SemanticVersion 2.0.0

Abstract

This project aims to implement the complete 2.0 semantic versions standard as a Netstandard library. In addition to 2.0 standard features it extends the standard to allow users to specify version ranges via simple to use and know C# operators.

Description

Current implementations of the semantic versions standard available on NuGet are either implemented as full .NET projects, or old PCL profiles. In many cases the last update to the codebase was from over a year ago and an update is not likely anymore. Since full .NET versions can't be used from ASP.NET/DnxCore projects and PCLs are sometimes a bit "wonky", a implementation based entirely on the new ASP.NET/DnxCore was in order. This library aims to provide a strict implementation of the version standard with extras added on top of it. This means, that every single semantic version is also a valid version for this library, but not necessary vice versa.

An extension of the the standard includes a method to parse multiple versions from a string into a set of versions (also called: version range) and partial versions. Partial versions are mostly syntactic sugar for a version range and will be described in more detail below.

Equality

By default this library compares two semantic versions as described in the standard. This means, that 1.0.0 == 1.0.0 == 1.0.0+1234 equals to true, but 1.2.0 == 1.2.0-alpha equals to false. If a different comparison behaviour is intended a user can roll out their own implementation of the IComparer<SemanticVersion> interface and pass it to the version via the static factory method SemanticVersion.ChangeComparer. Usually it is not necessary to implement the IEqualityComparer<T> interface, since two versions are considered equal if CompareTo == 0 applies. However the reference equality comparer implements this interface, too.

Parsing

This library supports implicit casting from strings into a suitable semantic version object. Parsing via an implicit conversion will -- like the SemanticVersion.Parse method -- throw an error, if the string has the wrong format. Additionally the SemanticVersion class includes a TryParse method which returns true if the cast was successful. See the documentation for additional details. Some users might want to convert from a C# version object into an appropriate semantic version. Since a C# version object handles builds and prereleases different from semantic versions and any conversion inevitably leads to data loss, this library only supports explicit casting. With this method, the C# Build property is identical to the Patch property, whereas the Revision property is equivalent to the Build property. A Prerelease property is never set.

Version Ranges

As describes above, this implementation supports a set of versions, mainly to describe dependencies against other APIs. A goal was to make version ranges as intuitive as possible. Thus, many C# logic operators apply to version ranges. Currently the supported operators are:

• OrElse (x || y)
• AndAlso (x && y)
• Not (!x)

In addition to the above operators, any equality (==/!=) and ordering (<, <=, >, >=) operators can be used to create version ranges. The syntax requires the variable to reside on the left side of the operator (i.e. x >= 1.0.0), however the variable may be omitted entirely.

If an expression has to be handled before another expression the expression can be wrapped into the ( and ) parentheses. This will raise the expressions precedence to the highest level. Nested parentheses are also possible.

Operator Precedence

All expressions in this library are left-associative, meaning if two expression with the same precedence have to be evaluated, they are looked at from left to right. Implicitly an expression with a higher precedence is evaluated before any expression with a lower precedence. The current precedence order is (high to low):

• Parentheses
• AndAlso
• OrElse
• Equality, Ordering, Not

Range parsing

Parsing a version range from a string can be beneficial on many occasions. Thus this library includes a version range parser, that parses a version range from a string into the appropriate Expression<Func<SemanticVersion, bool>>, which the user can further alter to suit his needs. In most cases the RangeParser.Evaluate method will suffice, since it compiles the expression into a usable Func<SemanticVersion, bool>, although this comes with a certain performance cost. Since the RangeParser.Parse and RangeParser.Evaluate methods throw exceptions when encountering an error, the library also includes a RangeParser.TryParse and RangeParser.TryEvaluate method.

Eamples

Example 1, Creating a version with a constructor

SemVer.SemanticVersion version = new SemVer.SemanticVersion(1,0,0, "alpha", "1234");

Example 2, Implicitly converting a string into a SemanticVersion

SemVer.SemanticVersion version = "1.0.0-alpha.1+1234"

Example 3, Parsing a version range and compare to specific version

SemVer.Parser.RangeParser parser = new SemVer.Parser.RangeParser();
Func<SemVer.SemanticVersion, bool> range = parser.Evaluate(">= 1.0.0 && < 2.0.0");

if(range(new SemVer.SemanticVersion(1,2,0, "alpha")))
    Console.WriteLine("Passed");
else
    Console.WriteLine("Failed");