# Using Nx to Build Projects

Bitwarden uses [Nx](https://nx.dev/) to make building projects from the monorepo easier. To build, lint, or test a project you'll want to reference the project's `project.json` file for availible commands and their names. Then you'll run `npx nx [your_command] [your_project] [your_options]`. Run `npx nx --help` to see availible options, there are many.

Please note: the Nx implementation is a work in progress. CI still uses the old npm builds, and we have many "legacy" libraries that use hacks to get them into the Nx project graph.

## Quick Start

### Basic Commands

```bash
# Build a project
npx nx build cli
npx nx build-native desktop # Some apps have special build commands
npx nx build state # Modern libs and apps have simple, all lowercase target names
npx nx build @bitwarden/common # Legacy libs have a special naming convention and include the @bitwarden prefix

# Test a project
npx nx test cli

# Lint a project
npx nx lint cli

# Serve/watch a project (for projects with serve targets)
npx nx serve cli

# Build all projects that differ from origin/main
nx affected --target=build --base=origin/main

# Build, lint, and test every project at once
npx nx run-many --target=build,test,lint --all

# Most projects default to the "oss-dev" build, so if you need the bitwarden license build add a --configuration
npx nx build cli --configuration=commercial-dev

# If you need a production build drop the "dev" suffix
npx nx build cli --configuration=oss # or "commercial"

# Configurations can also be passed to run-many
# For example: to run all Bitwarden licensed builds
npx nx run-many --target=build,test,lint --all --configuration=commercial

# Outputs are distrubuted in a root level /dist/ folder

# Run a locally built CLI
node dist/apps/cli/oss-dev/bw.js
```

### Global Commands

```bash
# See all projects
npx nx show projects

# Run affected projects only (great for local dev and CI)
npx nx affected:build
npx nx affected:test
npx nx affected:lint

# Show dependency graph
npx nx dep-graph
```

## Library Projects

Our libraries use two different Nx integration patterns depending on their migration status.

### Legacy Libraries

Most existing libraries use a facade pattern where `project.json` delegates to existing npm scripts. This approach maintains backward compatibility with the build methods we used before introducing Nx. These libraries are considered tech debt and Platform has a focus on updating them. For an example reference `libs/common/project.json`.

These libraries use `nx:run-script` executor to call existing npm scripts:

```json
{
  "targets": {
    "build": {
      "executor": "nx:run-script",
      "options": {
        "script": "build"
      }
    }
  }
}
```

#### Available Commands for Legacy Libraries

All legacy libraries support these standardized commands:

- **`nx build <library>`** - Build the library
- **`nx build:watch <library>`** - Build and watch for changes
- **`nx clean <library>`** - Clean build artifacts
- **`nx test <library>`** - Run tests
- **`nx lint <library>`** - Run linting

### Modern Libraries

Newer libraries like `libs/state` use native Nx executors for better performance and caching.

```json
{
  "targets": {
    "build": {
      "executor": "@nx/js:tsc",
      "outputs": ["{options.outputPath}"],
      "options": {
        "outputPath": "dist/libs/state"
      }
    }
  }
}
```

