Introduction Why Monorepo? Nowadays, the rapid evolution of software development cannot be denied. The teams are growing, projects tend to be more complex. Companies spend significant resources to maintain a distributed codebase consisting of many fragments. Enter the monorepo - a single, unified repository that brings together all of your code. Far from being a trend, monorepos have recently become an architectural approach to house the entire codebase in one place. Teams obtain enhanced context sharing, smooth collaboration and a tool that naturally encourages code reuse. Setting Up Yarn Workspaces Note: Throughout this article, whenever "Yarn" is mentioned, it specifically refers to Yarn v4—the latest version offering enhanced capabilities and improved performance. Note: Throughout this article, whenever "Yarn" is mentioned, it specifically refers to Yarn v4—the latest version offering enhanced capabilities and improved performance. What are Yarn Workspaces? Workspaces are the packages of the monorepo, often called packages. They help you manage multiple packages in a single repository effortlessly. With workspaces. you can: Share Dependencies Easily: Share common dependencies across your project seamlessly. Simplify Dependency Management: Yarn automatically links local packages, reducing duplication and easing development. Accelerate Installations: Benefit from Yarn’s performance optimizations and caching mechanisms (i.e., built-in plug’n’play). Improve Control Over Monorepo: Define constraints (rules) and use dozens of available plugins to maintain consistency. Share Dependencies Easily: Share common dependencies across your project seamlessly. Share Dependencies Easily: Share common dependencies across your project seamlessly. Simplify Dependency Management: Yarn automatically links local packages, reducing duplication and easing development. Simplify Dependency Management: Yarn automatically links local packages, reducing duplication and easing development. Accelerate Installations: Benefit from Yarn’s performance optimizations and caching mechanisms (i.e., built-in plug’n’play). Accelerate Installations: Benefit from Yarn’s performance optimizations and caching mechanisms (i.e., built-in plug’n’play). built-in plug’n’play Improve Control Over Monorepo: Define constraints (rules) and use dozens of available plugins to maintain consistency. Improve Control Over Monorepo: Define constraints (rules) and use dozens of available plugins to maintain consistency. constraints dozens of available plugins While Yarn is the selected manager for this article thanks to its simplicity, speed, and extensive configuration options - it’s important to note that the right choice depends on your project’s specific needs, team preferences, and overall workflow. For instance, PNPM and Turborepo are other modern tools that offer a wide range of features. PNPM Turborepo Initial Configuration Yarn setup is a straightforward process. Follow the official guide to install and configure Yarn in your project: Yarn Installation Guide. Yarn Installation Guide Once you’ve completed the installation, let’s move on to configuration. Since we’re using plug’n’play, you need to ensure that your IDE correctly recognizes dependencies. If you’re using VSCode, run: # Typescript is required for VSCode SDK to set up correctly yarn add -D typescript@^5 yarn dlx @yarnpkg/sdks vscode # Typescript is required for VSCode SDK to set up correctly yarn add -D typescript@^5 yarn dlx @yarnpkg/sdks vscode If you’re using another code editor, check for the available SDKs here: Yarn Editor SDKs. If you’re using another code editor, check for the available SDKs here: Yarn Editor SDKs. Yarn Editor SDKs At this point, you’re all set to start using Yarn. Organizing the Monorepo Structure Now that the package manager is configured, it’s time to design a scalable project organization. A clear, well-defined structure not only makes the repository easier to navigate but also promotes better code reuse. In this example, we’ll divide the codebase into three major categories: Apps: Client: Contains the final, deployable client products. Server: Contains the final, deployable server products. Features: Client: For standalone UI widgets. Server: For standalone backend business logic pieces. Libs: Houses shared code such as design system components, constants, assets, and utilities. This is the context-free zone for storing reusable logic. Apps: Client: Contains the final, deployable client products. Server: Contains the final, deployable server products. Apps: Apps Client: Contains the final, deployable client products. Server: Contains the final, deployable server products. Client: Contains the final, deployable client products. Server: Contains the final, deployable server products. Features: Client: For standalone UI widgets. Server: For standalone backend business logic pieces. Features: Features Client: For standalone UI widgets. Server: For standalone backend business logic pieces. Client: For standalone UI widgets. Server: For standalone backend business logic pieces. Libs: Houses shared code such as design system components, constants, assets, and utilities. This is the context-free zone for storing reusable logic. Libs: Libs Houses shared code such as design system components, constants, assets, and utilities. This is the context-free zone for storing reusable logic. To