Fixing Exclude Conditions In .NET Project Templates

Are you struggling with conditional file exclusion in your .NET project templates? You're not alone! Many developers encounter issues when trying to exclude files based on conditions within their templates. This article will guide you through the common pitfalls and provide solutions to ensure your exclude conditions work as expected. Let's dive in and get your templates working smoothly!

Understanding the Problem

The core issue often lies in the configuration of your template.json file, specifically within the symbols and sources sections. You might have defined symbols (parameters) and conditions, but the exclude rules aren't being applied correctly. This can be frustrating, especially when you expect certain files to be omitted based on user input or predefined settings.

The key is to understand how the template engine interprets your conditions and applies the exclude rules. Let’s break down a typical scenario and identify potential problems.

Scenario: Conditional MongoDB File Exclusion

Imagine you're building a .NET project template that supports optional MongoDB integration. You want to exclude MongoDB-related files (e.g., MongoRepository.cs, IMongoRepository.cs) if the user doesn't choose to include MongoDB during project creation. Your template.json might look something like this:

{
  "symbols": {
    "HostIdentifier": {
      "type": "bind",
      "binding": "HostIdentifier"
    },
    "mongoAddition": {
      "type": "parameter",
      "description": "Should mongo Provider be included",
      "allowMultipleValues": false,
      "enableQuotelessLiterals": true,
      "choices": [
        {
          "choice": "true",
          "description": "adds mongo to the provided service list",
          "displayName": "True"
        },
        {
          "choice": "None",
          "description": "No Mongo will be included"
        }
      ]
    },
    "Mongo": {
      "type": "computed",
      "value": "mongoAddition == true"
    }
  },
  "sources": [
    {
      "exclude": [
        ".template.config/**"
      ]
    },
    {
      "modifiers": [
        {
          "condition": "mongoAddition != true",
          "exclude": [
            "**/MongoRepository.cs",
            "**/IMongoRepository.cs"
          ]
        }
      ]
    }
  ]
}

In this setup, you have a mongoAddition parameter that determines whether MongoDB support should be included. The Mongo symbol is a computed value based on mongoAddition. The intention is to exclude MongoRepository.cs and IMongoRepository.cs if mongoAddition is not true. However, you might find that these files are not being excluded as expected.

Common Pitfalls and Solutions

Let's explore the common reasons why your exclude conditions might not be working and how to fix them.

1. Incorrect Condition Logic

One of the most frequent issues is the logic within your condition. Double-check your condition to ensure it accurately reflects when the files should be excluded. In the example above, the condition mongoAddition != true seems straightforward, but it might not behave as expected due to how the template engine handles string comparisons.

Solution:

Instead of directly comparing strings, consider using a boolean symbol or adjusting your condition to be more explicit. Here’s an improved approach:

1. Modify the mongoAddition choices to use boolean values (true and false instead of strings like `