Layer.Layer<Platform.HttpPlatform, never, never>Provides the Node HttpPlatform together with the filesystem and ETag
services it needs for file responses.
export const const layer: Layer.Layer<Platform.HttpPlatform>const layer: {
build: (memoMap: MemoMap, scope: Scope.Scope) => Effect<Context.Context<HttpPlatform>, never, never>;
pipe: { <A>(this: A): A; <A, B = never>(this: A, ab: (_: A) => B): B; <A, B = never, C = never>(this: A, ab: (_: A) => B, bc: (_: B) => C): C; <A, B = never, C = never, D = never>(this: A, ab: (_: A) => B, bc: (_: B) => C, cd: (_: C) => D): D; <…;
}
Provides the Node HttpPlatform together with the filesystem and ETag
services it needs for file responses.
layer: import LayerLayer.interface Layer<in ROut, out E = never, out RIn = never>A Layer describes how to build one or more services for dependency injection.
When to use
Use to model construction of application services for dependency injection,
especially when services have dependencies, can fail during construction, or
need scoped setup and release.
Details
A Layer<ROut, E, RIn> represents ROut as the services this layer
provides, E as the possible errors during layer construction, and RIn as
the services this layer requires as dependencies.
Layer<import PlatformPlatform.class HttpPlatformclass HttpPlatform {
key: Identifier;
Service: {
fileResponse: (path: string, options?: Response.Options.WithContent & { readonly bytesToRead?: FileSystem.SizeInput | undefined; readonly chunkSize?: FileSystem.SizeInput | undefined; readonly offset?: FileSystem.SizeInput | undefined }) => Effect.Effec…;
fileWebResponse: (file: Body.HttpBody.FileLike, options?: Response.Options.WithContent & { readonly bytesToRead?: FileSystem.SizeInput | undefined; readonly chunkSize?: FileSystem.SizeInput | undefined; readonly offset?: FileSystem.SizeInput | undefined })…;
};
}
Service for platform-specific HTTP response helpers, including file-backed server responses.
HttpPlatform> = pipe<Layer.Layer<Platform.HttpPlatform, never, EtagImpl.Generator | FileSystem>, Layer.Layer<Platform.HttpPlatform, never, EtagImpl.Generator>, Layer.Layer<Platform.HttpPlatform, never, never>>(a: Layer.Layer<Platform.HttpPlatform, never, EtagImpl.Generator | FileSystem>, ab: (a: Layer.Layer<Platform.HttpPlatform, never, EtagImpl.Generator | FileSystem>) => Layer.Layer<...>, bc: (b: Layer.Layer<...>) => Layer.Layer<...>): Layer.Layer<...> (+19 overloads)Pipes the value of an expression through a left-to-right sequence of
functions.
When to use
Use when you need to compose data-last functions into readable
transformation pipelines instead of method-style chains.
Details
Takes an initial value, passes it to the first function, then passes each
result to the next function in order. The final function result is returned.
Gotchas
Each function passed after the initial value must accept a single argument,
because pipe calls each step with only the previous result.
Example (Piping values through functions)
In this example, 1 is passed to the first function, and each result becomes
the input for the next function.
import { pipe } from "effect"
const result = pipe(
1,
(n) => n + 1,
(n) => n * 2,
(n) => `result: ${n}`
)
console.log(result) // "result: 4"
Example (Chaining methods before conversion)
const numbers = [1, 2, 3, 4]
const double = (n: number) => n * 2
const greaterThanFour = (n: number) => n > 4
const result = numbers.map(double).filter(greaterThanFour)
console.log(result) // [6, 8]
Example (Rewriting method chains with pipe)
The same transformation can be written with data-last functions.
