(chocolatey#2854) Add helper to read config values

This adds a PowerShell helper to get config values from the Chocolatey
configuration file. This helper is intended to be used to allow hook scripts
to access configuration values set in the config.

src/chocolatey.resources/chocolatey.resources.csproj

@@ -66,6 +66,7 @@
     <EmbeddedResource Include="helpers\chocolateyInstaller.psm1" />
     <EmbeddedResource Include="helpers\functions\Format-FileSize.ps1" />
     <EmbeddedResource Include="helpers\functions\Get-CheckSumValid.ps1" />
+    <EmbeddedResource Include="helpers\functions\Get-ChocolateyConfigValue.ps1" />
     <EmbeddedResource Include="helpers\functions\Get-ChocolateyPath.ps1" />
     <EmbeddedResource Include="helpers\functions\Get-ChocolateyUnzip.ps1" />
     <EmbeddedResource Include="helpers\functions\Get-ChocolateyWebFile.ps1" />

src/chocolatey.resources/helpers/functions/Get-ChocolateyConfigValue.ps1

@@ -0,0 +1,64 @@
+# Copyright © 2022 Chocolatey Software, Inc.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+#
+# You may obtain a copy of the License at
+#
+#   http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+function Get-ChocolateyConfigValue {
+    <#
+.SYNOPSIS
+Retrieve a value from the Chocolatey Configuration file
+
+.DESCRIPTION
+This function will attempt to retrieve the path according to the specified Path Type
+to a valid location that can be used by maintainers in certain scenarios.
+
+.NOTES
+Available in 2.1.0+
+
+.INPUTS
+None
+
+.OUTPUTS
+This function outputs the value of the specified configuration key.
+If the key is not found, there is no output.
+
+.PARAMETER configKey
+The name of the configuration value that should be looked up.
+
+.PARAMETER IgnoredArguments
+Allows splatting with arguments that do not apply. Do not use directly.
+
+.EXAMPLE
+>
+$value = Get-ChocolateyConfigValue -configKey 'cacheLocation'
+#>
+    param(
+        [parameter(Mandatory = $true)]
+        [string] $configKey,
+        [parameter(ValueFromRemainingArguments = $true)]
+        [Object[]] $ignoredArguments
+    )
+
+    try {
+        $installLocation = Get-ChocolateyPath -pathType 'InstallPath'
+        $configPath = Join-Path $installLocation "config\chocolatey.config"
+        [xml]$configContents = Get-Content -Path $configPath
+        return $configContents.chocolatey.config.add |
+                Where-Object { $_.key -eq $configKey } |
+                Select-Object -ExpandProperty value
+    }
+    catch {
+        Write-Warning "Unable to read config value '$configKey' with error"
+        Write-Warning $_
+    }
+}