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. It returns true if the constraint matches, or false if it does not match. 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 space or comma 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.

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,

Working With Prerelease Versions

Pre-releases, for those not familiar with them, are used for software releases prior to stable or generally available releases. Examples of prereleases include development, alpha, beta, and release candidate releases. A prerelease may be a version such as 1.2.3-beta.1 while the stable release would be 1.2.3. In the order of precedence, prereleases come before their associated releases. In this example 1.2.3-beta.1 < 1.2.3.

According to the Semantic Version specification prereleases 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 using constraints without a prerelease comparator will skip prerelease versions. For example, >=1.2.3 will skip prereleases when looking at a list of releases while >=1.2.3-0 will evaluate and find prereleases.

The reason for the 0 as a pre-release version in the example comparison is because pre-releases can only contain ASCII alphanumerics and hyphens (along with . separators), per the spec. Sorting happens in ASCII sort order, again per the spec. The lowest character is a 0 in ASCII sort order (see an ASCII Table)

Understanding ASCII sort ordering is important because A-Z comes before a-z. That means >=1.2.3-BETA will return 1.2.3-alpha. What you might expect from case sensitivity doesn’t apply here. This is due to ASCII sort ordering which is what the spec specifies.

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 patch 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 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