isolate-package

Isolate Package

• TLDR
• Introduction
• Features
• Motivation
• Installation
• Usage
• Troubleshooting
• Prerequisites
  • Define shared dependencies in the package manifest
  • Define "version" field in each package manifest
  • Define "files" field in each package manifest
  • Use a flat structure inside your packages folders
• Configuration Options
  • buildDirName
  • excludeLockfile
  • includeDevDependencies
  • isolateDirName
  • logLevel
  • targetPackagePath
  • tsconfigPath
  • workspacePackages
  • workspaceRoot
• Lockfiles
• API
• The internal packages strategy
• Working with Firebase
  • A Quick Start
  • Deploying from multiple packages
  • Deploying from the root
  • Using the Firebase Functions Emulator

TLDR

Run npx isolate-package isolate from the monorepo package you would like to isolate.

Introduction

Isolate a monorepo workspace package to form a self-contained deployable package that includes internal dependencies and a compatible lockfile. The internal packages structure is preserved. Code is not bundled.

Features

• Isolates a monorepo package with its internal dependencies to form a self-contained deployable directory.
• Generates an isolated / pruned lockfile based on the existing monorepo lockfile. See lockfiles for more information.
• Zero-config for the vast majority of use-cases, with no manual steps involved.
• Support for PNPM, NPM and Yarn.
• Compatible with the Firebase tools CLI, incl 1st and 2nd gen Firebase functions.
• Isolates internal workspace dependencies recursively. If package A depends on internal package B which depends on internal package C, all of them will be included.
• Optionally include devDependencies in the isolated output.

Motivation

This solution was born from a desire to deploy to Firebase from a monorepo without resorting to custom shell scripts and other hacks. Here is an article explaining the issue in more detail.

There is nothing Firebase-specific to this solution and there should be other use-cases for it, but that is why this documentation contains some instructions related to Firebase.

!! There is now a fork of firebase-tools, where isolate-package is integrated. This is preferred because it simplifies the setup and allows the isolation to run only as part of the deploy process, preserving live code updates when running the local Firebase emulators.

Installation

Run pnpm install isolate-package --dev or the equivalent for npm or yarn.

I recommend using pnpm for a number of reasons. In my experience it is the best package manager, especially for monorepo setups.

Usage

This package exposes a binary called isolate.

Run npx isolate from the root of the package you want to isolate. Make sure you build the package first.

The isolate binary will try to infer your build output location from a tsconfig file, but see the buildDirName configuration if you are not using Typescript.

By default the isolated output will become available at ./isolate.

If you are here to simplify and improve your Firebase deployments check out the Firebase quick start guide.

Troubleshooting

If something is not working as expected, add a isolate.config.json file, and set "logLevel" to "debug". This should give you detailed feedback in the console.

In addition define an environment variable to debug the configuration being used by setting DEBUG_ISOLATE_CONFIG=true before you execute isolate.

When debugging Firebase deployment issues it might be convenient to trigger the isolate process manually with npx isolate and possibly DEBUG_ISOLATE_CONFIG=true npx isolate

If you do not pass in any configuration, the function will try to read a isolate.config.json file from disk. You can set

Prerequisites

Because historically many different approaches to monorepos exist, we need to establish some basic rules for the isolate process to work.

Define shared dependencies in the package manifest

This one might sound obvious, but if the package.json from the package you are targeting does not list the other monorepo packages it depends on, in either the dependencies or devDependencies list, then the isolate process will not include them in the output.

How dependencies are listed with regards to versioning is not important, because packages are matched based on their name. For example the following flavors all work (some depending on your package manager):

// package.json
{
  "dependencies": {
    "shared-package": "0.0.0"
    "shared-package": "*",
    "shared-package": "workspace:*",
    "shared-package": "../shared-package",
  }
}

So if the a package name can be found as part of the workspace definition, it will be processed regardless of its version specifier.

Define "version" field in each package manifest

The version field is required for pack to execute, because it is use to generate part of the packed filename. A personal preference is to set it to "0.0.0" to indicate that the version does not have any real meaning.

Define "files" field in each package manifest

NOTE: This step is not required if you use the internal packages strategy but you could set it to ["src"] instead of ["dist"].

The isolate process uses (p)npm pack to extract files from package directories, just like publishing a package would.

For this to work it is required that you define the files property in each package manifest, as it declares what files should be included in the published output.

Typically the value contains an array with just the name of the build output directory, for example:

// package.json
{
  "files": ["dist"]
}

A few additional files from the root or your package will be included by pack automatically, like package.json, LICENSE and README files.

Tip If you deploy to Firebase 2nd generation functions, you might want to include some env files in the files list, so they are packaged and deployed together with your build output (as 1st gen functions config is no longer supported).

