Handle Gradle 8 HTML report compatibility

Issue: #2251
- Test: add a snapshot report regression on Gradle 8.14.3
- Impl: skip clipboard copy buttons when HtmlWriterTools is unavailable

Amp-Thread-ID: https://ampcode.com/threads/T-019d73e0-e0a5-7483-86c6-cc892c033432
Co-authored-by: Amp <amp@ampcode.com>

Author: tcmulcahy

paparazzi-gradle-plugin/src/main/java/app/cash/paparazzi/gradle/reporting/ClassPageRenderer.kt

@@ -5,7 +5,6 @@ import org.gradle.api.tasks.testing.TestOutputEvent
 import org.gradle.internal.html.SimpleHtmlWriter
 import org.gradle.internal.xml.SimpleMarkupWriter
 import org.gradle.reporting.CodePanelRenderer
-import org.gradle.reporting.HtmlWriterTools.addClipboardCopyButton
 import java.io.IOException
 
 internal class ClassPageRenderer(
@@ -175,7 +174,7 @@ internal class ClassPageRenderer(
               .characters("")
             resultsProvider.writeAllOutput(classId, TestOutputEvent.Destination.StdOut, htmlWriter)
             htmlWriter.endElement()
-            addClipboardCopyButton(htmlWriter, codeId)
+            addClipboardCopyButtonIfSupported(htmlWriter, codeId)
             htmlWriter.endElement()
           }
         }
@@ -196,11 +195,26 @@ internal class ClassPageRenderer(
               .characters("")
             resultsProvider.writeAllOutput(classId, TestOutputEvent.Destination.StdErr, htmlWriter)
             htmlWriter.endElement()
-            addClipboardCopyButton(htmlWriter, codeId)
+            addClipboardCopyButtonIfSupported(htmlWriter, codeId)
             htmlWriter.endElement()
           }
         }
       )
     }
   }
+
+  private fun addClipboardCopyButtonIfSupported(htmlWriter: SimpleHtmlWriter, codeId: String) {
+    addClipboardCopyButtonMethod?.invoke(null, htmlWriter, codeId)
+  }
+
+  private companion object {
+    // Gradle 8 does not expose HtmlWriterTools, so copy buttons are best-effort.
+    val addClipboardCopyButtonMethod = runCatching {
+      Class.forName("org.gradle.reporting.HtmlWriterTools").getMethod(
+        "addClipboardCopyButton",
+        SimpleHtmlWriter::class.java,
+        String::class.java
+      )
+    }.getOrNull()
+  }
 }

paparazzi-gradle-plugin/src/test/java/app/cash/paparazzi/gradle/PaparazziPluginTest.kt

@@ -1551,7 +1551,17 @@ class PaparazziPluginTest {
 
   @Test
   fun snapshotReport() {
+    assertSnapshotReport(gradleRunner)
+  }
+
+  @Test
+  fun snapshotReportGradle8_14_3() {
+    assertSnapshotReport(gradleRunner.withGradleVersion("8.14.3"))
+  }
+
+  private fun assertSnapshotReport(gradleRunner: GradleRunner) {
     val fixtureRoot = File("src/test/projects/report-snapshots")
+    fixtureRoot.resolve("build").registerForDeletionOnExit().deleteRecursively()
     val testReportDir = File(fixtureRoot, "build/reports/tests/testDebugUnitTest/classes")
 
     val result = gradleRunner