Tell `uv sync` to use a specific index for one package

by

Summary

The issue at hand involves using uv sync with a specific package index for torch while resolving other packages normally. The user wants to utilize the https://download.pytorch.org/whl/cpu index for torch and avoid conflicts with other packages.

Root Cause

The root cause of this issue is the presence of conflicting indexes for the torch package. This occurs when a dependency, in this case, torch, is referenced from a git source within a workspace member, leading to uv sync being unable to resolve the package index.

Why This Happens in Real Systems

This issue arises in real systems due to the following reasons:

  • Multiple package sources: When multiple sources are used to resolve dependencies, conflicts can occur if the same package is available in different sources.
  • Nested dependencies: Dependencies that are nested within other dependencies can lead to conflicts if they reference different package indexes.
  • Custom package indexes: Using custom package indexes, like the one for torch, can sometimes lead to conflicts with the default package indexes.

Real-World Impact

The real-world impact of this issue includes:

  • Failed dependency resolution: The uv sync command may fail to resolve dependencies due to conflicting indexes.
  • Package installation issues: Conflicting indexes can lead to issues with package installation, causing builds to fail.
  • Dependency management complexity: Managing dependencies with custom indexes can add complexity to the development process.

Example or Code

uv sync --index https://download.pytorch.org/whl/cpu torch

This command tells uv sync to use the specified index for the torch package.

How Senior Engineers Fix It

Senior engineers fix this issue by:

  • Specifying the package index: Using the --index flag to specify the package index for the conflicting package.
  • Resolving nested dependencies: Ensuring that nested dependencies are properly resolved to avoid conflicts.
  • Managing custom package indexes: Carefully managing custom package indexes to avoid conflicts with default indexes.

Why Juniors Miss It

Juniors may miss this issue due to:

  • Lack of understanding of dependency resolution: Not fully understanding how dependency resolution works in uv sync.
  • Insufficient experience with custom package indexes: Limited experience with using custom package indexes, leading to unawareness of potential conflicts.
  • Overlooking nested dependencies: Failing to consider the impact of nested dependencies on package resolution.