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yt-dlp-ejs can be built using multiple JavaScript runtimes: Deno, Bun, Node.js, or pnpm. The build process compiles TypeScript source files into bundled JavaScript using Rollup.

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Build Requirements

Before building, you need:
  • Python 3.10+ with pip
  • One of the following JavaScript runtimes:
    • Deno 2.0.0+
    • Bun 1.0.31+
    • Node.js 20.0+ with npm
    • pnpm 10+
The build system automatically detects and uses any available JavaScript runtime. You only need one runtime installed.

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Quick Build with hatch_build.py

The simplest way to build is using the hatch_build.py script, which automatically selects an available runtime: 
python hatch_build.py
This script will:
  1. Detect available JavaScript runtimes (pnpm, Deno, Bun, or npm/Node)
  2. Install dependencies
  3. Run the bundle script
  4. Generate JavaScript files in the dist/ directory
If you only have Python and a JS runtime, hatch_build.py is the recommended approach. It transparently invokes one of the supported runtimes.

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Building with Specific Runtimes

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Building with Deno

1

Install dependencies

deno install --frozen
The --frozen flag ensures the lockfile is used without modifications.
2

Run the bundle script

deno task bundle
This executes the bundle script defined in package.json, which runs Rollup.

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Building with Bun

1

Install dependencies

bun install --frozen-lockfile
2

Run the bundle script

bun --bun run bundle
The --bun flag ensures Bun’s native runtime is used.

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Building with Node.js

1

Install dependencies

npm ci
Use npm ci for reproducible builds from the lockfile.
2

Run the bundle script

npm run bundle

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Building with pnpm

1

Install dependencies

pnpm install --frozen-lockfile
2

Run the bundle script

pnpm run bundle

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Building the Python Package

To build the complete Python package with bundled JavaScript: 
python -m pip install -U build
python -m build
This creates:
  • Source distribution (tar.gz) in dist/
  • Wheel (.whl) in dist/
The build hook automatically invokes deno, bun, or node as required to bundle the JavaScript before packaging.
The Python package uses a PEP 518-compatible build system with hatchling. The build hook in hatch_build.py automatically bundles JavaScript during the build process.

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Using Rollup Directly

You can also invoke Rollup directly if you have dependencies installed: 
rollup -c
This uses the configuration in rollup.config.js to generate all build outputs.

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Build Outputs

The build process generates multiple JavaScript files in the dist/ directory:

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Core Solver Files

  • yt.solver.core.js - Unminified IIFE bundle for debugging
  • yt.solver.core.min.js - Minified IIFE bundle for production

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Library Files

  • yt.solver.lib.js - Unminified library build
  • yt.solver.lib.min.js - Minified library build

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Runtime-Specific Libraries

  • yt.solver.deno.lib.js - Deno-specific build with npm: imports
  • yt.solver.bun.lib.js - Bun-specific build
Each output file:
  • Uses Sucrase to transpile TypeScript
  • Includes license headers with bundled dependency information
  • Is processed with Terser (minified versions remove comments and optimize)
  • Is formatted with Prettier (non-minified versions)
  • Has its SHA3-512 hash printed during build
The build configuration in rollup.config.js defines separate outputs for different target formats (IIFE and ES modules).

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Build Artifacts in Python Package

When building the Python package, only the minified files are included:
  • yt_dlp_ejs/yt/solver/core.min.js
  • yt_dlp_ejs/yt/solver/lib.min.js
You can verify package contents: 
# For wheel
unzip -l dist/yt_dlp_ejs-*.whl

# For source distribution
tar -tvzf dist/yt_dlp_ejs-*.tar.gz

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Verifying Build Consistency

If you notice differences between builds from different runtimes, please open an issue.
All supported runtimes should produce identical output. The CI system verifies this by:
  1. Building with Deno as the control
  2. Generating SHA-256 hashes of all outputs
  3. Building with pnpm, Bun, and Node
  4. Comparing hashes to ensure consistency

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Troubleshooting

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”No suitable JavaScript runtime found”

This error occurs when hatch_build.py cannot find any supported runtime. Install one of:
  • Deno (deno --version)
  • Bun (bun --version)
  • Node.js (node --version)
  • pnpm (pnpm --version)

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Lockfile Errors

Always use the frozen lockfile flags:
  • Deno: --frozen
  • Bun: --frozen-lockfile
  • pnpm: --frozen-lockfile
  • npm: use npm ci instead of npm install
See Upgrading Packages for information on updating lockfiles.

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