fix: Handle null bullet point detection in update-changelog script (#125)

* fix: Handle null bullet point detection in update-changelog script

The script was failing when trying to detect bullet point characters
in changelogs that contained no existing bullet points. This occurred
because the Where-Object filter returned null, and calling .Trim() on
null caused a "You cannot call a method on a null-valued expression" error.

Fixed by wrapping the variable in quotes to convert null to empty string
before calling .Trim(), which effectively defaults to using "-" as the
bullet point character.

Added test case for this scenario to prevent regression.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

* docs: Add changelog entry for null bullet point fix

---------

Co-authored-by: Claude <noreply@anthropic.com>

Author: vaind

CHANGELOG.md

@@ -71,6 +71,7 @@
 
 ### Fixes
 
+- Updater - Fix null reference error when changelog has no existing bullet points ([#125](https://github.com/getsentry/github-workflows/pull/125))
 - Updater - Fix bullet-point resolution when plain text precedes bullet points ([#123](https://github.com/getsentry/github-workflows/pull/123))
 - Improve changelog generation for non-tagged commits and edge cases ([#115](https://github.com/getsentry/github-workflows/pull/115))
 

updater/scripts/update-changelog.ps1

@@ -180,7 +180,7 @@ if (!$updated)
 {
     # Find what character is used as a bullet-point separator - look for the first bullet-point object that wasn't created by this script.
     $bulletPoint = $lines | Where-Object { ($_ -match '^ *[-*] ') -and -not ($_ -match '(Bump .* to|\[changelog\]|\[diff\])') } | Select-Object -First 1
-    $bulletPoint = "$($bulletPoint.Trim())-"[0]
+    $bulletPoint = "$("$bulletPoint".Trim())-"[0]
     $entry = @("$bulletPoint Bump $Name from $oldTagNice to $newTagNice ($PullRequestMD)",
         "  $bulletPoint [changelog]($RepoUrl/blob/$MainBranch/CHANGELOG.md#$tagAnchor)",
         "  $bulletPoint [diff]($RepoUrl/compare/$OldTag...$NewTag)")

updater/tests/testdata/changelog/no-bullet-points/CHANGELOG.md.expected

@@ -0,0 +1,16 @@
+# Changelog
+
+## Unreleased
+
+### Dependencies
+
+- Bump Dependency from v7.16.0 to v7.17.0 ([#123](https://github.com/getsentry/dependant/pulls/123))
+  - [changelog](https://github.com/getsentry/dependency/blob/main/CHANGELOG.md#7170)
+  - [diff](https://github.com/getsentry/dependency/compare/7.16.0...7.17.0)
+
+## 0.14.0
+
+### Dependencies
+
+This section contains only plain text with no bullet points.
+The update-changelog script should handle this case gracefully.

updater/tests/testdata/changelog/no-bullet-points/CHANGELOG.md.original

@@ -0,0 +1,8 @@
+# Changelog
+
+## 0.14.0
+
+### Dependencies
+
+This section contains only plain text with no bullet points.
+The update-changelog script should handle this case gracefully.

updater/tests/update-changelog.Tests.ps1

@@ -32,4 +32,20 @@ Describe 'update-changelog' {
         #  verify the full output matches expected
         Get-Content "$testCasePath/CHANGELOG.md" | Should -Be (Get-Content "$testCasePath/CHANGELOG.md.expected")
     }
+
+    It 'should handle changelogs with no bullet points by defaulting to dash' {
+        $testCasePath = "$PSScriptRoot/testdata/changelog/no-bullet-points"
+        Copy-Item "$testCasePath/CHANGELOG.md.original" "$testCasePath/CHANGELOG.md"
+
+        pwsh -WorkingDirectory $testCasePath -File "$PSScriptRoot/../scripts/update-changelog.ps1" `
+            -Name 'Dependency' `
+            -PR 'https://github.com/getsentry/dependant/pulls/123' `
+            -RepoUrl 'https://github.com/getsentry/dependency' `
+            -MainBranch 'main' `
+            -OldTag '7.16.0' `
+            -NewTag '7.17.0' `
+            -Section 'Dependencies'
+
+        Get-Content "$testCasePath/CHANGELOG.md" | Should -Be (Get-Content "$testCasePath/CHANGELOG.md.expected")
+    }
 }