Expr Language Support

Complete language support for Expr language - syntax highlighting, intelligent formatting, and rainbow brackets all in one extension!

Features

✨ Syntax Highlighting

• Full syntax highlighting for Expr language
• Support for all Expr language constructs:
  • Keywords: let, if, else, in, and, or, not
  • Operators: arithmetic, comparison, logical, pipe, ternary
  • Literals: numbers, strings, booleans, nil
  • Comments: #, //, and /* */
  • Built-in functions
  • Special variables: $env, #, #acc, #index

🌈 Rainbow Brackets & Indent Guides

• Rainbow Brackets: Color-coded parentheses by nesting depth (5 colors)
  • Coral Pink, Amber Orange, Sky Blue, Mint Green, Lilac Violet
• Rainbow Indent Guides: Subtle colored vertical lines for each indent level
  • Dark Brown, Brown, Blue, Teal, Violet
• Helps visualize nested expressions and structure at a glance
• Automatically skips comments and strings
• Can be toggled on/off in settings

🎨 Intelligent Code Formatting

• Smart formatting with multiline expansion
• Preserves user intent: Already multiline expressions stay multiline
• Auto-indentation based on parentheses and brackets
• Smart spacing:
  • Automatically adds space after commas
  • Correctly handles unary vs binary minus (-1 vs x - 1)
  • No space between function name and opening paren
• Comment handling:
  • Preserves blank lines above standalone comments
  • Groups consecutive comment blocks together
  • Handles #, //, and /* */ style comments
• Format on save support (enabled by default)

🔗 Expr File Navigation

• Go to Definition: Cmd+Click (Mac) / Ctrl+Click (Windows) or F12 on "*.expr" strings to open referenced files
• Link Highlighting: .expr file references are automatically highlighted as clickable links
• Works everywhere: Supports file references in any file type (Markdown, JSON, YAML, etc.)
• Relative paths: Supports relative paths like "../data/input.expr" or "./config.expr"
• Tooltip preview: Hover to see the file path

Installation

From VS Code Marketplace

1. Open VS Code
2. Press Ctrl+Shift+X (Windows/Linux) or Cmd+Shift+X (Mac) to open Extensions
3. Search for "Expr Lang - Syntax & Formatter"
4. Click Install

Or visit the VS Code Marketplace

Usage

Syntax Highlighting

Automatically applied to .expr files!

Format on Save

Format on save is enabled by default. To disable:

{
  "[expr]": {
    "editor.formatOnSave": false
  }
}

Configuration

All settings are optional and have sensible defaults:

{
  // Formatter settings
  "expr.indentSize": 2,                    // Number of spaces for indentation (default: 2)
  "expr.maxLineLength": 120,               // Maximum line length before expanding (default: 120)

  // Rainbow brackets settings
  "expr.rainbowBrackets.enabled": true,    // Enable rainbow brackets and indent guides (default: true)

  // Format on save
  "[expr]": {
    "editor.formatOnSave": true,           // Auto-format on save (default: true)
    "editor.defaultFormatter": "daangn-ml-data-platform.expr-lang-support"
  }
}

Disable Rainbow Brackets

If you prefer plain brackets without colors:

{
  "expr.rainbowBrackets.enabled": false
}

Formatting Examples

Example 1: Auto-expansion for long expressions

Before:

IF(CANDIDATE_TYPE == candidate_type('ARTICLE'), calculate_score(Q_VALUE, P_IMPRESSION, OPERATION_SCORE), 0)

After:

IF(
  CANDIDATE_TYPE == candidate_type('ARTICLE'),
  calculate_score(Q_VALUE, P_IMPRESSION, OPERATION_SCORE),
  0
)

Example 2: Smart spacing and negative numbers

Before:

min(1.0,(exp(2.0) - 1))
IF(x > 0, - 1, - 2)

After:

min(1.0, (exp(2.0) - 1))
IF(x > 0, -1, -2)

Example 3: Comment handling

Before:

x * y
# Service weight
* 0.735
# Engagement score
* engagement
# Another comment
# Continuation of comment block
* decay

After:

x * y

# Service weight
* 0.735

# Engagement score
* engagement

# Another comment
# Continuation of comment block
* decay

Supported Language Features

• Literals: Numbers (decimal, hex, octal, binary), strings (single, double, backtick), booleans, nil
• Operators: +, -, *, /, %, **, ==, !=, <, >, <=, >=, &&, ||, !, ??, .., ?.
• Collections: Arrays [1, 2, 3], Maps {a: 1, b: 2}
• Functions: Function calls with any number of arguments
• Control Flow: if/else statements, let variable bindings
• Special Operators:
  • Ternary: condition ? true_value : false_value
  • Pipe: value | func1() | func2()
  • Range: 1..10
  • Slice: array[1:3]
  • Membership: value in array
• String Operators: contains, startsWith, endsWith, matches
• Special Variables: $env.VAR, # (predicate), #acc (accumulator), #index
• Comments: Line comments (#, //) and block comments (/* */)

Development & Deployment

Building from Source

# Clone the repository
git clone https://github.com/your-repo/expr-lang-support
cd expr-lang-support/packages/vscode

# Install dependencies
npm install

# Build the extension
npm run build

# Package the extension
npm run package

Development

# Watch mode (auto-rebuild on changes)
npm run watch

# Then press F5 in VS Code to launch Extension Development Host

Publishing to VS Code Marketplace

1. Get Publisher Access Token

   • Create an Azure DevOps account
   • Generate a Personal Access Token with Marketplace (Manage) scope
   • More info: https://code.visualstudio.com/api/working-with-extensions/publishing-extension

2. Login to vsce

   npm install -g @vscode/vsce
   vsce login <publisher-name>
   

3. Publish

   # Publish current version
   vsce publish
   
   # Or publish with version bump
   vsce publish patch  # 0.3.0 -> 0.3.1
   vsce publish minor  # 0.3.0 -> 0.4.0
   vsce publish major  # 0.3.0 -> 1.0.0
   

Troubleshooting

Extension not activating

• Make sure your file has .expr extension
• Reload VS Code: Ctrl+Shift+P → "Reload Window"

Formatting not working

• Check that the extension is set as default formatter:

  {
    "[expr]": {
      "editor.defaultFormatter": "daangn-ml-data-platform.expr-lang-support"
    }
  }
  

Rainbow brackets not showing

• Check that rainbow brackets are enabled:

  {
    "expr.rainbowBrackets.enabled": true
  }
  

• Reload VS Code after changing settings

License

MIT