## What Happens When You Run An Nx Command

```mermaid
flowchart TD
    Start([You just ran an nx command]) --> ParseCmd[Nx parses command args]
    ParseCmd --> ReadWorkspace[Nx reads nx.json, workspace configuration, cache settings, and plugins]
    ReadWorkspace --> ReadProject[Nx reads project.json, finds the target configuration, and checks executor to use]
    ReadProject --> CheckCache{Nx checks the cache: has this exact build been done before?}

    CheckCache -->|Cache hit| UseCached[Nx uses cached outputs, copies from .nx/cache, and skips execution]
    UseCached --> Done([Your command is done])

    CheckCache -->|Cache miss| DetermineExecutor{Which executor is configured?}

    DetermineExecutor -->|nx:run-script| FacadePattern[Legacy Facade Pattern]
    DetermineExecutor -->|nx/webpack:webpack| WebpackExecutor[Webpack Executor]
    DetermineExecutor -->|nx/js:tsc| TypeScriptExecutor[TypeScript Executor]
    DetermineExecutor -->|nx/jest:jest| JestExecutor[Jest Executor]
    DetermineExecutor -->|nx/eslint:lint| ESLintExecutor[ESLint Executor]

    %% Facade Pattern Flow
    FacadePattern --> ReadPackageJson[The run-script executor finds npm script to run in package.json]
    ReadPackageJson --> RunNpmScript[Npm script is executed]
    RunNpmScript --> NpmDelegates{What does the npm script do?}

    NpmDelegates -->|TypeScript| TSCompile[TypeScript compiles to JavaScript using tsconfig.json]
    NpmDelegates -->|Webpack| WebpackBuild[Webpack bundles and optimizes code]
    NpmDelegates -->|Jest| JestTest[Jest executes unit tests]

    TSCompile --> FacadeOutput[Outputs written to libs/LIB/dist/]
    WebpackBuild --> FacadeOutput
    JestTest --> FacadeOutput
    FacadeOutput --> CacheResults1[Nx caches results in .nx/cache/]

    %% Webpack Executor Flow
    WebpackExecutor --> ReadWebpackConfig[Webpack config read from apps/cli/webpack.config.js or bit-cli/webpack.config.js]
    ReadWebpackConfig --> ConfigureWebpack[Webpack configured with entry points, TypeScript paths, and plugins]
    ConfigureWebpack --> WebpackProcess[Webpack resolves paths, compiles TypeScript, bundles dependencies, and applies optimizations]
    WebpackProcess --> WebpackOutput[Single executable bundle written to dist/apps/cli/]
    WebpackOutput --> CacheResults2[Nx caches results in .nx/cache/]

    %% TypeScript Executor Flow
    TypeScriptExecutor --> ReadTSConfig[TypeScript reads tsconfig.lib.json compilation options]
    ReadTSConfig --> TSProcess[TypeScript performs type checking, emits declarations, and compiles to JavaScript]
    TSProcess --> TSOutput[Outputs written to dist/libs/LIB/]
    TSOutput --> CacheResults3[Nx caches results in .nx/cache/]

    %% Jest Executor Flow
    JestExecutor --> ReadJestConfig[Jest reads jest.config.js test configuration]
    ReadJestConfig --> JestProcess[Jest finds test files, runs suites, and generates coverage]
    JestProcess --> JestOutput[Test results and coverage reports output]
    JestOutput --> CacheResults4[Nx caches results in .nx/cache/]

    %% ESLint Executor Flow
    ESLintExecutor --> ReadESLintConfig[ESLint reads .eslintrc.json rules and configuration]
    ReadESLintConfig --> ESLintProcess[ESLint checks code style, finds issues, and applies auto-fixes]
    ESLintProcess --> ESLintOutput[Lint results with errors and warnings output]
    ESLintOutput --> CacheResults5[Nx caches results in .nx/cache/]

    %% All paths converge
    CacheResults1 --> UpdateGraph[Dependency graph updated to track project relationships]
    CacheResults2 --> UpdateGraph
    CacheResults3 --> UpdateGraph
    CacheResults4 --> UpdateGraph
    CacheResults5 --> UpdateGraph

    UpdateGraph --> Done
```

## Caching and Performance

### Nx Caching

Nx automatically caches build outputs and only rebuilds what changed:

```bash
# First run builds everything
npx nx build cli

# Second run uses cache (much faster)
npx nx build cli
```

### Clearing Cache

```bash
# Clear all caches
npx nx reset
```

## Additional Resources

- [Nx Intro Documentation](https://nx.dev/getting-started/intro)
- [Nx CLI Commands Reference](https://nx.dev/docs/reference/nx-commands)
- [Nx Workspace Configuration](https://nx.dev/reference/project-configuration)