prettier-plugin-apex-imo

IMO = In My Opinion. Because Prettier is opinionated, and so am I.

An opinionated enhancement for prettier-plugin-apex that enforces multiline formatting for Apex Lists, Sets, and Maps with multiple entries.

The Problem

When using prettier-plugin-apex, code like this:

final String expectedJson = String.join(new List<String>{
  '{',
  '  "tags" : [ "reading", "gaming", "coding" ]',
  '}'
}, '\n');

Gets reformatted to a single line, defeating the purpose of readable formatting:

final String expectedJson = String.join(new List<String>{ '{', '  \"tags\" : [ \"reading\", \"gaming\", \"coding\" ]', '}' }, '\n');

The Solution

This plugin wraps prettier-plugin-apex and modifies the printing behaviour:

• List literals with 2+ entries → Always multiline
• Map literals with 2+ entries → Always multiline
• Set literals with 2+ entries → Always multiline

This is non-configurable behaviour. Once installed, it just works.

Installation

pnpm add -D prettier prettier-plugin-apex prettier-plugin-apex-imo

Or with npm:

npm install --save-dev prettier prettier-plugin-apex prettier-plugin-apex-imo

Usage in Salesforce Projects

If you're working with a Salesforce project (created with sf project generate or Salesforce DX), follow these steps:

1. Install the plugin:

   npm install --save-dev prettier-plugin-apex-imo

   Standard Salesforce projects already include prettier and prettier-plugin-apex in their package.json, so you only need to install prettier-plugin-apex-imo.

2. Update your .prettierrc file:

   Replace prettier-plugin-apex with prettier-plugin-apex-imo in the plugins array:

   {
   	"trailingComma": "none",
   	"plugins": ["prettier-plugin-apex-imo", "@prettier/plugin-xml"]
   }

   The prettier-plugin-apex-imo plugin wraps prettier-plugin-apex, so you only need to specify prettier-plugin-apex-imo in your config. However, both plugins must be installed since prettier-plugin-apex is a peer dependency.

3. Verify the configuration:

   npm run prettier:verify

   Or format your files:

   npm run prettier

   Standard Salesforce projects typically include a prettier script in package.json that formats all relevant files including Apex classes (.cls) and triggers (.trigger).

Examples

Before (prettier-plugin-apex)

List<String> items = new List<String>{ 'one', 'two', 'three' };
Set<String> tags = new Set<String>{ 'reading', 'gaming', 'coding' };
Map<String, Integer> counts = new Map<String, Integer>{ 'a' => 1, 'b' => 2 };

After (prettier-plugin-apex-imo)

List<String> items = new List<String>{
  'one',
  'two',
  'three'
};
Set<String> tags = new Set<String>{
  'reading',
  'gaming',
  'coding'
};
Map<String, Integer> counts = new Map<String, Integer>{
  'a' => 1,
  'b' => 2
};

Single Items (unchanged)

// These stay on one line
List<String> single = new List<String>{ 'only' };
Set<String> singleSet = new Set<String>{ 'only' };
Map<String, Integer> singleMap = new Map<String, Integer>{ 'key' => 1 };

Requirements

• Node.js >= 20
• Prettier >= 3.0.0
• prettier-plugin-apex >= 2.0.0

Why "imo"?

Prettier has a strict option philosophy that discourages adding new formatting options. While I respect this philosophy, I believe the current behaviour for multi-item Lists and Maps is suboptimal for code readability.

Rather than fork prettier-plugin-apex or maintain options, this plugin provides a simple, opinionated wrapper that enforces the behaviour I (and hopefully others) prefer.

Contributing

Contributions are welcome! Please read CONTRIBUTING.md for details.

Security

For security issues, please email [email protected]. See SECURITY.md for details.

License

This project is licensed under the MIT License. See the LICENSE.md file for details.

Acknowledgements

• prettier-plugin-apex by Dang Mai
• Prettier for the amazing formatting engine