Analyzing the Build Output

Oct 13, 2025 by talynt.org 147 views

Problem

When working with snforge_std as a dev-dependency, it pulls in snforge_scarb_plugin due to its proc_macro plugin nature. However, the caching mechanism seems to be failing for this particular dependency, resulting in it being recompiled every time using Cargo. This is a problem because snforge_scarb_plugin shouldn't even be pulled when running scarb build, but that's a separate issue for the scarb project.

Understanding the Issue

The issue at hand is that the cache is not working as expected for snforge_scarb_plugin. This plugin is a proc_macro plugin, which means it's used to generate code at compile-time. As a result, it's not surprising that the cache is failing to work for it. However, this is still a problem because it's causing unnecessary recompilation and slowing down the build process.

Analyzing the Build Output

Let's take a closer look at the build output to understand what's happening:

# scarb build -p starknet_ibc_contracts
  
    Updating crates.io index
 Downloading crates ...
  Downloaded serde_derive v1.0.217
  Downloaded scarb-stable-hash v1.0.0
...
  Downloaded cairo-lang-primitive-token v1.0.0
  Downloaded libc v0.2.[16](https://github.com/informalsystems/ibc-starknet/actions/runs/13809907305/job/38628929334#step:8:17)9
   Compiling snforge_scarb_plugin v0.34.0
   Compiling proc-macro2 v1.0.93
...
   Compiling cairo-lang-parser v2.9.3
   Compiling snforge_scarb_plugin v0.34.0 (/home/runner/.cache/scarb/registry/src/scarbs.xyz-9djtpev4jug5q/snforge_scarb_plugin-0.34.0)
    Finished `release` profile [optimized] target(s) in 1m [23](https://github.com/informalsystems/ibc-starknet/actions/runs/13809907305/job/38628929334#step:8:24)s
   Compiling lib(starknet_ibc_contracts) starknet_ibc_contracts v0.1.0 (/home/runner/work/ibc-starknet/ibc-starknet/cairo-contracts/packages/contracts/Scarb.toml)
   Compiling starknet-contract(starknet_ibc_contracts) starknet_ibc_contracts v0.1.0 (/home/runner/work/ibc-starknet/ibc-starknet/cairo-contracts/packages/contracts/Scarb.toml)
    Finished `dev` profile target(s) in 3 minutes

As we can see, snforge_scarb_plugin is being recompiled every time, even though it's already been compiled. This is a clear indication that the cache is not working as expected.

Possible Causes

There are several possible causes for this issue:

Cache Invalidation: It's possible that the cache is being invalidated for some reason, causing snforge_scarb_plugin to be recompiled every time.
Dependency Issues: There might be some dependency issues that are causing snforge_scarb_plugin to be recompiled.
Cargo Configuration: There could be some configuration issues with Cargo that are causing the cache to fail.

Possible Solutions

Here are some possible solutions to this issue:

Check Cache Configuration: Make sure that the cache is properly configured and that it's not being invalidated for some reason.
Update Dependencies: Make sure that all dependencies are up-to-date and that there are no issues with them.
Check Cargo Configuration: Check the Cargo configuration to make sure that it's not causing any issues with the cache.

Conclusion

Q&A

Q: What is the issue with `snforge_scarb_plugin`?

A: The issue with snforge_scarb_plugin is that the caching mechanism is not working as expected, causing it to be recompiled every time.

Q: Why is `snforge_scarb_plugin` being recompiled every time?

A: snforge_scarb_plugin is being recompiled every time because it's a proc_macro plugin, which means it's used to generate code at compile-time. This is causing the cache to fail.

Q: What are the possible causes of this issue?

A: There are several possible causes of this issue, including:

Cache Invalidation: The cache might be being invalidated for some reason, causing snforge_scarb_plugin to be recompiled every time.
Dependency Issues: There might be some dependency issues that are causing snforge_scarb_plugin to be recompiled.
Cargo Configuration: There could be some configuration issues with Cargo that are causing the cache to fail.

Q: How can I fix this issue?

A: To fix this issue, you can try the following:

Check Cache Configuration: Make sure that the cache is properly configured and that it's not being invalidated for some reason.
Update Dependencies: Make sure that all dependencies are up-to-date and that there are no issues with them.
Check Cargo Configuration: Check the Cargo configuration to make sure that it's not causing any issues with the cache.

Q: What are the benefits of fixing this issue?

A: Fixing this issue will improve the build process by reducing the time it takes to compile snforge_scarb_plugin. This will also improve the overall performance of the project.

Q: How can I prevent this issue from happening in the future?

A: To prevent this issue from happening in the future, you can:

Regularly Update Dependencies: Make sure that all dependencies are up-to-date and that there are no issues with them.
Monitor Cache Configuration: Regularly check the cache configuration to make sure that it's properly configured and not being invalidated for some reason.
Check Cargo Configuration: Regularly check the Cargo configuration to make sure that it's not causing any issues with the cache.

Q: What are some best practices for caching in Cargo?

A: Some best practices for caching in Cargo include:

Use a consistent cache directory: Make sure that the cache directory is consistent across all builds.
Use a cache invalidation strategy: Implement a cache invalidation strategy to ensure that the cache is properly invalidated when necessary.
Monitor cache performance: Regularly monitor cache performance to ensure that it's not causing any issues with the build process.

Q: What are some common mistakes to avoid when caching in Cargo?

A: Some common mistakes to avoid when caching in Cargo include:

Not properly configuring the cache: Failing to properly configure the cache can cause issues with the build process.
Not regularly updating dependencies: Failing to regularly update dependencies can cause issues with the build process.
Not monitoring cache performance: Failing to regularly monitor cache performance can cause issues with the build process.