Use a flat structure inside your packages folders

At the moment, nesting packages inside packages is not supported.

When building the registry of all internal packages, isolate doesn't drill down into the folders. So if you declare your packages to live in packages/* it will only find the packages directly in that folder and not at packages/nested/more-packages.

You can, however, declare multiple workspace packages directories. Personally, I prefer to use ["packages/*", "apps/*", "services/*"]. It is only the structure inside them that should be flat.

Configuration Options

For most users no configuration should be necessary.

You can configure the isolate process by placing a isolate.config.json file in the package that you want to isolate, except when you're deploying to Firebase from the root of the workspace.

For the config file to be picked up, you will have to execute isolate from the same location, as it uses the current working directory.

Below you will find a description of every available option.

buildDirName

Type: string | undefined, default: undefined

The name of the build output directory name. When undefined it is automatically detected via tsconfig.json. When you are not using Typescript you can use this setting to specify where the build output files are located.

excludeLockfile

Type: boolean, default: Depends on package manager.

Deprecated This option exists from the time that lockfiles were not supported for all package managers. You should not need this escape hatch anymore.

Sets the inclusion or exclusion of the lockfile as part of the deployment.

Isolated / pruned lockfiles are generated for NPM, PNPM and Yarn v1 (classic) based on the existing root lockfile, and they are included by default.

For more information see lockfiles.

includeDevDependencies

Type: boolean, default: false

By default devDependencies are ignored and stripped from the isolated output package.json files. If you enable this the devDependencies will be included and isolated just like the production dependencies.

isolateDirName

Type: string, default: "isolate"

The name of the isolate output directory.

logLevel

Type: "info" | "debug" | "warn" | "error", default: "info".

Because the configuration loader depends on this setting, its output is not affected by this setting. If you want to debug the configuration set DEBUG_ISOLATE_CONFIG=true before you run isolate

targetPackagePath

Type: string, default: undefined

Only when you decide to place the isolate configuration in the root of the monorepo, you use this setting to point it to the target you want to isolate, e.g. ./packages/my-firebase-package.

If this option is used the workspaceRoot setting will be ignored and assumed to be the current working directory.

tsconfigPath

Type: string, default: "./tsconfig.json"

The path to the tsconfig.json file relative to the package you want to isolate. The tsconfig is only used for reading the compilerOptions.outDir setting. If no tsconfig is found, possibly because you are not using Typescript in your project, the process will fall back to the buildDirName setting.

workspacePackages

Type: string[] | undefined, default: undefined

When workspacePackages is not defined, isolate will try to find the packages in the workspace by looking up the settings in pnpm-workspace.yaml or package.json files depending on the detected package manager.

In case this fails, you can override this process by specifying globs manually. For example "workspacePackages": ["packages/*", "apps/*"]. Paths are relative from the root of the workspace.

workspaceRoot

Type: string, default: "../.."

The relative path to the root of the workspace / monorepo. In a typical setup you will have a packages directory and possibly also an apps and a services directory, all of which contain packages. So any package you would want to isolate is located 2 levels up from the root.

For example

packages
├─ backend
│  └─ package.json
└─ ui
   └─ package.json
apps
├─ admin
│  └─ package.json
└─ web
   └─ package.json
services
└─ api
   └─ package.json

When you use the targetPackagePath option, this setting will be ignored.

Lockfiles

A lockfile in a monorepo describes the dependencies of all packages, and does not translate to the isolated output without altering it.

If you copying the original lockfile and deploy it with the isolated code, a CI environment will not accept the lockfile. It is also not possibly to generate a brand new lockfile from the isolated code by mimicking a fresh install, because versions would be able to diverge and thus negate the whole point of having a lockfile in the first place.

For this to work, we need to re-generate or prune the original lockfile to keep the versions of the original but only describe the dependencies of the code in the isolated output.

Since every package manager works completely different in this regard, this part of the puzzle had to be solved in a different ways for each of them, and not all are supported yet.

At the moment lockfiles for the following package managers are supported:

• NPM
• PNPM
• Yarn Classic (v1)

More detailed information on the implementation can be found in the additional docs.

