Cargo Processor

Purpose

Builds Rust projects using Cargo. Each Cargo.toml produces a cached success marker, allowing RSConstruct to skip rebuilds when source files haven’t changed.

How It Works

Discovers files named Cargo.toml in the project. For each Cargo.toml found, the processor runs cargo build (or a configured command) in that directory.

Input Tracking

The cargo processor tracks all .rs and .toml files in the Cargo.toml’s directory tree as inputs. This includes:

Cargo.toml and Cargo.lock
All Rust source files (src/**/*.rs)
Test files, examples, benches
Workspace member Cargo.toml files

When any tracked file changes, rsconstruct will re-run cargo.

For Cargo workspaces, each Cargo.toml (root and members) is discovered as a separate product. To build only the workspace root, use exclude_paths to skip member directories, or configure scan_dir to limit discovery.

Source Files

Input: Cargo.toml plus all .rs and .toml files in the project tree
Output: None (mass_generator — produces output in target directory)

Configuration

[processor.cargo]
cargo = "cargo"          # Cargo binary to use
command = "build"        # Cargo command (build, check, test, clippy, etc.)
args = []                # Extra arguments passed to cargo
profiles = ["dev", "release"]  # Cargo profiles to build
scan_dir = ""            # Directory to scan ("" = project root)
extensions = ["Cargo.toml"]
extra_inputs = []        # Additional files that trigger rebuilds
cache_output_dir = true  # Cache the target/ directory for fast restore after clean

Key	Type	Default	Description
`cargo`	string	`"cargo"`	Path or name of the cargo binary
`command`	string	`"build"`	Cargo subcommand to run
`args`	string[]	`[]`	Extra arguments passed to cargo
`profiles`	string[]	`["dev", "release"]`	Cargo profiles to build (creates one product per profile)
`scan_dir`	string	`""`	Directory to scan for Cargo.toml files
`extensions`	string[]	`["Cargo.toml"]`	File names to match
`exclude_dirs`	string[]	`["/.git/", "/target/", ...]`	Directory patterns to exclude
`exclude_paths`	string[]	`[]`	Paths (relative to project root) to exclude
`extra_inputs`	string[]	`[]`	Extra files whose changes trigger rebuilds
`cache_output_dir`	boolean	`true`	Cache the `target/` directory so `rsconstruct clean && rsconstruct build` restores from cache. Consider disabling for large projects.

Examples

Basic Usage

[processor.cargo]

Release Only

[processor.cargo]
profiles = ["release"]

Dev Only

[processor.cargo]
profiles = ["dev"]

Use cargo check Instead of build

[processor.cargo]
command = "check"

Run clippy

[processor.cargo]
command = "clippy"
args = ["--", "-D", "warnings"]

Workspace Root Only

[processor.cargo]
exclude_paths = ["crates/"]

Notes

Cargo has its own incremental compilation, so rsconstruct’s caching mainly avoids invoking cargo at all when nothing changed
The target/ directory is automatically excluded from input scanning
For monorepos with multiple Rust projects, each Cargo.toml is built separately

RSConstruct - Rust Build Tool