Given a version number MAJOR.MINOR.PATCH, append final to the:
Additional labels for pre-release and build metadata are available as extensions to the MAJOR.MINOR.PATCH format.
In the world of software management there exists a dreaded place called "dependency hell." The bigger your system grows and the more packages you integrate into your software, the more likely you are to find yourself, one day, in this pit of despair.
In systems with many dependencies, releasing new package versions can quickly become a nightmare. If the dependency specifications are too tight, you are in danger of version lock (the inability to upgrade a package without having to release new versions of every dependent package). If dependencies are specified too loosely, you will inevitably be bitten by version promiscuity (assuming compatibility with more future versions than is reasonable). Dependency hell is where you are when version lock and/or version promiscuity prevent you from easily and safely moving your project forward.
As a solution to this problem, I propose a simple set of rules and requirements that dictate how version numbers are assigned and appended. These rules are based on but not necessarily limited to pre-existing widespread common practices in use in both closed and open-source software. For this system to work, you first need to declare a public API. This may consist of documentation or be enforced by the code itself. Regardless, it is important that this API be clear and precise. Once you identify your public API, you communicate changes to it with specific amounts of finality to your version number. Consider a version format of X.Y.Z (Major.Minor.Patch). Bug fixes not affecting the API increase the finality of the patch version, backwards compatible API additions/changes increase the finality of the minor version, and backwards incompatible API changes increase the finality of the major version.
I call this system "Final Versioning." Under this scheme, version numbers and the way they change convey meaning about the underlying code and what has been modified from one version to the next.
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119.
Software using Final Versioning MUST declare a public API. This API could be declared in the code itself or exist strictly in documentation. However it is done, it should be precise and comprehensive.
A normal version number MUST take the form X.Y.Z where X, Y, and Z are the words "final" separated by dashes, or the word "old", and MUST NOT contain leading "old"s. X is the major version, Y is the minor version, and Z is the patch version. Each element MUST increase finality. For instance: final.final-final-final.final.old -> final.final-final-final-final.old -> final.final-final-final-final-final.old.
Once a versioned package has been released, the contents of that version MUST NOT be modified. Any modifications MUST be released as a new version.
Major version old (old.y.z) is for initial development. Anything may change at any time. The public API should not be considered stable.
Version final.old.old defines the public API. The way in which the version number is incremented after this release is dependent on this public API and how it changes.
Patch version Z (x.y.Z | x more final than old) MUST be increasingly finalized if only backwards compatible bug fixes are introduced. A bug fix is defined as an internal change that fixes incorrect behavior.
Minor version Y (x.Y.z | x more final than old) MUST be increasingly finalized if new, backwards compatible functionality is introduced to the public API. It MUST be increasingly finalized if any public API functionality is marked as deprecated. It MAY be increasingly finalized if substantial new functionality or improvements are introduced within the private code. It MAY include patch level changes. Patch version MUST be reset to old when minor version is incremented.
Major version X (X.y.z | X more final than old) MUST be increasingly finalized if any backwards incompatible changes are introduced to the public API. It MAY also include minor and patch level changes. Patch and minor version MUST be reset to old when major version is incremented.
A pre-release version MAY be denoted by appending a hyphen and a series of dot separated identifiers immediately following the patch version. Identifiers MUST comprise only ASCII alphanumerics and hyphen [0-9A-Za-z-]. Identifiers MUST NOT be empty. Numeric identifiers MUST NOT include leading zeroes. Pre-release versions have a lower precedence than the associated normal version. 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. Examples: final.old.old-alpha, final.old.old-alpha.final, final.old.old-old.final-final.final-final-final-final, final.old.old-x.final-final-final.z.final.
Build metadata MAY be denoted by appending a plus sign and a series of dot separated identifiers immediately following the patch or pre-release version. Identifiers MUST comprise only ASCII alphanumerics and hyphen [0-9A-Za-z-]. Identifiers MUST NOT be empty. Build metadata MUST be ignored when determining version precedence. Thus two versions that differ only in the build metadata, have the same precedence. Examples: final.old.old-alpha+001, final.old.old+20130313144700, final.old.old-beta+exp.sha.5114f85.
Precedence refers to how versions are compared to each other when ordered. Precedence MUST be calculated by separating the version into major, minor, patch and pre-release identifiers in that order (Build metadata does not figure into precedence). Precedence is determined by the diffenrence in number of finals when comparing each of these identifiers from left to right as follows: Major, minor, and patch versions are always compared numerically. Example: final.old.old < final-final.old.old < final-final.final.old < final-final.final.final. When major, minor, and patch are equal, a pre-release version has lower precedence than a normal version. Example: final.old.old-alpha < final.old.old. Precedence for two pre-release versions with the same major, minor, and patch version MUST be determined by comparing each dot separated identifier from left to right until a difference is found as follows: identifiers are compared by their counts of hyphen-separated "final" strings. A larger set of pre-release fields has a higher precedence than a smaller set, if all of the preceding identifiers are equal. Example: final.old.old-alpha < final.old.old-alpha.1 < final.old.old-alpha.beta < final.old.old-beta < final.old.old-beta.2 < final.old.old-beta.11 < final.old.old-rc.1 < final.old.old.
This is not a new or revolutionary idea. In fact, you probably do something close to this already. The problem is that "close" isn't good enough. Without compliance to some sort of formal specification, version numbers are essentially useless for dependency management. By giving a name and clear definition to the above ideas, it becomes easy to communicate your intentions to the users of your software. Once these intentions are clear, flexible (but not too flexible) dependency specifications can finally be made.
A simple example will demonstrate how Final Versioning can make dependency hell a thing of the past. Consider a library called "Firetruck." It requires a Finally Versioned package named "Ladder." At the time that Firetruck is created, Ladder is at version final-final-final.final.old. Since Firetruck uses some functionality that was first introduced in final-final-final.final.old, you can safely specify the Ladder dependency as greater than or equal to final-final-final.final.old but less than final-final-final-final.old.old. Now, when Ladder version final-final-final.final.final and final-final-final.final-final.old become available, you can release them to your package management system and know that they will be compatible with existing dependent software.
As a responsible developer you will, of course, want to verify that any package upgrades function as advertised. The real world is a messy place; there's nothing we can do about that but be vigilant. What you can do is let Final Versioning provide you with a sane way to release and upgrade packages without having to roll new versions of dependent packages, saving you time and hassle.
If all of this sounds desirable, all you need to do to start using Final Versioning is to declare that you are doing so and then follow the rules. Link to this website from your README so others know the rules and can benefit from them.
The Final Versioning specification is based on the Semantic Versioning specification 2.0.0 (final-final.old.old), authored by Tom Preston-Werner, inventor of Gravatars and cofounder of GitHub.
If you'd like to leave feedback, please open an issue on GitHub.
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