Resolving EPERM Issues in Visual Studio 2015 Cordova Projects

When working with Cordova applications in Visual Studio 2015, developers often encounter a frustrating issue related to file permissions. This problem typically manifests when trying to build a Cordova project that’s under source control, particularly with Team Foundation Server (TFS). Understanding and resolving this issue is crucial for maintaining a smooth development workflow.

Understanding the Problem

The core issue stems from file permissions in the platforms directory of your Cordova project. Even though this directory is typically excluded from source control (as it should be), the files within it become marked as read-only. This creates a conflict when the build process attempts to modify these files, resulting in the “EPERM, operation not permitted” error.

This situation commonly occurs in the following scenario:

  1. You create a new Cordova application in Visual Studio 2015
  2. The project is added to TFS source control
  3. The platforms folder is correctly excluded from source control
  4. After checking out the project and making changes, the build fails
  5. The error occurs in clean.bat within the platforms folder

Root Cause Analysis

The read-only attribute is being applied to the platforms directory and its contents, even though these files aren’t under source control. This is a known behavior in Visual Studio 2015’s Cordova tools, where the build process expects to have full write access to these files. When the permissions are restricted, the build process cannot modify the necessary files, leading to the EPERM error.

Solution Implementation

To resolve this issue, we need to ensure that the read-only attribute is removed from the platforms directory before the build process begins. This can be achieved by modifying the project file to include a pre-build step.

Step 1: Modify Project File

First, you’ll need to edit the project file:

  1. Right-click the project in Solution Explorer
  2. Select “Unload Project”
  3. Right-click the unloaded project and choose “Edit Project File”

Step 2: Add Build Configuration

Add the following configuration to your project file (typically after the first PropertyGroup):

<Target Name="BeforeBuild">
  <Exec Command="attrib -r &quot;$(MSBuildProjectDirectory)\platforms&quot; /s /d" />
</Target>

This target runs before each build and removes the read-only attribute from the platforms directory and all its contents.

Step 3: Reload Project

  1. Save the project file
  2. Right-click the project and select “Reload Project”
  3. Build your project as normal

Understanding the Solution

The attrib command works as follows:

  • -r: Removes the read-only attribute
  • /s: Applies the command recursively to all subdirectories
  • /d: Processes folders as well as files
  • The $(MSBuildProjectDirectory) variable points to your project root

Best Practices

When implementing this solution, consider these best practices:

  1. Document the fix: Add a comment in your project file explaining why this step is needed
  2. Test thoroughly: Verify that the build process works correctly
  3. Team communication: Inform your team about this change
  4. Version control: Ensure everyone updates their project files

Alternative Approaches

If the above method doesn’t work for your setup, consider these alternatives:

  1. Git exclusions: If using Git instead of TFS, ensure proper .gitignore configuration
  2. Build server configuration: Ensure your build server has proper permissions
  3. Manual cleanup: Periodically clean the platforms directory manually

Preventing Future Issues

To prevent this issue from recurring:

  1. Ensure your source control is properly configured to exclude the platforms directory
  2. Use consistent build scripts across your team
  3. Document the Cordova build process for your team
  4. Consider using a pre-build checklist

Conclusion

While the EPERM error can be frustrating, it’s a solvable problem with a straightforward fix. By adding a pre-build step that removes file permissions, you can ensure that your Cordova builds proceed smoothly without permission-related errors. This approach works reliably and doesn’t require any external tools or complex workarounds.

Remember that maintaining proper source control configuration and understanding your build process are key to preventing similar issues in the future. The solution provided here is a best practice for Cordova projects in Team Foundation Server environments.

Note: Always back up your project files before making changes, and test the solution thoroughly in a development environment before applying it to your production builds.