feat(snapshot): Add io.sentry.android.snapshot.metadata plugin by runningcode · Pull Request #1113 · getsentry/sentry-android-gradle-plugin

runningcode · 2026-03-19T13:45:24Z

Summary

Add a new standalone Gradle plugin (io.sentry.android.snapshot.metadata) that exports all Compose @Preview metadata to a JSON file using ASM bytecode scanning at build time
Can be applied independently without Paparazzi — only requires com.android.library or com.android.application

This works using two passes with ASM, very similar to the emerge-android approach.

Here is a sample of the generated json file, we can also filter out the nulls if that is better:

 "previews": [
        {
            "className": "com.emergetools.hackernews.ui.components.MetadataTag",
            "methodName": "MetadataTagPreview",
            "sourceFileName": "MetadataTag.kt",
            "previewName": "light",
            "configuration": {
                "apiLevel": null,
                "locale": null,
                "fontScale": 1.0,
                "uiMode": 0,
                "showSystemUi": false,
                "showBackground": false,
                "backgroundColor": null,
                "group": null,
                "wallpaper": null
            },
            "device": null,
            "previewParameter": null
        },
        ...
]

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github-actions · 2026-03-19T13:45:41Z

Semver Impact of This PR

🟡 Minor (new features)

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github-actions · 2026-03-19T13:45:54Z

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📖	Do not forget to update Sentry-docs with your feature once the pull request gets approved.

Generated by 🚫 dangerJS against 47ee093

@Preview

Add a standalone Gradle plugin that exports Compose @Preview metadata to a JSON file using ASM bytecode scanning. This plugin can be applied independently without Paparazzi — it only requires an Android plugin and compiled Kotlin classes. New plugin components: - PreviewScanner: ASM-based bytecode scanner for @Preview annotations - ExportPreviewMetadataTask: Cacheable task that scans compiled classes and writes preview-metadata.json - SentrySnapshotMetadataPlugin: Plugin entry point (requires com.android.library or com.android.application) - SentrySnapshotMetadataExtension: Configuration extension with includePrivatePreviews and packageTrees properties Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Fix matchesPackage to require a path separator after the prefix, preventing com.example from matching com.exampleextended. Combine source file extraction into the existing PreviewClassVisitor to eliminate a redundant bytecode parse per class file. Add tests for JAR scanning, private preview filtering, prefix collisions, and multi-package scanning. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

@Preview

…s support Add full multipreview annotation support to the snapshot metadata plugin, bringing it to parity with emerge-android's scanning capabilities: - Two-pass custom annotation discovery with nested annotation support - @Preview.Container for repeatable @Preview annotations - Built-in multipreview expansion (PreviewLightDark, PreviewFontScale, PreviewScreenSizes, PreviewDynamicColors, and 5 Wear OS previews) - @PreviewParameter extraction (provider class, limit, index, param name) - group and wallpaper @Preview fields - MergeClassesTask to explode JARs into a single directory before scanning Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

sentry · 2026-03-24T14:20:43Z

+    val rawClassName = relativePath.removeSuffix(".class").replace('/', '.').replace('\\', '.')
+    // Strip Kt suffix — Kotlin top-level functions compile to FooKt.class
+    val className = rawClassName.removeSuffix("Kt")


Bug: The code unconditionally strips the "Kt" suffix from all class names, which can corrupt the name of a regular class that legitimately ends with "Kt".
_{Severity: HIGH}

Suggested Fix

Instead of unconditionally stripping the "Kt" suffix, inspect the class's bytecode for the @Metadata annotation. Check the metadata kind field (k) to reliably distinguish between a file facade (where k=2) and a regular class (where k=1). Only remove the "Kt" suffix if the class is identified as a file facade.

Prompt for AI Agent

Review the code at the location below. A potential bug has been identified by an AI agent. Verify if this is a real issue. If it is, propose a fix; if not, explain why it's not valid. Location: plugin-build/src/main/kotlin/io/sentry/android/gradle/snapshot/metadata/ExportPreviewMetadataTask.kt#L95-L97 Potential issue: The logic to determine the class name unconditionally strips the "Kt" suffix from any class name ending with it. This is intended to handle Kotlin file facades (e.g., `GreetingKt.class` for `Greeting.kt`), but it incorrectly alters the names of regular classes that happen to end in "Kt" (e.g., `class NetworkKt`). This results in an incorrect `className` in the exported metadata, causing downstream consumers that rely on this name to fail silently when trying to locate and render composable previews.

_{Did we get this right? 👍 / 👎 to inform future reviews.}

cursor · 2026-03-24T14:22:51Z

+        PreviewConfig(name = "Unfolded Foldable", device = FOLDABLE, showSystemUi = true),
+        PreviewConfig(name = "Tablet", device = TABLET, showSystemUi = true),
+        PreviewConfig(name = "Desktop", device = DESKTOP, showSystemUi = true),
+      )


PreviewScreenSizes missing Tablet Landscape configuration

Medium Severity

The PREVIEW_SCREEN_SIZES expansion only produces 5 configurations, but the actual @PreviewScreenSizes annotation defines 6 — the "Tablet - Landscape" configuration is missing. Methods annotated with @PreviewScreenSizes will have incomplete metadata, missing the landscape tablet preview variant.

