nsmith — multi-language contract compiler

nsmith is Nanvil’s Foundry-forge-style compiler suite. It compiles Neo N3 smart contracts written in Go, Python, Java, or C# into .nef and .manifest.json artifacts for deployment with ncast deploy.

Quick start

make build          # builds nanvil, ncast, and nsmith
./bin/nsmith compile ./contract.go --name MyContract
./bin/ncast deploy --wif <wif> -i MyContract.nef -m MyContract.manifest.json

Compile all four supported languages from the repo examples:

./scripts/test-nsmith-examples.sh

Repository examples

Ready-to-compile sample contracts live under integration/testcontracts/examples/:

# Go (no extra toolchain install)
./bin/nsmith compile --lang go --out /tmp/go integration/testcontracts/examples/go

# Python (requires: nsmith install --lang python)
./bin/nsmith compile --lang python --out /tmp/py integration/testcontracts/examples/python

# C# (requires: nsmith install --lang csharp, dotnet SDK)
./bin/nsmith compile --lang csharp --out /tmp/cs integration/testcontracts/examples/csharp

# Java (requires: JDK 17+; uses ./gradlew in the example project)
./bin/nsmith compile --lang java --out /tmp/java integration/testcontracts/examples/java

The Java example includes a Gradle wrapper. Projects from nsmith init --lang java need gradle wrapper (or copy the wrapper from the example).

Supported languages

Go contracts use the same compiler as neo-go. Other languages are invoked via managed toolchains under ~/.nanvil/toolchains/ (override with NANVIL_TOOLCHAINS).

nsmith auto-detects DOTNET_ROOT and JAVA_HOME when common system paths are present (for example /usr/share/dotnet and /usr/lib/jvm/java-17-openjdk).

Commands

nsmith compile [path]

Auto-detects language from project markers (.go + interop imports, neo3-boa, .csproj, build.gradle with neow3j).

Put flags before the path — nsmith compile --lang python ./contract.py (not ./contract.py --lang python).

nsmith compile ./contracts/main.go
nsmith compile --lang python ./contract.py
nsmith compile --out ./build/MyContract --config contract.yml ./main.go
nsmith compile --json ./main.go

Flags:

• --lang — force go, python, java, or csharp
  
• --out — output prefix (without extension); absolute paths write outside the source tree
  
• --name — manifest contract name
  
• --config — Go contract YAML (contract.yml)
  
• --debug — emit debug artifacts where supported
  

nsmith build [path]

Same as compile, with optional deploy:

nsmith build ./main.go --deploy --wif <wif> --rpc http://127.0.0.1:8545

nsmith init <name> --lang <lang>

Scaffold a minimal project:

nsmith init MyToken --lang go
nsmith init PyToken --lang python
nsmith init CsToken --lang csharp
nsmith init JavaToken --lang java

Java scaffolds include build.gradle with neow3jCompiler { className = ... }. Run gradle wrapper in the project directory (or copy from integration/testcontracts/examples/java/).

Toolchain management

nsmith install --lang python      # pin + install neo3-boa in managed venv
nsmith install --all
nsmith update --lang python       # refresh to latest PyPI version
nsmith toolchain list             # installed vs latest versions
nsmith doctor --all               # check host runtimes and installs

Versions are pinned on install and only change when you run nsmith update.

Toolchain cache

~/.nanvil/toolchains/
  manifest.json
  python/venv/          # neo3-boa
  dotnet/tools/         # nccs
  java/                 # version pins for neow3j plugin

Typical workflows

Go (no extra install)

nsmith compile ./main.go --config contract.yml --out ./out/contract
ncast deploy --wif $WIF -i ./out/contract.nef -m ./out/contract.manifest.json

Python

nsmith install --lang python
nsmith init Hello --lang python
cd Hello
nsmith compile --lang python contract.py

Python scaffolds use neo3-boa 1.5+ (from boa3.sc.compiletime import public).

C

nsmith install --lang csharp
nsmith init Token --lang csharp
cd Token
nsmith compile --lang csharp .

nsmith compile invokes nccs on the contract .cs file. You can pass a project directory or .csproj; artifacts land in bin/sc/ beside the source.

Java

nsmith init Token --lang java
cd Token
gradle wrapper    # once, if not copied from repo example
nsmith compile --lang java .

Gradle runs neow3jCompile; output is under build/neow3j/.

Integration tests

Optional Python integration test (requires Python 3.13+ and network for PyPI):

NSMITH_INTEGRATION=1 go test -tags=nsmith_integration ./pkg/nsmith/compiler/...

Compile all language examples in CI or locally:

./scripts/test-nsmith-examples.sh