SetPrereleaseVersionInProjectJson.ps1

# Changes the existing project.json "version" into a prerelease string for a given branch
# name and build number. Prerelease strings are truncated to < 20 characters to work within
# NuGet length restrictions. Non-alphanumeric characters are sanitized from the branch name.
# Accommodates build numbers up to 5 digits.
#
# Examples:
# 
#   Version:     1.5.0
#   Branch:      Foo
#   BuildNumber: 123
#   NewVersion:  1.5.0-Foo123
#
#   (Existing prerelease strings in the version field are preserved)
#   Version:     1.5.0-beta001
#   Branch:      Foo
#   BuildNumber: 123
#   NewVersion:  1.5.0-beta001Foo123
#
#   (Prerelease strings are truncated to < 20 characters)
#   Version:     1.5.0-beta001
#   Branch:      MyReallyLongBranchName
#   BuildNumber: 12345
#   NewVersion:  1.5.0-beta001MyReally12345

# Usage:
# SetPrereleaseVersionInProjectJson.ps1 <branch-name> <build-number>

if ($args.Length -ne 2) {
    throw [ArgumentException] "Usage: SetPrereleaseVersionInProjectJson.ps1 <branch-name> <build-number>"
}

$Branch = $args[0]
$BuildNumber = $args[1]

if ($Branch -eq "master") {
    "Will not append prerelease version for master branch" | Write-Output
    exit 0
}

$ProjectJsonFile = ".\project.json"
$JsonIn = (Get-Content $ProjectJsonFile) -join "`n" | ConvertFrom-Json

# NuGet has a 20-character limit on version length. We add 5 here to accommodate the build
# number that we're going to append to the prerelease version. We'll account for that limit
# when combining the version and prerelease here.
# https://nuget.codeplex.com/workitem/3426

$ParsedVersion = ($JsonIn.version | Select-String '(\d+\.\d+\.\d+)(-?)(.*)' | Select -Expand Matches)

"Building prerelease string from Branch={0} BuildNumber={1} ParsedVersion={2}" -f $Branch , $BuildNumber , $ParsedVersion.Groups[0].Value | Write-Output

# Groups[3] will be any existing prerelease that's hard-coded into the project.json. We'll
# keep that in the new version string we build (with the branch name and build number), but
# will have to subtract its length.
$VersionLength = $ParsedVersion.Groups[3].Length
$MaxBranchNameLength = (20 - ($VersionLength + 5))

# Remove any extraneous special characters from the branch. We just want an alphanumeric prerelease string.
$SanitizedBranch = ("${Branch}" -replace '[^a-zA-Z0-9]', '')
$SanitizedBranch = ($SanitizedBranch.Substring(0, [math]::min($MaxBranchNameLength, $SanitizedBranch.Length)) + $BuildNumber)

$NewVersion = "{0}-{1}{2}" -f $ParsedVersion.Groups[1].Value , $ParsedVersion.Groups[3].Value , $SanitizedBranch

"Built prerelease string NewVersion={0} VersionLength={1} MaxBranchNameLength={2} SanitizedBranch={3}" -f $NewVersion , $VersionLength , $MaxBranchNameLength , $SanitizedBranch | Write-Output

$JsonIn.version = $NewVersion
$JsonOut = ConvertTo-Json $JsonIn -Depth 999

"Writing JSON to {0}:`n{1}" -f $ProjectJsonFile , $JsonOut | Write-Output

$JsonOut | Out-File $ProjectJsonFile -Encoding "UTF8"