isolate-package

Isolate Package

Isolate a monorepo workspace package so that it can be deployed as a completely self-contained directory with the sources of all its local dependencies included.

Motivation

This solution was developed out of a desire to deploy to Firebase from a monorepo without resorting to hacks, shell scripts and manual tasks. I have written an article explaining the issue here.

There is nothing Firebase specific to this solution but I am currently not aware of other reasons to isolate a workspace package. If you find a different use-case, I would love to hear about it.

Features

• Zero-config for the vast majority of use-cases, with no manual steps involved.
• Designed to support NPM, Yarn and PNPM workspaces.
• Compatible with the Firebase tools CLI.
• Uses a pack/unpack approach to isolate only those files that would have been part of a published package, so the resulting output contains a minimal amount of files.
• Isolates dependencies recursively. If package A depends on local package B which depends on local package C, all of them will be isolated.
• Include and (in the case of PNPM) update the lockfile so the isolated deployment should be deterministic.
• Optionally choose to include dev dependencies in the isolated output.

Prerequisites

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

Define shared package dependencies in the 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:

// package.json
{
  "dependencies": {
    "shared-package": "workspace:*",
    "shared-package": "*",
    "shared-package": "../shared-package",
    "shared-package": "^1.0.0"
  }
}

So basically, version information is ignored, and if the package name can be found in the list of local monorepo packages, it will be processed regardless of its version specifier.

Define "files" and "version" in each manifest

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.json 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"]
}

Also version seems to be required by pack. I like setting it to "0.0.0" to make it clear that the version is not really being used.

A few additional files will be included by pack automatically, like the package.json and README.md files.

Use a flat structure inside your packages folders

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

When building the registry of all local 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 packages folders like ["packages/*", "apps/*"]. It's just that the structure inside them should be flat.

Usage

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

This package exposes the isolate executable. Once installed you can run npx isolate in any package directory after you have build the source files. By default this will produce a directory at ./isolate but this can be configured.

You will probably want to add the output directory to your .gitignore file.

Deploying to Firebase

You can deploy to Firebase from multiple packages in your monorepo, so I advise you to co-locate your firebase.json file with the source code, and not place it in the root of the monorepo. If you do want to keep the firebase config in the root, some additional configuration is required, so read on.

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 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 manifest file contains the field "main", or "module" if you set "type": "module", so Firebase knows the entry point to your source code.

Deploying to Firebase 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"]
  }
}

Configuration Options

For most users no configuration should be required. 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.

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 ISOLATE_CONFIG_LOG_LEVEL=debug 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 repository you will have a packages and possibly an apps directory, and both contain packages, so any package you would want to isolate is located 2 levels up from the root.

For example

apps
├─ api
│  ├─ package.json
│  └─ .eslintrc.js
└─ web
   ├─ package.json
   └─ .eslintrc.js
packages
└─ eslint-config-custom
   ├─ index.js
   └─ package.json

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

Troubleshooting

If something is not working, I advise you to 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 ISOLATE_CONFIG_LOG_LEVEL=debug before you execute isolate

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

Lockfiles

I inspected the NPM lockfile as well as the Yarn v1 and v3 lockfiles and they seem to have a flat structure unrelated to the workspace packages structure, so I have made the assumption that they can be copied to the isolate output as-is.

The PNPM lockfile clearly has a structure describing the different packages by their relative paths, and so to correct the lockfile it is adapted before being stored to the isolate directory.

I am not sure the Firebase deploy pipeline is actually detecting a pnpm-lock.yaml file and using PNPM to install its packages. This needs to be verified...

Used Terminology

The various package managers, while being very similar, seem to use a different definition for the term "workspace". If you want to read the code it might be good to know that I consider the workspace to be the monorepo itself, in other words, the overall structure that holds all the packages.

Also, in the code you see the word manifest a lot, and it simply means to the contents of a package.json file.

Binary as ESM module

The isolate binary is an ES module. It is required to have the .mjs file extension, otherwise a non-ESM workspace will try to execute it as commonJS. For details on this read this article from Alex Rauschmayer

For PNPM the hashbang at the top of the script was not required, but Yarn 3 did not seem to execute without it.