priority: critical

Workspace Dependency Management

Cargo Workspace Fundamentals

A workspace coordinates multiple crates under unified configuration. This is critical for polyglot projects with core library + language bindings.

workspace/Cargo.toml:

toml

[workspace]
members = [
    "crates/html-to-markdown",           # Core library
    "crates/html-to-markdown-py",        # PyO3 bindings
    "crates/html-to-markdown-node",      # NAPI-RS bindings
    "crates/html-to-markdown-rb",        # Magnus bindings
    "crates/html-to-markdown-php",       # PHP extension
    "crates/html-to-markdown-wasm",      # WebAssembly
    "crates/html-to-markdown-ffi",       # C FFI library
    "crates/html-to-markdown-cli",       # CLI binary
]

resolver = "2"  # Always use v2 for modern dependency resolution

[workspace.package]
version = "0.5.0"              # Single source of truth
authors = ["Team"]
edition = "2021"
rust-version = "1.70"

Version Synchronization

Golden Rule: Core library and all bindings must have the same version number.

Problem: Manual version updates across 8+ Cargo.toml files leads to inconsistency.

Solution: Use workspace.package version inheritance + sync script.

In each crate's Cargo.toml:

toml

[package]
name = "html-to-markdown-py"
version.workspace = true       # Inherit from workspace
authors.workspace = true
edition.workspace = true
rust-version.workspace = true

Version sync script (scripts/sync_versions.py):

python

#!/usr/bin/env python3
import tomllib
import toml
from pathlib import Path

def sync_versions(workspace_root: Path, new_version: str):
    """Sync version across all crates in workspace"""
    workspace_toml = workspace_root / "Cargo.toml"

    # Update workspace version
    with open(workspace_toml, "rb") as f:
        data = tomllib.load(f)
    data["workspace"]["package"]["version"] = new_version
    with open(workspace_toml, "w") as f:
        toml.dump(data, f)

    # Update all crates (non-workspace members)
    for crate_dir in (workspace_root / "crates").iterdir():
        if crate_dir.is_dir():
            crate_toml = crate_dir / "Cargo.toml"
            if crate_toml.exists():
                with open(crate_toml, "rb") as f:
                    data = tomllib.load(f)
                if "version" in data.get("package", {}):
                    data["package"]["version"] = new_version
                with open(crate_toml, "w") as f:
                    toml.dump(data, f)

    print(f"Synced all crates to version {new_version}")

if __name__ == "__main__":
    import sys
    if len(sys.argv) < 2:
        print("Usage: sync_versions.py <new_version>")
        sys.exit(1)
    sync_versions(Path.cwd(), sys.argv[1])

Usage:

bash

./scripts/sync_versions.py 0.6.0
cargo update -w  # Update workspace lockfile
git add -A && git commit -m "chore: bump version to 0.6.0"

Path Dependencies for Core Library

Binding crates depend on core via path dependency:

toml

# crates/html-to-markdown-py/Cargo.toml
[dependencies]
html-to-markdown = { path = "../html-to-markdown", version = "0.5.0" }
pyo3 = { version = "0.20", features = ["extension-module"] }

Why version constraint + path?

•Path ensures local development uses local code
•Version constraint ensures semver is respected if/when published to crates.io

MSRV Policy (Minimum Supported Rust Version)

Define in workspace.package:

toml

[workspace.package]
rust-version = "1.70"

Update workflow:

•Update rust-version in workspace Cargo.toml
•Add CI check to test MSRV
•Run: cargo +1.70 test to verify

CI workflow for MSRV:

yaml

- name: Test MSRV
  run: |
    rustup install 1.70
    cargo +1.70 test --all-features

Dependency Constraints Best Practices

Be explicit with version ranges:

toml

# BAD: Too permissive
pyo3 = "*"
tokio = "1"

# GOOD: Explicit ranges
pyo3 = "0.20"          # Patch updates OK
tokio = "1.35"         # Patch updates OK (1.35.x)
thiserror = "1.0"      # Conservative

