Is there a module for parsing TOML files in PowerShell?

Question

I'm trying to find a TOML file parser for PowerShell.

I can't find any information about it either in PowerShell Gallery or in the preinstalled PowerShell functions.

Coventry

Answer 1

Indeed, as of this writing, there seems to be no PowerShell module for TOML parsing published in the PowerShell Gallery:

• Searching for "TOML" yields no relevant matches as of this writing.

However, there is a .NET package available in the NuGet Gallery:

• Tomlyn, whose source-code repository is here.

---

While you can consume NuGet packages from PowerShell, doing so is nontrivial as of PowerShell Core 7.2.2, unfortunately.

• This answer discusses the current pitfalls and potential future enhancements.

• In this particular case, because the package has no dependencies, you can get away with downloading the package via Install-Package, as shown below:

Sample use:

# Determine the package's local installation location.
# If it isn't installed, install it first, in the current user's scope.
while (-not ($installDir = (Get-Package -ErrorAction Ignore -ProviderName NuGet Tomlyn).Source)) {
  $null = Install-Package -Scope CurrentUser -ErrorAction Stop -ProviderName NuGet Tomlyn
}

# Load the package's assembly into the session.
Add-Type -ErrorAction Stop -LiteralPath (Join-Path $installDir '../lib/netstandard2.0/Tomlyn.dll')

# Define a sample TOML string to parse.
$tomlStr = @'
global = "this is a string"
# This is a comment of a table
[my_table]
key = 1 # Comment a key
value = true
list = [4, 5, 6]
'@

# Parse the TOML string into an object mod)el (nested dictionaries).
$tomlTable = [Tomlyn.Toml]::ToModel($tomlStr)

# Output the '[my_table]' section's 'list' value.
#  -> 4, 5, 6
# IMPORTANT: Use ['<key>'] syntax; .<key> syntax does NOT work.
$tomlTable['my_table']['list']

Note:

• With with dictionary types, PowerShell usually allows interchangeable use of index syntax (e.g. ['my_table']) and dot notation , via ., the member-access operator (e.g. .my_table).

• However, dot notation is not supported for the dictionaries of type [Tomlyn.Model.Table], such as returned by [Tomlyn.Toml]::ToModel(), presumably because that type only implements the generic IDictionary`2 interface, and not also its non-generic counterpart, IDictionary.

  • See GitHub issue #17190 for a discussion.

Grammarian

Answer 2

Yes, see here: https://github.com/jborean93/PSToml "A TOML parser and writer for PowerShell."

Holladay