semver: Index | Files

package semver

import ""

Package semver provides the ability to work with Semantic Versions ( in Go.

Specifically it provides the ability to:

* Parse semantic versions
* Sort semantic versions
* Check if a semantic version fits within a set of constraints
* Optionally work with a `v` prefix

Parsing Semantic Versions

There are two functions that can parse semantic versions. The `StrictNewVersion` function only parses valid version 2 semantic versions as outlined in the specification. The `NewVersion` function attempts to coerce a version into a semantic version and parse it. For example, if there is a leading v or a version listed without all 3 parts (e.g. 1.2) it will attempt to coerce it into a valid semantic version (e.g., 1.2.0). In both cases a `Version` object is returned that can be sorted, compared, and used in constraints.

When parsing a version an optional error can be returned if there is an issue parsing the version. For example,

v, err := semver.NewVersion("1.2.3-beta.1+b345")

The version object has methods to get the parts of the version, compare it to other versions, convert the version back into a string, and get the original string. For more details please see the documentation at

Sorting Semantic Versions

A set of versions can be sorted using the `sort` package from the standard library. For example,

    raw := []string{"1.2.3", "1.0", "1.3", "2", "0.4.2",}
    vs := make([]*semver.Version, len(raw))
	for i, r := range raw {
		v, err := semver.NewVersion(r)
		if err != nil {
			t.Errorf("Error parsing version: %s", err)

		vs[i] = v


Checking Version Constraints and Comparing Versions

There are two methods for comparing versions. One uses comparison methods on `Version` instances and the other is using Constraints. There are some important differences to notes between these two methods of comparison.

1. When two versions are compared using functions such as `Compare`, `LessThan`,

and others it will follow the specification and always include prereleases
within the comparison. It will provide an answer valid with the comparison
spec section at

2. When constraint checking is used for checks or validation it will follow a

different set of rules that are common for ranges with tools like npm/js
and Rust/Cargo. This includes considering prereleases to be invalid if the
ranges does not include on. If you want to have it include pre-releases a
simple solution is to include `-0` in your range.

3. Constraint ranges can have some complex rules including the shorthard use of

~ and ^. For more details on those see the options below.

There are differences between the two methods or checking versions because the comparison methods on `Version` follow the specification while comparison ranges are not part of the specification. Different packages and tools have taken it upon themselves to come up with range rules. This has resulted in differences. For example, npm/js and Cargo/Rust follow similar patterns which PHP has a different pattern for ^. The comparison features in this package follow the npm/js and Cargo/Rust lead because applications using it have followed similar patters with their versions.

Checking a version against version constraints is one of the most featureful parts of the package.

c, err := semver.NewConstraint(">= 1.2.3")
if err != nil {
    // Handle constraint not being parsable.

v, err := semver.NewVersion("1.3")
if err != nil {
    // Handle version not being parsable.
// Check if the version meets the constraints. The a variable will be true.
a := c.Check(v)

Basic Comparisons

There are two elements to the comparisons. First, a comparison string is a list of comma or space separated AND comparisons. These are then separated by || (OR) comparisons. For example, `">= 1.2 < 3.0.0 || >= 4.2.3"` is looking for a comparison that's greater than or equal to 1.2 and less than 3.0.0 or is greater than or equal to 4.2.3. This can also be written as `">= 1.2, < 3.0.0 || >= 4.2.3"`

The basic comparisons are:

* `=`: equal (aliased to no operator)
* `!=`: not equal
* `>`: greater than
* `<`: less than
* `>=`: greater than or equal to
* `<=`: less than or equal to

Hyphen Range Comparisons

There are multiple methods to handle ranges and the first is hyphens ranges. These look like:

* `1.2 - 1.4.5` which is equivalent to `>= 1.2, <= 1.4.5`
* `2.3.4 - 4.5` which is equivalent to `>= 2.3.4 <= 4.5`

Wildcards In Comparisons

The `x`, `X`, and `*` characters can be used as a wildcard character. This works for all comparison operators. When used on the `=` operator it falls back to the tilde operation. For example,

* `1.2.x` is equivalent to `>= 1.2.0 < 1.3.0`
* `>= 1.2.x` is equivalent to `>= 1.2.0`
* `<= 2.x` is equivalent to `<= 3`
* `*` is equivalent to `>= 0.0.0`

Tilde Range Comparisons (Patch)

