Versions¶

Tako does not enforce any particular versioning scheme. Instead it implements a simple version parser and constraint resolver that is compatible with most versioning schemes, such as Semantic Versioning.

Patterns¶

Compatible versions are selected by matching versions against a pattern. A pattern is either a wildcard pattern or a bounds pattern.

• A wildcard pattern is a version that may end in *.
• A bounds pattern specifies an inclusive lower bound and an exclusive upper bound separated by <= v <.

Some examples:

• * matches any version.
• 1.* matches 1.0, 1.1, 1.2, etc., but not 2.0, or 0.1. It does match 1 and 1.0.0, which are both equivalent to 1.0.
• 1.13.7 matches 1.13.7. It also matches 1.13.7.0, 1.13.7.0.0, etc., which are equivalent to 1.13.7. Such a pattern can be used for version pinning.
• 1.0 <= v < 2.0 is the same as 1.*.
• 2.3 <= v < 3.0 matches versions that are semver-compatible with 2.3.

Syntax¶

Versions consist of parts separated by separators.

• A part is either numeric or a string. A numeric part is an unsigned integer.
• A separator is one of ., -, and _.

Versions map to a list of parts. Some examples:

• 1.0.0 ⇒ [1, 0, 0]
• 1.0.0-beta ⇒ [1, 0, 0, "beta"]
• 1.0.0-beta-25856-ge63d979e22 ⇒ [1, 1, 0, "beta", 25856, "ge63d979e22"]
• 1.0.0-beta.2 ⇒ [1, 0, 0, "beta", 2]
• 1.1.0.h-1 ⇒ [1, 1, 0, "h", 1]
• 66.0.3359.117-1 ⇒ [66, 0, 3359, 117, 1]
• 1.2a ⇒ [1, "2a"]

Ordering¶

Versions are ordered conventionally. They are compared part by part. String parts order before numeric parts, and string parts order lexicographically. Versions are implicitly padded with zero parts: when two versions with a different number of parts are compared, the shorter one is padded with zeros. It is generally a bad idea to use a versioning scheme with a variable number of parts though. Separator characters do not affect ordering.

Some examples:

• 1.0.0 < 2.0.0
• 1.0.0 < 1.1.0
• 1.0.0 < 1.0.1
• 1 = 1.0
• 1-0 = 1.0
• 1.a < 1.0 (string parts order before numeric parts)
• 1.0.0.a < 1.0.0 (string parts order before the implicit zero part)
• 1.0.a < 1.0.b
• 1.0.0-beta.1 < 1.0.0 (string parts order before the implicit zero part)
• 1.0.0-beta < 1.0.0-beta.1 (implicit zero orders before 1)
• 1.0.0-beta.1 < 1.0.0-beta.2
• 1.2a < 1.1 (string parts order before numeric parts)

Some of these might be counterintuitive. Unfortunately we cannot have both of the following be true without complicating the comparison rules.

• 1.0-beta.1 < 1.0.
• 1.0 < 1.0.a

Tako implements the first choice, and hence 1.0.a < 1.0. To avoid confusion, use a versioning scheme that has a fixed number of parts.