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VSC Documentation

Write, Test and Deploy a Smart Contract

This is a brief overview of VSC smart contract development with Go.

Environment Setup

Section titled “Environment Setup”

Prerequisites

Section titled “Prerequisites”

Install Dependencies

Section titled “Install Dependencies”
Terminal window
git clone https://github.com/vsc-eco/go-vsc-node
cd go-vsc-node
go mod download
go build -buildvcs=false -o vsc-contract-deploy vsc-node/cmd/contract-deployer

This will generate an executable named vsc-contract-deploy. You may move it to your PATH directory (i.e. /usr/bin for Linux or /usr/local/bin for macOS).

Writing Your First Contract

Section titled “Writing Your First Contract”

Setup

Section titled “Setup”

Clone the Go contract template:

Terminal window
git clone https://github.com/vsc-eco/go-contract-template

Project Structure

Section titled “Project Structure”
  • Directorycontract your contract code goes here
    • main.go
  • Directoryruntime
    • gc_leaking_exported.go
  • Directorysdk
    • address.go
    • env.go
    • sdk.go
  • Directorytest
    • contract_test.go
  • .gitignore
  • go.mod
  • go.sum

Hello World Contract

Section titled “Hello World Contract”

The below contract demonstrates calling SDK methods to interact with the contract database and defining WASM exports to mark a function as callable by VSC accounts or other contracts.

Find out more about the Go contract SDK methods here.

main.go
package main


import "contract-template/sdk"


//go:wasmexport hello_world
func HelloWorld(a *string) *string {
  ret := "Hello world"
  return &ret
}


//go:wasmexport setString
func SetString(a *string) *string {
  sdk.StateSetObject("myString", *a)
  return a
}


//go:wasmexport getString
func GetString(a *string) *string {
  return sdk.StateGetObject("myString")
}

Compile Contract

Section titled “Compile Contract”

To compile your contract:

Terminal window
tinygo build -gc=custom -scheduler=none -panic=trap -no-debug -target=wasm-unknown -o artifacts/main.wasm contract/main.go

To remove metadata from the output WASM binary to reduce file size:

Terminal window
wasm-strip -o artifacts/main-striped.wasm artifacts/main.wasm

To inspect the output WASM assembly:

Terminal window
wasm2wat artifacts/main.wasm

Test and Debug Contract

Section titled “Test and Debug Contract”

We provide a contract test environment for you to execute contract calls on a state engine that resembles the live network. Your contract test code will look something like this:

package contract_test


import (
  "encoding/json"
  "testing"


  "github.com/stretchr/testify/assert"
  "github.com/vsc-eco/go-vsc-node/lib/test_utils"
  "github.com/vsc-eco/go-vsc-node/modules/db/vsc/contracts"
  ledgerDb "github.com/vsc-eco/go-vsc-node/modules/db/vsc/ledger"
  stateEngine "github.com/vsc-eco/go-vsc-node/modules/state-processing"
)


//go:embed artifacts/main.wasm
var ContractWasm []byte


func TestContract(t *testing.T) {
  ct := test_utils.NewContractTest()
  ct.RegisterContract("vsccontractid", ContractWasm)
  ct.Deposit("hive:someone", 1000, ledgerDb.AssetHive) // deposit 1 HIVE
  ct.Deposit("hive:someone", 1000, ledgerDb.AssetHbd) // deposit 1 HBD


  result, gasUsed, logs := ct.Call(stateEngine.TxVscCallContract{
    Self: stateEngine.TxSelf{
      TxId:                 "sometxid",
      BlockId:              "abcdef",
      Index:                69,
      OpIndex:              0,
      Timestamp:            "2025-09-03T00:00:00",
      RequiredAuths:        []string{"hive:someone"},
      RequiredPostingAuths: []string{},
    },
    ContractId: contractId,
    Action:     "yourMethodName",
    Payload:    json.RawMessage([]byte("1000")),
    RcLimit:    1000,
    Intents:    []contracts.Intent{{
      Type: "transfer.allow",
      Args: map[string]string{
        "limit": "1.000",
        "token": "hive",
      },
    }},
  })
  assert.True(t, result.Success)                  // assert contract execution success
  assert.LessOrEqual(t, gasUsed, uint(10000000))  // assert this call uses no more than 10M WASM gas
  assert.GreaterOrEqual(t, len(logs), 1)          // assert at least 1 log emitted
}

Find out more about methods provided by the contract test utils here.