The tilde (`~`) comparison operator is for patch level ranges when a minor version is specified and major level changes when the minor number is missing. For example,

* `~1.2.3` is equivalent to `>= 1.2.3 < 1.3.0`
* `~1` is equivalent to `>= 1, < 2`
* `~2.3` is equivalent to `>= 2.3 < 2.4`
* `~1.2.x` is equivalent to `>= 1.2.0 < 1.3.0`
* `~1.x` is equivalent to `>= 1 < 2`

Caret Range Comparisons (Major)

The caret (`^`) comparison operator is for major level changes once a stable (1.0.0) release has occurred. Prior to a 1.0.0 release the minor versions acts as the API stability level. This is useful when comparisons of API versions as a major change is API breaking. For example,

* `^1.2.3` is equivalent to `>= 1.2.3, < 2.0.0`
* `^1.2.x` is equivalent to `>= 1.2.0, < 2.0.0`
* `^2.3` is equivalent to `>= 2.3, < 3`
* `^2.x` is equivalent to `>= 2.0.0, < 3`
* `^0.2.3` is equivalent to `>=0.2.3 <0.3.0`
* `^0.2` is equivalent to `>=0.2.0 <0.3.0`
* `^0.0.3` is equivalent to `>=0.0.3 <0.0.4`
* `^0.0` is equivalent to `>=0.0.0 <0.1.0`
* `^0` is equivalent to `>=0.0.0 <1.0.0`


In addition to testing a version against a constraint, a version can be validated against a constraint. When validation fails a slice of errors containing why a version didn't meet the constraint is returned. For example,

c, err := semver.NewConstraint("<= 1.2.3, >= 1.4")
if err != nil {
    // Handle constraint not being parseable.

v, _ := semver.NewVersion("1.3")
if err != nil {
    // Handle version not being parseable.

// Validate a version against a constraint.
a, msgs := c.Validate(v)
// a is false
for _, m := range msgs {

    // Loops over the errors which would read
    // "1.3 is greater than 1.2.3"
    // "1.3 is less than 1.4"


Package Files

collection.go constraints.go doc.go version.go


var (
    // ErrInvalidSemVer is returned a version is found to be invalid when
    // being parsed.
    ErrInvalidSemVer = errors.New("Invalid Semantic Version")

    // ErrEmptyString is returned when an empty string is passed in for parsing.
    ErrEmptyString = errors.New("Version string empty")

    // ErrInvalidCharacters is returned when invalid characters are found as
    // part of a version
    ErrInvalidCharacters = errors.New("Invalid characters in version")

    // ErrSegmentStartsZero is returned when a version segment starts with 0.
    // This is invalid in SemVer.
    ErrSegmentStartsZero = errors.New("Version segment starts with 0")

    // ErrInvalidMetadata is returned when the metadata is an invalid format
    ErrInvalidMetadata = errors.New("Invalid Metadata string")

    // ErrInvalidPrerelease is returned when the pre-release is an invalid format
    ErrInvalidPrerelease = errors.New("Invalid Prerelease string")

type Collection Uses

type Collection []*Version

Collection is a collection of Version instances and implements the sort interface. See the sort package for more details.

func (Collection) Len Uses

func (c Collection) Len() int

Len returns the length of a collection. The number of Version instances on the slice.

func (Collection) Less Uses

func (c Collection) Less(i, j int) bool

Less is needed for the sort interface to compare two Version objects on the slice. If checks if one is less than the other.

func (Collection) Swap Uses

func (c Collection) Swap(i, j int)

Swap is needed for the sort interface to replace the Version objects at two different positions in the slice.

type Constraints Uses

type Constraints struct {
    // contains filtered or unexported fields

Constraints is one or more constraint that a semantic version can be checked against.

func NewConstraint Uses

func NewConstraint(c string) (*Constraints, error)

NewConstraint returns a Constraints instance that a Version instance can be checked against. If there is a parse error it will be returned.

func (Constraints) Check Uses

func (cs Constraints) Check(v *Version) bool

Check tests if a version satisfies the constraints.

func (Constraints) String Uses

func (cs Constraints) String() string

func (Constraints) Validate Uses

func (cs Constraints) Validate(v *Version) (bool, []error)

Validate checks if a version satisfies a constraint. If not a slice of reasons for the failure are returned in addition to a bool.

