package-json-effect

An Effect library for reading, writing, parsing, validating and normalizing package.json files. It decodes a file into a typed Package model — version becomes a SemVer, optional fields become Option, dependency maps become HashMap — and writes it back with consistent key ordering. Reading, formatting, validation and dependency resolution are each a swappable Layer, so you keep the parts you want and replace the rest.

Features

• Typed Package model decoded from a package.json file: version is a SemVer, optional fields are Option, dependency and script maps are HashMap
• Computed getters (isScoped, isESM, isPrivate, hasDependency) and a dual-API for immutable mutations (data-first Package.setVersion(pkg, v), curried Package.setVersion(v)(pkg) and pipeable pkg.pipe(Package.setVersion(v)))
• Dependency, DevDependency, PeerDependency and OptionalDependency instances with a protocol taxonomy (isRange, isTag, isGit, isLocal, isWorkspace, isCatalog) that classifies any specifier
• A reader and writer backed by @effect/platform FileSystem, with sort-package-json-style key ordering and alphabetical dependency sorting applied on write
• Unknown top-level fields preserved through a read/write round-trip, so you never lose tooling config you do not model
• A validator with publish-readiness rules and a ValidationRule interface for writing your own
• A package-json-effect/schema entry point: extend the model with .extend() and rebuild the wire schema with makePackageJsonSchema to type custom fields
• catalog: and workspace: resolution through swappable CatalogResolver and WorkspaceResolver services

Install

effect and @effect/platform are peer dependencies. Install them alongside a platform adapter for your runtime — @effect/platform-node for Node.js.

npm install package-json-effect effect @effect/platform @effect/platform-node
# or
pnpm add package-json-effect effect @effect/platform @effect/platform-node

Quick start

Read a file, inspect it through the typed getters, make an immutable edit and write it back. The program yields the PackageJsonReader and PackageJsonWriter services and runs with the composite PackageJsonLive layer plus a FileSystem layer.

import { NodeFileSystem } from "@effect/platform-node";
import { Effect } from "effect";
import { Package, PackageJsonLive, PackageJsonReader, PackageJsonWriter } from "package-json-effect";

const program = Effect.gen(function* () {
  const reader = yield* PackageJsonReader;
  const writer = yield* PackageJsonWriter;

  const pkg = yield* reader.read("./package.json");
  console.log(pkg.name); // the "name" field, a string
  console.log(pkg.version.toString()); // the "version" field as a SemVer, e.g. "1.3.0"
  console.log(pkg.isESM); // true when "type": "module"

  // Mutations return a new Package; the original is untouched.
  const bumped = yield* Package.setVersion(pkg, "1.4.0");
  const withDep = Package.addDependency(bumped, "effect", "^3.10.0");

  yield* writer.write("./package.json", withDep);
});

Effect.runPromise(program.pipe(Effect.provide(PackageJsonLive), Effect.provide(NodeFileSystem.layer)));

PackageJsonLive provides every service in the library and requires FileSystem from @effect/platform, which NodeFileSystem.layer (or NodeContext.layer) supplies.

Documentation

• Getting started — install, the Effect mental model (Option, HashMap, Layer) and providing PackageJsonLive with a FileSystem layer
• Reading and writing — the reader and writer, formatter key ordering, the transformer and round-trip fidelity for unmodeled fields
• The Package model — computed getters, the Dependency instances and protocol taxonomy, and the dual-API for immutable mutations
• Validation — the default rules, publish-readiness rules, writing a ValidationRule and building a validator layer
• Extending the schema — adding custom fields with .extend() and makePackageJsonSchema via the package-json-effect/schema entry point
• Catalog and workspace resolution — the no-op default, providing a real resolver, modifier semantics and resolution on read versus write
• Testing — mock layers with Layer.succeed, asserting on typed errors and integration tests against the real filesystem
• Errors and troubleshooting — every error type, what triggers it and how to handle it

License

MIT