How can I write a nested arbitrary associative Array value set to a .psd1 file in powershell?

Question

I have a powershell Array object that is programmatically generated, something with arrays inside arrays, inside arrays, sometimes called a "property bag" or a "hashtable", but I think it's natively called an "Array containing Arrays" in the most native powershell terminology.

For example:

 @{
 Version  = '1.0.0'
 Name     = 'thing'
 Revision = 'c3a89cd20e19bb82f41e95e0806edc5b6cfd224e'
 Date     = '2016-12-09'
 Build    = '1234'
 Contents = @{
      "index.html" = "23dd7b993f40bb3ae8848fe104b3b767"
 }
 }

Generating a function to save only one specific set of contents to a .PSD1 file seems not general enough. I want to save that exact in-memory Array structure to a PSD1 file. Does any built-in way in Powershell exist to Persist an in-memory variable with the values above? The "opposite function" of Import-PowershellDataFile. I would have guessed it would be called Export-PowershellDatafile but no such function seems to exist.

Answer 1

Have you tried using New-ModuleManifest? Without knowing any additional details, it appears that you're creating something substantially similar to a manifest file used in a module... But even if your use case is different, you should still be able to use the cmdlet.

New-ModuleManifest has been around for a while (at least since v3, but I seem to recall using it with v2 as well). It allows you to define a hashtable of properties and save it down as a .psd1.

https://learn.microsoft.com/en-us/powershell/module/microsoft.powershell.core/new-modulemanifest?view=powershell-5.1

Answer 2

Originated from this Save hash table in PowerShell object notation (PSON) question, I created (and still maintaining) a PowerShell cmdlet that evolved to a ConvertTo-Expression. The ultimate goal of this script is to be able to export and import PowerShell objects between systems based on a correct PowerShell syntax rather than an exotic format like [JSON]( or [XML].
This includes differentiating between an array of bytes and a byte array but also correctly accepting (and formatting) singletons.
The output is [ScriptBlock] which can be easily save as an expression. The point is that (depending on the usage) it might create a security hole when eventually invoking (c.q. dot sourcing) it (see: Running partly trusted PowerShell code in a restricted security environment. #12377).
Anyways, I also included an -Explore parameter which I belief gives exactly the same output as required for the PSD1 PowerShell Data File. I actually never thought about this usage earlier but now considering to alias this parameter and give it an exclusive meaning for PSD1 files in my next version.
In other words:

$Data = @{
 Version  = '1.0.0'
 Name     = 'thing'
 Revision = 'c3a89cd20e19bb82f41e95e0806edc5b6cfd224e'
 Date     = '2016-12-09'
 Build    = '1234'
 Contents = @{
      "index.html" = "23dd7b993f40bb3ae8848fe104b3b767"
 }
 }

ConvertTo-Expression -Explore $Data # | Out-File .\MyData.psd1

Returns a [ScriptBlock] which automatically converts to the following expression when e.g. exporting it to a file or simply displaying it:

@{
        'Date' = '2016-12-09'
        'Revision' = 'c3a89cd20e19bb82f41e95e0806edc5b6cfd224e'
        'Version' = '1.0.0'
        'Build' = '1234'
        'Contents' = @{'index.html' = '23dd7b993f40bb3ae8848fe104b3b767'}
        'Name' = 'thing'
}