protoc-gen-go-micro/vendor/github.com/Masterminds/sprig/docs/semver.md

Semantic Version Functions

Some version schemes are easily parseable and comparable. Sprig provides functions for working with SemVer 2 versions.

semver

The semver function parses a string into a Semantic Version:

$version := semver "1.2.3-alpha.1+123"

If the parser fails, it will cause template execution to halt with an error.

At this point, $version is a pointer to a Version object with the following properties:

• $version.Major: The major number (1 above)
• $version.Minor: The minor number (2 above)
• $version.Patch: The patch number (3 above)
• $version.Prerelease: The prerelease (alpha.1 above)
• $version.Metadata: The build metadata (123 above)
• $version.Original: The original version as a string

Additionally, you can compare a Version to another version using the Compare function:

semver "1.4.3" | (semver "1.2.3").Compare

The above will return -1.

The return values are:

• -1 if the given semver is greater than the semver whose Compare method was called
• 1 if the version who's Compare function was called is greater.
• 0 if they are the same version

(Note that in SemVer, the Metadata field is not compared during version comparison operations.)

semverCompare

A more robust comparison function is provided as semverCompare. This version supports version ranges:

• semverCompare "1.2.3" "1.2.3" checks for an exact match
• semverCompare "^1.2.0" "1.2.3" checks that the major and minor versions match, and that the patch number of the second version is greater than or equal to the first parameter.

The SemVer functions use the Masterminds semver library, from the creators of Sprig.

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