Docs.rs Build Failure: Ratatui-widgets Issue

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Docs.rs Build Failure: Troubleshooting ratatui-widgets

Hey guys! We've got a bit of a situation on our hands with the ratatui-widgets crate. It seems like the docs.rs build is failing, and we need to figure out why. This article dives deep into the issue, exploring the potential causes and solutions. Let's get started!

Understanding the Problem

Specifically, the API documentation for ratatui-widgets (version 0.3.0-beta.0) is currently unavailable on docs.rs. The error logs point to a failure during the build process, indicating that the system couldn't resolve the ratatui module.

Here's a snippet from the error log:

[INFO] running `Command { std: "docker" "start" "-a" "a655db6a36aaf614ee66afa9aa4719c378e18405572fd22f9039f0d30842d7ff", kill_on_drop: false }`
[INFO] [stderr] Scraping ratatui-widgets v0.3.0-beta.0 (/opt/rustwide/workdir)
[INFO] [stderr] error[E0433]: failed to resolve: use of unresolved module or unlinked crate `ratatui`
[INFO] [stderr] --> examples/barchart.rs:20:5
[INFO] [stderr] |
[INFO] [stderr] 20 | use ratatui::layout::{Constraint, Layout, Rect};
[INFO] [stderr] | ^^^^^^^ use of unresolved module or unlinked crate `ratatui`
[INFO] [stderr] |
[INFO] [stderr] = help: if you wanted to use a crate named `ratatui`, use `cargo add ratatui` to add it to your `Cargo.toml`

The core issue revolves around the ratatui crate not being found during the documentation build process on docs.rs. This is particularly puzzling because the code works locally using cargo +nightly doc -Zunstable-options -Zrustdoc-scrape-examples. So, what's different between the local environment and the docs.rs build environment?

Potential Cause: Scrape Examples Feature

One leading theory suggests that the scrape-examples feature in rustdoc might be the culprit. This feature attempts to run the examples within the ratatui-widgets crate to generate documentation. The problem is that these examples depend on the ratatui crate itself. This might create a circular dependency or a situation where ratatui isn't available in the build environment for ratatui-widgets.

Deep Dive into Scrape Examples

The scrape-examples feature is a powerful tool that allows rustdoc to automatically include examples from your crate's source code in the generated documentation. This can significantly enhance the user experience by providing practical demonstrations of how to use your library. However, it also introduces some complexity, especially when dealing with dependencies.

When scrape-examples is enabled, rustdoc essentially tries to compile and run the examples in your code. This means that all the dependencies required by the examples must be available during the build process. In the case of ratatui-widgets, the examples rely on the ratatui crate. If ratatui isn't properly linked or available in the build environment, the compilation will fail, leading to the errors we're seeing.

Why Does It Work Locally?

You might be wondering, "If this is the issue, why does it work perfectly fine on my local machine?" The key lies in how ratatui is managed as a dependency. Locally, ratatui is included as a dev-dependency in the Cargo.toml file of ratatui-widgets. Dev-dependencies are dependencies that are only needed for development, testing, and examples, but not for the main library code.

When you run cargo +nightly doc -Zunstable-options -Zrustdoc-scrape-examples locally, Cargo resolves the dev-dependencies, including ratatui, and makes them available during the documentation build. This is why the examples compile and run without any issues.

However, docs.rs has a different build environment. It might not automatically resolve dev-dependencies when building documentation. This is a common practice to keep the build environment lean and focused on the core library dependencies. As a result, ratatui isn't available when docs.rs tries to build the documentation for ratatui-widgets, leading to the unresolved module error.

Potential Solutions

So, what can we do to fix this build failure? Here are a few potential solutions we can explore:

  1. Re-evaluate Dependency Structure: The most robust solution might involve rethinking the dependency structure. If ratatui-widgets examples heavily rely on ratatui, perhaps ratatui should be a regular dependency instead of just a dev-dependency. This ensures that ratatui is always available during the build process, both locally and on docs.rs.

    • To implement this, you would move the ratatui dependency from the [dev-dependencies] section to the [dependencies] section in the Cargo.toml file of ratatui-widgets. This change signals that ratatui is a fundamental dependency for the crate, not just for development-related tasks. However, this change needs careful consideration, as it might impact the crate's users if they don't intend to use ratatui directly.

  2. Conditional Compilation: Another approach is to use conditional compilation to exclude the examples from being built on docs.rs. This can be achieved by using feature flags. We can introduce a feature, for instance, build-examples, and only include the example code when this feature is enabled.

    • This involves wrapping the example code with #[cfg(feature = "build-examples")] directives. In the Cargo.toml file, we can specify that the build-examples feature is enabled by default locally but not on docs.rs. This way, the examples are built locally where ratatui is available as a dev-dependency, but they are skipped on docs.rs, preventing the build failure. This approach offers a balance between having working examples locally and ensuring successful documentation builds on docs.rs.

