[BUG] inc affects the inputed SemVer object.

[louis-bompart]

What / Why

inc when called with an instance of SemVer will affect the provided SemVer object (if no opts are given, see Steps to Reproduce). This leads to unexpected behaviour for a function that could be expected to be pure.

When

• n/a

Where

• n/a

How

Current Behavior

inc will do the operation on the SemVer object provided in parameters, except if semver is created with loose or includePrereleaseSemVer.

Steps to Reproduce

const { SemVer, inc } = require("semver");
const { equal } = require("assert");

const initalStrVer = "1.0.0";
const initialSemver = new SemVer(initalStrVer);
const looseSemver = new SemVer(initalStrVer, { loose: true });
const includePrereleaseSemVer = new SemVer(initalStrVer, {
  includePrerelease: true,
});

inc(initialSemver, "minor");
inc(looseSemver, "minor");
inc(includePrereleaseSemVer, "minor");
inc(initalStrVer, "minor");

equal(initalStrVer, looseSemver.version); // ✔️  Pass
equal(initalStrVer, includePrereleaseSemVer.version); // ✔️ Pass
equal(initalStrVer, initialSemver.version); // ❌ AssertionError [ERR_ASSERTION]: '1.0.0' == '1.1.0'

Expected Behavior

inc should never modify the provided SemVer object.

Who

• n/a

References

• Related to [ENHANCEMENT] add ability to clone a semver instance #378