#cargo-subcommand #screeps #cargo #build-tool

app cargo-screeps

Build tool for deploying Rust WASM code to Screeps game servers

20 releases

0.5.0 Mar 13, 2023
0.4.0 Sep 9, 2022
0.3.3 Jul 21, 2019
0.3.1 Feb 19, 2019
0.0.5 Mar 13, 2018

#59 in Cargo plugins

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100 downloads per month

MIT license

805 lines


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Build tool for deploying Rust WASM repositories to Screeps game servers.

cargo-screeps wraps wasm-pack, adding the ability to trim node.js and web javascript code from the output files, and allows uploading directly to Screeps servers.

The other main project in this organization is screeps-game-api, type-safe bindings to the in-game Screeps API.

These two tools go together well, but do not depend on eachother. cargo-screeps can compile and upload any screeps WASM project buildable with wasm-bindgen's wasm-pack, and screeps-game-api is usable in any project built with wasm-pack.

Build Options


Configured in [build] config section. No required settings.

  1. runs cargo-web build --release to build the rust source
  2. strips off header cargo-web generates for loading WASM file from a URL or the local filesystem
  3. appends initialization call using bytes from require('<compiled module name>')
  4. puts processed JS into target/main.js copy compiled WASM into target/compiled.wasm


Does not require configuration.

  1. performs type checking and lifetime checking without compiling code
  • runs cargo web check (see cargo check for non-WASM codebases)


Runs the deployment mode specified by the --mode setting, or the default_deploy_mode configuration setting if none is specified.

  1. runs build
  2. depending on whether the mode uploads (has authentication credentials) or copies (has a destination), proceeds to deploy the built code

If copying:

  1. copies compiled main file and WASM file (default main.js and compiled.wasm) from target/ to <destination directory>/<branch name>/
  2. if pruning is enabled, deletes all other files in <destination directory>/<branch name>/

If uploading:

  1. reads target/*.js and target/*.wasm, keeping track of filenames
  2. reads screeps.toml for upload options
  3. uploads all read files to server, using filenames as the filenames on the server


A shortcut for cargo screeps deploy -m upload.


A shortcut for cargo screeps deploy -m copy.

Configuration Options

No namespace

  • default_deploy_mode: controls what mode cargo screeps deploy uses if the --mode/-m option is not set.


This configures general build options.

  • output_js_file: the javascript file to export bindings and bootstrapping as (default "main.js")
  • output_wasm_file: the WASM file to rename compile WASM to (default "compiled.wasm")
  • initialize_header_file: a file containing the JavaScript for starting the WASM instance. See overriding the default initialization header
  • features: a list of crate features to be enabled during the build

Any of these options can be overridden for a given mode with its own build section. For instance,

features = ["alliance_behavior"]

would cause a feature on your crate named alliance_behavior to be built when running the upload mode.

Overriding the default initialization header

cargo-screeps tries to make a reasonable main.js file to load the WASM. However, it's pretty basic, and you might find you want to do some things in JavaScript before loading the WASM module.

Luckily, you can override this initialization! Set build.initialize_header_file to a file containing the JavaScript initialization code.

Two utility functions wasm_fetch_module_bytes and wasm_create_stdweb_vars will always be created, but the initialization header controls what actually runs.

See [docs/initialization-header.md] for more information on this.

Configuration modes

Configuration modes can either copy the built files to a destination directory, or upload to a destination server using the Screeps API.

A mode should either have a filesystem destination to copy to, or authentication credentials (and optionally, server information) to upload to.

Optionally, it also have a sub-table [mode.build] to override any of the global [build] options.

Copy Options

Options for deploying to a filesystem location.

  • destination: the directory to copy files into

    If this path is not absolute, it is interpreted as relative to screeps.toml.

  • branch: the "branch" to copy into

    This is the subdirectory of destination which the js/wasm files will be copied into. Default is "default".

  • prune: if true, extra files found in the destination/branch directory will be deleted. Default is false.

Upload Options

Options for deploying to a Screeps server.

  • auth_token: an auth token for your Screeps account

  • username: your Screeps username or email

  • password: your Screeps password

    Either an auth_token or your username/password can be supplied. When both are set the auth token is used. For private servers set a password using screepsmod-auth.

  • branch: the "branch" to copy into

    This is the "branch" on the screeps server to deploy to. Default is "default".

  • prefix: if set, adds a URL prefix to the upload path. Use "ptr" or "season" to upload to the public test realm and seasonal servers, respectively.

  • hostname: the hostname to upload to

    For example, this could be screeps.com, localhost or server1.screepsplu.us. Default is screeps.com.

  • ssl: whether to connect to the server using ssl

    This should generally be true for the main server and false for private servers. Default is true.

  • port: port to connect to server with

    This should generally be set to 21025 for private servers. Default is 443.

Updating cargo screeps

To update cargo-screeps, simply repeat the install process with the --force (-f) flag.

After updating, you'll want to do a full cargo clean to remove any old artifacts which were built using the older version of cargo-screeps.

cargo install -f cargo-screeps
cargo clean
cargo screeps build


~1M SLoC