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// Copyright 2018 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.
// Pseudo-versions
//
// Code authors are expected to tag the revisions they want users to use,
// including prereleases. However, not all authors tag versions at all,
// and not all commits a user might want to try will have tags.
// A pseudo-version is a version with a special form that allows us to
// address an untagged commit and order that version with respect to
// other versions we might encounter.
//
// A pseudo-version takes one of the general forms:
//
// (1) vX.0.0-yyyymmddhhmmss-abcdef123456
// (2) vX.Y.(Z+1)-0.yyyymmddhhmmss-abcdef123456
// (3) vX.Y.(Z+1)-0.yyyymmddhhmmss-abcdef123456+incompatible
// (4) vX.Y.Z-pre.0.yyyymmddhhmmss-abcdef123456
// (5) vX.Y.Z-pre.0.yyyymmddhhmmss-abcdef123456+incompatible
//
// If there is no recently tagged version with the right major version vX,
// then form (1) is used, creating a space of pseudo-versions at the bottom
// of the vX version range, less than any tagged version, including the unlikely v0.0.0.
//
// If the most recent tagged version before the target commit is vX.Y.Z or vX.Y.Z+incompatible,
// then the pseudo-version uses form (2) or (3), making it a prerelease for the next
// possible semantic version after vX.Y.Z. The leading 0 segment in the prerelease string
// ensures that the pseudo-version compares less than possible future explicit prereleases
// like vX.Y.(Z+1)-rc1 or vX.Y.(Z+1)-1.
//
// If the most recent tagged version before the target commit is vX.Y.Z-pre or vX.Y.Z-pre+incompatible,
// then the pseudo-version uses form (4) or (5), making it a slightly later prerelease.
package module
import (
"errors"
"fmt"
"strings"
"time"
"golang.org/x/mod/internal/lazyregexp"
"golang.org/x/mod/semver"
)
var pseudoVersionRE = lazyregexp.New(`^v[0-9]+\.(0\.0-|\d+\.\d+-([^+]*\.)?0\.)\d{14}-[A-Za-z0-9]+(\+[0-9A-Za-z-]+(\.[0-9A-Za-z-]+)*)?$`)
const PseudoVersionTimestampFormat = "20060102150405"
// PseudoVersion returns a pseudo-version for the given major version ("v1")
// preexisting older tagged version ("" or "v1.2.3" or "v1.2.3-pre"), revision time,
// and revision identifier (usually a 12-byte commit hash prefix).
func PseudoVersion(major, older string, t time.Time, rev string) string {
if major == "" {
major = "v0"
}
segment := fmt.Sprintf("%s-%s", t.UTC().Format(PseudoVersionTimestampFormat), rev)
build := semver.Build(older)
older = semver.Canonical(older)
if older == "" {
return major + ".0.0-" + segment // form (1)
}
if semver.Prerelease(older) != "" {
return older + ".0." + segment + build // form (4), (5)
}
// Form (2), (3).
// Extract patch from vMAJOR.MINOR.PATCH
i := strings.LastIndex(older, ".") + 1
v, patch := older[:i], older[i:]
// Reassemble.
return v + incDecimal(patch) + "-0." + segment + build
}
// ZeroPseudoVersion returns a pseudo-version with a zero timestamp and
// revision, which may be used as a placeholder.
func ZeroPseudoVersion(major string) string {
return PseudoVersion(major, "", time.Time{}, "000000000000")
}
// incDecimal returns the decimal string incremented by 1.
func incDecimal(decimal string) string {
// Scan right to left turning 9s to 0s until you find a digit to increment.
digits := []byte(decimal)
i := len(digits) - 1
for ; i >= 0 && digits[i] == '9'; i-- {
digits[i] = '0'
}
if i >= 0 {
digits[i]++
} else {
// digits is all zeros
digits[0] = '1'
digits = append(digits, '0')
}
return string(digits)
}
// decDecimal returns the decimal string decremented by 1, or the empty string
// if the decimal is all zeroes.
func decDecimal(decimal string) string {
// Scan right to left turning 0s to 9s until you find a digit to decrement.
digits := []byte(decimal)
i := len(digits) - 1
for ; i >= 0 && digits[i] == '0'; i-- {
digits[i] = '9'
}
if i < 0 {
// decimal is all zeros
return ""
}
if i == 0 && digits[i] == '1' && len(digits) > 1 {
digits = digits[1:]
} else {
digits[i]--
}
return string(digits)
}
// IsPseudoVersion reports whether v is a pseudo-version.
func IsPseudoVersion(v string) bool {
return strings.Count(v, "-") >= 2 && semver.IsValid(v) && pseudoVersionRE.MatchString(v)
}
// IsZeroPseudoVersion returns whether v is a pseudo-version with a zero base,
// timestamp, and revision, as returned by ZeroPseudoVersion.
func IsZeroPseudoVersion(v string) bool {
return v == ZeroPseudoVersion(semver.Major(v))
}
// PseudoVersionTime returns the time stamp of the pseudo-version v.
