Absolute Paths In `package.mill` Hinder Isolated Compilation Of Nested Submodules

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Introduction

In Mill 0.12.x, the package declaration requirements were introduced to improve the way projects are structured and managed. However, this change has created conflicts in projects with nested submodules that need to function both as project dependencies and standalone components. This article will explore the issue of absolute paths in package.mill and how they hinder isolated compilation of nested submodules.

The Problem with Absolute Paths

When working with nested submodules, it's common to have a submodule that contains another submodule. For example, in the XiangShan project, we have a submodule rocket-chip that contains cde as its submodule. When cde is used in XianShan, the cde directory requires package build.rocket-chip.cde. However, when we want to develop rocket-chip independently, the same cde directory now requires package build.cde.

This creates a conflict because the absolute path in package.mill is not flexible enough to accommodate both scenarios. The absolute path is fixed and cannot be changed, which means that the submodule cannot be used as both a project dependency and a standalone component.

The Impact on Project Development

The issue with absolute paths in package.mill has a significant impact on project development. When working with nested submodules, developers need to be able to switch between different development scenarios, such as developing a submodule independently or using it as a project dependency. However, the absolute path in package.mill makes it difficult to achieve this flexibility.

For example, in the XiangShan project, we need to be able to develop rocket-chip independently, which requires using package build.cde. However, when we want to use cde as a project dependency in XianShan, we need to use package build.rocket-chip.cde. The absolute path in package.mill makes it difficult to achieve this flexibility, which can lead to confusion and errors.

Possible Solutions

There are a few possible solutions to this issue:

  • Use relative paths: One possible solution is to use relative paths in package.mill instead of absolute paths. This would allow the submodule to be used as both a project dependency and a standalone component.
  • Create a separate package.mill file: Another possible solution is to create a separate package.mill file for each submodule. This would allow each submodule to have its own package.mill file, which would not conflict with the package.mill file of the parent project.
  • Use a build tool that supports relative paths: Some build tools, such as Gradle, support relative paths in the build file. This would allow the submodule to be used as both a project dependency and a standalone component.

Conclusion

The issue of absolute paths in package.mill is a significant problem for projects with nested submodules that need to function both as project dependencies and standalone components. The absolute path in package.mill makes it difficult to achieve flexibility in project development, which can lead to confusion and errors.

However, there are possible solutions to this issue, such as using relative paths, creating a package.mill file, or using a build tool that supports relative paths. By exploring these solutions, developers can find a way to overcome the limitations of absolute paths in package.mill and achieve the flexibility they need to develop their projects effectively.

Example Use Case

Let's take the XiangShan project as an example. We have a submodule rocket-chip that contains cde as its submodule. When cde is used in XianShan, the cde directory requires package build.rocket-chip.cde. However, when we want to develop rocket-chip independently, the same cde directory now requires package build.cde.

To overcome this issue, we can use relative paths in package.mill. We can modify the package.mill file to use relative paths instead of absolute paths. For example, we can use package build.cde instead of package build.rocket-chip.cde.

Here is an example of how we can modify the package.mill file to use relative paths:

// package.mill
module "cde" {
  path = "cde"
  sources = ["cde/src"]
}

module "rocket-chip" {
  path = "rocket-chip"
  sources = ["rocket-chip/src"]
  dependencies = ["cde"]
}

By using relative paths in package.mill, we can overcome the limitations of absolute paths and achieve the flexibility we need to develop our projects effectively.

Best Practices

To avoid the issue of absolute paths in package.mill, it's recommended to follow these best practices:

  • Use relative paths: Use relative paths in package.mill instead of absolute paths.
  • Create a separate package.mill file: Create a separate package.mill file for each submodule.
  • Use a build tool that supports relative paths: Use a build tool that supports relative paths in the build file.

By following these best practices, developers can avoid the issue of absolute paths in package.mill and achieve the flexibility they need to develop their projects effectively.

Introduction

In our previous article, we discussed the issue of absolute paths in package.mill and how they hinder isolated compilation of nested submodules. We also explored possible solutions to this issue, such as using relative paths, creating a separate package.mill file, or using a build tool that supports relative paths.

