pip-requirements-js

pip-requirements-js

A pure JavaScript/TypeScript parser for pip requirements files. Process requirements.txt, constraints.txt, or pip-tools' requirements.in – all without ever leaving JavaScript.

pip-requirements-js strictly adheres to pip's documentation of the requirements file format, along with PEP 508 – Dependency specification for Python Software Packages. You can sleep well knowing that no dependency will be misinterpreted (if that ever keeps you up at night).

API

Full extraction

Full extractions means complete requirement info, such as spec-conforming version constraints and complete validation of the environment marker tree.

To extract all the requirements from a given file, use

parsePipRequirementsFile(fileContent: string): Requirement[]

To extract a requirement from a given line, use

parsePipRequirementsLine(lineContent: string): Requirement | null

(null is returned for lines validly lacking a requirement, e.g. empty or comment-only)

Both functions also accept an optional options parameter with includeLocations: true to get source location information:

parsePipRequirementsFile(fileContent: string, options: { includeLocations: true }): WithLocation<Requirement>[]
parsePipRequirementsLine(lineContent: string, options: { includeLocations: true }): WithLocation<Requirement> | null

The WithLocation<T> wrapper includes data (the parsed requirement) and location (with startIdx and endIdx indicating the character positions in the source).

In both cases a RequirementsSyntaxError will be thrown if the provided content contains invalid syntax.

To make use of the resulting data, look up what Requirement is made up of in types.ts.

Loose extraction

There is also a loose mode, which is oriented for processing partially-written requirements. This is useful when handling live code editor input.

parsePipRequirementsFileLoosely and parsePipRequirementsLineLoosely work the same as their full versions, except they return LooseProjectNameRequirement in place of Requirement. This means that URL-based requirements are skipped, as are requirements/constraints files.

The loose parsing functions also support the includeLocations option:

parsePipRequirementsFileLoosely(fileContent: string, options: { includeLocations: true }): WithLocation<LooseProjectNameRequirement>[]
parsePipRequirementsLineLoosely(lineContent: string, options: { includeLocations: true }): WithLocation<LooseProjectNameRequirement> | null

Internals

pip-requirements-js is built with the robust parser generator Ohm.js – the core of this library is the pep-508.ohm grammar, which is an Ohm port of PEP 508's complete dependency specification grammar (originally defined for Parsley), with some pip-specific additions (such as the -r extra-requirements.txt syntax). This ensures the greatest possible compatibility with what pip itself does.

But why?

Well, I built this to power my other side project, the VS Code extension PyPI Assistant. Give that a try too!

Changelog

1.0.2 (2025-09-17)

Bug Fixes

• Standardize WithLocation typing (79a8266)