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Compile

Build your crate to a wasm32v1-none binary, read per-file diagnostics, and fix pre-flight validation errors.

Compile runs stellar contract build over your crate, produces a wasm32v1-none Wasm binary, optimizes it, and reports its size. Compile before you deploy and any time you want to check that your code builds.

Compile never signs and never touches your wallet. Run it as often as you like.

What the build does#

1. Validate the project before invoking cargo (see pre-flight).
2. Build with stellar contract build from the directory of your manifestPath. The whole crate, every module and, for a workspace, every member, is picked up from the files on disk.
3. Optimize the resulting Wasm and report the final byte size.
4. Extract the spec from the Wasm (function names, argument types, return types) so the Invoke panel can render typed forms.

A successful build ends with the produced Wasm and its size:

Compiling contract…
Running stellar contract build…
Compiling soroban-sdk v22.0.0
Compiling counter v0.1.0
Finished `release` profile [optimized] target(s)
Generated counter.wasm (1284 bytes).
Build complete.

The crate name in the filename uses underscores: a crate named my-counter produces my_counter.wasm.

Reading diagnostics#

Compiler errors and warnings are parsed out of the cargo output and routed to the file they came from. Each diagnostic carries a level, an optional code, a message, and a file:line:column location, so the error lands on the right line in the editor gutter, not in one opaque log blob.

Take this lib.rs:

#![no_std]
use soroban_sdk::{contract, contractimpl, Env};

#[contract]
pub struct Counter;

#[contractimpl]
impl Counter {
    pub fn increment(env: Env) -> u32 {
        let count: u32 = env.storage().instance().get(&COUNT).unwrap_or(0); // [!code highlight]
        count + 1
    }
}

COUNT is never defined. The build fails and produces this diagnostic:

error[E0425]: cannot find value `COUNT` in this scope
  --> src/lib.rs:10:62

Which is parsed into:

{
  "level": "error",
  "code": "E0425",
  "message": "cannot find value `COUNT` in this scope",
  "file": "src/lib.rs",
  "line": 10,
  "column": 62
}

Errors stop the build; warnings do not. A multi-file project reports each diagnostic against its own file by full path, so an error in src/storage.rs highlights storage.rs, never the wrong mod.rs.

The build cache#

A successful build is cached by a hash of your entire file tree, every path and its content. Re-running Compile with no edits returns the cached Wasm instantly:

Source unchanged, reusing cached build.
Compilation successful (cached).

Editing any file, lib.rs, Cargo.toml, a test, .cargo/config.toml, busts the cache and triggers a real build. You never compile a stale tree.

Pre-flight validation#

Compile validates the project before cargo runs, so you get a clear, file-attributed error instead of a cryptic compiler failure. Three checks fail fast.

A workspace also fails validation if [package] name is missing on a member, if a listed member has no Cargo.toml, or if no member is a deployable contract (a cdylib crate with a #[contract] entrypoint).

The project files#

A single-file template ships with this Cargo.toml:

[package]
name = "counter"
version = "0.1.0"
edition = "2021"

[dependencies]
soroban-sdk = "22.0.0"

[dev-dependencies]
soroban-sdk = { version = "22.0.0", features = ["testutils"] }

[lib]
crate-type = ["cdylib"]

[profile.release]
opt-level = "z"
overflow-checks = true

Multi-file and workspace crates use crate-type = ["cdylib", "rlib"] instead. The rlib lets integration tests under tests/ depend on the crate; the Stellar CLI still builds the cdylib for Wasm.

The target flags live in .cargo/config.toml:

[target.wasm32v1-none]
rustflags = ["-C", "target-feature=-crt-static", "-C", "link-arg=--no-entry"]

Next#

• Deploy the Wasm to testnet.
• Run unit and integration tests in Test.