feat: add LitRenderer.withFunction migration support

[javier-godoy]

Close #33

Summary by CodeRabbit

• New Features

  • Added support for registering LitRenderer event handlers across Vaadin versions, with automatic compatibility handling for Vaadin 25+.

• Tests

  • Added validation tests ensuring LitRenderer event handler registration works as expected.

• Chores

  • Updated build/tooling to support the migration and packaging workflow (internal post-processing and exclusions).

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: 351a9c22-445f-4513-87f4-a98d0965c5ca

📥 Commits

Reviewing files that changed from the base of the PR and between bfc8a5d and be33f24.

📒 Files selected for processing (4)

• pom.xml
• src/main/java/com/flowingcode/vaadin/jsonmigration/LitRendererAsmPostProcessor.java
• src/main/java/com/flowingcode/vaadin/jsonmigration/LitRendererMigrationExtension.java
• src/test/java/com/flowingcode/vaadin/jsonmigration/LitRendererMigrationExtensionTest.java

🚧 Files skipped from review as they are similar to previous changes (3)

• pom.xml
• src/main/java/com/flowingcode/vaadin/jsonmigration/LitRendererAsmPostProcessor.java
• src/test/java/com/flowingcode/vaadin/jsonmigration/LitRendererMigrationExtensionTest.java

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Walkthrough

Adds a build-time ASM post-processor and Maven config to remap a stub LitRenderer to Vaadin's LitRenderer, a runtime LitRendererMigrationExtension.withFunction adapter that converts JSON argument types across Vaadin versions, and a JUnit test that verifies handler registration.

Changes

LitRenderer Cross-Version Support

Layer / File(s)	Summary
Build-time ASM post-processor and configuration pom.xml, src/main/java/com/flowingcode/vaadin/jsonmigration/LitRendererAsmPostProcessor.java	Maven adds asm-commons and configures patch-lit-renderer to run LitRendererAsmPostProcessor during process-classes. The post-processor remaps LitRendererMigrationExtension$LitRenderer → com.vaadin.flow.data.renderer.LitRenderer, filters InnerClasses metadata, writes patched .class files, deletes the orphaned inner-class, and excludes the processor from javadoc/jar.
Runtime handler compatibility wrapper src/main/java/com/flowingcode/vaadin/jsonmigration/LitRendererMigrationExtension.java	Adds withFunction(renderer, name, handler) that on Vaadin ≥25 wraps incoming Jackson ArrayNode to elemental.json.JsonArray via JsonMigration.convertToJsonValue before invoking the provided SerializableBiConsumer, otherwise delegates directly. Includes a private nested LitRenderer<SOURCE> wrapper type.
Handler registration test src/test/java/com/flowingcode/vaadin/jsonmigration/LitRendererMigrationExtensionTest.java	JUnit test (Vaadin 24+ gated) reflectively creates a LitRenderer, calls withFunction for "click", asserts the same renderer instance is returned, and verifies the handler was registered by locating a Map-typed field containing "click".

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🎯 3 (Moderate) | ⏱️ ~25 minutes

Suggested reviewers:

• mlopezFC
• paodb

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 14.29% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title 'feat: add LitRenderer.withFunction migration support' clearly and accurately summarizes the main change: adding a new migration helper for LitRenderer.withFunction compatibility.
Linked Issues check	✅ Passed	The code implements all requirements from #33: provides LitRendererMigrationExtension.withFunction static helper, delegates to renderer.withFunction on Vaadin <25, wraps handler to convert ArrayNode to JsonArray on 25+, uses ASM post-processing to resolve LitRenderer at build time, and matches the add-on's existing elemental.json ↔ Jackson compatibility approach.
Out of Scope Changes check	✅ Passed	All changes are directly scoped to implementing LitRenderer.withFunction migration support: LitRendererMigrationExtension API, LitRendererAsmPostProcessor for build-time LitRenderer resolution, test coverage, and necessary pom.xml configuration. No unrelated modifications detected.

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✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch feat-33

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[coderabbitai]

🧹 Nitpick comments (1)

src/main/java/com/flowingcode/vaadin/jsonmigration/LitRendererMigrationExtension.java (1)

6-8: 💤 Low value

Remove unused imports.

MethodHandle, MethodHandles, and MethodType are imported but never used in this class.

♻️ Proposed fix

 import com.vaadin.flow.function.SerializableBiConsumer;
 import com.vaadin.flow.server.Version;
 import elemental.json.JsonArray;
-import java.lang.invoke.MethodHandle;
-import java.lang.invoke.MethodHandles;
-import java.lang.invoke.MethodType;
 import lombok.SneakyThrows;

🤖 Prompt for AI Agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

In
`@src/main/java/com/flowingcode/vaadin/jsonmigration/LitRendererMigrationExtension.java`
around lines 6 - 8, Remove the unused imports MethodHandle, MethodHandles, and
MethodType from the LitRendererMigrationExtension class: locate the import
statements for MethodHandle, MethodHandles, and MethodType at the top of
LitRendererMigrationExtension.java and delete them so only used imports remain.

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Nitpick comments:
In
`@src/main/java/com/flowingcode/vaadin/jsonmigration/LitRendererMigrationExtension.java`:
- Around line 6-8: Remove the unused imports MethodHandle, MethodHandles, and
MethodType from the LitRendererMigrationExtension class: locate the import
statements for MethodHandle, MethodHandles, and MethodType at the top of
LitRendererMigrationExtension.java and delete them so only used imports remain.

---

ℹ️ Review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: baf80680-775c-4bac-8fde-553e6e3d1da6

📥 Commits

Reviewing files that changed from the base of the PR and between 3c4fa9f and bfc8a5d.

📒 Files selected for processing (4)

• pom.xml
• src/main/java/com/flowingcode/vaadin/jsonmigration/LitRendererAsmPostProcessor.java
• src/main/java/com/flowingcode/vaadin/jsonmigration/LitRendererMigrationExtension.java
• src/test/java/com/flowingcode/vaadin/jsonmigration/LitRendererMigrationExtensionTest.java

[javier-godoy]

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[coderabbitai]

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