\TabExpansion) -and -not `
-    (Test-Path Function:\\_pip_completeBackup)) {
-    Rename-Item Function:\\TabExpansion _pip_completeBackup
-}
-function TabExpansion($line, $lastWord) {
-    $lastBlock = [regex]::Split($line, '[|;]')[-1].TrimStart()
-    if ($lastBlock.StartsWith("pip ")) {
-        $Env:COMP_WORDS=$lastBlock
-        $Env:COMP_CWORD=$lastBlock.Split().Length - 1
-        $Env:PIP_AUTO_COMPLETE=1
-        (& pip).Split()
-        Remove-Item Env:COMP_WORDS
-        Remove-Item Env:COMP_CWORD
-        Remove-Item Env:PIP_AUTO_COMPLETE
-    }
-    elseif (Test-Path Function:\\_pip_completeBackup) {
-        # Fall back on existing tab expansion
-        _pip_completeBackup $line $lastWord
+# pip powershell completion start
+Register-ArgumentCompleter -Native -CommandName 'pip' -ScriptBlock {
+    param($commandName, $commandAst, $cursorPosition)
+    $commandElements = $commandAst.CommandElements
+    $command = @(
+        'pip'
+        for ($i = 1; $i -lt $commandElements.Count; $i++) {
+            $element = $commandElements[$i]
+            if ($element -isnot [StringConstantExpressionAst] -or
+                $element.StringConstantType -ne`
+                    [StringConstantType]::BareWord -or
+                $element.Value.StartsWith('-')) {
+                break
+            }
+            $element.Value
+        }
+    ) -join ' '
+
+    $Env:COMP_WORDS = $command
+    $Env:COMP_CWORD = $commandElements.Count - 1
+    $Env:PIP_AUTO_COMPLETE = 1
+    $completions = & pip 2>$null
+    Remove-Item Env:COMP_WORDS
+    Remove-Item Env:COMP_CWORD
+    Remove-Item Env:PIP_AUTO_COMPLETE
+
+    if ($completions) {
+        $completions.Split() | ForEach-Object {
+            [System.Management.Automation.CompletionResult]::new(
+                $_, $_, 'ParameterValue', $_
+            )
+        }
     }
-}""",
+}
+# pip powershell completion end
+""",
     ),
 )