import { Array, pipe } from "effect"
const numbers = [1, 2, 3, 4]
const double = (n: number) => n * 2
const greaterThanFour = (n: number) => n > 4
const result = pipe(
numbers,
Array.map(double),
Array.filter(greaterThanFour)
)
console.log(result) // [6, 8]
Example (Chaining arithmetic operations)
import { pipe } from "effect"
// Define simple arithmetic operations
const increment = (x: number) => x + 1
const double = (x: number) => x * 2
const subtractTen = (x: number) => x - 10
// Sequentially apply these operations using `pipe`
const result = pipe(5, increment, double, subtractTen)
console.log(result)
// Output: 2
Example (Building a simple transformation pipeline)
import { pipe } from "effect"
// Simple transformation pipeline
const result = pipe(
5,
(x) => x * 2, // 10
(x) => x + 1, // 11
(x) => x.toString() // "11"
)
console.log(result) // "11"
pipe(
import LayerLayer.const effect: {
<I, S>(service: Context.Key<I, S>): <E, R>(
effect: Effect<S, E, R>
) => Layer<I, E, Exclude<R, Scope.Scope>>
<I, S, E, R>(
service: Context.Key<I, S>,
effect: Effect<Types.NoInfer<S>, E, R>
): Layer<I, E, Exclude<R, Scope.Scope>>
}
Constructs a layer from an effect that produces a single service.
When to use
Use when you need to construct a Layer-provided service with an Effect,
dependencies, or scoped resource acquisition.
Details
This allows you to create a Layer from an Effect that produces a service.
The Effect is executed in the scope of the layer, allowing for proper
resource management.
Example (Creating a layer from an effect)
import { Context, Effect, Layer } from "effect"
class Database extends Context.Service<Database, {
readonly query: (sql: string) => Effect.Effect<string>
}>()("Database") {}
const layer = Layer.effect(Database,
Effect.sync(() => ({
query: (sql: string) => Effect.succeed(`Query: ${sql}`)
}))
)
effect(import PlatformPlatform.class HttpPlatformclass HttpPlatform {
key: Identifier;
Service: {
fileResponse: (path: string, options?: Response.Options.WithContent & { readonly bytesToRead?: FileSystem.SizeInput | undefined; readonly chunkSize?: FileSystem.SizeInput | undefined; readonly offset?: FileSystem.SizeInput | undefined }) => Effect.Effec…;
fileWebResponse: (file: Body.HttpBody.FileLike, options?: Response.Options.WithContent & { readonly bytesToRead?: FileSystem.SizeInput | undefined; readonly chunkSize?: FileSystem.SizeInput | undefined; readonly offset?: FileSystem.SizeInput | undefined })…;
};
of: (this: void, self: { readonly fileResponse: (path: string, options?: ServerResponse.Options.WithContent & { readonly bytesToRead?: SizeInput | undefined; readonly chunkSize?: SizeInput | undefined; readonly offset?: SizeInput | undefined }…;
context: (self: { readonly fileResponse: (path: string, options?: ServerResponse.Options.WithContent & { readonly bytesToRead?: SizeInput | undefined; readonly chunkSize?: SizeInput | undefined; readonly offset?: SizeInput | undefined }) => Effect<…;
use: (f: (service: { readonly fileResponse: (path: string, options?: ServerResponse.Options.WithContent & { readonly bytesToRead?: SizeInput | undefined; readonly chunkSize?: SizeInput | undefined; readonly offset?: SizeInput | undefined }) => …;
useSync: (f: (service: { readonly fileResponse: (path: string, options?: ServerResponse.Options.WithContent & { readonly bytesToRead?: SizeInput | undefined; readonly chunkSize?: SizeInput | undefined; readonly offset?: SizeInput | undefined }) => …;
Identifier: Identifier;
stack: string | undefined;
pipe: { <A>(this: A): A; <A, B = never>(this: A, ab: (_: A) => B): B; <A, B = never, C = never>(this: A, ab: (_: A) => B, bc: (_: B) => C): C; <A, B = never, C = never, D = never>(this: A, ab: (_: A) => B, bc: (_: B) => C, cd: (_: C) => D): D; <…;
toString: () => string;
toJSON: () => unknown;
}
Service for platform-specific HTTP response helpers, including file-backed server responses.
