从 Schema 到 Standard Schema

Schema.standardSchemaV1 API 允许你从一个 Effect Schema 生成 Standard Schema v1 对象。

示例（生成 Standard Schema V1）

import { Schema } from "effect"

const schema = Schema.Struct({
  name: Schema.String,
})

// Convert an Effect schema into a Standard Schema V1 object
//
//      ┌─── StandardSchemaV1<{ readonly name: string; }>
//      ▼
const standardSchema = Schema.standardSchemaV1(schema)

同步校验与异步校验

Schema.standardSchemaV1 API 创建的 schema，其 validate 方法会尝试同步解码并校验传入的输入。如果底层 Schema 包含任何异步组件（例如异步的 message resolution 或 check），那么校验必然改为返回一个 Promise。

示例（处理同步与异步校验）

import { Effect, Schema } from "effect"

// Utility function to display sync and async results
const print = <T>(t: T) =>
  t instanceof Promise
    ? t.then((x) => console.log("Promise", JSON.stringify(x, null, 2)))
    : console.log("Value", JSON.stringify(t, null, 2))

// Define a synchronous schema
const sync = Schema.Struct({
  name: Schema.String,
})

// Generate a Standard Schema V1 object
const syncStandardSchema = Schema.standardSchemaV1(sync)

// Validate synchronously
print(syncStandardSchema["~standard"].validate({ name: null }))
/*
Output:
{
  "issues": [
    {
      "path": [
        "name"
      ],
      "message": "Expected string, actual null"
    }
  ]
}
*/

// Define an asynchronous schema with a transformation
const async = Schema.transformOrFail(
  sync,
  Schema.Struct({
    name: Schema.NonEmptyString,
  }),
  {
    // Simulate an asynchronous validation delay
    decode: (x) => Effect.sleep("100 millis").pipe(Effect.as(x)),
    encode: Effect.succeed,
  },
)

// Generate a Standard Schema V1 object
const asyncStandardSchema = Schema.standardSchemaV1(async)

// Validate asynchronously
print(asyncStandardSchema["~standard"].validate({ name: "" }))
/*
Output:
Promise {
  "issues": [
    {
      "path": [
        "name"
      ],
      "message": "Expected a non empty string, actual \"\""
    }
  ]
}
*/

Defect

如果校验期间出现意外的 defect，它会被报告为单个不带 path 的 issue。这样可以确保意外的错误不会中断 schema 校验，同时仍会被捕获并报告。

示例（处理 Defect）

import { Effect, Schema } from "effect"

// Define a schema with a defect in the decode function
const defect = Schema.transformOrFail(Schema.String, Schema.String, {
  // Simulate an internal failure
  decode: () => Effect.die("Boom!"),
  encode: Effect.succeed,
})

// Generate a Standard Schema V1 object
const defectStandardSchema = Schema.standardSchemaV1(defect)

// Validate input, triggering a defect
console.log(defectStandardSchema["~standard"].validate("a"))
/*
Output:
{ issues: [ { message: 'Error: Boom!' } ] }
*/