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Guia de Migração do AssemblyScript

Up until now, Subgraphs have been using one of the first versions of AssemblyScript⁠ (v0.6). Finally we’ve added support for the newest one available⁠ (v0.19.10)! 🎉

That will enable Subgraph developers to use newer features of the AS language and standard library.

This guide is applicable for anyone using graph-cli/graph-ts below version 0.22.0. If you’re already at a higher than (or equal) version to that, you’ve already been using version 0.19.10 of AssemblyScript 🙂

Note: As of 0.24.0, graph-node can support both versions, depending on the apiVersion specified in the Subgraph manifest.

Recursos

Novas funcionalidades

  • TypedArrays can now be built from ArrayBuffers by using the new wrap static method⁠ (v0.8.1⁠)
  • New standard library functions: String#toUpperCase, String#toLowerCase, String#localeCompareand TypedArray#set (v0.9.0⁠)
  • Added support for x instanceof GenericClass (v0.9.2⁠)
  • Added StaticArray<T>, a more efficient array variant (v0.9.3⁠)
  • Added Array<T>#flat (v0.10.0⁠)
  • Implemented radix argument on Number#toString (v0.10.1⁠)
  • Added support for separators in floating point literals (v0.13.7⁠)
  • Added support for first class functions (v0.14.0⁠)
  • Add builtins: i32/i64/f32/f64.add/sub/mul (v0.14.13⁠)
  • Implement Array/TypedArray/String#at (v0.18.2⁠)
  • Added support for template literal strings (v0.18.17⁠)
  • Add encodeURI(Component) and decodeURI(Component) (v0.18.27⁠)
  • Add toString, toDateString and toTimeString to Date (v0.18.29⁠)
  • Add toUTCString for Date (v0.18.30⁠)
  • Add nonnull/NonNullable builtin type (v0.19.2⁠)

Otimizações

  • Math functions such as exp, exp2, log, log2 and pow have been replaced by faster variants (v0.9.0⁠)
  • Slightly optimize Math.mod (v0.17.1⁠)
  • Cache more field accesses in std Map and Set (v0.17.8⁠)
  • Optimize for powers of two in ipow32/64 (v0.18.2⁠)

Outros

  • The type of an array literal can now be inferred from its contents (v0.9.0⁠)
  • Updated stdlib to Unicode 13.0.0 (v0.10.0⁠)

Como atualizar?

  1. Change your mappings apiVersion in subgraph.yaml to 0.0.9:
...dataSources:  ...    mapping:      ...      apiVersion: 0.0.9      ...
  1. Update the graph-cli you’re using to the latest version by running:
# caso o tenha instalado globalmentenpm install --global @graphprotocol/graph-cli@latest# ou no seu subgraph se o tiver como dependência de desenvolvimentonpm install --save-dev @graphprotocol/graph-cli@latest
  1. Do the same for graph-ts, but instead of installing globally, save it in your main dependencies:
npm install --save @graphprotocol/graph-ts@latest
  1. Siga o resto do guia para consertar as mudanças frágeis na linguagem.
  2. Run codegen and deploy again.

Breaking changes (mudanças frágeis)

Anulabilidade

Na versão mais antiga do AssemblyScript, podias criar códigos assim:

function load(): Value | null { ... }let maybeValue = load();maybeValue.aMethod();

Mas na versão mais nova, como o valor é anulável, ele exige que confira, assim:

let maybeValue = load()if (maybeValue) {  maybeValue.aMethod() // `maybeValue` is not null anymore}

…ou o force deste jeito:

let maybeValue = load()! // breaks in runtime if value is nullmaybeValue.aMethod()

If you are unsure which to choose, we recommend always using the safe version. If the value doesn’t exist you might want to just do an early if statement with a return in you Subgraph handler.

Sombreamento Varíavel

Before you could do variable shadowing⁠ and code like this would work:

let a = 10let b = 20let a = a + b

Porém, isto não é mais possível, e o compilador retorna este erro:

ERROR TS2451: Cannot redeclare block-scoped variable 'a' let a = a + b; ~~~~~~~~~~~~~in assembly/index.ts(4,3)

Renomeie as suas variáveis duplicadas, se tinha o sombreamento variável.

Comparações de Nulos

By doing the upgrade on your Subgraph, sometimes you might get errors like these:

ERROR TS2322: Type '~lib/@graphprotocol/graph-ts/common/numbers/BigInt | null' is not assignable to type '~lib/@graphprotocol/graph-ts/common/numbers/BigInt'.     if (decimals == null) {                     ~~~~ in src/mappings/file.ts(41,21)

To solve you can simply change the if statement to something like this:

if (!decimals) {  // or  if (decimals === null) {

O mesmo acontece se fizer o != em vez de ==.

