rationalize-deps

name	rationalize-deps
description	Analyze Cargo.toml dependencies and attempt to remove unused features to reduce compile times and binary size

Rationalize Dependencies

This skill analyzes Cargo.toml dependencies to identify and remove unused features.

Overview

Many crates enable features by default that may not be needed. This skill:

1. Identifies dependencies with default features enabled
2. Tests if default-features = false works
3. Identifies which specific features are actually needed
4. Verifies compilation after changes

Step 1: Identify the target

Ask the user which crate(s) to analyze:

• A specific crate name (e.g., "tokio", "serde")
• A specific workspace member (e.g., "quickwit-search")
• "all" to scan the entire workspace

Step 2: Analyze current dependencies

For the workspace Cargo.toml (quickwit/Cargo.toml), list dependencies that:

• Do NOT have default-features = false
• Have default features that might be unnecessary

Run: cargo tree -p <crate> -f "{p} {f}" --edges features to see what features are actually used.

Step 3: For each candidate dependency

3a: Check the crate's default features

Look up the crate on crates.io or check its Cargo.toml to understand:

• What features are enabled by default
• What each feature provides

Use: cargo metadata --format-version=1 | jq '.packages[] | select(.name == "<crate>") | .features'

3b: Try disabling default features

Modify the dependency in quickwit/Cargo.toml:

From:

some-crate = { version = "1.0" }

To:

some-crate = { version = "1.0", default-features = false }

3c: Run cargo check

Run: cargo check --workspace (or target specific packages for faster feedback)

If compilation fails:

1. Read the error messages to identify which features are needed
2. Add only the required features explicitly:

   some-crate = { version = "1.0", default-features = false, features = ["needed-feature"] }
   

3. Re-run cargo check

3d: Binary search for minimal features

If there are many default features, use binary search:

1. Start with no features
2. If it fails, add half the default features
3. Continue until you find the minimal set

Step 4: Document findings

For each dependency analyzed, report:

• Original configuration
• New configuration (if changed)
• Features that were removed
• Any features that are required

Step 5: Verify full build

After all changes, run:

cargo check --workspace --all-targets
cargo test --workspace --no-run

Common Patterns

Serde

Often only needs derive:

serde = { version = "1.0", default-features = false, features = ["derive", "std"] }

Tokio

Identify which runtime features are actually used:

tokio = { version = "1.0", default-features = false, features = ["rt-multi-thread", "macros", "sync"] }

Reqwest

Often doesn't need all TLS backends:

reqwest = { version = "0.11", default-features = false, features = ["rustls-tls", "json"] }

Rollback

If changes cause issues:

git checkout quickwit/Cargo.toml
cargo check --workspace

Tips

• Start with large crates that have many default features (tokio, reqwest, hyper)
• Use cargo bloat --crates to identify large dependencies
• Check cargo tree -d for duplicate dependencies that might indicate feature conflicts
• Some features are needed only for tests - consider using [dev-dependencies] features