demonstrate the power of this folder structure, let’s start by adding these major folders to Yarn’s workspaces list. In your root package.json, add the following: "workspaces": [ "apps/**", "features/**", "libs/**" ] "workspaces": [ "apps/**", "features/**", "libs/**" ] This configuration tells Yarn to treat packages in these folders as local packages. Subsequent installations will ensure that dependencies for each package are properly set up and linked. Bootstrapping Codebase In this section, we'll walk through a minimal codebase example that illustrates how to bootstrap the monorepo. Instead of including full code snippets, I'll provide short examples with links to the complete files in the repository created specifically for this article. the repository created specifically for this article Bootstrapping Server Application We begin with a simple Express API for user authentication. This server application exposes a single endpoint (/auth/signIn) that utilizes a handler from another package. Express API /auth/signIn import express from "express"; import cors from "cors"; import { signInHandler } from "@robust-monorepo-yarn-nx-changesets/sign-in-handler"; const app = express(); const port = process.env.PORT || 1234; app.use(express.json()); app.use( cors({ origin: process.env.CORS_ORIGIN || "http://localhost:3000", }) ); app.post("/auth/signIn", signInHandler); app.listen(port, () => { console.log(`Server is running at http://localhost:${port}`); }); import express from "express"; import cors from "cors"; import { signInHandler } from "@robust-monorepo-yarn-nx-changesets/sign-in-handler"; const app = express(); const port = process.env.PORT || 1234; app.use(express.json()); app.use( cors({ origin: process.env.CORS_ORIGIN || "http://localhost:3000", }) ); app.post("/auth/signIn", signInHandler); app.listen(port, () => { console.log(`Server is running at http://localhost:${port}`); }); Link to the package Link to the package As you can see, the /auth/signIn endpoint uses a handler imported from another package. That brings us to our next component: the server feature. /auth/signIn Bootstrapping Server Feature The server feature encapsulates the authentication logic. In this package, we define the sign-in handler, which leverages a shared validation utility from the libs. import type { RequestHandler } from "express"; import { passwordValidator, usernameValidator, } from "@robust-monorepo-yarn-nx-changesets/validator"; const signInHandler: RequestHandler = (req, res) => { if (!req.body) { res.status(422).send("Request body is missing"); return; } if (typeof req.body !== "object") { res.status(422).send("Request body expected to be an object"); return; } const { username, password } = req.body; const usernameValidationResult = usernameValidator(username); if (typeof usernameValidationResult === "string") { res .status(422) .send("Invalid username format: " + usernameValidationResult); return; } const passwordValidationResult = passwordValidator(password); if (typeof passwordValidationResult === "string") { res .status(422) .send("Invalid password format: " + passwordValidationResult); return; } // Emulate a successful sign-in if (username === "test" && password === "test1234") { res.status(200).send("Sign in successful"); return; } return res.status(422).send("Username or password is incorrect"); }; export default signInHandler; import type { RequestHandler } from "express"; import { passwordValidator, usernameValidator, } from "@robust-monorepo-yarn-nx-changesets/validator"; const signInHandler: RequestHandler = (req, res) => { if (!req.body) { res.status(422).send("Request body is missing"); return; } if (typeof req.body !== "object") { res.status(422).send("Request body expected to be an object"); return; } const { username, password } = req.body; const usernameValidationResult = usernameValidator(username); if (typeof usernameValidationResult === "string") { res .status(422) .send("Invalid username format: " + usernameValidationResult); return; } const passwordValidationResult = passwordValidator(password); if (typeof passwordValidationResult === "string") { res .status(422) .send("Invalid password format: " + passwordValidationResult); return; } // Emulate a successful sign-in if (username === "test" && password === "test1234") { res.status(200).send("Sign in successful"); return; } return res.status(422).send("Username or password is incorrect"); }; export default signInHandler; Link to the package Link to the package This approach sums up the authentication logic within its own package, allowing it to be developed and maintained independently. Notice how the validator utilities are imported from the shared lib. shared lib Bootstrapping Client Application Next, let’s look at the client side. In our client application, we build a simple website that enables user authentication by invoking the server API. "use client"; import { SignInForm } from "@robust-monorepo-yarn-nx-changesets/sign-in-form"; const API_URL = process.env.NEXT_PUBLIC_API_URL || "http://localhost:1234"; export default function Home() { const handleSubmit = async (username: string, password: string) => { const response = await fetch(`${API_URL}/auth/signIn`, { method: "POST", body: JSON.stringify({ username, password }), headers: { "Content-Type": "application/json", }, }); if (response.status === 200) { alert("Sign in successful"); return; } if (response.status === 422) { alert("Sign in failed: " + (await response.text())); return; } alert("Sign in failed"); }; return ( <div className="w-full h-screen overflow-hidden flex items-center justify-center"> <SignInForm onSubmit={handleSubmit} /> </div> ); } "use client"; import { SignInForm } from "@robust-monorepo-yarn-nx-changesets/sign-in-form"; const API_URL = process.env.NEXT_PUBLIC_API_URL || "http://localhost:1234"; export default function Home() { const handleSubmit = async (username: string, password: string) => { const response = await fetch(`${API_URL}/auth/signIn`, { method: "POST", body: JSON.stringify({ username, password }), headers: { "Content-Type": "application/json", }, }); if (response.status === 200) { alert("Sign in successful"); return; } if (response.status === 422) { alert("Sign in failed: " + (await response.text())); return; } alert("Sign in failed"); }; return ( <div className="w-full h-screen overflow-hidden flex items-center justify-center"> <SignInForm onSubmit={handleSubmit} /> </div> ); } Link to the package Link to the package In this example, the SignInForm component is imported from a client feature package, which leads us to our final component. SignInForm Bootstrapping Client Feature The client feature package provides the authentication form along with the shared validation logic. This avoids duplicating code and ensures consistency. import { passwordValidator, usernameValidator, } from "@robust-monorepo-yarn-nx-changesets/validator"; interface SignInFormProps { onSubmit: (username: string, password: string) => void; } const SignInForm = ({ onSubmit }: SignInFormProps) => { const handleSubmit = (event: React.FormEvent<HTMLFormElement>) => { event.preventDefault(); const username = (event.currentTarget[0] as HTMLInputElement).value; const usernameValidationResult = usernameValidator(username); if (typeof usernameValidationResult === "string") { alert(usernameValidationResult); return; } const password = (event.currentTarget[1] as HTMLInputElement).value; const passwordValidationResult = passwordValidator(password); if (typeof passwordValidationResult === "string") { alert(passwordValidationResult); return; } onSubmit(username!, password!); }; return ( <form onSubmit={handleSubmit}> <input type="text" placeholder="Username" /> <input type="password" placeholder="Password" /> <button type="submit">Submit</button> </form> ); }; export default SignInForm; import { passwordValidator, usernameValidator, } from "@robust-monorepo-yarn-nx-changesets/validator"; interface SignInFormProps { onSubmit: (username: string, password: string) => void; } const SignInForm = ({ onSubmit }: SignInFormProps) => { const handleSubmit = (event: React.FormEvent<HTMLFormElement>) => { event.preventDefault(); const username = (event.currentTarget[0] as HTMLInputElement).value; const usernameValidationResult = usernameValidator(username); if (typeof usernameValidationResult === "string") { alert(usernameValidationResult); return; } const password = (event.currentTarget[1] as HTMLInputElement).value; const passwordValidationResult = passwordValidator(password); if (typeof passwordValidationResult === "string") { alert(passwordValidationResult); return; } onSubmit(username!, password!); }; return ( <form onSubmit={handleSubmit}> <input type="text" placeholder="Username" /> <input type="password" placeholder="Password" /> <button type="submit">Submit</button> </form> ); }; export default SignInForm; Link to the package Link to the package Here, we again see the usage of the validator from our shared libs, ensuring that validation logic is centralized and easily maintained. validator That’s it for our minimal codebase example. Keep in mind that this code is a simplified illustration meant to demonstrate the basic structure and interconnection between Apps, Features, and Libs in a monorepo. You can expand upon these examples as needed to fit your project’s specific requirements. Running Scripts with NX Managing scripts in a monorepo can be challenging. While Yarn allows you to run scripts across multiple packages using various conditions, it may require custom scripting for more granular control. This is where NX comes in: it provides an out-of-the-box solution for efficient, targeted script execution. to run scripts across multiple packages Introduction to NX NX is a build system optimized for monorepos with advanced CI capabilities. With NX, you can: Run tasks efficiently in parallel: Leverage concurrency to speed up your builds. Identify dependency relationships: Understand connections among packages and scripts. Cache script execution results: Avoid redundant work by caching outputs. Customize behavior with plugins: Extend functionality through a rich ecosystem of plugins. Run tasks efficiently in parallel: Leverage concurrency to speed up your builds. Run tasks efficiently in parallel Identify dependency relationships: Understand connections among packages and scripts. Identify dependency relationships Cache script execution results: Avoid redundant work by caching outputs. Cache script execution results Customize behavior with plugins: Extend functionality through a rich ecosystem of plugins. Customize behavior with plugins: a rich ecosystem of plugins Targeted Script Execution To harness NX’s capabilities, we first need to create an nx.json file to define a set of rules for our scripts. Below is an example