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Creating a new package

A new package can be created using SPM Langugage.

SPM Syntax​

An SPM package definition file consists of two main sections: import and export.

Import Section​

packages {
  using std.package [as packageAlias1]
  using "./local_file.sol" [as packageAlias2]
}

You can import another package, based on the namespace. That is done with using keyword followed by a dot-separated set of nested namespaces (example std.contracts.erc20). You can also define an alias for the imported package, so that it's easier and shorter to reference it when using it.

note

When using aliases, you must make sure that they are unique.

Another kind of import is from a local file. By saying using "./local_file.sol", you are importing a whole Solidity file with all it's definitions, structures and contracts (inheritance and nested file imports are supported).

Export Section​

In an export section of the package definition, you are able to define what other packages will be able to use. It is a public interface for other packages.

You can define an arbitrary number of nested namespaces, and in those namespaces you can export a certain feature.

Just like there are two types of imports, depending on them we can have two types of exports. They do have the same result, but the way you define them is a bit different.

A feature is defined in the following format:

[@<type>] path.to.feature [as featureAlias]

where a @type can be: @function, @struct, @contract, @event, or @modifier.

note

@type is optional, if left blank then default value is @function.

Feature name is either explicitly defined using an alias, or otherwise the default behaviour is to take the last part of the path. So, if the feature path is path.to.feature.test, than feature name will be test. A fully qualified name of the feature (FQN), is the feature name with dot-separated namespace paths included.

info

If an export is done from the local Solidity file, than SPM expects the following format:

PackageAlias.[ContractName].export_item.

If ContractName is not defined, than SPM assumes that export_item is somewhere outside of any contract in that Solidity file.

package {{package_name}} {
  nested_package1 {
    @function packageAlias1.nested_package.FunctionName
  }

  nested_package2 {
    @struct packageAlias2.ContractName.StructName
    @struct packageAlias2.GlobalStructName
  }
}
info

Make sure to check our examples on the GitHub!