spdx-expression-validate

This package is refreshingly straightforward. The API is dead simple: pass a string to the validate function and get back an array of validation problems (empty array means valid). No configuration, no ceremony. I've used it in several projects for validating package.json license fields and it just works.

The error messages are clear and specific, pointing out exactly what's wrong with malformed expressions like 'MIT + Apache' (should be 'OR' not '+'). It correctly handles complex expressions with parentheses and compound operators. The one gotcha I hit was that it only validates syntax, not whether license identifiers actually exist in the SPDX list - you'll need spdx-correct or spdx-expression-parse for that.

Documentation is minimal but sufficient since the API surface is tiny. The README gives you everything you need in about 30 seconds of reading. No Stack Overflow presence to speak of, but honestly, you won't need it. The package hasn't been updated since 2019, but SPDX expression syntax is stable, so this isn't concerning for this particular use case.

This package is extremely straightforward to use - you literally call one function with a string and get back an array of validation problems (or an empty array if valid). The learning curve is essentially zero. I integrated it into a license compliance tool in about 5 minutes, including reading the (admittedly sparse) README. The function returns structured error objects with `message` and `offset` properties, making it trivial to display helpful feedback to users.

The error messages are clear and actionable, like "EMPTY PARENTHESES" or "UNKNOWN LICENSE". When debugging license expression parsing issues, the offset property tells you exactly where things went wrong. It correctly handles all the SPDX 2.0 operators (AND, OR, WITH) and catches malformed expressions like unbalanced parentheses or double operators.

The main limitation is lack of examples beyond the basic usage in the README. There's no guidance on integrating with build systems or handling edge cases. The package hasn't been updated since 2019, but SPDX expression syntax is stable, so this isn't really a concern for day-to-day use.

This package is refreshingly straightforward - you pass a string, it returns an array of error objects or an empty array if valid. The API is literally one function that validates SPDX license expressions like 'MIT', 'Apache-2.0 OR GPL-3.0', and complex expressions with parentheses. There's essentially no learning curve; I had it working in under a minute without reading docs.

Error messages are practical and specific, pointing to exact positions in the string where validation fails. When you mess up parentheses or use invalid operators, you get messages like 'Expected AND, OR, or WITH' with offset information. This makes debugging user input straightforward. The package handles all the nuances of SPDX expression syntax including the WITH operator for license exceptions.

The main limitation is that it only validates syntax, not whether license IDs are actually valid SPDX identifiers. You'd need spdx-expression-parse or spdx-correct for that. Documentation is minimal but honestly sufficient given the simplicity. The package hasn't been updated since 2019, but SPDX expression syntax is stable, so this isn't concerning for this specific use case.