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Monorepo Infrastructure & Tools

This document aims to provide an outline for the monorepo's infrastructure as well as the rationale behind the decisions we've made.

Task Orchestration

Our repository makes aggressive use of parallelization using PNPM's --filter syntax. This allows us to minimize the amount of time developers spend waiting for tasks like builds to complete. Each project within the monorepo will contain the following scripts if applicable:

{
	"scripts": {
		"build": "pnpm --if-present --workspace-concurrency=Infinity --stream --filter=\"$npm_package_name...\" '/^build:project:.*$/'",
		"build:project": "pnpm --if-present '/^build:project:.*$/'",
		"lint": "pnpm --if-present '/^lint:lang:.*$/'",
		"lint:fix": "pnpm --if-present '/^lint:fix:lang:.*$/'",
		"watch:build": "pnpm --if-present --workspace-concurrency=Infinity --filter=\"$npm_package_name...\" --parallel '/^watch:build:project:.*$/'",
		"watch:build:project": "pnpm --if-present run '/^watch:build:project:.*$/'"
	}
}

These scripts outline the naming scheme used in order to facilitate task parallelization using regular expressions. To ensure consistency across the monorepo, these scripts should not be edited. New scripts should be added using the naming scheme outlined by the above regular expressions, for example, build:project:bundle might be a script to run a tool like webpack. We also utilize a number of PNPM options to ensure a positive developer experience:

  • --if-present: Ensures that PNPM will not error if a script is not found.
  • --workspace-concurrency=Infinity: Runs as many of the tasks in parallel as possible.
  • --stream: Makes the script output legible by putting all of their output into a single stream.
  • --filter="$npm_package_name...": This filter tells PNPM that we want to run the script against the current project and all of its dependencies down the graph (dependencies first).

To further improve the build times, we used two additional techniques:

  • In the case of the build script, we offer both building packages with (build) and without (build:project) its dependencies.
  • Using wireit-based task output caching (details are below).

Task Output Caching

Our repository uses wireit to provide task output caching. In particular, this allows us to cache the output of build scripts so that they don't run unnecessarily. The goal is to minimize the amount of time that developers spend waiting for projects to build.

{
  "scripts": {
    "build": "pnpm --if-present --workspace-concurrency=Infinity --stream --filter=\"$npm_package_name...\" '/^build:project:.*$/'",
    "build:project": "pnpm --if-present '/^build:project:.*$/'",
    "build:project:bundle": "wireit"
  },
  "wireit": {
    "build:project:bundle": {
      "command": "webpack",
      "files": [
        "... - package resources as input"
      ],
      "output": [
        "... - package resources as output"
      ],
      "dependencies": [
        "dependencyOutputs"
      ]
    },
    "dependencyOutputs": {
      "files": [
        "... - dependencies resources as input",
        "... - updated automatically by monorepo tooling which hooks up into `pnpm install`",
        "... - see `.pnpmfile.cjs` file and https://pnpm.io/pnpmfile for details"
      ]
    }
  }
}

In the example above, build:project:bundle invokes wireit, which conditionally executes webpack (based on the state of resources). A simplified take on wireit is the following:

  • if input sources are changed or output sources are not generated yet, wireit will execute webpack command and cache output sources
  • if input sources are unchanged, wireit will create output sources from their cached version