Mops CLI

A Rust client implementation of the Motoko package manger.

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Conventions

• Cache directory: ~/.mops/, stores the Motoko compiler binary and library dependencies downloaded from mops or github. It can be changed by using the --cache-dir flag.
• Project root directory: The first occurance of mops.toml from the current directory to its parent directories. If mops.toml is missing, the current directory is the root directory, and a mops.toml will be auto-generated.
• Main Motoko file: mops-cli build <main_file>. If <main_file> is omitted, will use main.mo or Main.mo.
• Build artifacts: Stored in <root_directory>/target/<name>/<name>.wasm, where <name> can be specified by mops-cli build --name <name>. If --name is omitted, <name> will be the filename of the main Motoko file. If the filename is Main.mo or main.mo, <name> will be the parent directory name. If anything fails, we use wasm as the default <name>.
• Compiler flags: --release --idl --stable-types --public-metadata candid:service -o target/<name>/<name>.wasm --package <from_mops_lock>. If extra arguments are passed via mops-cli build -- <moc_args>, the default flags will be dropped, except -o and --package flags. If <moc_args> contains -o, the default -o flag will be dropped.

Import canisters in mops.toml

• import Backend "ic:ryjl3-tyaaa-aaaaa-aaaba-cai" adds the following section

  [[canister]]
  canister_id = "ryjl3-tyaaa-aaaaa-aaaba-cai"

• import Backend "canister:backend" can be configured as

  [[canister]]
  name = "backend"
  canister_id = "ryjl3-tyaaa-aaaaa-aaaba-cai"

• import Type "./BackendType" can be generated by

  [[canister]]
  candid = "Backend.did"
  output = "BackendType.mo"

Differences from the node client

• mops.toml can be auto-generated from main.mo if the packages are all on mops.
• Similar to cargo build, mops build generates a mops.lock file that records the precise dependencies of the project. Note that the lock file format is different from the node client.
• mops build can automatically download external dependencies specified in mops.lock, without the need to run mops install.
• The downloaded packages are stored globally at $HOME/.mops, similar to cargo.
• Overall, users can run mops build main.mo directly without any setup.

Pending issues

• Resolving package versions. Currently, we choose the largest version when package names collide, and errors out when we cannot decide on the version of a package. We need compiler support to allow the same package name to apply to different modules, and follow semantic versioning. The base library also need to follow semantic versioning.
• Removing a dependency doesn't remove the entries in mops.lock