sverweij/semver-try-require

Note

DEPRECATION NOTICE

version 7 is the last version of semver-try-require.

semver-try-require was created for dependency-cruiser, which now
incorporates semver-try-require's functionality. Looking at download stats
dependency-cruiser was the only dependent of semver-try-require - this means
semver-try-require is no longer needed and will go on a deprecation path.

As of 2024-06-28:
- it will no longer be possible to file issues
- pull requests on the repo will no longer be accepted
- the package will stop getting regular updates (functionality and bug fixes)
- as it is still used in older versions of dependency-cruiser, that still
  have a significant number of downloads it will still get security updates
  on its 3rd party dependencies (as this only uses semver this shouldn't be
  a big deal) or on itself.
As of 2024-12-28 (6 months later):
provided the number of downloads on the older versions of dependency-cruiser
that still use this package has dropped to an acceptable level:
- the repository will be archived
- the package will stop getting security updates
- this README will be updated to reflect the two facts above

What was this then?

A micro module that helped you require or import (versions of) modules
that might not be there.

Useful to test for the availability of optional and peer dependencies
before working with them.

Examples

See ESM below if you're using this in an ESM only context.

Commonjs

So you made the typescript compiler (v2) an optional dependency.
But you just want to keep running if it ain't there.

Do this:

const tryRequire = require("semver-try-require");

// import typescript if there's a version >= 2 available
const typescript = tryRequire("typescript", ">=2");

// now you can test if typescript is actually there
const lProgram = "const cube = x => x*x*x; console.log(cube(42))";

if (typescript !== false) {
  console.log(typescript.transpileModule(lProgram, {}).outputText);
  // Result:
  //   var cube = function (x) { return x * x * x; };
  //   console.log(cube(42));
} else {
  // typescript >=2 not found - use fallback
  console.log(lProgram);
  // Result:
  //    const cube = x => x*x*x; console.log(cube(42))
}

ESM

In ESM it's almost the same, except there dynamic imports are always
asynchronous, so you'll have to await it (or use promises):

import tryImport from "semver-try-require";

// import typescript if there's a version >= 5 available.
const typescript = await tryImport("typescript", >=5);

// now you can test if typescript is actually there
const lProgram = "const cube = x => x*x*x; console.log(cube(42))";

if (typescript !== false) {
  console.log(typescript.transpileModule(lProgram, {}).outputText);
  // Result:
  //   var cube = function (x) { return x * x * x; };
  //   console.log(cube(42));
} else {
  // typescript >=5 not found - use fallback
  console.log(lProgram);
  // Result:
  //    const cube = x => x*x*x; console.log(cube(42))
}

History

This module started to try a few non-run-of-the-mill things with the
npm registry (deprecate, beta publishing, renaming). The tryRequire
function in
dependency-cruiser
seemed like a good candidate as it was not a thing that'd be unique
to dependency-cruiser, and would probably be easier to maintain on its
own anyway.

dependency-cruiser
used to use semver-try-require in its transpiler wrappers
and it enabled it to cruise typescript, coffeescript and livescript
code without having to ship the heavy duty compilers for these
languages.

These days dependency-cruiser has embedded this functionality in its
codebase to simplify maintenance.