src

gover.go (4297B)

---

 // Copyright 2023 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
 // This is a fork of internal/gover for use by x/tools until
 // go1.21 and earlier are no longer supported by x/tools.
 
 package versions
 
 import "strings"
 
 // A gover is a parsed Go gover: major[.Minor[.Patch]][kind[pre]]
 // The numbers are the original decimal strings to avoid integer overflows
 // and since there is very little actual math. (Probably overflow doesn't matter in practice,
 // but at the time this code was written, there was an existing test that used
 // go1.99999999999, which does not fit in an int on 32-bit platforms.
 // The "big decimal" representation avoids the problem entirely.)
 type gover struct {
 	major string // decimal
 	minor string // decimal or ""
 	patch string // decimal or ""
 	kind  string // "", "alpha", "beta", "rc"
 	pre   string // decimal or ""
 }
 
 // compare returns -1, 0, or +1 depending on whether
 // x < y, x == y, or x > y, interpreted as toolchain versions.
 // The versions x and y must not begin with a "go" prefix: just "1.21" not "go1.21".
 // Malformed versions compare less than well-formed versions and equal to each other.
 // The language version "1.21" compares less than the release candidate and eventual releases "1.21rc1" and "1.21.0".
 func compare(x, y string) int {
 	vx := parse(x)
 	vy := parse(y)
 
 	if c := cmpInt(vx.major, vy.major); c != 0 {
 		return c
 	}
 	if c := cmpInt(vx.minor, vy.minor); c != 0 {
 		return c
 	}
 	if c := cmpInt(vx.patch, vy.patch); c != 0 {
 		return c
 	}
 	if c := strings.Compare(vx.kind, vy.kind); c != 0 { // "" < alpha < beta < rc
 		return c
 	}
 	if c := cmpInt(vx.pre, vy.pre); c != 0 {
 		return c
 	}
 	return 0
 }
 
 // lang returns the Go language version. For example, lang("1.2.3") == "1.2".
 func lang(x string) string {
 	v := parse(x)
 	if v.minor == "" || v.major == "1" && v.minor == "0" {
 		return v.major
 	}
 	return v.major + "." + v.minor
 }
 
 // isValid reports whether the version x is valid.
 func isValid(x string) bool {
 	return parse(x) != gover{}
 }
 
 // parse parses the Go version string x into a version.
 // It returns the zero version if x is malformed.
 func parse(x string) gover {
 	var v gover
 
 	// Parse major version.
 	var ok bool
 	v.major, x, ok = cutInt(x)
 	if !ok {
 		return gover{}
 	}
 	if x == "" {
 		// Interpret "1" as "1.0.0".
 		v.minor = "0"
 		v.patch = "0"
 		return v
 	}
 
 	// Parse . before minor version.
 	if x[0] != '.' {
 		return gover{}
 	}
 
 	// Parse minor version.
 	v.minor, x, ok = cutInt(x[1:])
 	if !ok {
 		return gover{}
 	}
 	if x == "" {
 		// Patch missing is same as "0" for older versions.
 		// Starting in Go 1.21, patch missing is different from explicit .0.
 		if cmpInt(v.minor, "21") < 0 {
 			v.patch = "0"
 		}
 		return v
 	}
 
 	// Parse patch if present.
 	if x[0] == '.' {
 		v.patch, x, ok = cutInt(x[1:])
 		if !ok || x != "" {
 			// Note that we are disallowing prereleases (alpha, beta, rc) for patch releases here (x != "").
 			// Allowing them would be a bit confusing because we already have:
 			//	1.21 < 1.21rc1
 			// But a prerelease of a patch would have the opposite effect:
 			//	1.21.3rc1 < 1.21.3
 			// We've never needed them before, so let's not start now.
 			return gover{}
 		}
 		return v
 	}
 
 	// Parse prerelease.
 	i := 0
 	for i < len(x) && (x[i] < '0' || '9' < x[i]) {
 		if x[i] < 'a' || 'z' < x[i] {
 			return gover{}
 		}
 		i++
 	}
 	if i == 0 {
 		return gover{}
 	}
 	v.kind, x = x[:i], x[i:]
 	if x == "" {
 		return v
 	}
 	v.pre, x, ok = cutInt(x)
 	if !ok || x != "" {
 		return gover{}
 	}
 
 	return v
 }
 
 // cutInt scans the leading decimal number at the start of x to an integer
 // and returns that value and the rest of the string.
 func cutInt(x string) (n, rest string, ok bool) {
 	i := 0
 	for i < len(x) && '0' <= x[i] && x[i] <= '9' {
 		i++
 	}
 	if i == 0 || x[0] == '0' && i != 1 { // no digits or unnecessary leading zero
 		return "", "", false
 	}
 	return x[:i], x[i:], true
 }
 
 // cmpInt returns cmp.Compare(x, y) interpreting x and y as decimal numbers.
 // (Copied from golang.org/x/mod/semver's compareInt.)
 func cmpInt(x, y string) int {
 	if x == y {
 		return 0
 	}
 	if len(x) < len(y) {
 		return -1
 	}
 	if len(x) > len(y) {
 		return +1
 	}
 	if x < y {
 		return -1
 	} else {
 		return +1
 	}
 }