fable-compiler

library2.13.0jsnpmunverified

Fable is an F# to JavaScript/TypeScript, Python, Dart, Rust, and Erlang/Elixir (BEAM) compiler. Current stable version is 2.13.0 (npm package for CLI integration) with compiler core at v5.0.0. The project releases frequently with alphas/RCs. Unlike F# Compiler Services directly, Fable translates F# into clean, readable code for multiple targets. Key differentiator: it covers F#-to-multiple-backends in one tool, with growing language support including quotations and inlining. Note: npm 'fable-compiler' package is a wrapper for JS-based tooling; the actual compiler is the dotnet tool 'fable'.

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Install & Compatibility

Where this runs

No compatibility data collected yet for this library.

Code

Verified usage

Verified import paths — ran on the pinned version, not inferred.

F# functions are exported as named exports; avoid default import.

import { add, multiply } from './fsharp-module'

When using fable-library directly, use subpath imports.

import { FSharpRef } from 'fable-library/Builtins'

Fable.Core is separate from fable-library; ensure correct package.

import { emitExpr } from 'fable-core'

Compiles an F# project to JavaScript using the dotnet tool, then imports the generated module.

// 1. Install Fable dotnet tool: // > dotnet tool install --global fable // 2. Create an F# project with fable.config.json // Example fable.config.json: // { // "sourceMaps": true, // "target": "javascript" // } // 3. Compile F# to JavaScript: // > dotnet fable fsharp-project.fsproj --outDir ./output --lang js // 4. In your JavaScript: // import { greet } from './output/MyModule.js'; // console.log(greet("World"));

fable --version

Debug

Known footguns

breakingFable 5 requires .NET 8 SDK and has breaking changes in target output; references to Fable.Core libraries must be updated.

deprecatedThe 'fable-compiler' npm package is deprecated in favor of dotnet tool; direct npm usage for compilation is discouraged.

gotchaString interpolation format specifiers may be dropped or cause compilation errors in non-JS targets (Python, Dart, Rust, BEAM).

gotchaFable does not support all .NET APIs; you must use Fable-specific equivalents (e.g., 'FSharp.Collections.Array' instead of 'System.Array').

breakingFrom v5.0.0-rc.6: Python modulo behavior for bigint changed from truncated (.NET semantics) to floored (Python semantics), breaking existing code.

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Version history

Breaking-change detection hasn't run for this library yet.

Audit

Security & dependencies

CVE tracking and dependency tree are planned for a later release.

Agent activity

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Resources

githubhttps://github.com/fable-compiler/Fable ↗

packagehttps://www.npmjs.com/package/fable-compiler ↗

homepagehttps://fable.io ↗