[LG-5129] feat(code-editor): add undo/redo functionality #3063 (#3091)

* feat(CodeEditor): add undo and redo functionality to the editor

- Implemented handleUndo and handleRedo methods to allow users to undo and redo editor actions.
- Updated CodeEditorHandle interface to include undo and redo methods, enhancing the editor's capabilities.
- Improved user experience by providing feedback when undo/redo actions are unavailable.

* feat(CodeEditor): add undo and redo methods to context and editor

- Introduced undo and redo functions in the CodeEditorContext to enhance user interaction.
- Updated the CodeEditor component to integrate these new functionalities, improving the overall editing experience.

* feat(Panel): integrate undo and redo functionality in the editor panel

- Added handleUndoClick and handleRedoClick methods to the Panel component to utilize the new undo and redo functions from the CodeEditorContext.
- Updated the onClick handlers for the Undo and Redo menu items to call the new methods, enhancing user interaction and experience.

* feat(CodeEditor): implement undo and redo methods in tests and utilities

- Added tests for undo and redo functionalities in the CodeEditor component, ensuring they work correctly with content changes.
- Enhanced test utilities to include getContent, undo, and redo methods, providing a more comprehensive testing framework for the editor.
- Updated the Panel component tests to verify the integration of undo and redo actions in the user interface, improving overall test coverage.

* feat(CodeEditor): enhance imperative handle API and testing utilities

- Updated the imperative handle test to expose a complete API, including methods for undo, redo, getContents, formatCode, and getEditorViewInstance.
- Added a new utility function, getHandle, to retrieve the editor handle instance for testing imperative methods.
- Modified the insertText function to default to inserting text at the end of the document, improving usability in tests.

* feat(CodeEditor): enhance documentation and add imperative API details

- Updated the README to clarify the various methods for formatting code in the CodeEditor, emphasizing the programmatic access through the CodeEditor ref.
- Introduced a new section detailing the imperative API, including methods for content manipulation, formatting, and undo/redo operations.
- Added examples for using the imperative methods, improving the documentation for developers.
- Adjusted the formatting options description to enhance clarity and usability.

* changeset

* chore: remove obsolete clever-editors-undo changeset file

* refactor(CodeEditor): reorganize testing utilities

- Moved `codeSnippets` to a dedicated testing file for better organization and accessibility.
- Updated import paths in the CodeEditor stories and specs to reflect the new location of `codeSnippets`.
- Introduced comprehensive test utilities for CodeMirror extension hooks, enhancing the testing framework's capabilities.

* feat(CodeEditor): add comprehensive testing utilities for Panel component

- Introduced `renderPanel` function to facilitate rendering of the Panel component with necessary context for testing.
- Added `PanelSelectors` for consistent access to panel elements in tests.
- Implemented various interaction methods for testing user interactions with the Panel, including format and copy button actions.
- Enhanced README documentation to include new testing utilities and examples for better guidance on testing Panel interactions.

* refactor(CodeEditor): update import paths for testing utilities

- Changed import paths in various extension spec files to reflect the new location of testing utilities, improving organization and accessibility.
- Ensured consistency across all extension tests by standardizing the import structure.

* refactor(CodeEditor): update module references for undo/redo functionality

- Changed references from `modules` to `coreModules` in the `handleUndo` and `handleRedo` functions to align with the updated module loading structure.
- Improved code clarity and maintainability by ensuring consistent usage of the core modules for command handling.

* refactor(CodeEditor): update testing utilities and documentation

- Renamed mock functions to default stub functions for clarity in the CodeEditor context.
- Updated the README to reflect changes in the testing utilities, including new context configuration options for overriding default functions in tests.
- Enhanced test cases to utilize the new stub functions, improving consistency and maintainability in testing the Panel component.

* refactor(CodeEditor): update import structure in useIndentExtension tests

- Reorganized import statements in the useIndentExtension.spec.ts file to improve clarity and maintainability.
- Moved the IndentUnits import to align with the updated structure of testing utilities.

* refactor(CodeEditor): update Panel tests to use default context functions

- Removed the use of mockPanelFunctions in Panel tests, replacing them with defaultPanelContextFunctions for improved clarity and consistency.
- Updated test cases to directly utilize context configuration for undo and redo actions, enhancing maintainability and readability of the tests.

Author: tsck

.changeset/sixty-turtles-tell.md

@@ -0,0 +1,15 @@
+---
+'@leafygreen-ui/code-editor': minor
+---
+
+**Feature**: Add comprehensive undo/redo functionality to CodeEditor component
+
+- **Imperative API**: Added `undo()` and `redo()` methods to CodeEditor ref handle that return boolean success indicators
+- **Panel integration**: Existing undo/redo buttons in Panel secondary menu now perform actual operations instead of just triggering callbacks
+- **Context support**: Undo/redo functions available to child components via `CodeEditorContext` for custom UI implementations
+- **Enhanced TypeScript**: Complete `CodeEditorHandle` interface documentation with all imperative methods (`getContents`, `formatCode`, `undo`, `redo`, `getEditorViewInstance`)
+- **Test utilities**: New testing helpers including `editor.getContent()`, `editor.getHandle()`, `editor.interactions.undo()`, and `editor.interactions.redo()`
+- **Improved testing**: Functional tests verify actual content changes rather than just mock function calls
+- **Documentation**: New "Imperative API" section in README with comprehensive examples and reorganized structure
+
+**Technical implementation**: Leverages CodeMirror's built-in `@codemirror/commands` module with proper error handling and integration into existing lazy-loading architecture. Maintains full backward compatibility while extending functionality.