HttpPlatform)(const make: Effect<
{
readonly fileResponse: (
path: string,
options?: ServerResponse.Options.WithContent & {
readonly bytesToRead?:
| SizeInput
| undefined
readonly chunkSize?: SizeInput | undefined
readonly offset?: SizeInput | undefined
}
) => Effect<
ServerResponse.HttpServerResponse,
PlatformError
>
readonly fileWebResponse: (
file: HttpBody.FileLike,
options?: ServerResponse.Options.WithContent & {
readonly bytesToRead?:
| SizeInput
| undefined
readonly chunkSize?: SizeInput | undefined
readonly offset?: SizeInput | undefined
}
) => Effect<ServerResponse.HttpServerResponse>
},
never,
EtagImpl.Generator | FileSystem
>
const make: {
pipe: { <A>(this: A): A; <A, B = never>(this: A, ab: (_: A) => B): B; <A, B = never, C = never>(this: A, ab: (_: A) => B, bc: (_: B) => C): C; <A, B = never, C = never, D = never>(this: A, ab: (_: A) => B, bc: (_: B) => C, cd: (_: C) => D): D; <…;
toString: () => string;
toJSON: () => unknown;
}
Creates the Node HttpPlatform, serving file responses from Node readable
streams and adding MIME type and content-length headers when needed.
make),
import LayerLayer.const provide: {
<RIn, E, ROut>(that: Layer<ROut, E, RIn>): <
RIn2,
E2,
ROut2
>(
self: Layer<ROut2, E2, RIn2>
) => Layer<
ROut2,
E | E2,
RIn | Exclude<RIn2, ROut>
>
<Layers extends [Any, ...Array<Any>]>(
that: Layers
): <A, E, R>(
self: Layer<A, E, R>
) => Layer<
A,
E | Error<Layers[number]>,
| Services<Layers[number]>
| Exclude<R, Success<Layers[number]>>
>
<RIn2, E2, ROut2, RIn, E, ROut>(
self: Layer<ROut2, E2, RIn2>,
that: Layer<ROut, E, RIn>
): Layer<
ROut2,
E | E2,
RIn | Exclude<RIn2, ROut>
>
<A, E, R, Layers extends [Any, ...Array<Any>]>(
self: Layer<A, E, R>,
that: Layers
): Layer<
A,
E | Error<Layers[number]>,
| Services<Layers[number]>
| Exclude<R, Success<Layers[number]>>
>
}
Feeds the output services of the dependency layer into the requirements of
this layer, returning a layer that only provides the services from this layer.
When to use
Use when you need to hide an implementation dependency layer from callers.
Details
In serviceLayer.pipe(Layer.provide(dependencyLayer)), the dependency layer is
built first and is used to satisfy the requirements of serviceLayer.
Example (Providing layer dependencies)
import { Context, Effect, Layer } from "effect"
class Database extends Context.Service<Database, {
readonly query: (sql: string) => Effect.Effect<string>
}>()("Database") {}
class UserService extends Context.Service<UserService, {
readonly getUser: (id: string) => Effect.Effect<{
id: string
name: string
}>
}>()("UserService") {}
class Logger extends Context.Service<Logger, {
readonly log: (msg: string) => Effect.Effect<void>
}>()("Logger") {}
// Create dependency layers
const databaseLayer = Layer.succeed(Database, {
query: Effect.fn("Database.query")((sql: string) => Effect.succeed(`DB: ${sql}`))
})
const loggerLayer = Layer.succeed(Logger, {
log: Effect.fn("Logger.log")((msg: string) => Effect.sync(() => console.log(`[LOG] ${msg}`)))
})
// UserService depends on Database and Logger
const userServiceLayer = Layer.effect(UserService, Effect.gen(function*() {
const database = yield* Database
const logger = yield* Logger
return {
getUser: Effect.fn("UserService.getUser")(function*(id: string) {
yield* logger.log(`Looking up user ${id}`)
const result = yield* database.query(
`SELECT * FROM users WHERE id = ${id}`
)
return { id, name: result }
})
}
}))
// Provide dependencies to UserService layer
const userServiceWithDependencies = userServiceLayer.pipe(
Layer.provide(Layer.mergeAll(databaseLayer, loggerLayer))
)
// Now UserService layer has no dependencies
const program = Effect.gen(function*() {
const userService = yield* UserService
return yield* userService.getUser("123")
}).pipe(
Effect.provide(userServiceWithDependencies)
)
provide(import NodeFileSystemNodeFileSystem.const layer: Layer.Layer<FileSystem>const layer: {
build: (memoMap: MemoMap, scope: Scope.Scope) => Effect<Context.Context<FileSystem>, never, never>;
pipe: { <A>(this: A): A; <A, B = never>(this: A, ab: (_: A) => B): B; <A, B = never, C = never>(this: A, ab: (_: A) => B, bc: (_: B) => C): C; <A, B = never, C = never, D = never>(this: A, ab: (_: A) => B, bc: (_: B) => C, cd: (_: C) => D): D; <…;
}
Provides the FileSystem service backed by Node filesystem APIs.
