GitHub Copilot modernization - upgrade for Java

Scans the entire Java project structure, parses build configuration (Maven/Gradle), and inventories all direct and transitive dependencies. Generates a customizable upgrade plan that identifies outdated libraries, framework versions, and Java language features, presenting recommendations in a VS Code UI panel that developers can review, edit, and approve before execution. Uses AST-level analysis to understand dependency usage patterns across the codebase.

Executes code transformations against the Java project using OpenRewrite, an open-source framework that applies composable, recipe-based code modifications. Transformations are applied at the AST level, ensuring structural correctness (not regex-based). The extension runs transformations in a controlled manner, validates syntax, and automatically resolves build issues by re-running Maven/Gradle builds and fixing compilation errors.

After code transformation completes, scans all dependencies and transitive libraries for known Common Vulnerabilities and Exposures (CVEs) using a vulnerability database. Identifies vulnerable versions, cross-references with available patches, and uses GitHub Copilot's 'Agent Mode' to automatically apply fixes by updating dependency versions or applying security patches. Detects code inconsistencies introduced by upgrades and suggests corrections.

Generates new unit test cases using GitHub Copilot to increase test coverage for code modified during the upgrade process. Analyzes which methods and classes were changed, understands their new signatures and behavior, and generates test cases that validate the upgraded code. Tests are generated separately from the upgrade process, allowing developers to review and integrate them independently. Uses LLM-based code understanding to infer test scenarios from method signatures and documentation.

Generates a detailed summary report after the upgrade process completes, documenting all file changes, updated dependencies with version deltas, test results, and remaining issues. Tracks commits and logs changes in a working branch, providing a complete audit trail. Summary includes metrics like number of files modified, dependencies upgraded, CVEs resolved, and test coverage delta. Enables developers to review the entire upgrade impact before merging to main branch.

Presents the generated upgrade plan in a VS Code UI panel where developers can review, edit, and customize recommendations before execution. Allows selective enabling/disabling of specific upgrades, version pinning, and dependency exclusions. Changes to the plan are validated in real-time (e.g., checking for version conflicts) and reflected in the execution preview. Developers can add notes or justifications for customizations, which are preserved in the audit trail.

Analyzes Java source code to identify opportunities for using newer language features (e.g., lambda expressions, records, sealed classes, pattern matching) available in the target Java version. Generates recommendations for code patterns that can be simplified or improved using modern syntax. Uses AST analysis to understand code structure and LLM reasoning to suggest idiomatic Java patterns. Recommendations are presented alongside upgrade plans and can be applied selectively.

Validates that upgraded dependencies are compatible with the project's build system (Maven or Gradle) and Java version. Checks for plugin version compatibility, enforces dependency constraint rules, and detects conflicts between transitive dependencies. Runs the build system to validate that the project compiles and tests pass after upgrades. Automatically suggests build configuration changes (e.g., updating plugin versions) if needed to resolve incompatibilities.

Executes all upgrade operations in an isolated Git working branch, preserving the main branch in its original state. All changes (code transformations, dependency updates, test generation) are committed to the working branch with detailed commit messages. Developers can review changes in the working branch, run additional tests, and merge to main when confident. If issues arise, developers can discard the working branch and start over, or cherry-pick specific commits. Provides Git diff visualization in VS Code for easy review.

Collects anonymized usage telemetry about extension behavior, including which features are used, upgrade success rates, and performance metrics. Data is sent to Microsoft for product improvement purposes. Developers can disable telemetry by setting the `telemetry.enableTelemetry` VS Code configuration to `false`. Telemetry data is governed by the VS Code privacy statement and GitHub Copilot Product Specific Terms.