Add macro expansion on hover

package.json

@@ -162,6 +162,11 @@
 					"default": false,
 					"description": "Show symbol information when mouse is hover."
 				},
+				"crystal-lang.macroExpansionHover": {
+					"type": "boolean",
+					"default": false,
+					"description": "Show macro expansion when mouse hovers over a macro."
+				},
 				"crystal-lang.completion": {
 					"type": "boolean",
 					"default": false,
@@ -215,6 +220,20 @@
 					"description": "[Reload required]\nEnables support for Windows Subsystem Linux."
 				}
 			}
+		},
+		"commands": [
+			{
+				"command": "crystal-lang.showMacroExpansion",
+				"title": "Show macro expansion"
+			}
+		],
+		"menus": {
+			"editor/context": [
+				{
+					"command": "crystal-lang.showMacroExpansion",
+					"group": "z_commands"
+				}
+			]
 		}
 	},
 	"scripts": {

src/crystalMacro.ts

@@ -0,0 +1,93 @@
+import * as vscode from "vscode";
+import { spawnSync } from 'node:child_process';
+
+export async function registerCrystalMacroHoverProvider(context: vscode.ExtensionContext) {
+    let macroExpansionChannel = vscode.window.createOutputChannel("Crystal Macro Expansion", "crystal")
+
+    vscode.languages.registerHoverProvider({ scheme: 'file', language: 'crystal' }, {
+        provideHover(document, position, token) {
+            return expandMacroToHover(document, position);
+        }
+    })
+
+    vscode.commands.registerCommand('crystal-lang.showMacroExpansion', function() {
+        const activeEditor = vscode.window.activeTextEditor;
+        const document = activeEditor.document;
+        const position = activeEditor.selection.active;
+        const positionString = `${document.uri.path}:${position.line + 1}:${position.character + 1}`;
+
+        let stdout = execExpandMacro(document, position)
+
+        if (stdout === undefined || stdout === "") {
+            return;
+        }
+
+        if (stdout.startsWith("no expansion found")) {
+            stdout = `# No macro expansion for ${positionString}`;
+        } else {
+            stdout = `# Macro expansion for ${positionString}:\n\n${stdout}\n`
+        }
+
+        macroExpansionChannel.appendLine(stdout)
+        macroExpansionChannel.show()
+    })
+}
+
+function execExpandMacro(document: vscode.TextDocument, position: vscode.Position): string {
+    const config = vscode.workspace.getConfiguration("crystal-lang")
+
+    let currentWorkspacePath = vscode.workspace.getWorkspaceFolder(document.uri).uri.path
+
+    let documentPath = document.uri.path;
+    let line = position.line + 1;
+    let column = position.character + 1;
+
+    let expandArgs: string[] = ['tool', 'expand']
+
+    let mainFile = '';
+    if (config["mainFile"]) {
+        mainFile = config["mainFile"].replace("${workspaceRoot}", currentWorkspacePath)
+
+        if (mainFile !== documentPath) {
+            expandArgs.push(mainFile)
+        }
+    }
+
+    expandArgs.push(documentPath, '--cursor', `${documentPath}:${line}:${column}`)
+
+    let result = spawnSync(
+        config["compiler"], expandArgs,
+        { cwd: currentWorkspacePath }
+    );
+
+    if (result.status !== 0) {
+        console.error(result.stderr.toString());
+        return;
+    }
+
+    let stdout = result.output.join('\n').replace(/^\n+|\n+$/g, '');
+
+    return stdout
+}
+
+function expandMacroToHover(document: vscode.TextDocument, position: vscode.Position): vscode.Hover {
+    const config = vscode.workspace.getConfiguration("crystal-lang")
+    if (!config["macroExpansionHover"]) {
+        return;
+    }
+
+    let stdout = execExpandMacro(document, position)
+
+    if (stdout.startsWith("no expansion found")) {
+        return;
+    }
+
+    let markdownResult = new vscode.MarkdownString("```\n" + stdout + "\n```");
+
+    let lineText = document.lineAt(position).text;
+    let lineStart = document.offsetAt(new vscode.Position(position.line, 0));
+    let lineEnd = lineStart + lineText.length;
+    let range = new vscode.Range(document.positionAt(lineStart), document.positionAt(lineEnd));
+
+    return new vscode.Hover(markdownResult, range)
+}

src/crystalMain.ts

@@ -10,6 +10,7 @@ import { CrystalDocumentSymbolProvider } from "./crystalSymbols"
 import { CrystalCompletionItemProvider } from "./crystalCompletion"
 import { CrystalImplementationsProvider } from "./crystalImplementations"
 import { registerCrystalTask } from "./crystalTasks"
+import { registerCrystalMacroHoverProvider } from "./crystalMacro"
 
 // Language configuration for identation and patterns. Based on vscode-ruby
 const crystalConfiguration = {
@@ -47,6 +48,8 @@ export async function activate(context: vscode.ExtensionContext) {
 	// Register Tasks
 	registerCrystalTask(context)
 
+	registerCrystalMacroHoverProvider(context)
+
 	// Detect server and set configuration
 	let scry = config["server"]
 	if (fs.existsSync(scry)) {