configuration: nx.json { "targetDefaults": { "build": { "dependsOn": [ "^build" ], "outputs": [ "{projectRoot}/dist" ], "cache": true }, "typecheck": { "dependsOn": [ "^build", "^typecheck" ] }, "lint": { "dependsOn": [ "^build", "^lint" ] } }, "defaultBase": "main" } { "targetDefaults": { "build": { "dependsOn": [ "^build" ], "outputs": [ "{projectRoot}/dist" ], "cache": true }, "typecheck": { "dependsOn": [ "^build", "^typecheck" ] }, "lint": { "dependsOn": [ "^build", "^lint" ] } }, "defaultBase": "main" } In plain English, this configuration means: Build The build script for a package depends on the successful build of its dependencies, and its output is cached. Typecheck The typecheck script for a package depends on both the build and typecheck scripts of its dependencies. Lint The lint script for a package depends on both the build and lint scripts of its dependencies. Build The build script for a package depends on the successful build of its dependencies, and its output is cached. Build Build The build script for a package depends on the successful build of its dependencies, and its output is cached. build Typecheck The typecheck script for a package depends on both the build and typecheck scripts of its dependencies. Typecheck Typecheck The typecheck script for a package depends on both the build and typecheck scripts of its dependencies. typecheck Lint The lint script for a package depends on both the build and lint scripts of its dependencies. Lint Lint The lint script for a package depends on both the build and lint scripts of its dependencies. lint Now, let’s add scripts to the package.json: package.json "scripts": { "build:all": "yarn nx run-many -t build", "build:affected": "yarn nx affected -t build --base=${BASE:-origin/main} --head=${HEAD:-HEAD}", "typecheck:all": "yarn nx run-many -t typecheck", "typecheck:affected": "yarn nx affected -t typecheck --base=${BASE:-origin/main} --head=${HEAD:-HEAD}", "lint:all": "yarn nx run-many -t lint", "lint:affected": "yarn nx affected -t lint --base=${BASE:-origin/main} --head=${HEAD:-HEAD}", "quality:all": "yarn nx run-many --targets=typecheck,lint", "quality:affected": "yarn nx affected --targets=typecheck,lint --base=${BASE:-origin/main} --head=${HEAD:-HEAD}" } "scripts": { "build:all": "yarn nx run-many -t build", "build:affected": "yarn nx affected -t build --base=${BASE:-origin/main} --head=${HEAD:-HEAD}", "typecheck:all": "yarn nx run-many -t typecheck", "typecheck:affected": "yarn nx affected -t typecheck --base=${BASE:-origin/main} --head=${HEAD:-HEAD}", "lint:all": "yarn nx run-many -t lint", "lint:affected": "yarn nx affected -t lint --base=${BASE:-origin/main} --head=${HEAD:-HEAD}", "quality:all": "yarn nx run-many --targets=typecheck,lint", "quality:affected": "yarn nx affected --targets=typecheck,lint --base=${BASE:-origin/main} --head=${HEAD:-HEAD}" } Here, we define four types of execution scripts: build: Builds a package. typecheck: Checks the package’s types. lint: Lints a package. quality: Runs both typecheck and lint.' build: Builds a package. build: Builds a package. build: typecheck: Checks the package’s types. typecheck: Checks the package’s types. typecheck: lint: Lints a package. lint: Lints a package. lint: quality: Runs both typecheck and lint.' quality: Runs both typecheck and lint.' quality: Each script has two variations: all: Runs the script on all packages. affected: Runs the script only on packages affected by recent changes. The BASE and HEAD environment variables allow you to specify a range (defaulting to origin/main and the current HEAD), enabling granular execution on pull requests. This can significantly save time and resources. all: Runs the script on all packages. all: affected: Runs the script only on packages affected by recent changes. The BASE and HEAD environment variables allow you to specify a range (defaulting to origin/main and the current HEAD), enabling granular execution on pull requests. This can significantly save time and resources. affected: BASE HEAD origin/main HEAD Managing Circular Dependencies NX also provides a built-in command to generate a dependency graph, which can help in dependency cycles detection. The following script uses the NX graph output to check for circular dependencies and fails if any are found. a built-in command Create a file at scripts/check-circulardeps.mjs with the following content: scripts/check-circulardeps.mjs import { execSync } from "child_process"; import path from "path"; import fs from "fs"; const hasCycle = (node, graph, visited, stack, path) => { if (!visited.has(node)) { visited.add(node); stack.add(node); path.push(node); const dependencies = graph.dependencies[node] || []; for (const dep of dependencies) { const depNode = dep.target; if ( !visited.has(depNode) && hasCycle(depNode, graph, visited, stack, path) ) { return true; } if (stack.has(depNode)) { path.push(depNode); return true; } } } stack.delete(node); path.pop(); return false; }; const getGraph = () => { const cwd = process.cwd(); const tempOutputFilePath = path.join(cwd, "nx-graph.json"); execSync(`nx graph --file=${tempOutputFilePath}`, { encoding: "utf-8", }); const output = fs.readFileSync(tempOutputFilePath, "utf-8"); fs.rmSync(tempOutputFilePath); return JSON.parse(output).graph; }; const checkCircularDeps = () => { const graph = getGraph(); const visited = new Set(); const stack = new Set(); for (const