type Version Uses

type Version struct {
    // contains filtered or unexported fields

Version represents a single semantic version.

func MustParse Uses

func MustParse(v string) *Version

MustParse parses a given version and panics on error.

func NewVersion Uses

func NewVersion(v string) (*Version, error)

NewVersion parses a given version and returns an instance of Version or an error if unable to parse the version. If the version is SemVer-ish it attempts to convert it to SemVer. If you want to validate it was a strict semantic version at parse time see StrictNewVersion().

func StrictNewVersion Uses

func StrictNewVersion(v string) (*Version, error)

StrictNewVersion parses a given version and returns an instance of Version or an error if unable to parse the version. Only parses valid semantic versions. Performs checking that can find errors within the version. If you want to coerce a version, such as 1 or 1.2, and perse that as the 1.x releases of semver provided use the NewSemver() function.

func (*Version) Compare Uses

func (v *Version) Compare(o *Version) int

Compare compares this version to another one. It returns -1, 0, or 1 if the version smaller, equal, or larger than the other version.

Versions are compared by X.Y.Z. Build metadata is ignored. Prerelease is lower than the version without a prerelease. Compare always takes into account prereleases. If you want to work with ranges using typical range syntaxes that skip prereleases if the range is not looking for them use constraints.

func (*Version) Equal Uses

func (v *Version) Equal(o *Version) bool

Equal tests if two versions are equal to each other. Note, versions can be equal with different metadata since metadata is not considered part of the comparable version.

func (*Version) GreaterThan Uses

func (v *Version) GreaterThan(o *Version) bool

GreaterThan tests if one version is greater than another one.

func (Version) IncMajor Uses

func (v Version) IncMajor() Version

IncMajor produces the next major version. Sets patch to 0. Sets minor to 0. Increments major number. Unsets metadata. Unsets prerelease status.

func (Version) IncMinor Uses

func (v Version) IncMinor() Version

IncMinor produces the next minor version. Sets patch to 0. Increments minor number. Unsets metadata. Unsets prerelease status.

func (Version) IncPatch Uses

func (v Version) IncPatch() Version

IncPatch produces the next patch version. If the current version does not have prerelease/metadata information, it unsets metadata and prerelease values, increments patch number. If the current version has any of prerelease or metadata information, it unsets both values and keeps current patch value

func (*Version) LessThan Uses

func (v *Version) LessThan(o *Version) bool

LessThan tests if one version is less than another one.

func (Version) Major Uses

func (v Version) Major() uint64

Major returns the major version.

func (Version) MarshalJSON Uses

func (v Version) MarshalJSON() ([]byte, error)

MarshalJSON implements JSON.Marshaler interface.

func (Version) Metadata Uses

func (v Version) Metadata() string

Metadata returns the metadata on the version.

func (Version) Minor Uses

func (v Version) Minor() uint64

Minor returns the minor version.

func (*Version) Original Uses

func (v *Version) Original() string

Original returns the original value passed in to be parsed.

func (Version) Patch Uses

func (v Version) Patch() uint64

Patch returns the patch version.

func (Version) Prerelease Uses

func (v Version) Prerelease() string

Prerelease returns the pre-release version.

func (*Version) Scan Uses

func (v *Version) Scan(value interface{}) error

Scan implements the SQL.Scanner interface.

func (Version) SetMetadata Uses

func (v Version) SetMetadata(metadata string) (Version, error)

SetMetadata defines metadata value. Value must not include the required 'plus' prefix.

func (Version) SetPrerelease Uses

func (v Version) SetPrerelease(prerelease string) (Version, error)

SetPrerelease defines the prerelease value. Value must not include the required 'hyphen' prefix.

func (Version) String Uses

func (v Version) String() string

String converts a Version object to a string. Note, if the original version contained a leading v this version will not. See the Original() method to retrieve the original value. Semantic Versions don't contain a leading v per the spec. Instead it's optional on implementation.

func (*Version) UnmarshalJSON Uses

func (v *Version) UnmarshalJSON(b []byte) error

UnmarshalJSON implements JSON.Unmarshaler interface.

func (Version) Value Uses

func (v Version) Value() (driver.Value, error)

Value implements the Driver.Valuer interface.

Package semver imports 8 packages (graph) and is imported by 635 packages. Updated 2020-04-22. Refresh now. Tools for package owners.