Version Key

A version is defined by assigning a value to the version key. It’s important to understand how Antora uses the version and its related facets before committing to a versioning scheme.

What’s a version?

In Antora, a version is the value resolved from the version key in a component version descriptor file (antora.yml) or inherited from the content source in the playbook. A version is a semantic or named identifier that represents a unique release or instance of the documentation for a project. The resolved value of the version key, in combination with the value of the name key, defines a component version.

Although the version is typically a literal value, it can also be interpreted. The version can be defined as unversioned by assigning a tilde, ~, to the version key. The version can be configured as the refname in which it resides by assigning true to the version key. The version can also be derived from the refname by assigning a map of refname projections to the version key.

Occasionally, the value assigned to the version key is referred to as the actual version in this documentation when a distinction between version and the other version facets—prerelease, display, and symbolic—needs to be made in a description or example.

How Antora uses version

The version is fundamental to many of Antora’s operations. Antora uses the version:

to sort component versions
identify the latest version of a component
apply routing rules
as the version segment in publishable resource URLs, except when:
- the assigned value is the tilde (~) that defines an unversioned component version
- a component version is identified as the latest stable or latest prerelease version and the latest_version_segment key or latest_prerelease_version_segment key is set in the playbook
for display purposes in the reference UI component version selector and page version selector menus, except when:
- the display_version key is set and assigned a value in the component version’s antora.yml file
- the display_version key is set by Antora at runtime because the prerelease key is assigned an identifier

Content writers use the version as the version coordinate in resource IDs when referencing a resource in another component version.

version key

The version key accepts a named identifier, such as jesse, a semantic identifier, such as '1.5.0', the reserved value true, a map of refname projections, such as v/(?<version>*): $<version>, or the reserved value ~. The ~ values defines a component version as unversioned. To learn how to specify an unversioned component version, see Define a Component with No Version.

If the version key is defined in the component version descriptor file for a component version, it takes precedence over a value defined on the content source in the playbook. If you prefer the playbook to control the value of the version key, don’t set the version key in the component version descriptor file.

Named identifier as version

The following example shows how to assign a named identifier to the version key.

Example 1. antora.yml with named identifier assigned to version

name: star
version: rigel (1)

1	On a new line, type `version`, directly followed by a colon and a space (`:` ). Then type the value you want assigned to `version`.

Semantic identifier as version

A semantic identifier is either an integer or begins with an integer and contains at least one dot (.). 10, 1.0.0, and 5.1 are all examples of semantic identifiers. Although a semantic identifier looks like a number, it’s actually a string. If the semantic identifier matches the syntax of a number (integer or decimal), like the one shown in Example 2, you should enclose the value in a pair of single quotes ('), which coerces it to a string.

The following example shows how to assign a semantic identifier to the version key.

Example 2. antora.yml with semantic identifier assigned to version

name: colorado
version: '5.6.0' (1)

1	Enclose a value that matches the syntax of a number in a pair of single quote marks (`'`).

Antora recognizes semantic identifiers according to semantic versioning rules. Semantic versioning is often referred to as semver. Antora allows a semantic identifier to begin with v. Although this prefix is preserved in the value, Antora will ignore it when sorting versions. For example, v9.0.2 will be sorted as though the value is 9.0.2.

refname as version

Since content in Antora is retrieved from a git repository, you may want to use the git refname (branch or tag name) in which the component version descriptor is stored as the version. To do so, assign the reserved value true to the version, as shown in Example 3.

Example 3. antora.yml with true assigned to version

name: colorado
version: true (1)

1	The value `true` tells Antora to use the refname as the value.

Antora will substitute the value true with the refname automatically. The value Antora uses is always the short refname (e.g., v1.0), not the full refname (e.g., refs/heads/v1.0).

refname projection as version

The refname may not be granular enough to use as the version. Furthermore, the same git tree could be passed through git references that have different naming schemes, such as feature branches. In these cases, you want the version to be extracted or derived from the refname rather than using the value as is. That’s when you’d define the version using a refname projection.

A refname projection is expressed as a map of patterns (the keys) and replacements (the values). The refname projection allows you to match the refname using a pattern, then build a version based on that match. The pattern tells Antora which entry to use and what parts to extract from it. The replacement tells Antora how to derive a version from the matched refname.

The following example shows how to use a projection to compute the value of the version key from the refname.

Example 4. antora.yml with version computed from a refname projection

name: colorado
version:
  v(?<version>+({0..9}).+({0..9})).x: $<version> (1)
  feature/(*)/*: $1 (2)

1	Matches the semantic identifier in a refname like `v2.0.x` and extracts it
2	Extracts the value between the first and second slash for a refname that begins with `feature/`

The key in the projection is a glob pattern (a combination of extglobs, ranges, and some regex constructs). The pattern has the same matching capabilities as the pattern used to match branches or tags for a content source in the playbook.

The characters between parentheses (i.e., round brackets) in the pattern defines a match group. If the opening brace begins with ?<name>, that group is assigned to the name specified between the angle brackets. Otherwise, the group is assigned to a 1-based index according to the group’s position in the pattern.

The match groups can be referenced in the replacement. A match group reference is preceded by a dollar sign ($). A named group can be referenced using $<name>, where the name is once again specified between the angle brackets. An indexed group can be referenced by its number, such as $1. You can reference the entire refname using $&.

If the match group contains any forward slashes, Antora will replace each one with a hyphen.

Antora will use the value of the first pattern it matches. If none of the patterns match the refname, Antora will fallback to using the refname as the version.

Value requirements

A literal value assigned to the version key can contain letters, numbers, periods (.), underscores (_), and hyphens (-). To ensure portability between host platforms, letters used in the version value should be lowercase.

The value cannot contain spaces, forward slashes (/), or HTML special characters (&, <, or >). See Customize the Display Version to learn how to represent a version that contains spaces, uppercase letters, and other characters in the UI menus.