Custom handlebars helper results in `ClassCastException` on `options.fn(this)`

[jgremmen]

I followed the documentation on adding additional HandleBars, like this:

tasks.named('gitChangelog', se.bjurr.gitchangelog.plugin.gradle.GitChangelogTask) {
  templateContent.set(layout.projectDirectory.dir("gradle").file("changelog.mustache").asFile.getText("UTF-8"))

  handlebarsHelpers.set([
      new HelperParam("ifCommitFeature", (String message, Options options) -> {
        return message.startsWith('feat: ')
            ? options.fn(this)
            : options.inverse(this)
      }),
  ])

When I use {{#ifCommitFeature messageTitle}} inside {{#commits}} I get the following exception from Gradle:

GitChangelog
com.github.jknack.handlebars.HandlebarsException: inline@79e75c35:23:9: java.lang.ClassCastException: class changelog_485vat4mka7v2dyta2ln8v3vq cannot be cast to class se.bjurr.gitchangelog.api.model.Commit (changelog_485vat4mka7v2dyta2ln8v3vq is in unnamed module of loader org.gradle.groovy.scripts.internal.DefaultScriptCompilationHandler$ScriptClassLoader @5923efd9; se.bjurr.gitchangelog.api.model.Commit is in unnamed module of loader org.gradle.internal.classloader.VisitableURLClassLoader$InstrumentingVisitableURLClassLoader @fa8fde4)
    inline@79e75c35:23:9
	at com.github.jknack.handlebars.internal.Block.merge(Block.java:199)
	at com.github.jknack.handlebars.internal.BaseTemplate.apply(BaseTemplate.java:97)
	at com.github.jknack.handlebars.internal.TemplateList.merge(TemplateList.java:81)
	at com.github.jknack.handlebars.internal.BaseTemplate.apply(BaseTemplate.java:97)
	at com.github.jknack.handlebars.internal.BaseTemplate.apply(BaseTemplate.java:86)
	at com.github.jknack.handlebars.Options.apply(Options.java:511)
	at com.github.jknack.handlebars.Options.fn(Options.java:417)
	at org.codehaus.groovy.vmplugin.v8.IndyInterface.fromCache(IndyInterface.java:321)

Initially the helper had Commit as its 1st parameter. Based on the exception I changed the commit to a regular string. Now I can at least see it enter my helper but on options.fn(this) it throws the exception.

I know the current code I posted doesn't justify its own helper but it is a starting point for a more complex evaluation.

Is there a way to solve this?

[tomasbjerre]

Works on my machine:
https://github.com/tomasbjerre/git-changelog-gradle-plugin/tree/feature/issue-58-custom-helper

bjerre@bjerre-hp ~/workspace/git-changelog-gradle-plugin/git-changelog-gradle-plugin-example (feature/issue-58-custom-helper) $ ./gradlew gitChangelogTaskWithHandlebarsHelpers -s
To honour the JVM settings for this build a single-use Daemon process will be forked. For more on this, please refer to https://docs.gradle.org/8.6/userguide/gradle_daemon.html#sec:disabling_the_daemon in the Gradle documentation.
Daemon will be stopped at the end of the build 
Reusing configuration cache.

BUILD SUCCESSFUL in 3s
1 actionable task: 1 executed
Configuration cache entry reused.
bjerre@bjerre-hp ~/workspace/git-changelog-gradle-plugin/git-changelog-gradle-plugin-example (feature/issue-58-custom-helper) $ cat CHANGELOG.md 

feature!: feat: expose git-changelog-lib as api
feature!: feat: stepping git-changelog-lib
feature!: feat: enable version change to be triggered by property 'setVersionConventional'
feature!: feat: sorting properties when setting version
feature!: feat: use special default template when prepending
feature!: feat: add filtering for footer tokens
feature!: feat: from/toRevision and prioritizing commits semantically when adding to tags
feature!: feat: stringHelpers
feature!: feat: add ignoreTagsIfNameMatches to gitChangelogSemanticVersion
feature!: feat: Move file default to task
feature!: feat: Add root gradle project as default git repository directory
feature!: feat: gitChangelogSemanticVersion
feature!: feat: adjusting to Gradle 7.6 (refs #40)
feature!: feat: enable partial templates by exposing missing Git Changelog lib properties
feature!: feat: prependToFile
feature!: feat: support conventional commits
bjerre@bjerre-hp ~/workspace/git-changelog-gradle-plugin/git-changelog-gradle-plugin-example (feature/issue-58-custom-helper) $ 

[jgremmen]

The test case is running under Gradle 8.6. I'm using Gradle 9.1.

[tomasbjerre]

Can you supply a complete failing example?

[jgremmen]

Sure, try my project over here
Just run the gitChangelog task

[tomasbjerre]

Change your helper like:

diff --git a/gradle/changelog.gradle b/gradle/changelog.gradle
index 758b92a..b5f01a8 100644
--- a/gradle/changelog.gradle
+++ b/gradle/changelog.gradle
@@ -35,8 +35,8 @@ tasks.named('gitChangelog', GitChangelogTask) {
       }),
       new HelperParam("ifCommitFeature", (String message, Options options) -> {
         return message.startsWith('feat: ')
-            ? options.fn(this)
-            : options.inverse(this)
+            ? options.fn(options.context)
+            : options.inverse(options.context)
       }),
   ])
 }

[jgremmen]

Awesome, thank you very much!