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245 lines
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Markdown
245 lines
10 KiB
Markdown
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# SemVer
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The `semver` package provides the ability to work with [Semantic Versions](http://semver.org) in Go. Specifically it provides the ability to:
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* Parse semantic versions
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* Sort semantic versions
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* Check if a semantic version fits within a set of constraints
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* Optionally work with a `v` prefix
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[![Stability:
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Active](https://masterminds.github.io/stability/active.svg)](https://masterminds.github.io/stability/active.html)
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[![](https://github.com/Masterminds/semver/workflows/Tests/badge.svg)](https://github.com/Masterminds/semver/actions)
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[![GoDoc](https://img.shields.io/static/v1?label=godoc&message=reference&color=blue)](https://pkg.go.dev/github.com/Masterminds/semver/v3)
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[![Go Report Card](https://goreportcard.com/badge/github.com/Masterminds/semver)](https://goreportcard.com/report/github.com/Masterminds/semver)
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If you are looking for a command line tool for version comparisons please see
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[vert](https://github.com/Masterminds/vert) which uses this library.
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## Package Versions
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There are three major versions fo the `semver` package.
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* 3.x.x is the new stable and active version. This version is focused on constraint
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compatibility for range handling in other tools from other languages. It has
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a similar API to the v1 releases. The development of this version is on the master
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branch. The documentation for this version is below.
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* 2.x was developed primarily for [dep](https://github.com/golang/dep). There are
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no tagged releases and the development was performed by [@sdboyer](https://github.com/sdboyer).
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There are API breaking changes from v1. This version lives on the [2.x branch](https://github.com/Masterminds/semver/tree/2.x).
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* 1.x.x is the most widely used version with numerous tagged releases. This is the
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previous stable and is still maintained for bug fixes. The development, to fix
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bugs, occurs on the release-1 branch. You can read the documentation [here](https://github.com/Masterminds/semver/blob/release-1/README.md).
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## Parsing Semantic Versions
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There are two functions that can parse semantic versions. The `StrictNewVersion`
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function only parses valid version 2 semantic versions as outlined in the
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specification. The `NewVersion` function attempts to coerce a version into a
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semantic version and parse it. For example, if there is a leading v or a version
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listed without all 3 parts (e.g. `v1.2`) it will attempt to coerce it into a valid
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semantic version (e.g., 1.2.0). In both cases a `Version` object is returned
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that can be sorted, compared, and used in constraints.
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When parsing a version an error is returned if there is an issue parsing the
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version. For example,
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v, err := semver.NewVersion("1.2.3-beta.1+build345")
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The version object has methods to get the parts of the version, compare it to
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other versions, convert the version back into a string, and get the original
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string. Getting the original string is useful if the semantic version was coerced
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into a valid form.
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## Sorting Semantic Versions
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A set of versions can be sorted using the `sort` package from the standard library.
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For example,
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```go
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raw := []string{"1.2.3", "1.0", "1.3", "2", "0.4.2",}
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vs := make([]*semver.Version, len(raw))
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for i, r := range raw {
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v, err := semver.NewVersion(r)
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if err != nil {
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t.Errorf("Error parsing version: %s", err)
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}
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vs[i] = v
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}
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sort.Sort(semver.Collection(vs))
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```
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## Checking Version Constraints
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There are two methods for comparing versions. One uses comparison methods on
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`Version` instances and the other uses `Constraints`. There are some important
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differences to notes between these two methods of comparison.
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1. When two versions are compared using functions such as `Compare`, `LessThan`,
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and others it will follow the specification and always include prereleases
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within the comparison. It will provide an answer that is valid with the
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comparison section of the spec at https://semver.org/#spec-item-11
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2. When constraint checking is used for checks or validation it will follow a
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different set of rules that are common for ranges with tools like npm/js
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and Rust/Cargo. This includes considering prereleases to be invalid if the
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ranges does not include one. If you want to have it include pre-releases a
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simple solution is to include `-0` in your range.
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3. Constraint ranges can have some complex rules including the shorthand use of
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~ and ^. For more details on those see the options below.
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There are differences between the two methods or checking versions because the
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comparison methods on `Version` follow the specification while comparison ranges
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are not part of the specification. Different packages and tools have taken it
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upon themselves to come up with range rules. This has resulted in differences.
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For example, npm/js and Cargo/Rust follow similar patterns while PHP has a
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different pattern for ^. The comparison features in this package follow the
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npm/js and Cargo/Rust lead because applications using it have followed similar
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patters with their versions.
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Checking a version against version constraints is one of the most featureful
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parts of the package.
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```go
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c, err := semver.NewConstraint(">= 1.2.3")
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if err != nil {
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// Handle constraint not being parsable.
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}
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v, err := semver.NewVersion("1.3")
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if err != nil {
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// Handle version not being parsable.
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}
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// Check if the version meets the constraints. The a variable will be true.
