isolate-package

Isolate Package

• TLDR
• 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.

If you would like to see an example of a modern monorepo with this tool integrated, check out mono-ts

Features

• Isolate a monorepo workspace package to form a self-contained package that includes internal dependencies and an adapted lockfile for deterministic deployments.
• Preserve packages file structure, without code bundling
• Should work with any package manager, and tested with NPM, PNPM, and Yarn (both classic and modern)
• Zero-config for the vast majority of use-cases
• Isolates dependencies recursively. If package A depends on internal package B which depends on internal package C, all of them will be included
• Optionally force output to use NPM with matching versions
• Optionally include devDependencies in the isolated output
• Optionally pick or omit scripts from the manifest
• Compatible with the Firebase tools CLI, including 1st and 2nd generation Firebase Functions

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, but any other package manager should work.

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 an 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.

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.

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

forceNpm

Type: boolean, default: false

By default the isolate process will generate output based on the package manager that you are using for your monorepo. But your deployment target might not be compatible with that package manager, or it might not be the best choice given the available tooling.

Also, it should not really matter what package manager is used in de deployment as long as the versions match your original lockfile.

By setting this option to true you are forcing the isolate output to use NPM. A package-lock file will be generated based on the contents of node_modules and therefore should match the versions in your original lockfile.

This way you can enjoy using PNPM or Yarn for your monorepo, while your deployment uses NPM with modules locked to the same versions.

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.

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.

pickFromScripts

Type: string[], default: undefined

Select which scripts to include in the output manifest scripts field. For example if you want your test script included set it to ["test"].

By default, all scripts are omitted.

omitFromScripts

Type: string[], default: undefined

Select which scripts to omit from the output manifest scripts field. For example if you want the build script interferes with your deployment target, but you want to preserve all of the other scripts, set it to ["build"].

By default, all scripts are omitted, and the pickFromScripts configuration overrules this configuration.

isolateDirName

Type: string, default: "isolate"

The name of the isolate output directory.

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

The isolate process tries to generate an isolated / pruned lockfile for the package manager that you use in your monorepo. If the package manager is not supported (modern Yarn versions), it can still generate a matching NPM lockfile based on the installed versions in node_modules.

In case your package manager is not supported by your deployment target you can also choose NPM to be used by setting the makeNpmLockfile to true in your configuration.

NPM

For NPM we use a tool called Arborist which is an integral part of the NPM codebase. It is executed in the isolate output directory and requires the adapted lockfile and the node_modules directory from the root of the repository. As this directory is typically quite large, copying it over as part of the isolate flow is not very desirable.

To work around this, we move it to the isolate output and then move it back after Arborist has finished doing its thing. Luckily it doesn't take long and hopefully this doesn't create any unwanted side effects for IDEs and other tools that depend on the content of the directory.

When errors occur in this process, the folder should still be moved back.

PNPM

The PNPM lockfile format is very readable (YAML) but getting it adapted to the isolate output was a bit of a trip.

It turns out, at least up to v10, that the isolated output has to be formatted as a workspace itself, otherwise dependencies of internally linked packages are not installed by PNPM. Therefore, the output looks a bit different from other package managers:

• Links are preserved
• Versions specifiers like "workspace:*" are preserved
• A pnpm-workspace.yaml file is added to the output

Classic Yarn

For Yarn v1 we can simply copy the root lockfile to the isolate output, and run a yarn install to prune that lockfile. The command finds the installed node modules in the root of the monorepo so versions are preserved.

Note: I expect this to break down if you configure the isolate output directory to be located outside the monorepo tree.

Modern Yarn

For modern Yarn versions we fall back to using NPM for the output lockfile, because the strategy of running yarn install does not seem to apply here.

Based on the installed node_modules we generate an NPM lockfile that matches the versions in the Yarn lockfile. It should not really matter what package manager your deployed code uses, as long as the lockfile versions match with the original lockfile.

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,
});

If no configuration is passed in, the process will try to read isolate.config.json from the current working directory.

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, you can 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.