Deploy Contract

Section titled “Deploy Contract”

Firstly, initialize the deployer configuration:

Terminal window
vsc-contract-deploy -init

This will generate some config files in data/config folder in your current directory. Insert your Hive username and active key of the deployer account in identityConfig.json:

identityConfig.json
{
  "BlsPrivKeySeed": "9e264692ced37...",
  "HiveActiveKey": "ADD_YOUR_PRIVATE_WIF",
  "HiveUsername": "ADD_YOUR_USERNAME",
  "Libp2pPrivKey": "125cd98aed75d..."
}

Then deploy your contract to VSC:

Terminal window
vsc-contract-deploy -wasmPath artifacts/main-striped.wasm -name "my first contract"

You should see an output similar to this:

WASM_CODE: 1130 [0 97 115 109 1 0 0 0 1 9] ...
peer ID: 12D3KooWS7N7zmrkMHxGX9ibNXbKk4byfkx8ckEhfgXM8eQcgBtK
NAT Status {Private}
12D3KooWS7N7zmrkMHxGX9ibNXbKk4byfkx8ckEhfgXM8eQcgBtK pubsub /vsc/mainnet/data-availability/v1 peers: 20
pubsub handling error: message did not add any signatures
pubsub handling error: message did not add any signatures
pubsub handling error: message did not add any signatures
pubsub handling error: message did not add any signatures
pubsub handling error: message did not add any signatures
pubsub handling error: message did not add any signatures
pubsub handling error: message did not add any signatures
pubsub handling error: message did not add any signatures
{bafkreibwwj3fypek5uz6l3scacy47yw3b2adgbxmfab2ybmkarljaggbey {i_TLUMJVJb6n6X-5_lKvBibiLvP0RUVz2tn20KJTw5Q_lQ-tcVt9jrZr4s1WVga1CR7q0Ldnrc-EjNpqgaY7GpnhE2d3pC3nfNhUKkmN1za6h9SwCEUuo3CByNnmnqYE __f9}}
{"__v":"0.1","code":"bafkreibwwj3fypek5uz6l3scacy47yw3b2adgbxmfab2ybmkarljaggbey","description":"","name":"go test","net_id":"vsc-mainnet","owner":"techcoderx.vsc","runtime":"go","storage_proof":{"hash":"bafkreibwwj3fypek5uz6l3scacy47yw3b2adgbxmfab2ybmkarljaggbey","signature":{"sig":"i_TLUMJVJb6n6X-5_lKvBibiLvP0RUVz2tn20KJTw5Q_lQ-tcVt9jrZr4s1WVga1CR7q0Ldnrc-EjNpqgaY7GpnhE2d3pC3nfNhUKkmN1za6h9SwCEUuo3CByNnmnqYE","bv":"__f9"}}}
pubsub handling error: message did not add any signatures
pubsub handling error: message did not add any signatures
tx id: bef70add6d21cd812cf68da2caee72da05de48b4
contract id: vsc1Bem8RnoLgGPP7E2MBN52ekrdVqy2LNpSqF
Error in subscription: subscription cancelled

Call Contract

Section titled “Call Contract”

Contracts may be called from L1 using Hive accounts or on VSC using offchain accounts.

Call From L1

Section titled “Call From L1”

Contract invokation from L1 involves sending a custom_json_operation with vsc.call as its ID and the following JSON format:

{
  "net_id": "vsc-mainnet",
  "contract_id": "vsc1...",
  "action": "methodName",
  "payload": "your payload string here",
  "rc_limit": 2000,
  "intents": []
}

An example transaction may be seen here.

Intents

Section titled “Intents”

A contract call transaction may include a list of intents which authorizes the contract to spend up to a specific amount of assets from your account. For example, an intent of 1 HIVE allowance may be specified as follows:

{
  "type": "transfer.allow",
  "args": {
    "limit": "1.000",
    "token": "hive"
  }
}