func comparePrerelease()

in semver/semver.go [333:393]
47 lines of code
14 McCabe index (conditional complexity)

func comparePrerelease(x, y string) int {
	// "When major, minor, and patch are equal, a pre-release version has
	// lower precedence than a normal version.
	// Example: 1.0.0-alpha < 1.0.0.
	// Precedence for two pre-release versions with the same major, minor,
	// and patch version MUST be determined by comparing each dot separated
	// identifier from left to right until a difference is found as follows:
	// identifiers consisting of only digits are compared numerically and
	// identifiers with letters or hyphens are compared lexically in ASCII
	// sort order. Numeric identifiers always have lower precedence than
	// non-numeric identifiers. A larger set of pre-release fields has a
	// higher precedence than a smaller set, if all of the preceding
	// identifiers are equal.
	// Example: 1.0.0-alpha < 1.0.0-alpha.1 < 1.0.0-alpha.beta <
	// 1.0.0-beta < 1.0.0-beta.2 < 1.0.0-beta.11 < 1.0.0-rc.1 < 1.0.0."
	if x == y {
		return 0
	}
	if x == "" {
		return +1
	}
	if y == "" {
		return -1
	}
	for x != "" && y != "" {
		x = x[1:] // skip - or .
		y = y[1:] // skip - or .
		var dx, dy string
		dx, x = nextIdent(x)
		dy, y = nextIdent(y)
		if dx != dy {
			ix := isNum(dx)
			iy := isNum(dy)
			if ix != iy {
				if ix {
					return -1
				} else {
					return +1
				}
			}
			if ix {
				if len(dx) < len(dy) {
					return -1
				}
				if len(dx) > len(dy) {
					return +1
				}
			}
			if dx < dy {
				return -1
			} else {
				return +1
			}
		}
	}
	if x == "" {
		return -1
	} else {
		return +1
	}
}