Julia Cell Highlighter

A VS Code extension that highlights the current Julia code cell in .jl files and adds optional CodeLens actions for running cells.

[!NOTE] For Julia extension users

Since version 1.178.0, the Julia extension already provides CodeLens run buttons. If you prefer to use only Julia's built-in buttons, add this to settings.json:

"juliaCellHighlighter.codeLensMode": "never"

For JETLS Client users

This extension also provides a Run Current File action. Add this to settings.json to show the run button in the editor title area:

"juliaCellHighlighter.showRunFileButton": true

After enabling it, a small run icon (▷) appears in the top-right editor title area. Clicking it starts (or reuses) a Julia REPL in the integrated terminal and runs the current file.

Features

• Custom cell highlight styling, including top border, background fill, and bottom border
• Independent delimiter separator lines
• Configurable cell delimiters via juliaCellHighlighter.defaultDelimiters (not limited to ##, #%%, and # %%)
• Exclude patterns to control where highlighting and CodeLens are applied

Quick Start

1. Install from the VS Code Marketplace.
2. Open a .jl file and add cell delimiters, for example:

## Cell 1
x = 1

## Cell 2
x + 1

The current cell is highlighted automatically as you move the cursor.

What Counts as a Cell

Delimiter rules are aligned with the Julia extension:

• If julia.cellDelimiters is set, that value is used.
• Otherwise, built-in defaults are used: ##, #%%, # %%.

You can enable or disable built-in delimiters with juliaCellHighlighter.defaultDelimiters.

By default, the delimiter line is included in the highlighted range. When the cursor is on a delimiter line, the next cell is highlighted (if the delimiter is the last line, nothing is highlighted).

CodeLens (Run Cell)

When enabled, CodeLens buttons appear above delimiter lines:

• Run Cell
• Run Cell and Move (runs the current cell, then moves to the next one after a short delay)

Execution backend is configurable:

• auto (default): use Julia extension commands when available; otherwise fall back to a persistent terminal Julia REPL
• julia: always use Julia extension commands
• terminal: always use a persistent terminal Julia REPL (one session per workspace folder)

Run Current File

You can run the full active Julia file from this extension:

• Command palette: Julia Cell Highlighter: Run Current File
• Editor title button (run icon): controlled by juliaCellHighlighter.showRunFileButton (default: false)

Run Current File always uses the terminal backend and executes the active editor buffer, including unsaved edits.

Separator Lines (Independent)

You can show a visual separator line above delimiters even when highlighting is turned off.

• Controlled by juliaCellHighlighter.showDelimiterSeparator
• Uses its own delimiter list via juliaCellHighlighter.separatorDelimiters

Excluding Files or Folders

Exclude paths from cell highlighting and CodeLens (separator lines still apply):

"juliaCellHighlighter.excludePatterns": [
  "**/src/**",
  "**/test/**",
  "**/deps/**",
  "**/docs/**"
]

Settings

Full key format: juliaCellHighlighter.<setting>.
For example: "juliaCellHighlighter.showRunFileButton": true.

^[1] Execution backend details:

• julia: Uses execution commands provided by the Julia extension (language-julia.executeCell / language-julia.executeCellAndMove). This extension treats that API as a black box and delegates execution to it.
• terminal: Uses this extension's built-in terminal backend. It can send either a cell or the whole active script to a persistent Julia REPL terminal session managed by this extension (reused per workspace, created automatically if needed).

Keybindings

• Toggle highlighting: Ctrl+Shift+H (Windows/Linux) / Cmd+Shift+H (macOS)