// It returns an error if v is not a pseudo-version or if the time stamp
// embedded in the pseudo-version is not a valid time.
func PseudoVersionTime(v string) (time.Time, error) {
_, timestamp, _, _, err := parsePseudoVersion(v)
if err != nil {
return time.Time{}, err
}
t, err := time.Parse("20060102150405", timestamp)
if err != nil {
return time.Time{}, &InvalidVersionError{
Version: v,
Pseudo: true,
Err: fmt.Errorf("malformed time %q", timestamp),
}
}
return t, nil
}
// PseudoVersionRev returns the revision identifier of the pseudo-version v.
// It returns an error if v is not a pseudo-version.
func PseudoVersionRev(v string) (rev string, err error) {
_, _, rev, _, err = parsePseudoVersion(v)
return
}
// PseudoVersionBase returns the canonical parent version, if any, upon which
// the pseudo-version v is based.
//
// If v has no parent version (that is, if it is "vX.0.0-[…]"),
// PseudoVersionBase returns the empty string and a nil error.
func PseudoVersionBase(v string) (string, error) {
base, _, _, build, err := parsePseudoVersion(v)
if err != nil {
return "", err
}
switch pre := semver.Prerelease(base); pre {
case "":
// vX.0.0-yyyymmddhhmmss-abcdef123456 → ""
if build != "" {
// Pseudo-versions of the form vX.0.0-yyyymmddhhmmss-abcdef123456+incompatible
// are nonsensical: the "vX.0.0-" prefix implies that there is no parent tag,
// but the "+incompatible" suffix implies that the major version of
// the parent tag is not compatible with the module's import path.
//
// There are a few such entries in the index generated by proxy.golang.org,
// but we believe those entries were generated by the proxy itself.
return "", &InvalidVersionError{
Version: v,
Pseudo: true,
Err: fmt.Errorf("lacks base version, but has build metadata %q", build),
}
}
return "", nil
case "-0":
// vX.Y.(Z+1)-0.yyyymmddhhmmss-abcdef123456 → vX.Y.Z
// vX.Y.(Z+1)-0.yyyymmddhhmmss-abcdef123456+incompatible → vX.Y.Z+incompatible
base = strings.TrimSuffix(base, pre)
i := strings.LastIndexByte(base, '.')
if i < 0 {
panic("base from parsePseudoVersion missing patch number: " + base)
}
patch := decDecimal(base[i+1:])
if patch == "" {
// vX.0.0-0 is invalid, but has been observed in the wild in the index
// generated by requests to proxy.golang.org.
//
// NOTE(bcmills): I cannot find a historical bug that accounts for
// pseudo-versions of this form, nor have I seen such versions in any
// actual go.mod files. If we find actual examples of this form and a
// reasonable theory of how they came into existence, it seems fine to
// treat them as equivalent to vX.0.0 (especially since the invalid
// pseudo-versions have lower precedence than the real ones). For now, we
// reject them.
return "", &InvalidVersionError{
Version: v,
Pseudo: true,
Err: fmt.Errorf("version before %s would have negative patch number", base),
}
}
return base[:i+1] + patch + build, nil
default:
// vX.Y.Z-pre.0.yyyymmddhhmmss-abcdef123456 → vX.Y.Z-pre
// vX.Y.Z-pre.0.yyyymmddhhmmss-abcdef123456+incompatible → vX.Y.Z-pre+incompatible
if !strings.HasSuffix(base, ".0") {
panic(`base from parsePseudoVersion missing ".0" before date: ` + base)
}
return strings.TrimSuffix(base, ".0") + build, nil
}
}
var errPseudoSyntax = errors.New("syntax error")
func parsePseudoVersion(v string) (base, timestamp, rev, build string, err error) {
if !IsPseudoVersion(v) {
return "", "", "", "", &InvalidVersionError{
Version: v,
Pseudo: true,
Err: errPseudoSyntax,
}
}
build = semver.Build(v)
v = strings.TrimSuffix(v, build)
j := strings.LastIndex(v, "-")
v, rev = v[:j], v[j+1:]
i := strings.LastIndex(v, "-")
if j := strings.LastIndex(v, "."); j > i {
base = v[:j] // "vX.Y.Z-pre.0" or "vX.Y.(Z+1)-0"
timestamp = v[j+1:]
} else {
base = v[:i] // "vX.0.0"
timestamp = v[i+1:]
}
return base, timestamp, rev, build, nil
}