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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Surprising behavior of @() (array subexpression operator) with arrays/collections created with New-Object","articleBody":"**tl; dr**:\r\n\r\nThis issue is written based on the following, currently unfulfilled expectation:\r\n\r\n* When you wrap a `New-Object` call that outputs an array / collection in `@()`, it should not create an array wrapper around it.\r\n\r\n@PetSerAl disagrees with my expectation (quotes from the comments on this [SO post](https://stackoverflow.com/a/45091504/45375) that inspired this issue, part of which is reprinted below):\r\n\r\n\u003e What is unexpected about this behavior? `New-Object` writes a single element to the pipeline and `@()` wraps it in an array.\r\n\r\nOn the tangentially related issue that `@()` preserves the specific array type:\r\n\r\n\u003e Also, IMHO, `@([int[]] (1, 2)).GetType().Name` [returning `Int32[]`] is a bug (over-optimization; it returns `Object[]` in v2)\r\n\r\n---\r\n\r\nAs of Windows PowerShell v5.1 / PowerShell Core v6.0.0-beta.4, **`@()` unexpectedly wraps arrays / collections instantiated directly as .NET types with the `New-Object` cmdlet in an outer, single-element array**; in other words: it doesn't recognize that the results already _are_ array-valued:\r\n\r\n```powershell\r\n\u003e @(New-Object 'Object[]' 2).Count; @(New-Object 'Object[]' 2)[0].Count\r\n1  # !! The array was unexpectedly wrapped in an outer single-item array.\r\n2  # !! Element [0] contains the original array.\r\n\r\n\u003e @(New-Object 'System.Collections.ArrayList').Count; @(New-Object 'System.Collections.ArrayList')[0].Count\r\n1  # !! The array list was unexpectedly wrapped in an outer single-item array.\r\n0  # !! Element [0] contains the original (empty) array list.\r\n```\r\n---\r\n\r\nTo contrast the surprising `New-Object` behavior above with commands that _should_ be equivalent, but work as expected:\r\n\r\n```powershell\r\n\u003e @((New-Object 'Object[]' 2)).Count\r\n2 # OK - !! Simply enclosing the New-Object call in (...) made the difference.\r\n\r\n\u003e @([int[]] (1, 2)).Count\r\n2 # OK - using a cast in lieu of New-Object\r\n\r\n\u003e @([System.Collections.ArrayList]::new()).Count\r\n0 # OK - using the static ::new() method in lieu of New-Object\r\n```\r\n\r\n\r\nEnvironment data\r\n----------------\r\n\r\n```powershell\r\nPowerShell Core v6.0.0-beta.4 on macOS 10.12.5\r\nPowerShell Core v6.0.0-beta.4 on Ubuntu 16.04.2 LTS\r\nPowerShell Core v6.0.0-beta.4 on Microsoft Windows 10 Pro (64-bit; v10.0.15063)\r\nWindows PowerShell v5.1.15063.413 on Microsoft Windows 10 Pro (64-bit; v10.0.15063)\r\n```\r\n","author":{"url":"https://github.com/mklement0","@type":"Person","name":"mklement0"},"datePublished":"2017-07-14T19:57:25.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":16},"url":"https://github.com/4257/PowerShell/issues/4257"}