Proper echo context handling

[pearmini]

function add(a, b) {
  return echo(a + b);
}

// Transpile to:
const __cellEcho__ = __getEcho__();
function add(a, b) {
  const echo = __getEcho__() || __cellEcho__;
  return echo(a + b);
}

function add(a, b) {
  return setTimeout(() => echo(a + b));
}

// Transpile to:
const __cellEcho__ = __getEcho__();
function add(a, b) {
  const echo = __getEcho__() || __cellEcho__;
  return setTimeout(() => {
    if(__getEcho__()) { 
      const echo = __getEcho__();
      return echo(a + b) 
    };
    return echo(a + b);
  });
}

function adder(x, y) {
  return () => echo(x + y);
}

// Transpile to:
const __cellEcho__ = __getEcho__();
function adder(x, y) {
  const echo = __getEcho__() || __cellEcho__;
  return () => {
    if(__getEcho__()) { 
      const echo = __getEcho__();
      return echo(a + b);
    }
    return echo(a + b);
  }
}

setTimeout(() => echo(a + b));

// Transpile to:
const __cellEcho__ = __getEcho__();
setTimeout(() => {
  const echo = __getEcho__() || __cellEcho__;
  return echo(a + b);
});

• clear -> echo.clear()

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Project	Deployment	Preview	Comments	Updated (UTC)
recho-notebook	Ready	Preview	Comment	Oct 27, 2025 7:57pm

[Copilot]

Pull Request Overview

This PR implements proper echo context handling to ensure that echo calls within functions output to the executing cell rather than the cell where the function was defined. This addresses issues with nested functions, async callbacks, and functions passed as arguments.

Key Changes:

• Introduces a transpilation system that rewrites function bodies to capture and manage echo context
• Migrates from standalone clear() function to echo.clear() method for API consistency
• Adds comprehensive test coverage for various echo usage patterns (functions, classes, recursion, async operations)

Reviewed Changes

Copilot reviewed 31 out of 35 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
runtime/transpile.js	New transpiler that rewrites echo calls in functions to handle context properly
runtime/sourcemap.js	New source mapping utility for code transformations
runtime/index.js	Updated runtime to integrate transpiler and manage echo context with __getEcho__/__setEcho__
test/transile.spec.js	New test validating transpiler output for block statements
test/js/*.js	New test fixtures for various echo usage patterns
test/output/*.js	Expected output files for test cases
app/docs/*.recho.js	Updated documentation examples to use echo.clear()
editor/completion.js	Updated autocomplete to suggest echo.clear()
runtime/stdlib/index.js	Fixed import path for controls
test/stdlib.spec.js	Fixed import path for stdlib
package.json	Added acorn-walk dependency
LICENCE	Added license notice for Observable Notebook Kit

Files not reviewed (1)

• pnpm-lock.yaml: Language not supported

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