René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"ConvertFrom-Json sends objects converted from a JSON array as an *array* through the pipeline.","articleBody":"Note: **Perhaps the behavior in question will rarely be noticed as problematic in the real world, so perhaps the only thing that's needed is adding a note to the _documentation_** - I'm unclear on whether this ultimately a non-issue.\r\n\r\nalpha.17 fixed issue #3153 with respect to `ConvertTo-Json` no longer wrapping `ConvertFrom-Json`  array output in an extraneous object with `value` and `count` properties.\r\n\r\nHowever, `ConvertFrom-Json` still sends the objects resulting from converting a JSON _array_ as a _single array_ through the pipeline, which is a deviation from the usual cmdlet behavior of _unwrapping_ collections and sending the items _one by one_.\r\n\r\n```powershell\r\n\u003e ('[ 1, 2 ]' | ConvertFrom-Json | Measure-Object).Count\r\n1  # !! PS array `1, 2` was sent as a *single* object through the pipeline.\r\n```\r\n\r\n**Workaround**: Enclose the `ConvertFrom-Json` part of the pipeline in `(...)`, which forces enumeration:\r\n\r\n```powershell\r\n\u003e (('[ 1, 2 ]' | ConvertFrom-Json) | Measure-Object).Count\r\n2  # OK, (...) forced enumeration\r\n```\r\n\r\nAlternatively, simply insert a `Write-Output` pipeline segment:\r\n\r\n```powershell\r\n\u003e ('[ 1, 2 ]' | ConvertFrom-Json | Write-Output | Measure-Object).Count\r\n2  # OK, Write-Output forced enumeration\r\n```\r\n\r\n\u003csup\u003eNote: On _Windows PowerShell_, as of v5.1, you paradoxically need `Write-Output -NoEnumerate` to prevent unwrapping  from getting applied to the individual array elements as well.\u003c/sup\u003e\r\n\r\nOn the plus side, as @PetSerAl  points out, this preserves the input structure in a round-trip in the case of _single_-element JSON arrays:\r\n\r\n```powershell\r\n\u003e '[ 1 ]' | ConvertFrom-Json | ConvertTo-Json\r\n[\r\n  1\r\n]\r\n```\r\nIt is only `ConvertFrom-Json`'s send-the-array-as-a-whole approach that enables the above round trip.\r\n\r\nBy contrast, **when you start with a PS array**, it doesn't work that way (which illustrates the difference in pipeline behavior):\r\n\r\n```powershell\r\n\u003e , 1 | ConvertTo-Json\r\n1 # !! Input PS array was unwrapped on sending it through the pipeline\r\n```\r\n\r\nTo preserve the array, you must _explicitly_ _nest_ the array:\r\n\r\n```powershell\r\n\u003e , , 1 | ConvertTo-Json\r\n[\r\n  1\r\n]\r\n\r\n# Alternative: explicitly prevent enumeration\r\n\u003e Write-Output -NoEnumerate (, 1) | ConvertTo-Json\r\n[\r\n  1\r\n]\r\n```\r\n\r\nEnvironment data\r\n----------------\r\n\r\n```powershell\r\nPowerShell Core v6.0.0-alpha (v6.0.0-alpha.17) on Darwin Kernel Version 16.4.0: Thu Dec 22 22:53:21 PST 2016; root:xnu-3789.41.3~3/RELEASE_X86_64\r\n```\r\n","author":{"url":"https://github.com/mklement0","@type":"Person","name":"mklement0"},"datePublished":"2017-03-25T18:28:36.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":47},"url":"https://github.com/3424/PowerShell/issues/3424"}