Managing Long Error Output In Bazel Monorepos With Ty

by StackCamp Team 54 views

Hey guys! Let's dive into a common issue faced when working with large Bazel monorepos and Ty, especially when dealing with Python dependencies. We'll explore how to manage those super long error outputs that can be a bit overwhelming. If you've ever been lost in a sea of error messages, this is for you!

The Problem: Overwhelming Error Output

So, you're working in a Bazel monorepo with tons of Python dependencies, right? Everything's humming along, and then BAM! A missing module import throws a massive error output at you. It's like trying to find a needle in a haystack, but the haystack is made of error messages. Let's break down why this happens and what we can do about it.

When a missing module import is detected in a large Bazel monorepo, the error output can become excessively long. This is particularly noticeable when using Ty, a fast type checker for Python. The verbosity stems from the extensive search paths Ty explores to resolve module imports. Imagine having hundreds of Python dependencies; each possible path gets listed in the error message. For example:

error[unresolved-import]: Cannot resolve imported module `deploy.cdk_stack`
 --> services/some_app/some_file.py:10:6
 |
10 | from does.not.exist import SomeClass
 | ^^^^^^^^^^^^^^^^
 |
info: Searched in the following paths during module resolution:
info: 1. /my-repo (first-party code)
info: 2. vendored://stdlib (stdlib typeshed stubs vendored by ty)
info: 3. /my-reppo/.venv/lib/python3.12/site-packages (site-packages)
info: 4. /home/my-user/.cache/bazel/_bazel_my-user/0b37e5958ef8909453aa6cc50b6ee420/execroot/_main/bazel-out/aarch64-fastbuild/bin/build_tools/python_tools/venv.runfiles (editable install)
...
[800 more bazel "editable install" locations]

Why Is This Happening?

The main reason for these lengthy outputs is that Ty meticulously lists every path it searches during module resolution. This includes:

  1. First-party code paths: Your project's internal directories.
  2. Vendored standard library stubs: Typeshed stubs vendored by Ty.
  3. Site-packages directories: Locations where Python packages are installed.
  4. Bazel editable install locations: Often, this is where the real trouble begins. Bazel's "editable install" can create numerous entries, especially in large monorepos. Each entry represents a symlink or a path to a package being developed, and these can quickly multiply.

Having 800+ paths listed is not only burdensome but also obscures the core issue: the unresolved import. While explicitness is appreciated, the sheer volume of information dilutes the message's clarity. It's like trying to read a book where every word is bolded – nothing stands out.

The Impact

  1. Reduced Readability: Sifting through hundreds of lines to identify the root cause of an import error is time-consuming and frustrating.
  2. Obscured Core Issue: The actual problem (e.g., a typo in an import statement or a missing dependency) gets buried under the noise of search paths.
  3. Developer Frustration: Spending more time deciphering error messages than fixing code can lead to developer burnout.

So, what's the solution? How can we tame this beast of verbose output and get back to coding?

Potential Solutions for Managing Verbose Output

Alright, so we know the problem – now let's talk solutions. The goal here is to make the error output more manageable without losing valuable information. Here are a few ideas on how we might achieve that.

1. Verbose vs. Less Verbose Modes

One straightforward approach is to introduce different verbosity modes. Think of it like having a volume control for your error messages. Sometimes you want to blast the details, and sometimes you just need a quiet hum.

  • Less Verbose Mode (Default):
    • In the default mode, Ty could provide a concise summary of the issue. Instead of listing all 800 paths, it might show the first few and then indicate that more paths were searched.
    • For example: "Searched in 800+ paths. See full list by running ty --verbose."
    • This keeps the initial output clean and focused, highlighting the essential information (the unresolved import and its location).
  • Verbose Mode:
    • When more detail is needed, developers could use a flag (e.g., --verbose or --debug) to see the complete list of search paths.
    • This mode would provide the full output, just as it does now, for those deep-dive debugging sessions.

This approach provides a balance between clarity and completeness. Most of the time, the less verbose mode will suffice, but the full details are readily available when needed.

2. Collapsing Similar Paths

Another way to reduce noise is to collapse similar paths in the output. Often, the long list of search locations includes many variations of the same base path, especially with Bazel's editable installs.

  • Grouping Paths:
    • Ty could identify common prefixes in the search paths and group them. For example, instead of listing numerous bazel-out/... paths individually, it could display a collapsed entry like:
Bazel editable install locations:
 - /path/to/bazel-out/aarch64-fastbuild/bin/...
[+799 more]
  • Pattern Recognition:
    • Implement pattern recognition to identify and collapse paths that follow a specific structure (e.g., Bazel's output directories). This could significantly reduce the output length without sacrificing precision.

By collapsing similar paths, we can distill the output to its most meaningful components, making it easier to spot relevant locations.

3. Providing an Invocation to Get the Full List

This is a neat idea that combines brevity with access to full details. The initial error message could suggest a command to run for a complete listing of search paths.

  • Suggestion in Error Message:
    • The error output could include a line like: "Run ty --show-search-paths to see the full list of searched locations."
    • This keeps the default output concise while providing a clear path to more information.
  • Ease of Use:
    • Since Ty is known for its speed, re-running it with a flag to show the full path list is a viable option. It doesn't add significant overhead to the development workflow.

This approach puts the developer in control. They can choose when and if they need the full list of paths, preventing information overload in most cases.

4. Prioritizing Relevant Paths

Not all search paths are created equal. Some are far more likely to contain the missing module than others. Ty could prioritize the display of these paths.

  • Heuristic-Based Prioritization:
    • Use heuristics to determine which paths are most relevant. For instance, paths within the project's source directories or those explicitly listed in the project's configuration might be shown first.
    • Paths related to third-party dependencies or standard library stubs could be de-emphasized or collapsed by default.
  • Configurable Prioritization:
    • Allow developers to configure path prioritization. This could involve specifying patterns to include or exclude, or assigning weights to different path types.

By showing the most likely locations first, developers can quickly narrow their focus and resolve import errors more efficiently.

5. Interactive Mode or Enhanced UI

For a more advanced solution, consider an interactive mode or a richer user interface (UI) for displaying error information.

  • Interactive Mode:
    • Ty could offer an interactive session where developers can explore the search paths, filter them, and view additional details on demand.
    • This could be a command-line interface (CLI) with navigation and filtering options or a more graphical tool.
  • Enhanced UI:
    • Integrate with IDEs or other development tools to display error information in a structured and interactive way. This could involve collapsible sections, tooltips, and links to relevant files or documentation.

An interactive or UI-based approach provides a more engaging and efficient way to explore complex error information, particularly in large projects.

Choosing the Right Approach

So, which of these solutions is the best? Well, it depends on the specific needs and preferences of the developers and the project. A combination of these approaches might be the most effective.

For instance, a default less verbose mode with path collapsing and an option to show the full list could strike a good balance. Prioritizing relevant paths could further enhance the experience.

Ultimately, the goal is to make error messages a helpful tool rather than a hindrance. By managing the verbosity of Ty's output, we can ensure that developers spend less time deciphering errors and more time building great software.

Conclusion

Managing long error outputs in large monorepos is a real challenge, but with the right strategies, it's totally manageable. By implementing features like verbose modes, path collapsing, and prioritized output, we can make Ty's error messages more helpful and less overwhelming. Remember, the goal is to help developers quickly identify and fix issues, so let's keep those error messages clear, concise, and actionable. Keep coding, guys! And let's make those error messages work for us, not against us!