Module FileExplorerViewProvider 

FileExplorerViewProvider (FileSystem)

A native (Rust-implemented) TreeViewProvider that provides the data for the file explorer (tree) view in Mountain. This is a native provider, meaning it is implemented directly in Rust rather than being provided by an extension.

RESPONSIBILITIES

1. Root-Level Items (Workspace Folders)

• Return the list of workspace folders as root tree nodes
• Each folder appears as a collapsible node at the top level
• Folder names are displayed as labels

2. Directory Listing

• Provide children for a given directory URI (via GetChildren)
• Read filesystem to enumerate files and subdirectories
• Return appropriate TreeItemDTO for each entry
• Handle permissions errors gracefully

3. Tree Item Construction

• Build TreeItemDTO JSON objects with proper structure:
  • handle: Unique identifier (file URI)
  • label: Display name
  • collapsibleState: 1 for directories, 0 for files
  • resourceUri: File URI with external property
  • command: Open file command for leaf nodes

ARCHITECTURAL ROLE

The FileExplorerViewProvider is a native TreeViewProvider:

TreeView API ──► FileExplorerViewProvider ──► FileSystem ReadDirectory/ReadFile
                         │
                         └─► Returns TreeItemDTO JSON

Position in Mountain

• FileSystem module: File system operations
• Implements CommonLibrary::TreeView::TreeViewProvider trait
• Registered as provider in ApplicationState::ActiveTreeViews

Differences from Extension Providers

• Native Provider: Direct Rust implementation, no extension hosting
• Read-Only: Only implements “pull” methods (GetChildren, GetTreeItem)
• No Push Methods: Does not use RegisterTreeDataProvider, RefreshTreeView, etc.
• No Sidecar: No extension host communication overhead

Dependencies

• CommonLibrary::FileSystem::ReadDirectory and ReadFile: Filesystem access
• CommonLibrary::TreeView::TreeViewProvider: Provider trait
• ApplicationRunTime: Effect execution
• ApplicationState: Workspace folder access

Dependents

• Binary::Main::Fn: Creates and registers provider instance
• TreeView UI component: Requests data via provider methods
• Command handlers: Trigger tree view operations

TREE ITEM DTO STRUCTURE

Each tree item is a JSON object compatible with VS Code’s TreeItem:

{
  "handle": "file:///path/to/item",
  "label": { "label": "itemName" },
  "collapsibleState": 1,
  "resourceUri": { "external": "file:///path/to/item" },
  "command": {
    "id": "vscode.open",
    "title": "Open File",
    "arguments": [{ "external": "file:///path/to/item" }]
  }
}

METHODS OVERVIEW

• GetChildren: Returns child items for a given parent directory
• GetTreeItem: Returns a single tree item for a given handle (URI)
• Other TreeViewProvider methods (push-based) are no-ops for native providers

ERROR HANDLING

• Filesystem errors are converted to CommonError::FileSystemIO
• Invalid URIs return CommonError::InvalidArgument
• Permission errors are logged and empty results returned

PERFORMANCE

• Directory reads are async via ApplicationRunTime
• Each GetChildren call reads the directory from disk
• Consider caching for large directories (TODO)
• Stat calls are minimized by using directory entry metadata

VS CODE REFERENCE

Patterns from VS Code:

• vs/workbench/contrib/files/browser/filesViewProvider.ts: File tree provider
• vs/platform/workspace/common/workspace.ts: Tree item DTO structure

TODO

• Implement tree item caching for better performance
• Add file icon decoration based on file type
• Support drag-and-drop operations
• Add file/folder filtering (gitignore, exclude patterns)
• Implement tree state persistence (expanded/collapsed)
• Add file change notifications (watch for file system events)
• Support virtual workspace folders (non-file URIs)

MODULE CONTENTS

• FileExplorerViewProvider: Main provider struct
• CreateTreeItemDTO: Helper to build tree item JSON

Structs

FileExplorerViewProvider