Build the released packages when a nightly publish has nothing to release

ci/build-package.ps1

@@ -6,9 +6,12 @@ $ErrorActionPreference = "Stop"
 . (Join-Path $PSScriptRoot 'packages.ps1')
 
 # Builds the packages this publish releases, each at its own version from the
-# release plan. $Version is common-ci's label for the run and is not used.
+# release plan. When nothing is to be released, every package is built at its
+# released version, so that the tests have packages to install and the nightly
+# publish passes without publishing anything. $Version is common-ci's label for
+# the run and is not used.
 
-$plan = @(Get-ReleasePlan $RepoName)
+$plan = @(Get-BuildPlan $RepoName)
 
 # fiftyone_pipeline_did carries the OWID source inside itself, copied in by the
 # pipeline product's script; see pipeline/ci/copy-owid-source.ps1.

ci/packages.Tests.ps1

@@ -249,6 +249,36 @@ Describe 'Get-ReleasePlan' {
     }
 }
 
+Describe 'Get-BuildPlan' {
+    It 'is the release plan when a package is to be released' {
+        $script:Repo = New-Repo $script:AllFiles ($script:AllTags + 'ipi/4.5.0')
+        Add-Commit $script:Repo @('pipeline/engines/a.py')
+        $plan = @(Get-BuildPlan $script:Repo $script:Graph)
+        $plan.Name | Should -Be @('engines', 'dd', 'ipi')
+        ($plan | Where-Object Name -eq 'engines').Version | Should -Be '4.5.39'
+    }
+
+    It 'builds every published package at its released version when nothing changed' {
+        $script:Repo = New-Repo $script:AllFiles ($script:AllTags + 'ipi/4.5.0')
+        Add-Commit $script:Repo @()
+        @(Get-ReleasePlan $script:Repo $script:Graph).Count | Should -Be 0
+        $plan = @(Get-BuildPlan $script:Repo $script:Graph)
+        $plan.Name | Should -Be @('core', 'did', 'engines', 'location', 'dd', 'ipi')
+        ($plan | Where-Object Name -eq 'core').Version | Should -Be '4.5.38'
+        ($plan | Where-Object Name -eq 'dd').Version | Should -Be '4.5.96'
+        ($plan | Where-Object Name -eq 'location').Version | Should -Be '4.5.4'
+        ($plan | Where-Object Name -eq 'ipi').Version | Should -Be '4.5.0'
+    }
+
+    It 'builds the released versions from a commit already released' {
+        $script:Repo = New-Repo $script:AllFiles ($script:AllTags + 'ipi/4.5.0')
+        Add-Commit $script:Repo @('device/dd/a.py')
+        git -C $script:Repo tag 'dd/4.5.97'
+        ($plan = @(Get-BuildPlan $script:Repo $script:Graph)).Count | Should -Be 6
+        ($plan | Where-Object Name -eq 'dd').Version | Should -Be '4.5.97'
+    }
+}
+
 Describe 'the real packages.json' {
     BeforeAll {
         $script:Real = Get-Packages (Split-Path $PSScriptRoot)

ci/packages.ps1

@@ -292,3 +292,29 @@ function Get-ReleasePlan([string]$RepoPath, $Packages = $null) {
         }
     }
 }
+
+# What a build of HEAD makes: the release plan, or, when nothing changed since
+# the last release, every published package at its released version. Nothing
+# is published then, because package-update-required.ps1 finds the release
+# plan empty, but the publish's tests still have the packages to install.
+function Get-BuildPlan([string]$RepoPath, $Packages = $null) {
+    if ($null -eq $Packages) {
+        $Packages = Get-Packages $RepoPath
+    }
+    $plan = @(Get-ReleasePlan $RepoPath $Packages)
+    if ($plan.Count -gt 0) {
+        return $plan
+    }
+    $published = @($Packages | Where-Object { $_.Publish -eq $true })
+    foreach ($name in (Sort-ByDependency $published @($published.Name))) {
+        $package = $published | Where-Object { $_.Name -eq $name }
+        $last = @(Get-ReleasedVersions $RepoPath $name)[-1]
+        [pscustomobject]@{
+            Name = $name
+            Path = $package.Path
+            Version = "$last"
+            Previous = $last
+            Reason = 'already released, built for the tests'
+        }
+    }
+}