node of Object.keys(graph.dependencies)) { const path = []; if (hasCycle(node, graph, visited, stack, path)) { console.error("🔴 Circular dependency detected:", path.join(" → ")); process.exit(1); } } console.log("✅ No circular dependencies detected."); }; checkCircularDeps(); import { execSync } from "child_process"; import path from "path"; import fs from "fs"; const hasCycle = (node, graph, visited, stack, path) => { if (!visited.has(node)) { visited.add(node); stack.add(node); path.push(node); const dependencies = graph.dependencies[node] || []; for (const dep of dependencies) { const depNode = dep.target; if ( !visited.has(depNode) && hasCycle(depNode, graph, visited, stack, path) ) { return true; } if (stack.has(depNode)) { path.push(depNode); return true; } } } stack.delete(node); path.pop(); return false; }; const getGraph = () => { const cwd = process.cwd(); const tempOutputFilePath = path.join(cwd, "nx-graph.json"); execSync(`nx graph --file=${tempOutputFilePath}`, { encoding: "utf-8", }); const output = fs.readFileSync(tempOutputFilePath, "utf-8"); fs.rmSync(tempOutputFilePath); return JSON.parse(output).graph; }; const checkCircularDeps = () => { const graph = getGraph(); const visited = new Set(); const stack = new Set(); for (const node of Object.keys(graph.dependencies)) { const path = []; if (hasCycle(node, graph, visited, stack, path)) { console.error("🔴 Circular dependency detected:", path.join(" → ")); process.exit(1); } } console.log("✅ No circular dependencies detected."); }; checkCircularDeps(); This script: Executes the NX command to generate a dependency graph. Reads the graph from a temporary JSON file. Recursively checks for cycles. Logs an error and exits if a circular dependency is detected. Executes the NX command to generate a dependency graph. Reads the graph from a temporary JSON file. Recursively checks for cycles. Logs an error and exits if a circular dependency is detected. Validating Dependencies with Yarn Constraints As projects grow, maintaining consistency across dependencies becomes challenging. Enforcing strict rules around dependencies, Node versions, and other configurations is essential to avoid unnecessary technical debt. Yarn Constraints offer a way to automate these validations. Understanding Yarn Constraints Yarn Constraints are the set of rules for packages in your monorepo. Significant advantage of using them is that you are the manager of these rules. For example, you can create a rule to force all the packages to use the same React version. Once it’s set, you’ll never run into a problem when a host application cannot use a feature/lib with a higher React version. While migrating a large monorepo to a new major version of a dependency might be complex, using constraints ultimately brings consistency and stability to the entire project. Enforcing Consistency In our example repository, we use a yarn.config.cjs file to enforce consistency for: yarn.config.cjs Node Version Yarn Version Dependencies’ Versions Node Version Node Version Yarn Version Yarn Version Dependencies’ Versions Dependencies’ Versions To allow for flexibility during transitions, you can define exclusions to temporarily bypass certain checks. For instance: const workspaceCheckExclusions = []; const dependencyCheckExclusions = []; const workspaceCheckExclusions = []; const dependencyCheckExclusions = []; These constants let you exclude specific workspaces or dependencies from the validation process, ensuring smooth migrations when necessary. Managing Versioning with Changesets Another problem you may face with the growth of the repository is the version management and releasing. Changesets provide an elegant solution to automate this process, ensuring that every change is tracked, versioned and released. Introduction to Changesets Changesets is an open-source tool designed to manage versioning in monorepo repositories. It simplifies the process of keeping track of changes by allocating them into small, human-readable documents that capture the intent of the change. These documents are called changesets. Key benefits include: Changesets Clear Documentation Each changeset outlines the changes made, which helps both developers and consumers understand what to expect in a new release. Granular Version Control Each package is versioned independently, ensuring that only the affected packages are updated. This minimizes risk of empty version bumps and dependency breaks. Collaboration-Friendly As every change is recorded through a changeset, teams can review and approve updates before the actual release. Clear Documentation Each changeset outlines the changes made, which helps both developers and consumers understand what to expect in a new release. Clear Documentation Clear Documentation Each changeset outlines the changes made, which helps both developers and consumers understand what to expect in a new release. Granular Version Control Each package is versioned independently, ensuring that only the affected packages are updated. This minimizes risk of empty version bumps and dependency breaks. Granular Version Control Granular Version Control Each package is versioned independently, ensuring that only the affected packages are updated. This minimizes risk of empty version bumps and dependency breaks. Collaboration-Friendly As every change is recorded through a changeset, teams can review and approve updates before