README.md
1# SemVer
2
3The `semver` package provides the ability to work with [Semantic Versions](http://semver.org) in Go. Specifically it provides the ability to:
4
5* Parse semantic versions
6* Sort semantic versions
7* Check if a semantic version fits within a set of constraints
8* Optionally work with a `v` prefix
9
10[](https://masterminds.github.io/stability/active.html)
12[](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)
13
14## Parsing Semantic Versions
15
16To parse a semantic version use the `NewVersion` function. For example,
17
18```go
19 v, err := semver.NewVersion("1.2.3-beta.1+build345")
20```
21
22If there is an error the version wasn't parseable. The version object has methods
23to get the parts of the version, compare it to other versions, convert the
24version back into a string, and get the original string. For more details
25please see the [documentation](https://godoc.org/github.com/Masterminds/semver).
26
27## Sorting Semantic Versions
28
29A set of versions can be sorted using the [`sort`](https://golang.org/pkg/sort/)
30package from the standard library. For example,
31
32```go
33 raw := []string{"1.2.3", "1.0", "1.3", "2", "0.4.2",}
34 vs := make([]*semver.Version, len(raw))
35 for i, r := range raw {
36 v, err := semver.NewVersion(r)
37 if err != nil {
38 t.Errorf("Error parsing version: %s", err)
39 }
40
41 vs[i] = v
42 }
43
44 sort.Sort(semver.Collection(vs))
45```
46
47## Checking Version Constraints
48
49Checking a version against version constraints is one of the most featureful
50parts of the package.
51
52```go
53 c, err := semver.NewConstraint(">= 1.2.3")
54 if err != nil {
55 // Handle constraint not being parseable.
56 }
57
58 v, _ := semver.NewVersion("1.3")
59 if err != nil {
60 // Handle version not being parseable.
61 }
62 // Check if the version meets the constraints. The a variable will be true.
63 a := c.Check(v)
64```
65
66## Basic Comparisons
67
68There are two elements to the comparisons. First, a comparison string is a list
69of comma separated and comparisons. These are then separated by || separated or
70comparisons. For example, `">= 1.2, < 3.0.0 || >= 4.2.3"` is looking for a
71comparison that's greater than or equal to 1.2 and less than 3.0.0 or is
72greater than or equal to 4.2.3.
73
74The basic comparisons are:
75
76* `=`: equal (aliased to no operator)
77* `!=`: not equal
78* `>`: greater than
79* `<`: less than
80* `>=`: greater than or equal to
81* `<=`: less than or equal to
82
83_Note, according to the Semantic Version specification pre-releases may not be
84API compliant with their release counterpart. It says,_
85
86> _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._
87
88_SemVer comparisons without a pre-release value will skip pre-release versions.
89For example, `>1.2.3` will skip pre-releases when looking at a list of values
90while `>1.2.3-alpha.1` will evaluate pre-releases._
91
92## Hyphen Range Comparisons
93
94There are multiple methods to handle ranges and the first is hyphens ranges.
95These look like:
96
97* `1.2 - 1.4.5` which is equivalent to `>= 1.2, <= 1.4.5`
98* `2.3.4 - 4.5` which is equivalent to `>= 2.3.4, <= 4.5`
99
100## Wildcards In Comparisons
101
102The `x`, `X`, and `*` characters can be used as a wildcard character. This works
103for all comparison operators. When used on the `=` operator it falls
104back to the pack level comparison (see tilde below). For example,
105
106* `1.2.x` is equivalent to `>= 1.2.0, < 1.3.0`
107* `>= 1.2.x` is equivalent to `>= 1.2.0`
108* `<= 2.x` is equivalent to `<= 3`
109* `*` is equivalent to `>= 0.0.0`
110
111## Tilde Range Comparisons (Patch)
112
113The tilde (`~`) comparison operator is for patch level ranges when a minor
114version is specified and major level changes when the minor number is missing.
115For example,
116
117* `~1.2.3` is equivalent to `>= 1.2.3, < 1.3.0`
118* `~1` is equivalent to `>= 1, < 2`
119* `~2.3` is equivalent to `>= 2.3, < 2.4`
120* `~1.2.x` is equivalent to `>= 1.2.0, < 1.3.0`
121* `~1.x` is equivalent to `>= 1, < 2`
122
123## Caret Range Comparisons (Major)
124
125The caret (`^`) comparison operator is for major level changes. This is useful
126when comparisons of API versions as a major change is API breaking. For example,
127
128* `^1.2.3` is equivalent to `>= 1.2.3, < 2.0.0`
129* `^1.2.x` is equivalent to `>= 1.2.0, < 2.0.0`
130* `^2.3` is equivalent to `>= 2.3, < 3`
131* `^2.x` is equivalent to `>= 2.0.0, < 3`
132
133# Validation
134
135In addition to testing a version against a constraint, a version can be validated
136against a constraint. When validation fails a slice of errors containing why a
137version didn't meet the constraint is returned. For example,
138
139```go
140 c, err := semver.NewConstraint("<= 1.2.3, >= 1.4")
141 if err != nil {
142 // Handle constraint not being parseable.
143 }
144
145 v, _ := semver.NewVersion("1.3")
146 if err != nil {
147 // Handle version not being parseable.
148 }
149
150 // Validate a version against a constraint.
151 a, msgs := c.Validate(v)
152 // a is false
153 for _, m := range msgs {
154 fmt.Println(m)
155
156 // Loops over the errors which would read
157 // "1.3 is greater than 1.2.3"
158 // "1.3 is less than 1.4"
159 }
160```
161
162# Contribute
163
164If you find an issue or want to contribute please file an [issue](https://github.com/Masterminds/semver/issues)
165or [create a pull request](https://github.com/Masterminds/semver/pulls).
166
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