Move annotation descriptors, device specs, UI mode constants, and builtinMultipreviewConfigs() out of PreviewScanner.kt into a dedicated PreviewConstants.kt file for better organization. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Emerge-android doesn't have package filtering — the scope is controlled entirely by what MergeClasses puts into the directory. Remove scanPackages, namespace, packageTrees, matchesPackage, and scannedPackages to match that approach. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

cursor · 2026-03-24T14:53:06Z

+
+    // Inherit configs from already-discovered custom annotations
+    if (descriptor != null && customAnnotations.containsKey(descriptor)) {
+      current.previewConfigs.addAll(customAnnotations[descriptor]!!.previewConfigs)


Inherited custom configs not defensively copied

Low Severity

In FindCustomPreviewClassVisitor, configs inherited from custom annotations are added by reference (addAll without .map { it.copy() }), whereas PreviewMethodVisitor correctly copies them with .map { it.copy() }. Since PreviewConfig uses mutable var fields, this creates shared mutable state across entries in the customAnnotations map—an inconsistency that could lead to subtle mutation bugs if the code evolves.

Additional Locations (1)

plugin-build/src/main/kotlin/io/sentry/android/gradle/snapshot/metadata/PreviewScanner.kt#L217-L218

…1121) Instead of merging all classes into an intermediate directory, ExportPreviewMetadataTask now scans directories and JARs directly from the classpath. Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

cursor · 2026-03-26T08:54:40Z

+    val customAnnotations = mutableMapOf<String, CustomPreviewAnnotation>()
+    repeat(2) {
+      forEachClassEntry { _, bytes -> scanner.findCustomAnnotations(bytes, customAnnotations) }
+    }


Custom annotation nesting fails beyond one level deep

Low Severity

repeat(2) only resolves one level of custom annotation indirection under worst-case file ordering. For example, @Level2 → @Level1 → @Preview: if classes are visited in order Level2, Level1, Base, the second iteration still sees Level1 with zero configs when processing Level2. An iterate-until-stable loop would handle arbitrary nesting depth correctly.

Yup. this is a known bug. not worth adding the extra complexity until it becomes an issue with a customer.

@Preview

- Capitalize PreviewLightDark names to "Light"/"Dark" matching the actual @Preview annotations in Compose - Swap Blue/Green wallpaper values in PreviewDynamicColors to match Wallpapers.GREEN_DOMINATED_EXAMPLE=1 and BLUE_DOMINATED_EXAMPLE=2 - Only register classes with non-empty previewConfigs in FindCustomPreviewClassVisitor to avoid polluting the map Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

cursor

Cursor Bugbot has reviewed your changes and found 1 potential issue.

There are 4 total unresolved issues (including 3 from previous reviews).

^{Bugbot Autofix is OFF. To automatically fix reported issues with cloud agents, enable autofix in the Cursor dashboard.}

cursor · 2026-03-26T09:11:07Z

+    fun register(
+      project: Project,
+      extension: SentrySnapshotMetadataExtension,
+      android: BaseExtension,


Unused android parameter in task registration method

Low Severity

The android: BaseExtension parameter in ExportPreviewMetadataTask.register() is declared and passed by the caller in SentrySnapshotMetadataPlugin.wireWithAndroid() but never referenced inside the method body. This means project.extensions.getByType(BaseExtension::class.java) in the plugin is also unnecessary work. The parameter likely was intended for future variant-awareness (matching the TODO about hardcoded debug), but currently it's dead code.

Additional Locations (1)

plugin-build/src/main/kotlin/io/sentry/android/gradle/snapshot/metadata/SentrySnapshotMetadataPlugin.kt#L17-L19

runningcode and others added 4 commits March 24, 2026 14:18

style: Apply spotless formatting

c0e5852

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

runningcode force-pushed the no/snapshot-metadata-plugin branch from 770d9a2 to 0ede350 Compare March 24, 2026 14:12

runningcode marked this pull request as ready for review March 24, 2026 14:16

runningcode requested review from adinauer, chromy, markushi, rbro112 and romtsn as code owners March 24, 2026 14:16

sentry bot reviewed Mar 24, 2026

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cursor bot reviewed Mar 24, 2026

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Comment thread plugin-build/src/main/kotlin/io/sentry/android/gradle/snapshot/metadata/PreviewConstants.kt

Comment thread plugin-build/src/main/kotlin/io/sentry/android/gradle/snapshot/metadata/PreviewScanner.kt

cursor bot reviewed Mar 24, 2026

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rbro112 approved these changes Mar 25, 2026

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cursor bot reviewed Mar 26, 2026

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runningcode merged commit ae7ed20 into main Mar 26, 2026
20 of 21 checks passed

runningcode deleted the no/snapshot-metadata-plugin branch March 26, 2026 09:08

cursor bot reviewed Mar 26, 2026

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Summary

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PreviewScreenSizes missing Tablet Landscape configuration

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Inherited custom configs not defensively copied

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Custom annotation nesting fails beyond one level deep

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Unused android parameter in task registration method

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runningcode commented Mar 19, 2026 •

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Unused `android` parameter in task registration method