the actual release. Collaboration-Friendly Collaboration-Friendly As every change is recorded through a changeset, teams can review and approve updates before the actual release. Automating Releases One of the most powerful features of Changesets is the ability to automate the process. You can integrate Changesets into your CI/CD pipeline and forget about manual version changes and NPM publishing. Take a look at the release.yaml workflow in the example repository. It has create-release-pull-request-or-publish step. The step backed by changesets/action GitHub action creates all the magic. You only need to set up NPM_TOKEN for publishing your packages. Then, every push to the main branch will: release.yaml create-release-pull-request-or-publish changesets/action NPM_TOKEN main Check if there are any Changeset documents. If changeset documents are present, the action creates a pull request with the necessary version bumps and changelog updates. If no changes are detected, nothing happens. Check if there are any packages ready to publish. If packages are ready to be released, the action publishes the new versions to NPM using the provided NPM_TOKEN. If there are no packages ready to publish, the action exits without making changes. Check if there are any Changeset documents. If changeset documents are present, the action creates a pull request with the necessary version bumps and changelog updates. If no changes are detected, nothing happens. Check if there are any Changeset documents. Check if there are any Changeset documents If changeset documents are present, the action creates a pull request with the necessary version bumps and changelog updates. If no changes are detected, nothing happens. Check if there are any packages ready to publish. If packages are ready to be released, the action publishes the new versions to NPM using the provided NPM_TOKEN. If there are no packages ready to publish, the action exits without making changes. Check if there are any packages ready to publish. Check if there are any packages ready to publish If packages are ready to be released, the action publishes the new versions to NPM using the provided NPM_TOKEN. If there are no packages ready to publish, the action exits without making changes. NPM_TOKEN By automating these tasks, Changesets ensure that your releases are consistent and reliable, reducing the potential for human error and streamlining your development workflow. Workflow Integration with GitHub Actions This section delves into how to unleash the power of the architecture we’ve just built. Using GitHub Actions, we’ll automate PR quality checks, version releases for libraries and features, and application deployments. The focus is on maximizing automation while maintaining code quality and job granularity. Verify PR Quality To ensure that pull request code remains consistent and stable, we create a dedicated quality.yaml workflow. This workflow performs several tasks, such as ensuring that manual version changes aren’t introduced (since versioning is managed by Changesets): quality.yaml - id: check_version name: Check version changes run: | BASE_BRANCH=${{ github.event.pull_request.base.ref }} git fetch origin $BASE_BRANCH CHANGED_FILES=$(git diff --name-only origin/$BASE_BRANCH HEAD) VERSION_CHANGED=false for FILE in $CHANGED_FILES; do if [[ $FILE == */package.json ]]; then if [ -f "$FILE" ]; then HEAD_VERSION=$(grep '"version":' "$FILE" | awk -F '"' '{print $4}') else continue fi HEAD_VERSION=$(cat $FILE | grep '"version":' | awk -F '"' '{print $4}') if git cat-file -e origin/$BASE_BRANCH:$FILE 2>/dev/null; then BASE_VERSION=$(git show origin/$BASE_BRANCH:$FILE | grep '"version":' | awk -F '"' '{print $4}') else BASE_VERSION=$HEAD_VERSION fi if [ "$BASE_VERSION" != "$HEAD_VERSION" ]; then VERSION_CHANGED=true echo "Version change detected in $FILE" fi fi done if [ "$VERSION_CHANGED" = true ]; then echo "Manual version changes are prohibited. Use changesets instead." exit 1 fi env: GITHUB_REF: ${{ github.ref }} - id: check_version name: Check version changes run: | BASE_BRANCH=${{ github.event.pull_request.base.ref }} git fetch origin $BASE_BRANCH CHANGED_FILES=$(git diff --name-only origin/$BASE_BRANCH HEAD) VERSION_CHANGED=false for FILE in $CHANGED_FILES; do if [[ $FILE == */package.json ]]; then if [ -f "$FILE" ]; then HEAD_VERSION=$(grep '"version":' "$FILE" | awk -F '"' '{print $4}') else continue fi HEAD_VERSION=$(cat $FILE | grep '"version":' | awk -F '"' '{print $4}') if git cat-file -e origin/$BASE_BRANCH:$FILE 2>/dev/null; then BASE_VERSION=$(git show origin/$BASE_BRANCH:$FILE | grep '"version":' | awk -F '"' '{print $4}') else BASE_VERSION=$HEAD_VERSION fi if [ "$BASE_VERSION" != "$HEAD_VERSION" ]; then VERSION_CHANGED=true echo "Version change detected in $FILE" fi fi done if [ "$VERSION_CHANGED" = true ]; then echo "Manual version changes are prohibited. Use changesets instead." exit 1 fi env: GITHUB_REF: ${{ github.ref }} Alongside this check, the check-quality job installs dependencies, validates constraints, checks for circular dependencies and verifies overall code quality using the script we defined earlier with NX: check-quality - id: install-dependencies name: Install dependencies run: yarn --immutable - id: check-constraints name: Check constraints run: yarn constraints - id: check-circulardeps name: Check circular dependencies run: yarn check-circulardeps:all - id: check-quality name: Check quality run: BASE=origin/${{ github.event.pull_request.base.ref }} yarn quality:affected - id: install-dependencies name: Install dependencies run: yarn --immutable - id: check-constraints name: Check constraints run: yarn constraints - id: check-circulardeps name: Check circular dependencies run: yarn check-circulardeps:all - id: check-quality name: Check quality run: BASE=origin/${{ github.event.pull_request.base.ref }} yarn quality:affected The quality check is designed to run only on the packages affected by the current pull request. Successful completion of these jobs signals the pull request is ready to merge (in addition to receiving code reviews). If additional checks are required for your project, you can update your nx.json and quality script keeping the workflow unchanged. nx.json Publish Libraries and Features After a PR is merged, the release workflow (as described in the Changesets chapter) is triggered. This workflow builds the affected packages and creates a PR with the version bumps. Once this PR is approved and merged, release.yaml runs again - this time, instead of creating a PR, it detects version changes and releases the updated packages to NPM: release.yaml - id: build-packages name: Build packages run: yarn build:affected - id: create-release-pull-request-or-publish name: Create Release Pull Request or Publish to NPM uses: changesets/action@v1 with: version: yarn changeset version publish: yarn release commit: "chore: publish new release" title: "chore: publish new release" env: GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }} NPM_TOKEN: ${{ secrets.NPM_TOKEN }} release-apps: needs: release-libs-features uses: ./.github/workflows/release-apps.yaml with: publishedPackages: ${{ needs.release-libs-features.outputs.publishedPackages }} - id: build-packages name: Build packages run: yarn build:affected - id: create-release-pull-request-or-publish name: Create Release Pull Request or Publish to NPM uses: changesets/action@v1 with: version: yarn changeset version publish: yarn release commit: "chore: publish new release" title: "chore: publish new release" env: GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }} NPM_TOKEN: ${{ secrets.NPM_TOKEN }} release-apps: needs: release-libs-features uses: ./.github/workflows/release-apps.yaml with: publishedPackages: ${{ needs.release-libs-features.outputs.publishedPackages }} Following this, a job called release-apps is executed, which is responsible for application deployments. It receives a list of published packages from the previous step and brings us to the next chapter. release-apps Publish Apps The final part of the release process involves deploying your applications (applications are not published to NPM, because they are set private in package.json). The release-apps.yaml workflow is automatically triggered by release.yaml, or can be executed directly from the Actions tab on GitHub: private package.json release-apps.yaml release.yaml name: Release Apps on: workflow_call: inputs: publishedPackages: description: "List of published packages" required: false type: string default: "[]" workflow_dispatch: inputs: publishedPackages: description: "List of published packages (optional)" required: false type: string default: "[]" name: Release Apps on: workflow_call: inputs: publishedPackages: description: "List of published packages" required: false type: string default: "[]" workflow_dispatch: inputs: publishedPackages: description: "List of published packages (optional)" required: false type: string default: "[]" This workflow accepts publishedPackages input to determine which packages have been published. Using a matrix strategy, it checks each application of the matrix for the presence of published dependencies: publishedPackages - id: check-dependency-published name: Check if any app dependency is published run: | PUBLISHED_PACKAGES="${{ inputs.publishedPackages }}" PACKAGE_NAME="${{ matrix.package }}" APP="${{ matrix.app }}" DEPENDENCIES=$(jq -r '.dependencies // {} | keys[]' "apps/$APP/package.json") for DEP in $DEPENDENCIES; do if echo "$PUBLISHED_PACKAGES" | grep -w "$DEP"; then echo "published=true" >> $GITHUB_OUTPUT exit 0 fi done echo "published=false" >> $GITHUB_OUTPUT - id: check-dependency-published name: Check if any app dependency is published run: | PUBLISHED_PACKAGES="${{ inputs.publishedPackages }}" PACKAGE_NAME="${{ matrix.package }}" APP="${{ matrix.app }}" DEPENDENCIES=$(jq -r '.dependencies // {} | keys[]' "apps/$APP/package.json") for DEP in $DEPENDENCIES; do if echo "$PUBLISHED_PACKAGES" | grep -w "$DEP"; then echo "published=true" >> $GITHUB_OUTPUT exit 0 fi done echo "published=false" >> $GITHUB_OUTPUT This check is one condition for initiating an app deployment. The other condition ensures that the app’s version has been changed (indicating that a redeploy is necessary even if no dependencies have been updated): - id: check-version-change name: Check if app version has changed run: | APP="${{ matrix.app }}" PACKAGE_JSON_PATH="apps/$APP/package.json" CURRENT_VERSION=$(jq -r '.version' "$PACKAGE_JSON_PATH") PREVIOUS_VERSION=$(git show HEAD~1:"$PACKAGE_JSON_PATH" | jq -r '.version' || echo "") if [[ "$CURRENT_VERSION" == "$PREVIOUS_VERSION" ]]; then echo "changed=false" >> $GITHUB_OUTPUT else echo "changed=true" >> $GITHUB_OUTPUT fi - id: check-version-change name: Check if app