Sieve Language Support

A Visual Studio Code extension that provides syntax highlighting for the Sieve email filtering language, as defined in RFC 5228 and related extensions.

Features

• 🎨 Syntax Highlighting: Complete syntax highlighting for Sieve scripts including:

  • Keywords (if, elsif, else, require, stop)
  • Commands (keep, discard, redirect, fileinto, reject, vacation)
  • Tests (address, header, body, size, exists)
  • Operators (:is, :contains, :matches, :regex, etc.)
  • Comments (line comments with # and block comments)
  • Strings and multiline text blocks
  • Numbers with optional size suffixes (K, M, G)

• 🔍 Smart Linting System: Real-time error detection and validation

  • Syntax Validation: Missing semicolons, malformed statements, empty constructs
  • Extension Requirements: Automatic detection of missing require statements
  • Logic Analysis: Detection of unreachable code after keep, discard, stop
  • Best Practice Suggestions: Recommendations to add stop after actions
  • Performance Optimization: Smart expiration validation (only warns when exceeding limits)
  • Configurable Rules: Customizable linting behavior through VS Code settings

• 🚀 ProtonMail-Specific Support: Specialized features for ProtonMail users

  • Extension Detection: Recognition of ProtonMail-specific extensions (vnd.proton.*)
  • Contact List Validation: Support for :addrbook: and :incomingdefaults: usage
  • Smart Expiration Limits: Warnings only when expiration exceeds 730-day maximum
  • Regex Validation: Error detection for unsupported regex shorthand (\b, \w, \d)
  • Folder Path Suggestions: Guidance for proper folder/label escaping
  • Size Filtering Info: Notes about encrypted vs. actual message size
  • Vacation Optimization: Suggestions for :handle parameter usage

• 📁 File Association: Automatically recognizes .sieve and .siv file extensions

• 🌐 Cross-Platform Support: Works in both desktop VS Code and web environments

  • Full compatibility with VS Code for the Web (vscode.dev, github.dev)
  • GitHub Codespaces support
  • Virtual workspace environments
  • Untrusted workspace environments

Supported Sieve Features

This extension supports syntax highlighting for:

• Core Sieve (RFC 5228): Basic filtering constructs
• Common Extensions: Including fileinto, reject, vacation, envelope, and body tests
• Advanced Features: Regular expressions, date tests, and metadata handling

Email Providers Supporting Sieve

The following online email providers support Sieve email filtering:

Full Sieve Support

• FastMail - Complete Sieve implementation with ManageSieve protocol and web interface
• Migadu - Full Sieve support with advanced filtering capabilities
• Posteo - Privacy-focused email with comprehensive Sieve filtering
• Runbox - Norwegian email provider with complete Sieve support
• Zoho Mail - Business email with extensive Sieve filtering options
• Kolab Now - Collaboration platform with full Sieve implementation
• Mailbox.org - German email provider with Sieve filtering
• ProtonMail - Encrypted email with server-side Sieve filtering
• Tuta (formerly Tutanota) - Secure email with basic Sieve capabilities

Installation

VS Code Desktop / VS Code Insiders

1. Open Visual Studio Code
2. Go to the Extensions view (Ctrl+Shift+X)
3. Search for "Sieve Language Support"
4. Click Install

VS Code for the Web

This extension now supports VS Code web environments:

• vscode.dev - VS Code in the browser
• github.dev - GitHub's web editor (press . on any GitHub repository)
• GitHub Codespaces - Cloud development environments

To install in web environments:

1. Open any of the web environments above
2. Go to the Extensions view (Ctrl+Shift+X)
3. Search for "Sieve Language Support"
4. Click Install

Manual Installation (for self-hosted environments)

If the extension isn't available in your marketplace, download and install manually:

# Download the extension package
curl -L "https://marketplace.visualstudio.com/_apis/public/gallery/publishers/MattyStacks/vsextensions/sieve-language-support/latest/vspackage" -o sieve-language-support.vsix

# Install the extension
code --install-extension sieve-language-support.vsix

Usage

Simply open any .sieve or .siv file in VS Code and the syntax highlighting will be automatically applied.

Getting Started with Syntax Highlighting

1. Create a new file with .sieve or .siv extension
2. Start writing your Sieve email filtering rules
3. Enjoy automatic syntax highlighting and language features

Using the Smart Linting System

The extension provides real-time error detection and suggestions:

1. Automatic Validation: Errors and warnings appear as you type
2. Problems Panel: Press Ctrl+Shift+M to see all issues in one place
3. Hover Information: Hover over squiggly lines for detailed explanations
4. Configurable Rules: Adjust linting behavior in VS Code Settings (Ctrl+,)

Linting Categories:

• 🔴 Errors: Syntax issues, missing requirements, invalid constructs
• 🟡 Warnings: Missing best practices, potential problems
• 🔵 Information: ProtonMail features detected, optimization suggestions

Configuring ProtonMail Support

By default, ProtonMail linting is enabled to provide helpful suggestions for ProtonMail-specific extensions like expire statements.

To disable ProtonMail linting:

1. Open VS Code Settings (Ctrl+,)
2. Search for "sieve.linting.protonmail"
3. Uncheck the setting
4. Or add to your settings.json: "sieve.linting.protonmail": false

When ProtonMail linting is disabled, you can use expire and other commands without needing ProtonMail-specific require statements.