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a := c.Check(v)
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```
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### Basic Comparisons
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There are two elements to the comparisons. First, a comparison string is a list
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of space or comma separated AND comparisons. These are then separated by || (OR)
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comparisons. For example, `">= 1.2 < 3.0.0 || >= 4.2.3"` is looking for a
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comparison that's greater than or equal to 1.2 and less than 3.0.0 or is
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greater than or equal to 4.2.3.
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The basic comparisons are:
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* `=`: equal (aliased to no operator)
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* `!=`: not equal
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* `>`: greater than
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* `<`: less than
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* `>=`: greater than or equal to
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* `<=`: less than or equal to
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### Working With Prerelease Versions
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Pre-releases, for those not familiar with them, are used for software releases
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prior to stable or generally available releases. Examples of prereleases include
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development, alpha, beta, and release candidate releases. A prerelease may be
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a version such as `1.2.3-beta.1` while the stable release would be `1.2.3`. In the
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order of precedence, prereleases come before their associated releases. In this
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example `1.2.3-beta.1 < 1.2.3`.
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According to the Semantic Version specification prereleases may not be
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API compliant with their release counterpart. It says,
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> 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.
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SemVer comparisons using constraints without a prerelease comparator will skip
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prerelease versions. For example, `>=1.2.3` will skip prereleases when looking
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at a list of releases while `>=1.2.3-0` will evaluate and find prereleases.
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The reason for the `0` as a pre-release version in the example comparison is
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because pre-releases can only contain ASCII alphanumerics and hyphens (along with
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`.` separators), per the spec. Sorting happens in ASCII sort order, again per the
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spec. The lowest character is a `0` in ASCII sort order
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(see an [ASCII Table](http://www.asciitable.com/))
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Understanding ASCII sort ordering is important because A-Z comes before a-z. That
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means `>=1.2.3-BETA` will return `1.2.3-alpha`. What you might expect from case
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sensitivity doesn't apply here. This is due to ASCII sort ordering which is what
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the spec specifies.
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### Hyphen Range Comparisons
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There are multiple methods to handle ranges and the first is hyphens ranges.
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These look like:
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* `1.2 - 1.4.5` which is equivalent to `>= 1.2 <= 1.4.5`
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* `2.3.4 - 4.5` which is equivalent to `>= 2.3.4 <= 4.5`
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### Wildcards In Comparisons
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The `x`, `X`, and `*` characters can be used as a wildcard character. This works
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for all comparison operators. When used on the `=` operator it falls
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back to the patch level comparison (see tilde below). For example,
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* `1.2.x` is equivalent to `>= 1.2.0, < 1.3.0`
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* `>= 1.2.x` is equivalent to `>= 1.2.0`
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* `<= 2.x` is equivalent to `< 3`
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* `*` is equivalent to `>= 0.0.0`
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### Tilde Range Comparisons (Patch)
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The tilde (`~`) comparison operator is for patch level ranges when a minor
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version is specified and major level changes when the minor number is missing.
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For example,
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* `~1.2.3` is equivalent to `>= 1.2.3, < 1.3.0`
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* `~1` is equivalent to `>= 1, < 2`
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* `~2.3` is equivalent to `>= 2.3, < 2.4`
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* `~1.2.x` is equivalent to `>= 1.2.0, < 1.3.0`
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* `~1.x` is equivalent to `>= 1, < 2`
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### Caret Range Comparisons (Major)
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The caret (`^`) comparison operator is for major level changes once a stable
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(1.0.0) release has occurred. Prior to a 1.0.0 release the minor versions acts
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as the API stability level. This is useful when comparisons of API versions as a
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major change is API breaking. For example,
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* `^1.2.3` is equivalent to `>= 1.2.3, < 2.0.0`
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* `^1.2.x` is equivalent to `>= 1.2.0, < 2.0.0`
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* `^2.3` is equivalent to `>= 2.3, < 3`
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* `^2.x` is equivalent to `>= 2.0.0, < 3`
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* `^0.2.3` is equivalent to `>=0.2.3 <0.3.0`
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* `^0.2` is equivalent to `>=0.2.0 <0.3.0`
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* `^0.0.3` is equivalent to `>=0.0.3 <0.0.4`
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* `^0.0` is equivalent to `>=0.0.0 <0.1.0`
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* `^0` is equivalent to `>=0.0.0 <1.0.0`
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## Validation
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In addition to testing a version against a constraint, a version can be validated
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against a constraint. When validation fails a slice of errors containing why a
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version didn't meet the constraint is returned. For example,
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```go
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c, err := semver.NewConstraint("<= 1.2.3, >= 1.4")
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if err != nil {
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// Handle constraint not being parseable.
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}
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v, err := semver.NewVersion("1.3")
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if err != nil {
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// Handle version not being parseable.
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}
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// Validate a version against a constraint.
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a, msgs := c.Validate(v)
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// a is false
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for _, m := range msgs {
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fmt.Println(m)
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// Loops over the errors which would read
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// "1.3 is greater than 1.2.3"
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// "1.3 is less than 1.4"
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}
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```
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## Contribute
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If you find an issue or want to contribute please file an [issue](https://github.com/Masterminds/semver/issues)
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or [create a pull request](https://github.com/Masterminds/semver/pulls).
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