API

Alternatively, isolate can be integrated in other programs by importing it as a function. You optionally pass it a some user configuration and possibly a logger to handle any output messages should you need to write them to a different location as the standard node:console.

import { isolate } from "isolate-package";

await isolate({
  config: { logLevel: "debug" },
  logger: customLogger,
});

The internal packages strategy

An alternative approach to using internal dependencies in a Typescript monorepo is the internal packages strategy, in which the package manifest entries point directly to Typescript source files, to omit intermediate build steps. The approach is compatible with isolate-package and showcased in my example monorepo setup

In summary this is how it works:

1. The package to be deployed lists its internal dependencies as usual, but the package manifests of those dependencies point directly to the Typescript source (and types).
2. You configure the bundler of your target package to include the source code for those internal packages in its output bundle. In the case of TSUP for the API service in the mono-ts that configuration is: noExternal: ["@mono/common"]
3. When isolate runs, it does the same thing as always. It detects the internal packages, copies them to the isolate output folder and adjusts any links.
4. When deploying to Firebase, the cloud pipeline will treat the package manifest as usual, which installs the listed dependencies and any dependencies listed in the linked internal package manifests.

Steps 3 and 4 are no different from a traditional setup.

Note that the manifests for the internal packages in the output will still point to the Typescript source files, but since the shared code was embedded in the bundle, they will never be referenced via import statements. So the manifest the entry declarations are never used. The reason the packages are included in the isolated output is to instruct package manager to install their dependencies.

Working with Firebase

!! There is now a fork of firebase-tools, where isolate-package is integrated. This is preferred because it simplifies the setup and allows the isolation to run only as part of the deploy process, preserving live code updates when running the local Firebase emulators.

A Quick Start

If you are not confident that your monorepo setup is solid, please check out my in-dept example at mono-ts where many different aspects are discussed and isolate-package is used to demonstrate Firebase deployments.

This section describes the steps required for Firebase deployment, assuming:

• You use a fairly typical monorepo setup
• Your firebase.json config lives in the root of the package that you like to deploy to Firebase, hereafter referred to as the "target package".

If your setup diverges from a traditional one, please continue reading the Prerequisites section.

1. In the target package, install isolate-package and firebase-tools by running pnpm add isolate-package firebase-tools -D or the Yarn / NPM equivalent. I tend to install firebase-tools as a devDependency in every Firebase package, but you could also use a global install if you prefer that.
2. In the firebase.json config set "source" to "./isolate" and "predeploy" to ["turbo build", "isolate"] or whatever suits your build tool. The important part here is that isolate is being executed after the build stage.
3. From the target package folder, you should now be able to deploy with npx firebase deploy.

I recommend keeping a firebase.json file inside each Firebase package (as opposed to the monorepo root), because it allows you to deploy from multiple independent packages. It makes it easy to deploy 1st gen functions next to 2nd gen functions, deploy different node versions, and decrease the built output size and dependency lists for each package, improving deployment and cold-start times.

Deploying from multiple packages

You can deploy to Firebase from multiple packages in your monorepo, in which case you co-locate your firebase.json file with the source code, and not in the root of the monorepo. If you do want to keep the firebase config in the root, read the instructions for deploying to Firebase from the root.

In order to deploy to Firebase, the functions.source setting in firebase.json needs to point to the isolated output folder, which would be ./isolate when using the default configuration.

The predeploy phase should first build and then isolate the output.

Here's an example using Turborepo:

// firebase.json
{
  "functions": {
    "source": "./isolate",
    "predeploy": ["turbo build", "isolate"]
  }
}

With this configuration you can then run npx firebase deploy --only functions from the package.

If you like to deploy to Firebase Functions from multiple packages you will also need to configure a unique codebase identifier for each of them. For more information, read this.

Make sure your Firebase package adheres to the things mentioned in prerequisites and its package manifest contains the field "main", or "module" if you set "type": "module", so Firebase knows the entry point to your source code.

Deploying from the root

If, for some reason, you choose to keep the firebase.json file in the root of the monorepo you will have to place a configuration file called isolate.config.json in the root with the following content:

// isolate.config.json
{
  "targetPackagePath": "./packages/your-firebase-package"
}

The Firebase configuration should then look something like this:

// firebase.json
{
  "functions": {
    "source": "./packages/your-firebase-package/isolate",
    "predeploy": ["turbo build", "isolate"]
  }
}

Using the Firebase Functions Emulator

The Firebase functions emulator runs on the code that firebase.json source points to. Unfortunately, this is the same field as is used for declaring the code for deployment, which means the emulator is looking at the isolated output.

As a result, any changes to your code have to go through the isolate process in order to be picked up by the emulator. In other words, changes do not propagate automatically while the emulator is running.

The workaround I use at the moment is to create a "emulate" script in the package manifest which does the same as the Firebase predeploy, and then starts the emulator. For example:

turbo build && isolate && firebase emulators:start --only functions

You will still have to stop and restart the emulator on every code change, which is unfortunate of course.

A real solution to this would be to integrate isolate-package into the firebase-tools deploy command, so it is only executed as part of the deployment process and the source property can still point to the original code.

I plan to work on this once isolate-package is bit more mature.