version has changed run: | APP="${{ matrix.app }}" PACKAGE_JSON_PATH="apps/$APP/package.json" CURRENT_VERSION=$(jq -r '.version' "$PACKAGE_JSON_PATH") PREVIOUS_VERSION=$(git show HEAD~1:"$PACKAGE_JSON_PATH" | jq -r '.version' || echo "") if [[ "$CURRENT_VERSION" == "$PREVIOUS_VERSION" ]]; then echo "changed=false" >> $GITHUB_OUTPUT else echo "changed=true" >> $GITHUB_OUTPUT fi Finally, after confirming that the app either has updated dependencies or its version has changed, the workflow retrieves the new version and proceeds to build and deploy the application: - id: set-up-docker name: Set up Docker Buildx uses: docker/setup-buildx-action@v3 - id: get-app-version name: Get the app version from package.json run: echo "app-version=$(cat ./apps/${{ matrix.app }}/package.json | jq -r '.version')" >> $GITHUB_OUTPUT - id: build-image name: Build image if: steps.check-dependency-published.outputs.published == 'true' || steps.check-version-change.outputs.changed == 'true' uses: docker/build-push-action@v4 with: build-contexts: | workspace=./ context: "./apps/${{ matrix.app }}" load: true push: false tags: | ${{ matrix.app }}:v${{ steps.get-app-version.outputs.app-version }} - id: set-up-docker name: Set up Docker Buildx uses: docker/setup-buildx-action@v3 - id: get-app-version name: Get the app version from package.json run: echo "app-version=$(cat ./apps/${{ matrix.app }}/package.json | jq -r '.version')" >> $GITHUB_OUTPUT - id: build-image name: Build image if: steps.check-dependency-published.outputs.published == 'true' || steps.check-version-change.outputs.changed == 'true' uses: docker/build-push-action@v4 with: build-contexts: | workspace=./ context: "./apps/${{ matrix.app }}" load: true push: false tags: | ${{ matrix.app }}:v${{ steps.get-app-version.outputs.app-version }} In this example, we build the Docker image without pushing it to a registry. In your production workflow, replace this step with the actual deployment process. Conclusion Recap of Best Practices Throughout this article, we explored setup of a robust monorepo and the tools that help manage it efficiently. By centralizing your codebase, you not only simplify dependency management but also streamlines collaboration across teams. We demonstrated how Yarn can be leveraged to share dependencies, accelerate installation with PnP and improve overall project consistency. Additionally, integrating NX for targeted script execution ensures that CI is fast and efficient. Changesets helped to automate versioning, reducing manual errors and streamlining releases. Finally, we’ve made a production-ready CI/CD pipeline with GitHub actions that performs only the necessary tasks. Next Steps Experiment and Adapt: Begin by setting up a small-scale monorepo to test these best practices. Experiment with different folder structures, and gradually expand to include more packages as your confidence grows. Integrate Additional Tools: Consider integrating complementary tools like PNPM or Turborepo based on your project’s unique requirements and team preferences. Enhance CI/CD Pipelines: Fine-tune your GitHub Actions workflows to include additional quality checks, code coverage, and security scans tailored to your project. Community and Updates: Stay updated with the latest releases of Yarn, NX, and Changesets. Engage with the community to share insights and learn about emerging trends in monorepo management. Experiment and Adapt: Begin by setting up a small-scale monorepo to test these best practices. Experiment with different folder structures, and gradually expand to include more packages as your confidence grows. Experiment and Adapt Integrate Additional Tools: Consider integrating complementary tools like PNPM or Turborepo based on your project’s unique requirements and team preferences. Integrate Additional Tools Enhance CI/CD Pipelines: Fine-tune your GitHub Actions workflows to include additional quality checks, code coverage, and security scans tailored to your project. Enhance CI/CD Pipelines Community and Updates: Stay updated with the latest releases of Yarn, NX, and Changesets. Engage with the community to share insights and learn about emerging trends in monorepo management. Community and Updates Resources Example Repository: Access the complete example repository created for this guide. Explore the project structure, code samples, and scripts that showcase the monorepo setup in action. Published NPM Packages: Check out the actual NPM package published as part of this project. These packages demonstrate real-world usage and implementation of the concepts discussed in the article. Example Repository: Access the complete example repository created for this guide. Explore the project structure, code samples, and scripts that showcase the monorepo setup in action. Example Repository: Example Repository Access the complete example repository created for this guide. Explore the project structure, code samples, and scripts that showcase the monorepo setup in action. Published NPM Packages: Check out the actual NPM package published as part of this project. These packages demonstrate real-world usage and implementation of the concepts discussed in the article. Published NPM Packages: Published NPM Packages Check out the actual NPM package published as part of this project. These packages demonstrate real-world usage and implementation of the concepts discussed in the article.
