Add document formatting provider for MIDL3 with configurable brace style, context-aware attributes, and import separation

FORMATTING.md

@@ -0,0 +1,137 @@
+# MIDL3 Document Formatting
+
+This document describes the document formatting feature added to the MIDL3 language server.
+
+## Overview
+
+The MIDL3 language server now includes a document formatter, similar to `clang-format` for C++. This feature automatically formats MIDL 3.0 code according to consistent style rules.
+
+## Features
+
+- **Automatic indentation**: Properly indents code blocks based on braces
+- **Configurable indentation**: Respects VSCode settings for tabs vs spaces and tab size
+- **Spacing normalization**: Ensures consistent spacing around:
+  - Keywords (`namespace`, `runtimeclass`, `interface`, etc.)
+  - Operators (`:`, `,`)
+  - Braces and property accessors (`{ get; set; }`)
+- **Comment preservation**: Maintains single-line (`//`) and block (`/* */`) comments
+- **Attribute formatting**: Properly formats attribute blocks (`[...]`)
+
+## Usage
+
+### Format Entire Document
+
+- **Windows/Linux**: Press `Shift+Alt+F`
+- **macOS**: Press `Shift+Option+F`
+- **Command Palette**: Run "Format Document"
+
+### Format Selection
+
+1. Select the code you want to format
+2. **Windows/Linux**: Press `Ctrl+K Ctrl+F`
+3. **macOS**: Press `Cmd+K Cmd+F`
+4. **Command Palette**: Run "Format Selection"
+
+### Configuration
+
+The formatter respects your VSCode editor settings:
+
+```json
+{
+  "editor.tabSize": 4,           // Number of spaces per indentation level
+  "editor.insertSpaces": true,   // Use spaces instead of tabs
+  "editor.formatOnSave": true    // Automatically format on save (optional)
+}
+```
+
+## Example
+
+### Before Formatting
+
+```midl
+namespace   WindowsDemo
+{
+[contract(DemoContract, 1.0)]
+interface   IDemoInterface
+{
+void   DoWork();
+String GetData(Int32   value);
+}
+
+runtimeclass   DemoControl:IDemoInterface
+{
+DemoControl();
+String   Title{get;set;};
+Int32 Value{get;};
+}
+}
+```
+
+### After Formatting
+
+```midl
+namespace WindowsDemo
+{
+    [contract(DemoContract, 1.0)]
+    interface IDemoInterface
+    {
+        void   DoWork();
+        String GetData(Int32   value);
+    }
+
+    runtimeclass DemoControl : IDemoInterface
+    {
+        DemoControl();
+        String   Title{ get; set; };
+        Int32 Value{ get; };
+    }
+}
+```
+
+## Formatting Rules
+
+### Indentation
+
+- Each level of nesting increases indentation by one level
+- Opening braces `{` increase indent for following lines
+- Closing braces `}` decrease indent for the current line
+
+### Spacing
+
+- **Keywords**: Single space after keywords (`namespace Name`, not `namespace  Name`)
+- **Inheritance**: Space around colon (`: Interface`, not `:Interface`)
+- **Commas**: Space after commas (`, `, not `,`)
+- **Property accessors**: Space around braces and semicolons (`{ get; set; }`, not `{get;set;}`)
+- **Braces**: Space before opening brace on same line (`Name {`, not `Name{`)
+
+### Comments
+
+- Comments are preserved with their content unchanged
+- Comments are indented to match the surrounding code
+- Both single-line (`//`) and multi-line (`/* */`) comments are supported
+
+### Attributes
+
+- Attribute blocks `[...]` are preserved and indented
+- Multiple attributes on separate lines are supported
+- Attribute content is not modified
+
+## Implementation
+
+The formatter is implemented in `server/src/formatter.ts` and integrates with the Language Server Protocol's document formatting capabilities:
+
+- `documentFormattingProvider`: Formats entire document
+- `documentRangeFormattingProvider`: Formats selected range
+
+## Testing
+
+The formatter includes comprehensive unit tests in `server/src/test/formatter.test.ts` covering:
+
+- Basic namespace and class formatting
+- Property accessor normalization
+- Comment preservation
+- Attribute formatting
+- Configurable indentation (tabs vs spaces)
+- Keyword spacing normalization
+
+All tests pass and validate the formatter's behavior.

README.md

@@ -11,9 +11,24 @@ Provides syntax highlighting, autocomplete, and diagnostics for [MIDL 3](https:/
 - [x] Syntax highlighting
 - [x] Basic semantic parsing
 - [x] Diagnostics ("squigglies") and context-free auto-completions
+- [x] Document formatting (similar to clang-format)
+  - Format entire document or selection
+  - Configurable indentation (tabs or spaces)
+  - Normalizes spacing around keywords, operators, and braces
+  - Preserves comments
 
 This extension collects basic usage telemetry (e.g. which version is being used).
 
+## Usage
+
+### Formatting
+
+To format a MIDL 3.0 file:
+- **Format entire document**: Press `Shift+Alt+F` (Windows/Linux) or `Shift+Option+F` (Mac)
+- **Format selection**: Select code and press `Ctrl+K Ctrl+F` (Windows/Linux) or `Cmd+K Cmd+F` (Mac)
+
+The formatter respects your VSCode settings for indentation (`editor.tabSize` and `editor.insertSpaces`).
+
 ## Feedback / bug reports
 
 https://github.com/asklar/midl-langserv

client/package.json

@@ -16,6 +16,7 @@
 		"vscode-languageclient": "^7.0.0"
 	},
 	"devDependencies": {
+		"@types/node": "^16.18.126",
 		"@types/vscode": "^1.52.0",
 		"vscode-test": "^1.3.0"
 	}

package.json

@@ -78,6 +78,22 @@
 					],
 					"default": "off",
 					"description": "Traces the communication between VS Code and the language server."
+				},
+				"midl3.format.braceStyle": {
+					"scope": "resource",
+					"type": "string",
+					"enum": [
+						"newLine",
+						"sameLine"
+					],
+					"default": "newLine",
+					"description": "Controls brace placement style. 'newLine' places opening braces on a new line, 'sameLine' places them on the same line."
+				},
+				"midl3.format.indentSize": {
+					"scope": "resource",
+					"type": "number",
+					"default": 4,
+					"description": "Number of spaces per indentation level when using spaces. Overrides editor.tabSize for MIDL3 formatting."
 				}
 			}
 		}
@@ -95,13 +111,13 @@
 	},
 	"devDependencies": {
 		"@types/mocha": "^8.0.3",
-		"@types/node": "^12.12.0",
+		"@types/node": "^16.18.126",
 		"@types/pegjs": "^0.10.3",
 		"@typescript-eslint/parser": "^2.3.0",
 		"copyfiles": "^2.4.1",
 		"eslint": "^6.4.0",
 		"mocha": "^8.1.1",
-		"typescript": "^4.2.2",
+		"typescript": "^5.9.3",
 		"vsce": "^1.96.1"
 	},
 	"dependencies": {

server/package.json

@@ -18,6 +18,8 @@
 	"scripts": {},
 	"devDependencies": {
 		"@types/glob": "^7.1.4",
+		"@types/mocha": "^8.2.3",
+		"@types/node": "^16.18.126",
 		"glob": "^7.1.7"
 	}
 }