Automating .net library versioning - Process

December 26, 2019

This is the second post in a series on a method of automating .net library versioning. The first post described the synver dotnet tool which can be used to find the magnitude of library API changes according to the semantic versioning rules.

Semantic versioning is a popular method for versioning software libraries. It describes three different types of change that can happen in libraries, Major, Minor and Patch. To decide the type of a change in the library, from one version to the next, one needs to take into account library behaviour and API changes.

Unlike public API changes, It’s impossible to detect and verify the magnitude of changes in behaviour of code in an automated way, the responsibility of documenting behaviour changes is left to the developer.

Conventional commits

Library changes can be described alongside the code, using a method called conventional commits. The commit message describes the magnitude of the changes using certain message prefixes.

  • BREAKING CHANGE is used in the messages of commits that contain Major level changes.
  • feat is used to denote Minor level changes.
  • fix or chore are used to denote Patch level changes.

Using this convention it is possible to derive the next version number and generate documentation from the commit messages since the last version.

An example of conventional commits can be seen in the following git log --oneline for a fictitious DSL parser:

d7dfb26 fix: Merge conflicts.
c00e854 BREAKING CHANGE: Removed key words for new client.  # c3c552a -> c00e854 = v2.0.0
51fb925 chore: Tweaked build script
88732bd feat: Added new key word                            # c3c552a -> 88732bd = v1.1.0
c61a4b3 chore: Tidied code up                               # c3c552a -> c61a4b3 = v1.0.1
0918831 fix: Fixed bug with parser
c3c552a (tag: v1.0.0) Changes for v1.0.0                    # c3c552a = v1.0.0

In the example version v1.0.0 is tagged at the commit c3c552a. If a new version is at the commit c61a4b3 the commits between the two are prefixed with fix and chore and this introduces a Patch level change to produce v1.0.1. If the new version was at 88732bd then the commit history between c3c552a -> 88732bd includes feat which calls for a Minor change and produces v1.1.0. If the version were to be introduced at c00e854 the version would include a Major change commit and therefore be v2.0.0

Automated workflow.

Behavioural changes can be described in commit messages using conventional commits and API (syntactic) changes can be derived with the synver tool. Combining these methods we can automate nuget package library versioning.

We need to store the last published library version and public API to be able to determine the next version number. The version can be stored on the commit as a git tag and the public API can be stored in a text file MyProject.lson in the repository using synver’s --surface-of command. These will be updated in the repo when the package is published during the build process.

From a developer’s perspective the workflow should be:

  • Develop library changes.
  • Push to master (or other publishing branch)
  • CI process builds and publishes package with new version number
  • Developer consumes package

For this to work the CI process needs to:

  • If no commits since last tag, do nothing (to stop infinite loops from git push at end of process)
  • Code is built, tests are run, all OK
  • Previous version is retrieved from tags
  • Run a script to determine the new version from the MyProject.lson file and commit messages since last tag
  • Package is built with new version number
  • MyProject.lson file is updated from built MyProject.dll
  • Changes to MyProject.lson are committed with version documentation
  • Commit tagged with version and pushed to master
  • Package is published to nuget feed

The version determining script in the CI process needs to:

  • Determine behaviour changes magnitude according to conventional commits
  • Determine API changes magnitude derived from MyProject.lson in repo and built MyProject.dll
  • Biggest magnitude from the two above becomes the version type change where Major > Minor > Patch
  • New version number is calculated from magnitude plus current version number


The above steps can be implemented as part of a CI process using scripts that are located in the library repository. An example of this can be seen in the AutoSemVerLib github repository. The library contains the following powershell scripts:

  • versioning/AutoSemVer.ps1 - Contains generic functions to call synver and calculate version magnitude differences. Can be treated like a re-usable module. The script is configured with environment variables:
    • TAG_VERSION_REGEX - Regex that defines version format in git tags.
    • BUILT_NAME_REL - Path of the .dll file when built.
    • CURRENT_API_NAME - Path of the lson representation of the API file in the repository.
  • BuildVersioning.ps1 - Contains functions that are specific to the build, source control and publishing technologies. In this case dotnet core, GitHub and GitHub packages. It also contains code to generate the documentation produced by the automated process. The script is configured with environment variables that define the git and github config.
  • BuildAndPublish.ps1 - High level script which runs the build, pack and publish. This script imports the BuildVersioning.ps1 script, which imports the AutoSemVer.ps1 script and uses the functions.

The BuildAndPublish.ps1 script shows the process at a high level:

. "./BuildVersioning.ps1"

if((NeedToRun) -eq $false){
    Write-Host "Dont need to run script"
    exit 0

$projFile = "src/MyProject.csproj"

dotnet build $projFile -c Release 

$nextVersion = Bump

dotnet pack $projFile -c Release /p:Version=$nextVersion -o out


$packagePath = ls -Path ./out -Filter "*.nupkg" | sort LastWriteTime `
                | select -last 1 | select -ExpandProperty FullName
PushToFeed $packagePath

This flowchart shows the logic of the script:


A CI technology is required to be the execution platform and a package feed is required to host the package. The next post describes the steps and code needed to achieve this with Github Actions and the GitHub Package Registry.

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