# SemVer
The `semver` package provides the ability to work with [Semantic Versions](http://semver.org) 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
[](https://travis-ci.org/Masterminds/semver) [](https://ci.appveyor.com/project/mattfarina/semver/branch/master) [](https://godoc.org/github.com/Masterminds/semver) [](https://goreportcard.com/report/github.com/Masterminds/semver)
## Parsing Semantic Versions
To parse a semantic version use the `NewVersion` function. For example,
```go
v, err := semver.NewVersion("1.2.3-beta.1+build345")
```
If there is an error the version wasn't parseable. 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](https://godoc.org/github.com/Masterminds/semver).
## Sorting Semantic Versions
A set of versions can be sorted using the [`sort`](https://golang.org/pkg/sort/)
package from the standard library. For example,
```go
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
}
sort.Sort(semver.Collection(vs))
```
## Checking Version Constraints
Checking a version against version constraints is one of the most featureful
parts of the package.
```go
c, err := semver.NewConstraint(">= 1.2.3")
if err != nil {
// Handle constraint not being parseable.
}
v, _ := semver.NewVersion("1.3")
if err != nil {
// Handle version not being parseable.
}
// 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 separated and comparisons. These are then separated by || separated 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.
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
_Note, according to the Semantic Version specification pre-releases may not be
API compliant with their release counterpart. It says,_
> _A pre-release version indicates that the version is unstable and might not satisfy the intended compatibility requirements as denoted by its associated normal version._
_SemVer comparisons without a pre-release value will skip pre-release versions.
For example, `>1.2.3` will skip pre-releases when looking at a list of values
while `>1.2.3-alpha.1` will evaluate pre-releases._
## 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 pack level comparison (see tilde below). 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. 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`
# Validation
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,
```go
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 {
fmt.Println(m)
// Loops over the errors which would read
// "1.3 is greater than 1.2.3"
// "1.3 is less than 1.4"
}
```
# Contribute
If you find an issue or want to contribute please file an [issue](https://github.com/Masterminds/semver/issues)
or [create a pull request](https://github.com/Masterminds/semver/pulls).