📘 XML Key Substitution Action

This GitHub Action updates XML files by replacing values in <add> elements based on matching environment variables.

It supports:

• <add key="VAR" value="..."> → replaces value
• <add name="VAR" connectionString="..."> → replaces connectionString

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✅ Features

• 🔁 Replaces values of <add> elements with matching key or name from environment variables
• 🔠 Case-insensitive matching for variable names
• ✨ Supports glob patterns like **/*.config
• 🚫 Automatically deduplicates matched files
• 🛡️ Ignores files that aren’t valid XML
• 🛡️ Fails cleanly if no files matched
• 🧾 Works for web.config, app.config, and other XML files
• ⚙️ Fully cross-platform (Windows, Linux, macOS)

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🔧 Inputs

Input	Description	Required
files	Newline-separated list of XML file paths	✅

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🖥️ Compatibility

• ✅ ubuntu-latest
• ✅ windows-latest
• ✅ macos-latest

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🚀 Usage

Because GitHub Actions composite actions cannot directly access the vars, inputs, or secrets contexts, you must manually pass any required values through the env block (see example below). Alternatively you can dump all variables as environment variables using the following script in a step before calling this action:

⚠️ Warning: Dumping all variables may expose sensitive information. Use with caution.

- name: Export all GitHub vars
  run: |
    $json = '${{ toJson(vars) }}'
	$vars = ConvertFrom-Json $json
	foreach ($property in $vars.PSObject.Properties) {
	  $key = $property.Name
	  $value = $property.Value
	  Write-Host "Setting $key to $value"
	  $output = "${key}<<EOF`n${value}`nEOF" # Needed if any value contains a new-line (\r\n)
	  Add-Content -Path $Env:GITHUB_ENV -Value $output
    }
    Write-Host "Variables exported successfully."

🧪 Example workflow step setting environment variables manually

- name: Substitute XML values
  uses: CasperWSchmidt/substitute-xml-action@v1
  with:
    files: |
      deploy/**/*.config
      web.config
  env: # required to pass variables into the action
    ENVIRONMENT: ${{ inputs.environment }}
    CONNECTION_STRING: ${{ secrets.MY_DATABASE_CONNECTION  }}
	ROOT_DIRECTORY: ${{ vars.MY_ROOT_DIRECTORY }}

🧪 Example workflow step using dynamic variable export

- name: Export all GitHub vars
  run: |
    $json = '${{ toJson(vars) }}'
	$vars = ConvertFrom-Json $json
	foreach ($property in $vars.PSObject.Properties) {
	  $key = $property.Name
	  $value = $property.Value
	  Write-Host "Setting $key to $value"
	  $output = "${key}<<EOF`n${value}`nEOF" # Needed if any value contains a new-line (\r\n)
	  Add-Content -Path $Env:GITHUB_ENV -Value $output
    }
    Write-Host "Variables exported successfully."
	
- name: Substitute XML values
  uses: CasperWSchmidt/substitute-xml-action@v1
  with:
    files: |
      deploy/**/*.config
      web.config

🗂️ Example web.config (before)

<configuration>
  <appSettings>
    <add key="Environment" value="Dummy" />
    <add key="RootDirectory" value="Dummy" />
  </appSettings>
  <connectionStrings>
    <add name="DefaultConnection" connectionString="..." />
  </connectionStrings>
</configuration>

✅ Result (after)

<configuration>
  <appSettings>
    <add key="Environment" value="Production" />
    <add key="RootDirectory" value="C:\Some\Path" />
  </appSettings>
  <connectionStrings>
    <add name="DefaultConnection" connectionString="Server=sql;Database=prod;User Id=admin;" />
  </connectionStrings>
</configuration>