A Visual Studio Code extension that provides comprehensive language support for MARC MRK (machine-readable cataloging) files, including syntax highlighting, hover documentation, auto-completion, and validation.

• Syntax Highlighting: Color-coded MARC tags, indicators, and subfields with custom grammar
• Hover Documentation: Detailed information about MARC fields and subfields fetched from Library of Congress documentation
• Auto-completion: Intelligent suggestions for MARC tags and subfields as you type
• Real-time Validation: Syntax checking for MRK format with error highlighting
• Dynamic Documentation: Always up-to-date field definitions from Library of Congress
• Precise Hover Ranges: Accurate highlighting of individual subfields, including repeated subfields

• Python: 3.9 or higher
• MARC LSP Server: Installed via pipx or pip

1. Install the MARC LSP server (recommended with pipx for isolation):

   # Install pipx if you don't have it
   python -m pip install --user pipx
   python -m pipx ensurepath
   
   # Install MARC LSP server
   pipx install marc-lsp-server

   Alternative with pip:

   pip install marc-lsp-server

2. Install this VS Code extension from the marketplace (once published)

3. Start using MARC files - the extension will automatically detect .mrk files and activate

1. Install the LSP server from source:

   git clone <your-marc-lsp-repo>
   cd marc-lsp
   pipx install -e .

2. Build and test the VS Code extension:

   cd vscode-marc-lsp
   npm install
   npm run compile
   # Press F5 in VS Code to launch Extension Development Host

The extension can be configured via VS Code settings:

{
  "marcLsp.serverCommand": "marc-lsp-server",
  "marcLsp.trace.server": "off"
}

• marcLsp.serverCommand: Command to run the MARC LSP server (default: "marc-lsp-server")
• marcLsp.trace.server: LSP communication tracing level ("off", "messages", "verbose")

Create a .mrk file with content like this to test the extension:

=LDR  00000nam a2200000 a 4500
=001  123456789
=008  230101s2023    cau     b    001 0 eng d
=020  \\$a9781234567890$qhardcover
=035  \\$a(OCoLC)123456789$z(OCoLC)987654321
=040  \\$aCLU$beng$cCLU$dNST$dDLC$dOCLCQ$dOCLCF$dOCLCO$dGILDS$dOCLCO$dOCLCQ
=100  1\$aSmith, John,$d1980-
=245  10$aExample MARC record$bfor testing language server$cby John Smith
=260  \\$aLos Angeles :$bUCLA Library,$c2023.
=300  \\$a200 pages :$billustrations ;$c24 cm
=504  \\$aIncludes bibliographical references and index.
=650  \0$aLibrary science$xAutomation.
=856  40$uhttp://example.com/resource$zOnline version

• Hover over MARC tags (=245, =040) to see field descriptions from Library of Congress
• Hover over subfields ($a, $b, $d) to see subfield definitions and descriptions
• Hover over repeated subfields (multiple $d in 040 field) - each instance highlights correctly
• Hover over indicators (10, \) to see indicator value meanings
• Type completion: Start typing = to get tag suggestions, $ for subfield suggestions
• Syntax highlighting: Tags, indicators, and subfields are color-coded differently

1. Clone and setup:

   git clone <repo-url>
   cd marc-lsp/vscode-marc-lsp
   npm install
   npm run compile

2. Open in VS Code and press F5 to launch Extension Development Host

3. In the new window, open a .mrk file and test all features

# Package the extension
npm install -g @vscode/vsce
vsce package

# Install locally
code --install-extension marc-lsp-0.1.0.vsix

Error: Launching server using command marc-lsp-server failed

Solutions:

1. Install the LSP server: pipx install marc-lsp-server
2. Check if it's in PATH: which marc-lsp-server
3. Configure custom path: Set marcLsp.serverCommand to full path

1. Check file extension: Must be .mrk or .mrc
2. Verify language mode: Bottom right of VS Code should show "MARC MRK"
3. Reload window: Ctrl+Shift+P → "Developer: Reload Window"

1. Check Output panel: View → Output → "MARC Language Server"
2. Enable verbose logging: "marcLsp.trace.server": "verbose"
3. Test simple line: =245 10$aTest title
4. Check internet: Extension fetches documentation from Library of Congress

1. Cache location: Documentation cached in ~/.cache/marc-lsp-server/
2. Clear cache: Delete cache directory if needed
3. Network delays: First-time field lookups may be slow

• LSP Server: Standalone Python application (marc-lsp-server)
• VS Code Extension: TypeScript client that communicates with LSP server
• Documentation Source: Live data fetched from Library of Congress
• Caching: HTML responses cached locally for performance

vscode-marc-lsp/
├── package.json                    # Extension manifest  
├── src/extension.ts               # Main extension client
├── syntaxes/mrk.tmLanguage.json   # Syntax highlighting grammar
└── language-configuration.json    # Language features (brackets, etc.)

npm install           # Install dependencies
npm run compile       # Compile TypeScript
npm run watch         # Watch for changes
npx vsce package      # Create .vsix package

1. Fork the repository
2. Install development dependencies: pipx install -e . and npm install
3. Test your changes using Extension Development Host (F5)
4. Submit a pull request with clear description

[Add your license here]

Keywords: MARC, MRK, cataloging, library, bibliographic, metadata, LSP, language server