semver-try-require

What's this then?

A micro module that helps 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. I named it tigerclaws-try-require until I realized the semver check was what distinguished it from the other try-require like npm modules out there.

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

License

MIT

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