Nx Plugin Authoring

Nx Plugin Authoring

Navigation hub for creating custom Nx plugins, generators, and executors.

When to Use

• You need to scaffold files/projects with repeatable conventions (generators).
• You need custom task execution logic (executors).
• You are building reusable plugin automation for Nx workspaces.
• You want to enforce organization-specific standards and patterns.

When Not to Use

• The task is generic Nx workspace setup unrelated to custom plugin development.
• You only need to use existing plugins, not create new ones.

Principles

• Keep plugins as orchestration tools, not business-logic containers.
• Prefer small, composable generation steps over large mutation passes.
• Keep executors deterministic and cache-aware.
• Use Tree API exclusively for filesystem operations in generators.

Workflow

1. Create Plugin Structure

Start new workspace with plugin:

npx create-nx-plugin my-plugin

Add plugin to existing workspace:

npx nx add @nx/plugin
npx nx g plugin tools/my-plugin

2. Build Generators

Create a generator:

npx nx g generator my-plugin/src/generators/library-with-readme

Implement with Tree API:

• Use tree.write, generateFiles, updateJson for filesystem edits
• Define typed schema with required fields
• Add templates with EJS syntax
• Validate with --dry-run before execution

Validate: Run npx nx g my-plugin:library-with-readme mylib --dry-run

Stop if: Unexpected files appear or required options fail validation

3. Build Executors

Create executor structure:

mkdir -p tools/executors/my-executor

Implement with ExecutorContext:

• Define schema.json with required fields and defaults
• Return { success: boolean } from executor
• Use package notation for registration
• Declare outputs for cache awareness

Validate: Run npx nx run my-project:my-target --help

Stop if: Executor fails to resolve or schema is invalid

4. Test and Publish

Run tests:

npx nx test my-plugin

Validate in real workspace:

npx nx g my-plugin:my-generator sample --dry-run
npx nx run my-project:my-target

Quick Commands

npx create-nx-plugin my-plugin

npx nx add @nx/plugin

npx nx g generator my-plugin/src/generators/my-gen

npx nx g my-plugin:my-gen sample --dry-run

npx nx run my-project:my-target --skip-nx-cache

npx nx reset

rg -n "generateFiles|updateJson|readProjectConfiguration" plugins tools

Anti-Patterns

NEVER modify files outside the Tree API

• WHY: direct filesystem writes bypass dry-run and change tracking.
• BAD: writeFileSync("libs/my-lib/src/index.ts", content).
• GOOD: tree.write("libs/my-lib/src/index.ts", content).

NEVER hardcode project paths in generator logic

• WHY: brittle paths fail when workspace layout evolves.
• BAD: fixed libs/my-lib/... writes.
• GOOD: derive paths from readProjectConfiguration(tree, name).root.

NEVER skip schema validation and typed options

• WHY: invalid inputs fail late with unclear errors.
• BAD: schema: any and no guardrails.
• GOOD: typed schema.json with required fields, types, defaults, descriptions.

NEVER generate across project boundaries without explicit checks

• WHY: hidden boundary violations introduce circular dependencies.
• BAD: generator writes imports into disallowed scopes without verification.
• GOOD: verify tags and dependency direction before cross-scope imports.

NEVER mutate project configuration blindly

• WHY: naive updates remove existing targets/tags.
• BAD: overwrite full project.json.
• GOOD: const config = readProjectConfiguration(tree, name); config.targets.build = {...}; updateProjectConfiguration(tree, name, config);.

NEVER put business logic directly inside executor entrypoints

• WHY: bloated executors are hard to test and reuse.
• BAD: 200 lines of transformation logic in executor.ts.
• GOOD: delegate to composable library functions.

NEVER use relative executor references in targets

• WHY: relative paths are fragile across workspace changes.
• BAD: "executor": "../../tools/executors:task".
• GOOD: "executor": "@scope/tools:task".

NEVER omit outputs and dependencies semantics for cacheable work

• WHY: Nx cache quality depends on deterministic inputs and outputs.
• BAD: no outputs declared, implicit file writes.
• GOOD: declare outputs in target config: "outputs": ["{options.outputPath}"].

NEVER block executor runs with synchronous file I/O in hot paths

• WHY: sync I/O hurts parallel throughput.
• BAD: fs.readFileSync in main execution flow.
• GOOD: await fs.promises.readFile with structured error handling.

NEVER skip formatFiles after generating code

• WHY: inconsistent formatting causes noisy diffs and CI failures.
• BAD: generateFiles() without calling formatFiles(tree).
• GOOD: await generateFiles(...); await formatFiles(tree);.

NEVER ignore existing project structure when generating files

• WHY: overwriting existing files destroys user work.
• BAD: tree.write(path, content) without checking tree.exists(path).
• GOOD: if (tree.exists(path)) { throw new Error('File already exists'); }.

NEVER forget to export generator/executor from plugin index

• WHY: unregistered functions cannot be invoked by Nx CLI.
• BAD: generator implemented but missing from src/index.ts and generators.json.
• GOOD: export in src/index.ts and register in generators.json with factory path.

Constraint vs Flexibility Guidelines

Hard Constraints (MUST)

Generators:

• MUST use Tree API for filesystem edits
• MUST validate generator options via schema and explicit guards
• MUST respect Nx project graph boundaries and existing tags
• MUST test with --dry-run before broad rollouts

Executors:

• MUST return { success: boolean } from executor function
• MUST use package notation for executor references in targets
• MUST declare outputs for cacheable tasks
• MUST implement schema validation with required fields

Flexible Choices (CAN)

• CAN choose template style (EJS-heavy vs minimal placeholders)
• CAN choose option naming conventions if documented in schema
• CAN compose other generators to reduce duplication
• CAN delegate executor work to external libraries

Fallback Behaviors

References

Getting Started

Generators

Executors

Shared Resources

• Nx Plugin Development
• Nx Devkit API
• Enforce Best Practices Tutorial
• Tool Integration Tutorial
• Local Executors Recipe
• Plugin Registry