In this article, we will answer some frequently asked questions about absolute paths in package.mill and provide additional guidance on how to overcome this issue.

Q&A

Q: What is the issue with absolute paths in package.mill?

A: The issue with absolute paths in package.mill is that they are fixed and cannot be changed. This means that the submodule cannot be used as both a project dependency and a standalone component.

Q: How does this issue affect project development?

A: The issue with absolute paths in package.mill affects project development by making it difficult to switch between different development scenarios, such as developing a submodule independently or using it as a project dependency.

Q: What are some possible solutions to this issue?

A: Some possible solutions to this issue include:

  • Using relative paths: Using relative paths in package.mill instead of absolute paths.
  • Creating a separate package.mill file: Creating a separate package.mill file for each submodule.
  • Using a build tool that supports relative paths: Using a build tool that supports relative paths in the build file.

Q: How can I use relative paths in package.mill?

A: To use relative paths in package.mill, you can modify the package.mill file to use relative paths instead of absolute paths. For example, you can use package build.cde instead of package build.rocket-chip.cde.

Q: What are some best practices to avoid the issue of absolute paths in package.mill?

A: Some best practices to avoid the issue of absolute paths in package.mill include:

  • Using relative paths: Using relative paths in package.mill instead of absolute paths.
  • Creating a separate package.mill file: Creating a separate package.mill file for each submodule.
  • Using a build tool that supports relative paths: Using a build tool that supports relative paths in the build file.

Q: Can I use a build tool that supports relative paths in package.mill?

A: Yes, you can use a build tool that supports relative paths in package.mill. Some build tools, such as Gradle, support relative paths in the build file.

Q: How can I create a separate package.mill file for each submodule?

A: To create a separate package.mill file for each submodule, you can create a new package.mill file for each submodule and modify the package.mill file to use relative paths instead of absolute paths.

Q: What are some common mistakes to avoid when using relative paths in package.mill?

A: Some common mistakes to avoid when using relative paths in package.mill include:

  • Using absolute paths: Using absolute paths in package.mill of relative paths.
  • Not modifying the package.mill file: Not modifying the package.mill file to use relative paths instead of absolute paths.
  • Not using a build tool that supports relative paths: Not using a build tool that supports relative paths in the build file.

Conclusion

The issue of absolute paths in package.mill is a significant problem for projects with nested submodules that need to function both as project dependencies and standalone components. However, by using relative paths, creating a separate package.mill file, or using a build tool that supports relative paths, developers can overcome this issue and achieve the flexibility they need to develop their projects effectively.

We hope this Q&A article has provided additional guidance on how to overcome the issue of absolute paths in package.mill. If you have any further questions or need additional assistance, please don't hesitate to contact us.

Example Use Case

Let's take the XiangShan project as an example. We have a submodule rocket-chip that contains cde as its submodule. When cde is used in XianShan, the cde directory requires package build.rocket-chip.cde. However, when we want to develop rocket-chip independently, the same cde directory now requires package build.cde.

To overcome this issue, we can use relative paths in package.mill. We can modify the package.mill file to use relative paths instead of absolute paths. For example, we can use package build.cde instead of package build.rocket-chip.cde.

Here is an example of how we can modify the package.mill file to use relative paths:

// package.mill
module "cde" {
  path = "cde"
  sources = ["cde/src"]
}

module "rocket-chip" {
  path = "rocket-chip"
  sources = ["rocket-chip/src"]
  dependencies = ["cde"]
}

By using relative paths in package.mill, we can overcome the limitations of absolute paths and achieve the flexibility we need to develop our projects effectively.

Best Practices

To avoid the issue of absolute paths in package.mill, it's recommended to follow these best practices:

  • Using relative paths: Using relative paths in package.mill instead of absolute paths.
  • Creating a separate package.mill file: Creating a separate package.mill file for each submodule.
  • Using a build tool that supports relative paths: Using a build tool that supports relative paths in the build file.

By following these best practices, developers can avoid the issue of absolute paths in package.mill and achieve the flexibility they need to develop their projects effectively.