hydrogen-next

A package provide an interactive coding environment that supports Python, R, JavaScript and other Jupyter kernels.

Installation

To install hydrogen-next search for hydrogen-next in the Install pane of the Pulsar settings or run ppm install hydrogen-next. Alternatively, you can run ppm install asiloisad/pulsar-hydrogen-next to install a package directly from the GitHub repository.

Useful links

• https://github.com/nteract/hydrogen
• https://nteract.gitbooks.io/hydrogen/content/
• https://blog.nteract.io/hydrogen-interactive-computing-in-atom-89d291bcc4dd

Features

Hydrogen & hydrogen-next core features:

• Execute a line, selection, or block of code.
• Rich media output: plots, images, video, HTML, LaTeX, and more.
• Watch expressions to automatically re-run and track variables.
• Kernel-powered completions (similar to Chrome DevTools autocomplete).
• Inline inspection of code objects from the running kernel.
• One kernel per language (share the same namespace across files).
• Interrupt or restart kernels when needed (Windows excluded).
• Support for custom kernel connections (e.g. inside Docker).
• Cell markers compatible with navigation-panel.
• Cell markers compatible with scroll-map.

Enhancements exclusive to hydrogen-next:

• Full compatibility with Pulsar and PulsarNext without rebuilding.
• Updated dependencies: jmp and zeromq now use latest versions.
• Repaired socket monitoring for improved kernel stability.
• TypeScript code converted to JavaScript.
• Removed outdated text-editor context menu.
• Integrated hydrogen-run.
• Integrated cell-navigation.
• Removed breakpoints grammar, because tree-sitter is missing.
• Integrated hydrogen-cell-separator as markers.
• Correct evaluation of Python if/elif/else and try/except/else/finally.
• Run command supports multiple cursors and multi-selections.
• Run is no longer trimmed to the cell range.
• Added new command: hydrogen-next:open-examples.
• Updated inspector workflow.
• Fixed problem of "busy" stuck.
• Fixed notebook import command.
• Added variable explorer for Python.
• Fixed overcount issue by internal queue.
• Inline methods in sequence.
• Added exec panel with history.

Code Block Detection

When you run code without a selection, hydrogen-next intelligently detects what to execute based on cursor position.

Priority Order

1. Selection - If text is selected, execute exactly that
2. Language Specials - Python compound statements (see below)
3. Brackets - Multi-line bracket expressions (), [], {}
4. Folds - Foldable language constructs
5. Single Line - Current line as fallback

Python Support

Cursor Position	What Gets Executed
On def/class line	Entire function/class (with decorators)
On @decorator line	Decorated function/class
On if/elif/else line	Entire if-elif-else chain
On try/except/finally line	Entire try block
On for/while line	Loop with optional else
On with/match line	Entire block
Inside body	Single line only

Bracket Expressions

Cursor Position	What Gets Executed
On line ending with [, (, {	Entire bracket block
On line starting with ], ), }	Entire bracket block
Inside bracket block	Single line only

Examples

# Cursor on "if" → executes entire if-elif-else
if x > 0:
    print("positive")
elif x < 0:
    print("negative")
else:
    print("zero")

# Cursor on "print" inside body → executes only that line
if x > 0:
    print("positive")  # ← cursor here = single line

# Cursor on "[" → executes entire list
data = [
    1,
    2,
    3,
]

# Cursor on "2," inside list → executes only "2,"
data = [
    1,
    2,  # ← cursor here = single line
    3,
]

This allows you to execute entire blocks from control lines, while still being able to inspect individual lines inside bodies.

Plugin API (v1.3.0)

Hydrogen-next provides a service API for other packages to interact with Jupyter kernels.

Consuming the Service

In your package.json:

{
  "consumedServices": {
    "hydrogen.provider": {
      "versions": {
        "^1.3.0": "consumeHydrogen"
      }
    }
  }
}

In your package:

module.exports = {
  consumeHydrogen(hydrogen) {
    this.hydrogen = hydrogen;
  },

  async example() {
    const kernel = this.hydrogen.getActiveKernel();
    const result = await kernel.execute("print('Hello')");
    console.log(result.status); // 'ok' or 'error'
  }
};

HydrogenProvider Methods

Method	Description
getActiveKernel()	Get the kernel for the active editor
onDidChangeKernel(callback)	Subscribe to kernel changes
getCellRange(editor)	Get the current cell range

HydrogenKernel API

Execution

Method	Description
execute(code)	Execute code, returns Promise<{status, outputs, error}>
executeWithCallback(code, callback)	Execute with streaming callback

State & Control

Property/Method	Description
executionState	Current state: 'idle', 'busy', 'starting'
executionCount	Current execution count
lastExecutionTime	Last execution time string (e.g., "1.23s")
onDidChangeExecutionState(callback)	Subscribe to state changes, returns Disposable
interrupt()	Interrupt running execution
restart([callback])	Restart the kernel
shutdown()	Shutdown the kernel

Introspection

Method	Description
complete(code)	Get completions, returns Promise<{matches, ...}>
inspect(code, cursorPos)	Get documentation, returns Promise<{data, found}>

Kernel Info

Property/Method	Description
language	Kernel language (e.g., "python")
displayName	Kernel display name (e.g., "Python 3")
kernelSpec	Full kernel spec object
getConnectionFile()	Path to kernel connection file

Events & Middleware

Method	Description
onDidDestroy(callback)	Called when kernel is destroyed
addMiddleware(middleware)	Add execution middleware

Example: Execute and Handle Results

async function runCode(hydrogen) {
  const kernel = hydrogen.getActiveKernel();

  // Simple execution
  const result = await kernel.execute("x = 42\nprint(x)");

  if (result.status === "ok") {
    console.log("Outputs:", result.outputs);
  } else {
    console.error(`${result.error.ename}: ${result.error.evalue}`);
  }

  // Monitor state
  const disposable = kernel.onDidChangeExecutionState((state) => {
    console.log("Kernel state:", state);
  });

  // Get completions
  const completions = await kernel.complete("import nu");
  console.log(completions.matches); // ['numpy', 'numbers', ...]

  // Cleanup
  disposable.dispose();
}

Contributing

Got ideas to make this package better, found a bug, or want to help add new features? Just drop your thoughts on GitHub — any feedback's welcome!