  3. Docs.rs Configuration: Docs.rs provides some configuration options that might help in this situation. We could explore if there's a way to instruct docs.rs to build with dev-dependencies or to disable the scrape-examples feature altogether.

    • Docs.rs uses a Cargo.toml-like file called docs.rs/config.toml to configure the build process. We can add settings in this file to customize the build, such as enabling features or setting environment variables. Investigating the available configuration options and experimenting with them might provide a solution without modifying the crate's code directly. This approach keeps the crate's dependencies clean and allows for specific build configurations for documentation purposes.

  4. Patching the Crate: As a last resort (and generally not recommended for long-term solutions), we could consider patching the crate on docs.rs. This involves modifying the crate's source code directly within the docs.rs build environment. This could involve temporarily removing the examples or modifying the dependencies.

    • Patching is a powerful but potentially risky approach. It involves making direct changes to the crate's source code within the build environment, which can lead to inconsistencies between the published documentation and the actual crate code. Patching should only be considered as a temporary workaround when other solutions are not feasible, and it should be accompanied by a clear plan to address the underlying issue and remove the patch as soon as possible.

Diving Deeper: Practical Steps

Let's break down each potential solution with practical steps you can take.

1. Re-evaluating Dependency Structure

  • Modify Cargo.toml: Open your ratatui-widgets Cargo.toml file.
  • Move Dependency: Find the ratatui dependency under [dev-dependencies] and move it to the [dependencies] section.
  • Test Locally: Run cargo build and cargo test to ensure your library still builds and tests pass.
  • Push Changes: Commit and push your changes to your repository.
  • Check Docs.rs: Monitor docs.rs to see if the build now succeeds.

This is the most straightforward approach, but it's crucial to consider the implications of making ratatui a regular dependency. If users of ratatui-widgets don't need ratatui directly, this change might add unnecessary dependencies to their projects.

2. Conditional Compilation

  • Define Feature: In your Cargo.toml, add a feature under the [features] section:
    [features]
build-examples = []
  • Conditional Compilation Directives: In your example files, wrap the code that uses ratatui with #[cfg(feature = "build-examples")]:
    #[cfg(feature = "build-examples")]
use ratatui::layout::{Constraint, Layout, Rect};

#[cfg(feature = "build-examples")]
fn main() {
    // ... your example code ...
}
  • Enable Feature Locally: When building locally, use cargo +nightly doc -Zunstable-options -Zrustdoc-scrape-examples --features build-examples.
  • Disable Feature on Docs.rs: This is the tricky part. You'll need to create a docs.rs/config.toml file in your repository and configure it to build without the build-examples feature. The exact syntax for this might vary, so consult the docs.rs documentation for the most up-to-date instructions.

Conditional compilation provides a flexible way to manage dependencies and features in different build environments. However, it adds complexity to your codebase and requires careful management of feature flags.

3. Docs.rs Configuration

  • Create docs.rs/config.toml: If it doesn't exist, create a docs.rs directory in your repository and add a config.toml file inside it.
  • Explore Options: Consult the docs.rs documentation to see if there are options to enable dev-dependencies or disable scrape-examples. Look for settings related to build flags or feature flags.
  • Configure Build: Add the appropriate configuration settings to your config.toml file.
  • Test and Monitor: Push your changes and monitor docs.rs to see if the build succeeds.

Using docs.rs configuration is a clean way to customize the documentation build process without modifying your crate's code. However, it requires familiarity with docs.rs's configuration options.

4. Patching the Crate

  • Identify Problematic Code: Determine which examples or code sections are causing the build failure.
  • Create a Patch: Create a patch file that removes or modifies the problematic code. This might involve temporarily commenting out the examples or removing the use ratatui statements.
  • Apply Patch on Docs.rs: Docs.rs might have a mechanism for applying patches, but this is likely an advanced feature and might not be readily available.
  • Monitor and Revert: If you manage to apply a patch, monitor the build and ensure it succeeds. Remember that this is a temporary solution, and you'll need to address the underlying issue and remove the patch as soon as possible.

Patching is a last resort and should be avoided if possible. It's a temporary fix that can lead to inconsistencies and maintenance issues.

Conclusion

Troubleshooting build failures on docs.rs can be challenging, but by understanding the potential causes and exploring different solutions, we can get ratatui-widgets documentation back on track. In this case, the scrape-examples feature and the handling of dev-dependencies seem to be the primary suspects. We've outlined several approaches, from re-evaluating dependencies to using conditional compilation and docs.rs configuration. By systematically trying these solutions, we can hopefully resolve the issue and ensure that the documentation for ratatui-widgets is available to everyone. Good luck, and let me know if you have any other questions! We are in this together to solve the issue :)