Casting (Conversão de tipos)

The common way to do casting before was to just use the as keyword, like this:

let byteArray = new ByteArray(10)let uint8Array = byteArray as Uint8Array // equivalent to: <Uint8Array>byteArray

Porém, isto só funciona em dois casos:

  • Primitive casting (between types such as u8, i32, bool; eg: let b: isize = 10; b as usize);
  • Upcasting em herança de classe (subclass → superclass)

Exemplos:

// primitive castinglet a: usize = 10let b: isize = 5let c: usize = a + (b as usize)
// upcasting on class inheritanceclass Bytes extends Uint8Array {}let bytes = new Bytes(2)// <Uint8Array>bytes // same as: bytes as Uint8Array

There are two scenarios where you may want to cast, but using as/<T>var isn’t safe:

  • Downcasting em herança de classe (superclass → subclass)
  • Entre dois tipos que compartilham uma superclasse
// downcasting on class inheritanceclass Bytes extends Uint8Array {}let uint8Array = new Uint8Array(2)// <Bytes>uint8Array // breaks in runtime :(
// between two types that share a superclassclass Bytes extends Uint8Array {}class ByteArray extends Uint8Array {}let bytes = new Bytes(2)// <ByteArray>bytes // breaks in runtime :(

For those cases, you can use the changetype<T> function:

// downcasting on class inheritanceclass Bytes extends Uint8Array {}let uint8Array = new Uint8Array(2)changetype<Bytes>(uint8Array) // works :)
// between two types that share a superclassclass Bytes extends Uint8Array {}class ByteArray extends Uint8Array {}let bytes = new Bytes(2)changetype<ByteArray>(bytes) // works :)

If you just want to remove nullability, you can keep using the as operator (or <T>variable), but make sure you know that value can’t be null, otherwise it will break.

// remove anulabilidadelet previousBalance = AccountBalance.load(balanceId) // AccountBalance | nullif (previousBalance != null) {  return previousBalance as AccountBalance // safe remove null}let newBalance = new AccountBalance(balanceId)

For the nullability case we recommend taking a look at the nullability check feature⁠, it will make your code cleaner 🙂

Também adicionamos alguns métodos estáticos em alguns tipos para facilitar o casting, sendo:

  • Bytes.fromByteArray
  • Bytes.fromUint8Array
  • BigInt.fromByteArray
  • ByteArray.fromBigInt

Checagem de anulabilidade com acesso à propriedade

To use the nullability check feature⁠ you can use either if statements or the ternary operator (? and :) like this:

let something: string | null = 'data'let somethingOrElse = something ? something : 'else'// oulet somethingOrElseif (something) {  somethingOrElse = something} else {  somethingOrElse = 'else'}

However that only works when you’re doing the if / ternary on a variable, not on a property access, like this:

class Container {  data: string | null}let container = new Container()container.data = 'data'let somethingOrElse: string = container.data ? container.data : 'else' // doesn't compile

O que retorna este erro:

ERROR TS2322: Type '~lib/string/String | null' is not assignable to type '~lib/string/String'.   let somethingOrElse: string = container.data ? container.data : "else";                                 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Para consertar este problema, vale criar uma variável para aquele acesso à propriedade, para que o compilador faça a magia da checagem de anulabilidade:

class Container {  data: string | null}let container = new Container()container.data = 'data'let data = container.datalet somethingOrElse: string = data ? data : 'else' // compiles just fine :)

Sobrecarga de operador com acesso à propriedade

Se tentar somar (por exemplo) um tipo anulável (de um acesso de propriedade) com um não-anulável, em vez de soltar um aviso de erro de tempo de compilação a dizer que um dos valores é anulável, o compilador AssemblyScript só compilará em silêncio, o que abre chances para o código quebrar em meio ao tempo de execução.

class BigInt extends Uint8Array {  @operator('+')  plus(other: BigInt): BigInt {    // ...  }}class Wrapper {  public constructor(public n: BigInt | null) {}}let x = BigInt.fromI32(2)let y: BigInt | null = nullx + y // dá o erro de tempo de complação sobre anulabilidadelet wrapper = new Wrapper(y)wrapper.n = wrapper.n + x // não dá erros de tempo de compilação como deveria

We’ve opened a issue on the AssemblyScript compiler for this, but for now if you do these kind of operations in your Subgraph mappings, you should change them to do a null check before it.

let wrapper = new Wrapper(y)if (!wrapper.n) {  wrapper.n = BigInt.fromI32(0)}wrapper.n = wrapper.n + x // agora o `n` é garantido a ser um BigInt