ProtonMail Users

The extension includes specialized support for ProtonMail's Sieve implementation:

• Validates ProtonMail-specific extensions (vnd.proton.*)
• Checks expiration limits (warns only when exceeding 730 days)
• Detects unsupported regex patterns
• Provides folder path escaping guidance

Web Environment Usage

When using VS Code for the Web:

1. Open vscode.dev or press . on any GitHub repository
2. Install the Sieve Language Support extension
3. Open or create .sieve files directly in the browser
4. Full syntax highlighting works without any additional setup

Example

Basic Sieve Script with Syntax Highlighting

# Example Sieve script with smart linting
require ["fileinto", "reject"];

if header :contains "subject" "SPAM" {
    fileinto "Junk";
    stop;  # ✅ Good: stop prevents further processing
}

if size :over 1M {
    reject "Message too large";
}

keep;

ProtonMail-Specific Example

# ProtonMail example with specialized linting
require ["fileinto", "vnd.proton.expire", "extlists"];

# ✅ Good: 30 days is under the 730-day limit
if header :list "from" ":addrbook:personal" {
    expire "day" "30";
    fileinto "Personal";
    stop;
}

# ⚠️ Warning: Would warn if days > 730
# expire "day" "1000";  # This would show a warning

Here's how the syntax highlighting looks in VS Code:

Test Files & Examples

The extension includes comprehensive test files in the test-files/ directory to help you explore features:

Basic Examples

• simple-test.sieve - Basic Sieve syntax demonstration
• example.sieve - Common filtering patterns
• test-extension.sieve - Extension testing

Advanced Features

• test-advanced.sieve - Complex Sieve constructs and advanced features

Linting Demonstrations

• test-linting-demo.sieve - Shows basic linting errors and suggestions
• test-expire-validation.sieve - Demonstrates smart expiration validation
• test-protonmail-linter.sieve - Comprehensive ProtonMail linting showcase

ProtonMail-Specific

• test-protonmail-demo.sieve - ProtonMail implementation examples

To test the extension: Press F5 to launch the Extension Development Host and open any of these files to see syntax highlighting and linting in action.

Requirements

No additional requirements or dependencies.

Extension Settings

This extension provides configurable linting settings:

• sieve.linting.enabled (boolean, default: true) - Enable/disable Sieve linting and error detection
• sieve.linting.protonmail (boolean, default: true) - Enable/disable ProtonMail-specific linting rules and extension requirements. When enabled, the linter will suggest ProtonMail-specific extensions like vnd.proton.expire for expire statements
• sieve.linting.bestPractices (boolean, default: true) - Enable/disable best practice suggestions
• sieve.linting.severity (string, default: "warning") - Minimum severity level for linting messages (error, warning, info)

Settings can be configured in VS Code Preferences (Ctrl+,) by searching for "sieve".

Known Issues

• Complex nested string interpolation in multiline text blocks may not be perfectly highlighted
• Some advanced Sieve extensions beyond RFC 5228 may need additional grammar rules

Roadmap & Future Features

🚀 Planned Features

Language Server Protocol (LSP) Support

• Auto-completion: Intelligent suggestions for Sieve commands, tests, and operators
• Hover Information: Contextual help and documentation for Sieve elements
• Go to Definition: Navigate to variable and capability definitions
• Symbol Navigation: Outline view and breadcrumb navigation

Enhanced Grammar Support

• Extended Sieve RFCs: Support for additional Sieve extensions (vacation, notify, etc.)
• Custom Extensions: Grammar support for provider-specific Sieve extensions
• Improved Regex Highlighting: Better syntax highlighting for regular expressions

Developer Experience

• Code Snippets: Pre-built templates for common Sieve patterns
• Folding Regions: Collapsible sections for better code organization
• Bracket Matching: Enhanced bracket and quote pair matching

Testing & Validation

• Sieve Script Testing: Built-in tools to test Sieve scripts against sample emails
• Integration Testing: Connect with email providers for live script validation
• Debug Mode: Step-through debugging for complex Sieve logic

Contributing

Contributions are welcome! Please feel free to submit issues or pull requests to improve the Sieve language support.

Release Notes

1.2.1

• 🚀 Stable Release: All smart linting features now available in stable channel (promoted from pre-release)

1.2.0

• 🎉 Major Feature: Complete smart linting system with real-time error detection
• 🚀 ProtonMail Support: Specialized linting rules for ProtonMail's Sieve implementation
• ⚙️ Configurable Settings: User-customizable linting behavior and severity levels
• 🔧 Smart Validation: Intelligent expiration limit checking and extension requirements
• 📁 Test Organization: Comprehensive test files moved to dedicated test-files/ directory

1.1.5

• Web Compatibility: Fixed remaining web environment compatibility issues
• Engine Requirements: Updated VS Code engine requirements for pre-release support

1.1.2

• Image Display: Fixed broken image links in VS Code marketplace and web environments
• Documentation: Improved README with absolute GitHub URLs for better web compatibility

1.1.1

• Web Support: Extension now works in VS Code for the Web (vscode.dev, github.dev, GitHub Codespaces)
• Virtual Workspaces: Full compatibility with virtual workspace environments
• Untrusted Workspaces: Safe operation in untrusted/web environments

1.1.0

• VS Code Web Support: Initial web compatibility implementation
• Build System: Enhanced build configuration for cross-platform compatibility
• Linter Framework: Added comprehensive Sieve linting infrastructure (disabled by default)

1.0.0

• General Availability: Ready for production use
• Documentation: Enhanced README with provider information and examples

0.0.1

• Initial Release: Complete syntax highlighting for Sieve email filtering scripts
• File Support: Support for .sieve and .siv file extensions
• Language Configuration: Proper bracket matching and commenting
• Examples: Documentation and sample files

License

This extension is released under the MIT License.