nodemon.json

Overview

The `nodemon.json` file is a configuration file used by **Nodemon**, a utility that monitors changes in source files and automatically restarts the Node.js application during development. This file specifies how Nodemon should behave for the particular project, defining which files or directories to watch or ignore, the file extensions that trigger restarts, and the command to execute when changes are detected.

This configuration optimizes the development workflow by ensuring that the application rebuilds and restarts only when relevant source files change, improving efficiency and reducing unnecessary restarts.

Configuration Properties

The file is a JSON object with the following properties:

Detailed Explanation of Properties

ignore

• Type: Array of strings

• Purpose: Prevents Nodemon from restarting the app when files matching these paths change.

• Current value: ["src/routes.ts"]

• Usage: This ignores changes in the specific file src/routes.ts. This is useful if changes to this file do not require a restart or if it causes unnecessary reloads.

watch

• Type: Array of strings

• Purpose: Specifies which files or directories Nodemon should monitor for changes.

• Current value:

  [
    "../../../packages/*/dist/tsconfig.tsbuildinfo",
    "../../common/api/dist/tsconfig.tsbuildinfo",
    "src"
  ]
  

• Explanation:

  • The watcher monitors build info files (tsconfig.tsbuildinfo) in certain package directories to detect TypeScript build changes.

  • It also watches the src directory for source code changes.

• Usage: Watching these files ensures Nodemon restarts the app when relevant compiled files or source files are updated.

ext

• Type: String

• Purpose: Defines the file extensions that Nodemon should monitor for changes.

• Current value: "ts"

• Usage: Nodemon will only trigger restarts when .ts (TypeScript) files change, ignoring other file types.

exec

• Type: String

• Purpose: The command run by Nodemon upon detecting a file change.

• Current value: "yarn build && node dist/ethereum/api/src/app.js"

• Explanation:

  • First, it runs yarn build to compile the TypeScript project.

  • Then, it starts the Node.js server by running the compiled JavaScript file located at dist/ethereum/api/src/app.js.

• Usage: This ensures the app always runs the latest build after changes.

Usage Example

When running Nodemon with this configuration, the developer would typically execute:

nodemon

Nodemon will:

1. Watch all .ts files inside the src directory and the specified build info files.

2. Ignore changes in src/routes.ts.

3. On relevant changes, run yarn build to compile the project.

4. Start or restart the Node.js server by running the compiled app at dist/ethereum/api/src/app.js.

This setup is particularly useful in a TypeScript monorepo or multi-package workspace, where build artifacts and incremental builds are important to track.

Implementation Details and Notes

• Watching tsconfig.tsbuildinfo files:
  These files are incremental build info files generated by TypeScript. Watching them allows Nodemon to restart the process when the build state changes, even if source files don't change directly. This is useful in complex monorepos where compiled outputs affect runtime behavior.

• Ignoring specific source files:
  Sometimes certain source files change frequently but don't require a restart or cause undesirable reloads. Ignoring them prevents unnecessary rebuilds, optimizing development speed.

• Sequential command execution:
  The exec command chains yarn build and then runs the compiled app with node. This guarantees the app runs the latest compiled code. However, if yarn build fails, the app will not start, preventing running outdated or invalid code.

Interaction with the System

• Build system:
  The file assumes the use of yarn as the package manager and a build script named build that compiles TypeScript sources.

• Runtime:
  Runs the compiled JavaScript application dist/ethereum/api/src/app.js.

• Development workflow:
  Nodemon uses this config to monitor relevant files and streamline the rebuild and restart cycle during local development.

• Monorepo structure:
  The paths in watch point to relative directories outside the current folder, indicating this project is part of a larger monorepo with shared packages and APIs.

Mermaid Diagram

The diagram below illustrates the workflow of this `nodemon.json` configuration during development:

flowchart TD
    A[File Change Detected] --> B{Is file ignored?}
    B -- Yes --> C[No Restart]
    B -- No --> D{Is file extension '.ts'?}
    D -- No --> C
    D -- Yes --> E{Is file in watch list?}
    E -- No --> C
    E -- Yes --> F[Run "yarn build"]
    F --> G{Build successful?}
    G -- No --> H[Do not restart app]
    G -- Yes --> I[Run "node dist/ethereum/api/src/app.js"]
    I --> J[App Restarted]

Summary

• nodemon.json defines how Nodemon watches and restarts the Node.js application during development.

• It watches .ts files in specified directories, ignoring src/routes.ts.

• On change, it runs a build command and starts the compiled app.

• This configuration is tailored for a TypeScript monorepo environment, improving developer productivity by automating rebuilds and restarts efficiently.

If you want to customize the behavior, you can adjust the paths in `watch` and `ignore`, change the file extensions in `ext`, or modify the `exec` command to fit your build and launch scripts.