Inicialização de valor

Se tiver algum código como este:

var value: Type // nullvalue.x = 10value.y = 'content'

It will compile but break at runtime, that happens because the value hasn’t been initialized, so make sure your Subgraph has initialized their values, like this:

var value = new Type() // initializedvalue.x = 10value.y = 'content'

E também se tiver propriedades anuláveis numa entidade GraphQL, como assim:

type Total @entity {  id: Bytes!  amount: BigInt}

E tiver código parecido com este:

let total = Total.load('latest')if (total === null) {  total = new Total('latest')}total.amount = total.amount + BigInt.fromI32(1)

You’ll need to make sure to initialize the total.amount value, because if you try to access like in the last line for the sum, it will crash. So you either initialize it first:

let total = Total.load('latest')if (total === null) {  total = new Total('latest')  total.amount = BigInt.fromI32(0)}total.tokens = total.tokens + BigInt.fromI32(1)

Or you can just change your GraphQL schema to not use a nullable type for this property, then we’ll initialize it as zero on the codegen step 😉

type Total @entity {  id: Bytes!  amount: BigInt!}
let total = Total.load('latest')if (total === null) {  total = new Total('latest') // já inicializa propriedades não-anuláveis}total.amount = total.amount + BigInt.fromI32(1)

Iniciação de propriedade de classe

Se exportar quaisquer classes com propriedades que sejam outras classes (declaradas por você ou pela biblioteca padrão) como esta:

class Thing {}export class Something {  value: Thing}

The compiler will error because you either need to add an initializer for the properties that are classes, or add the ! operator:

export class Something {  constructor(public value: Thing) {}}// ouexport class Something {  value: Thing  constructor(value: Thing) {    this.value = value  }}// ouexport class Something {  value!: Thing}

Iniciação de arranjo

The Array class still accepts a number to initialize the length of the list, however you should take care because operations like .push will actually increase the size instead of adding to the beginning, for example:

let arr = new Array<string>(5) // ["", "", "", "", ""]arr.push('something') // ["", "", "", "", "", "something"] // size 6 :(

Dependendo dos tipos que usa, por ex., anuláveis, e como os acessa, pode encontrar um erro de tempo de execução como este:

ERRO Handler skipped due to execution failure, error: Mapping aborted at ~lib/array.ts, line 110, column 40, with message: Element type must be nullable if array is holey  wasm backtrace:     0: 0x19c4 - <unknown>!~lib/@graphprotocol/graph-ts/index/format         1: 0x1e75 - <unknown>!~lib/@graphprotocol/graph-ts/common/collections/Entity#constructor        2: 0x30b9 - <unknown>!node_modules/@graphprotocol/graph-ts/global/global/id_of_type

To actually push at the beginning you should either, initialize the Array with size zero, like this:

let arr = new Array<string>(0) // []arr.push('something') // ["something"]

Ou pode mudá-lo através do index:

let arr = new Array<string>(5) // ["", "", "", "", ""]arr[0] = 'something' // ["something", "", "", "", ""]

Schema GraphQL

This is not a direct AssemblyScript change, but you may have to update your schema.graphql file.

Agora não há mais como definir campos nos seus tipos que são Listas Não Anuláveis. Se tiver um schema como este:

type Something @entity {  id: Bytes!}type MyEntity @entity {  id: Bytes!  invalidField: [Something]! # no longer valid}

You’ll have to add an ! to the member of the List type, like this:

type Something @entity {  id: Bytes!}type MyEntity @entity {  id: Bytes!  invalidField: [Something!]! # valid}

This changed because of nullability differences between AssemblyScript versions, and it’s related to the src/generated/schema.ts file (default path, you might have changed this).

Outros

  • Aligned Map#set and Set#add with the spec, returning this (v0.9.2⁠)
  • Arrays no longer inherit from ArrayBufferView, but are now distinct (v0.10.0⁠)
  • Classes initialized from object literals can no longer define a constructor (v0.10.0⁠)
  • The result of a ** binary operation is now the common denominator integer if both operands are integers. Previously, the result was a float as if calling Math/f.pow (v0.11.0⁠)
  • Coerce NaN to false when casting to bool (v0.14.9⁠)
  • When shifting a small integer value of type i8/u8 or i16/u16, only the 3 respectively 4 least significant bits of the RHS value affect the result, analogous to the result of an i32.shl only being affected by the 5 least significant bits of the RHS value. Example: someI8 << 8 previously produced the value 0, but now produces someI8 due to masking the RHS as 8 & 7 = 0 (3 bits) (v0.17.0⁠)
  • Bug fix of relational string comparisons when sizes differ (v0.17.8⁠)