Axial.FileSystem 0.12.0

Axial

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Write asynchronous F# workflows whose expected failures and required dependencies are visible in their types.

Your first flow

A handler usually needs services and can fail, but a Task signature shows neither fact. Flow<'env, 'error, 'value> makes both part of the contract.

open Axial

type CheckoutError =
    | OrderNotFound of orderId: int
    | PaymentDeclined of reason: string

type Receipt = { OrderId: int; Total: decimal; Reference: string }

type CheckoutEnv =
    { FindTotal: int -> ColdTask<Result<decimal, CheckoutError>>
      Charge: decimal -> ColdTask<Result<string, CheckoutError>> }

let checkout orderId : Flow<CheckoutEnv, CheckoutError, Receipt> =
    flow {
        let! findTotal = Flow.envWith _.FindTotal
        let! charge = Flow.envWith _.Charge
        let! total = findTotal orderId
        let! reference = charge total
        return { OrderId = orderId; Total = total; Reference = reference }
    }

The application supplies live functions. A test supplies a record of fakes. The workflow does not change.

Adding a timeout and a retry policy leaves the Flow<CheckoutEnv, CheckoutError, Receipt> signature unchanged. The runtime supplies its clock and owns cancellation, retries, and cleanup:

open System

let checkoutOrder orderId : Flow<CheckoutEnv, CheckoutError, Receipt> =
    checkout orderId
    |> Flow.retry (Schedule.recurs 2)
    |> Flow.timeout (TimeSpan.FromSeconds 5.0) (PaymentDeclined "checkout timed out")

Flow also carries concurrency, scheduling, streams, and structured child fibers through the same runtime. Clock, random and GUID values are scoped runtime services; application authority stays in 'env. Use Flow.withClock, Flow.withRandom and Flow.withGuid to override values for a flow and its descendants. Log.info writes to the current ILogSink (Information+ on stderr by default); install or decorate destinations with Flow.withLogSink / Flow.mapLogSink, and observation callbacks with Flow.withTelemetry.

Core Axial ships these runtime services under the Axial namespace. Flow.runTest env creates a fresh epoch manual clock, seeded random, sequential GUIDs and a recording log. Timed tests explicitly advance TestClock after observing sleeper registration; time never advances automatically. See runtime services.

Install

dotnet add package Axial

Package family

• Axial: the core workflow model: typed failures, dependencies, concurrency, resources, schedules, streams, and runtime platform services.
• Axial.Process: external process composition, pipelines, streaming output, typed failures, cancellation, and cleanup. Process docs
• Axial.HttpClient: typed HTTP requests, response handling, and reliability policies. HTTP docs
• Axial.Configuration: layered environment, argument, JSON, browser, and Microsoft configuration decoded by Reified, with redacted secrets. Configuration docs
• Axial.Console: standard streams, redirection, and terminal control. Console docs
• Axial.FileSystem: file-system access, streaming traversal, atomic writes, and the append log. FileSystem docs
• Axial.WebSocket: typed WebSocket client sessions and errors. WebSocket docs
• Axial.Hosting, Axial.Hosting.AspNetCore, Axial.Hosting.GenHttp, Axial.Hosting.Node, and Axial.Hosting.Browser: host adapters. Hosting docs
• Axial.ElmishFlows: Elmish commands and subscriptions backed by workflows. Elmish docs
• Axial.Telemetry and Axial.Telemetry.JavaScript: .NET and Fable tracing, metrics, and dumps. Telemetry docs
• Axial.Guardrails and Axial.Tool: effect-boundary analysis and the axial policy CLI. Guardrails docs

See the package maturity table for each package's rating and application evidence. The package catalogue links the first-class libraries and the complete compatibility matrix.

Documentation and examples

• Getting started
• Add Axial to an existing Task application
• Failures and defects
• Dependencies and services
• Concurrency
• Process
• HTTP client
• Runnable examples
• Integration reference application and HTTP host examples

Reified integration

Reified declares value, model, JSON, and HTTP contracts. Axial's optional server adapters execute Reified HTTP contracts as workflows; neither core depends on the other. Axial 0.12 requires Reified 0.12.1 or later, whose Fable schema builder supports typed schema construction and Config.load decoding on Fable.