# Exact versions for unstable features
napi = "= 2.13.0"

Shared Dependencies

Prevent duplicate dependency trees by centralizing versions:

toml

[workspace.dependencies]
tokio = { version = "1.35", features = ["full"] }
serde = { version = "1.0", features = ["derive"] }
thiserror = "1.0"
tracing = "0.1"

Each crate imports from workspace:

toml

[dependencies]
tokio = { workspace = true, features = ["rt-multi-thread"] }
serde = { workspace = true }

Lock File Strategy

Commit Cargo.lock for reproducible builds:

bash

git add Cargo.lock
git commit -m "chore: update lockfile"

This ensures:

•CI builds are deterministic
•Language bindings get same underlying Rust code
•Security updates are tracked

Workspace Member Discovery

Common pitfall: Forgetting to add crate to workspace members.

Verify workspace integrity:

bash

cargo metadata --format-version 1 | jq '.workspace_members'

Should list all crates. If missing:

toml

[workspace]
members = [
    "crates/html-to-markdown",
    "crates/html-to-markdown-py",
    # ... add missing member here
]

Cross-Crate Dependencies

Problem: Circular dependencies between crates in workspace.

Solution: Clearly defined dependency graph.

code

html-to-markdown (core library)
├── html-to-markdown-py (depends on core)
├── html-to-markdown-node (depends on core)
├── html-to-markdown-rb (depends on core)
├── html-to-markdown-ffi (depends on core)
└── html-to-markdown-cli (depends on core)

Bad structure (avoid):

code

- html-to-markdown depends on html-to-markdown-py
- html-to-markdown-py depends on html-to-markdown
# Circular!

Building Specific Members

bash

# Build single crate
cargo build -p html-to-markdown-py

# Build all members
cargo build --all

# Build all but exclude certain platform bindings
cargo build --all --exclude html-to-markdown-wasm

# Test single member
cargo test -p html-to-markdown

Feature Gate Coordination

Workspace-level features for conditional compilation:

toml

[workspace.dependencies]
tokio = { version = "1.35", optional = true, features = ["full"] }

# In core library Cargo.toml
[package]
features = ["default"]

[features]
default = ["sync"]
async-runtime = ["tokio", "dep:tokio"]
ffi = []

Binding crates enable needed features:

toml

# html-to-markdown-py/Cargo.toml
[dependencies]
html-to-markdown = { path = "../html-to-markdown", version = "0.5.0", features = ["sync"] }

Example: Real Workspace with Version Sync

Initial setup:

bash

cargo new --lib crates/html-to-markdown
cargo new --lib crates/html-to-markdown-py
cargo new --lib crates/html-to-markdown-node
# ... etc

# Create workspace at root
echo '[workspace]
members = ["crates/*"]
resolver = "2"
[workspace.package]
version = "0.5.0"
' > Cargo.toml

Sync versions for 0.6.0 release:

bash

./scripts/sync_versions.py 0.6.0
cargo test --all          # Verify all members still work
cargo build --release --all
git add -A && git commit -m "chore: bump version to 0.6.0"

Anti-Patterns to Avoid

•

Mismatched versions across crates:

toml

# BAD: Different versions
# html-to-markdown/Cargo.toml: version = "0.5.0"
# html-to-markdown-py/Cargo.toml: version = "0.4.9"

# GOOD: Use workspace.package inheritance
version.workspace = true

•

Circular dependencies:

toml

# BAD: Core depends on binding
# html-to-markdown/Cargo.toml:
html-to-markdown-py = { path = "../html-to-markdown-py" }

# GOOD: Only bindings depend on core

•

Uncommitted Cargo.lock:

bash

# BAD: Cargo.lock in .gitignore

# GOOD: Commit for reproducibility
git add Cargo.lock

•

Too many nested workspaces:

toml

# BAD: Nested workspaces confuse resolution
# /Cargo.toml: workspace with members
# /crates/sub/Cargo.toml: another workspace!

# GOOD: Single root workspace

Cross-references to Related Skills

•rust-module-organization-public-api-design: APIs exposed across workspace members
•binding-crate-architecture-patterns: Structure of binding crates within workspace
•build-profiles: Coordinating build modes across workspace
•release-and-deployment-processes: Version bumping workflow