Module umbrella_crate

Learn about the Polkadot Umbrella crate that re-exports all other crates.

Umbrella Crate

The Polkadot-SDK “umbrella” is a crate that re-exports all other published crates. This makes it possible to have a very small Cargo.toml file that only has one dependency, the umbrella crate. This helps with selecting the right combination of crate versions, since otherwise 3rd party tools are needed to select a compatible set of versions.

Features

The umbrella crate supports no-std builds and can therefore be used in the runtime and node. There are two main features: runtime and node. The runtime feature enables all no-std crates, while the node feature enables all std crates. It should be used like any other crate in the repo, with default-features = false.

For more fine-grained control, additionally, each crate can be enabled selectively. The umbrella exposes one feature per dependency. For example, if you only want to use the frame-support crate, you can enable the frame-support feature.

The umbrella exposes a few more general features:

• tuples-96: Needs to be enabled for runtimes that have more than 64 pallets.
• serde: Specifically enable serde en/decoding support.
• experimental: Experimental enable experimental features - should not yet used in production.
• with-tracing: Enable tracing support.
• try-runtime, runtime-benchmarks and std: These follow the standard conventions.
• runtime: As described above, enable all no-std crates.
• node: As described above, enable all std crates.
• There does not exist a dedicated docs feature. To generate docs, enable the runtime and node feature. For docs.rs the manifest contains specific configuration to make it show up all re-exports.

There is a specific zepter check in place to ensure that the features of the umbrella are correctly configured. This check is run in CI and locally when running zepter.

Generation

The umbrella crate needs to be updated every time when a new crate is added or removed from the workspace. It is checked in CI by calling its generation script. The generation script is located in ./scripts/generate-umbrella.py and needs dependency cargo_workspace.

Example: python3 scripts/generate-umbrella.py --sdk . --version 1.9.0

Usage

Note: You can see a live example in the staging-node-cli and kitchensink-runtime crates.

The umbrella crate can be added to your runtime crate like this:

polkadot-sdk = { path = "../../../../umbrella", features = ["runtime"], default-features = false }

or for a node:

polkadot-sdk = { path = "../../../../umbrella", features = ["node"], default-features = false }

In the code, it is then possible to bring all dependencies into scope via:

use polkadot_sdk::*;

Known Issues

The only known issue so far is the fact that the use statement brings the dependencies only into the outer module scope - not the global crate scope. For example, the following code would need to be adjusted:

use polkadot_sdk::*;

mod foo {
   // This does sadly not compile:
   frame_support::parameter_types! { }

   // Instead, we need to do this (or add an equivalent `use` statement):
   polkadot_sdk::frame_support::parameter_types! { }
}

Apart from this, no issues are known. There could be some bugs with how macros locate their own re-exports. Please report issues that arise from using this crate.

Dependencies

The umbrella crate re-exports all published crates, with a few exceptions:

• Runtime crates like rococo-runtime etc are not exported. This otherwise leads to very weird compile errors and should not be needed anyway.
• Example and fuzzing crates are not exported. This is currently detected by checking the name of the crate for these magic words. In the future, it will utilize custom metadata, as it is done in the rococo-runtime crate.
• The umbrella crate itself. Should be obvious :)