layer),
import LayerLayer.const provide: {
<RIn, E, ROut>(that: Layer<ROut, E, RIn>): <
RIn2,
E2,
ROut2
>(
self: Layer<ROut2, E2, RIn2>
) => Layer<
ROut2,
E | E2,
RIn | Exclude<RIn2, ROut>
>
<Layers extends [Any, ...Array<Any>]>(
that: Layers
): <A, E, R>(
self: Layer<A, E, R>
) => Layer<
A,
E | Error<Layers[number]>,
| Services<Layers[number]>
| Exclude<R, Success<Layers[number]>>
>
<RIn2, E2, ROut2, RIn, E, ROut>(
self: Layer<ROut2, E2, RIn2>,
that: Layer<ROut, E, RIn>
): Layer<
ROut2,
E | E2,
RIn | Exclude<RIn2, ROut>
>
<A, E, R, Layers extends [Any, ...Array<Any>]>(
self: Layer<A, E, R>,
that: Layers
): Layer<
A,
E | Error<Layers[number]>,
| Services<Layers[number]>
| Exclude<R, Success<Layers[number]>>
>
}
Feeds the output services of the dependency layer into the requirements of
this layer, returning a layer that only provides the services from this layer.
When to use
Use when you need to hide an implementation dependency layer from callers.
Details
In serviceLayer.pipe(Layer.provide(dependencyLayer)), the dependency layer is
built first and is used to satisfy the requirements of serviceLayer.
Example (Providing layer dependencies)
import { Context, Effect, Layer } from "effect"
class Database extends Context.Service<Database, {
readonly query: (sql: string) => Effect.Effect<string>
}>()("Database") {}
class UserService extends Context.Service<UserService, {
readonly getUser: (id: string) => Effect.Effect<{
id: string
name: string
}>
}>()("UserService") {}
class Logger extends Context.Service<Logger, {
readonly log: (msg: string) => Effect.Effect<void>
}>()("Logger") {}
// Create dependency layers
const databaseLayer = Layer.succeed(Database, {
query: Effect.fn("Database.query")((sql: string) => Effect.succeed(`DB: ${sql}`))
})
const loggerLayer = Layer.succeed(Logger, {
log: Effect.fn("Logger.log")((msg: string) => Effect.sync(() => console.log(`[LOG] ${msg}`)))
})
// UserService depends on Database and Logger
const userServiceLayer = Layer.effect(UserService, Effect.gen(function*() {
const database = yield* Database
const logger = yield* Logger
return {
getUser: Effect.fn("UserService.getUser")(function*(id: string) {
yield* logger.log(`Looking up user ${id}`)
const result = yield* database.query(
`SELECT * FROM users WHERE id = ${id}`
)
return { id, name: result }
})
}
}))
// Provide dependencies to UserService layer
const userServiceWithDependencies = userServiceLayer.pipe(
Layer.provide(Layer.mergeAll(databaseLayer, loggerLayer))
)
// Now UserService layer has no dependencies
const program = Effect.gen(function*() {
const userService = yield* UserService
return yield* userService.getUser("123")
}).pipe(
Effect.provide(userServiceWithDependencies)
)
provide(import EtagImplEtagImpl.const layer: Layer.Layer<Generator>const layer: {
build: (memoMap: MemoMap, scope: Scope.Scope) => Effect<Context.Context<Generator>, never, never>;
pipe: { <A>(this: A): A; <A, B = never>(this: A, ab: (_: A) => B): B; <A, B = never, C = never>(this: A, ab: (_: A) => B, bc: (_: B) => C): C; <A, B = never, C = never, D = never>(this: A, ab: (_: A) => B, bc: (_: B) => C, cd: (_: C) => D): D; <…;
}
Layer that provides a Generator which produces strong ETags from file size
and modification time metadata.
When to use
Use when you need the Generator service to produce strong ETags and file
size plus modification time reliably change for every byte-level change.
Gotchas
This layer marks metadata-derived tags as strong. If the underlying storage
can update file contents without changing the recorded size or modification
time, those tags can stop representing byte-for-byte identity.
layer)
)