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Bastian Köcher
36770979bb
Instead of just testing `cargo` and `rustup run nightly`, we now test the `CARGO` env variable and also scan non default nightlies. The user is also now able to select the toolchain with `WASM_BUILD_TOOLCHAIN`.
71 lines
3.1 KiB
Markdown
71 lines
3.1 KiB
Markdown
# WASM builder is a utility for building a project as a WASM binary
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The WASM builder is a tool that integrates the process of building the WASM binary of your project into the main
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`cargo` build process.
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## Project setup
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A project that should be compiled as a WASM binary needs to:
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1. Add a `build.rs` file.
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2. Add `substrate-wasm-builder` as dependency into `build-dependencies`.
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The `build.rs` file needs to contain the following code:
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```rust
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use wasm_builder_runner::{build_current_project, WasmBuilderSource};
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fn main() {
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build_current_project(
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// The name of the file being generated in out-dir.
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"wasm_binary.rs",
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// How to include wasm-builder, in this case from crates.io.
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WasmBuilderSource::Crates("1.0.0"),
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);
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}
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```
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As the final step, you need to add the following to your project:
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```rust
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include!(concat!(env!("OUT_DIR"), "/wasm_binary.rs"));
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```
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This will include the generated WASM binary as two constants `WASM_BINARY` and `WASM_BINARY_BLOATY`.
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The former is a compact WASM binary and the latter is not compacted.
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## Environment variables
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By using environment variables, you can configure which WASM binaries are built and how:
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- `SKIP_WASM_BUILD` - Skips building any wasm binary. This is useful when only native should be recompiled.
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- `BUILD_DUMMY_WASM_BINARY` - Builds dummy wasm binaries. These dummy binaries are empty and useful
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for `cargo check` runs.
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- `WASM_BUILD_TYPE` - Sets the build type for building wasm binaries. Supported values are `release` or `debug`.
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By default the build type is equal to the build type used by the main build.
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- `TRIGGER_WASM_BUILD` - Can be set to trigger a wasm build. On subsequent calls the value of the variable
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needs to change. As WASM builder instructs `cargo` to watch for file changes
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this environment variable should only be required in certain circumstances.
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- `WASM_BUILD_RUSTFLAGS` - Extend `RUSTFLAGS` given to `cargo build` while building the wasm binary.
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- `WASM_BUILD_NO_COLOR` - Disable color output of the wasm build.
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- `WASM_TARGET_DIRECTORY` - Will copy any build wasm binary to the given directory. The path needs
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to be absolute.
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- `WASM_BUILD_TOOLCHAIN` - The toolchain that should be used to build the wasm binaries. The
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format needs to be the same as used by cargo, e.g. `nightly-2020-02-20`.
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Each project can be skipped individually by using the environment variable `SKIP_PROJECT_NAME_WASM_BUILD`.
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Where `PROJECT_NAME` needs to be replaced by the name of the cargo project, e.g. `node-runtime` will
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be `NODE_RUNTIME`.
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## Prerequisites:
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WASM builder requires the following prerequisites for building the WASM binary:
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- rust nightly + `wasm32-unknown-unknown` toolchain
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If a specific rust nightly is installed with `rustup`, it is important that the wasm target is installed
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as well. For example if installing the rust nightly from 20.02.2020 using `rustup install nightly-2020-02-20`,
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the wasm target needs to be installed as well `rustup target add wasm32-unknown-unknown --toolchain nightly-2020-02-20`.
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License: GPL-3.0
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