René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Asymmetry between CSV serialization of properties with `AutomationNull` or `$null` values","articleBody":"### Prerequisites\r\n\r\n- [X] Write a descriptive title.\r\n- [X] Make sure you are able to repro it on the [latest released version](https://github.com/PowerShell/PowerShell/releases)\r\n- [X] Search the existing issues.\r\n- [X] Refer to the [FAQ](https://github.com/PowerShell/PowerShell/blob/master/docs/FAQ.md).\r\n- [X] Refer to [Differences between Windows PowerShell 5.1 and PowerShell](https://learn.microsoft.com/powershell/scripting/whats-new/differences-from-windows-powershell).\r\n\r\nThere is asymmetry between the serialization of properties with either `AutomationNull` (`[Management.Automation.Internal.AutomationNull]::Value`) or `$null` values, that affects the following formats:\r\n\r\n- CSV\r\n- CLIXML\r\n- XML\r\n\r\nThis issue focuses on CSV. I will address (CLI)XML in a separate issue as the behavior differs.\r\n\r\nConsider the following contrived example:\r\n\r\n```powershell\r\n[pscustomobject] @{\r\n    Prop = if ($false) { 'Foo' } else { $null }\r\n} | ConvertTo-Csv\r\n\r\n# \"Prop\"\r\n\r\n[pscustomobject] @{\r\n    # Statement assignments have pipeline semantics, so Prop receives AutomationNull.\r\n    Prop = if ($false) { 'Foo' }\r\n} | ConvertTo-Csv\r\n\r\n# \"Prop\"\r\n# \"\"\r\n```\r\n\r\nA typical PS user who is unaware of `AutomationNull` (and arguably _should not_ have to be) would reasonably expect equivalent CSV serialization. Yet, the result differs because `AutomationNull` as a property value serializes as a quoted (`\"\"`) empty field whereas `$null` serializes as unquoted. \r\n\r\n**Notes:**\r\n- Due to https://github.com/PowerShell/PowerShell/issues/17702, this issue is especially problematic when the resultant CSV data is deserialized with `ConvertFrom-Csv`/`Import-Csv` .\r\n- This issue is similar to a problem affecting JSON/`ConvertTo-Json` in _Windows PowerShell_, but has since been addressed. In the latest PS version, `AutomationNull` and `$null` both serialize as `null` in JSON.\r\n\r\n\r\n### Steps to reproduce\r\n\r\n```powershell\r\n[pscustomobject] @{ P1 = \u0026 {}; P2 = $null } | ConvertTo-Csv\r\n```\r\n\r\n### Expected behavior\r\n\r\nCSV serialization of `AutomationNull` and `$null` property values should be identical.\r\n\r\nThe result should be **_either_**:\r\n\r\n```powershell\r\n# \"P1\",\"P2\"\r\n# \"\",\"\"\r\n\r\n# Or...\r\n\r\n# \"P1\",\"P2\"\r\n# ,\r\n```\r\n\r\nDepending on whether `AutomationNull`/`$null` should both be a quoted or unquoted empty field. Note that this has deserialization implications, as noted in the aforementioned https://github.com/PowerShell/PowerShell/issues/17702 issue.\r\n\r\n\r\n### Actual behavior\r\n\r\nSerialization of `AutomationNull` and `$null` property values differs.\r\n- `AutomationNull`: `\"\"` (quoted)\r\n- `$null`: Nothing (unquoted)\r\n\r\n```powershell\r\n\"P1\",\"P2\"\r\n\"\",\r\n```\r\n\r\n\r\n### Environment data\r\n\r\n```powershell\r\nName                           Value\r\n----                           -----\r\nPSVersion                      7.5.0-rc.1\r\nPSEdition                      Core\r\nGitCommitId                    7.5.0-rc.1\r\nOS                             Microsoft Windows 10.0.19045\r\nPlatform                       Win32NT\r\nPSCompatibleVersions           {1.0, 2.0, 3.0, 4.0…}\r\nPSRemotingProtocolVersion      2.3\r\nSerializationVersion           1.1.0.1\r\nWSManStackVersion              3.0\r\n```","author":{"url":"https://github.com/surfingoldelephant","@type":"Person","name":"surfingoldelephant"},"datePublished":"2024-12-22T18:20:15.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":6},"url":"https://github.com/24699/PowerShell/issues/24699"}