fix(save): make format-on-save await the formatter and target the saved file

- Await the format command so the document write captures the formatted
  content instead of racing an async formatter
- Only format when the file being saved is the active file: formatters
  operate on the active editor document, so a tab switch mid-save could
  previously rewrite the wrong file
- Toggle markChanged on the file being saved, not whatever tab is active
- Abort the save when the formatter fails instead of writing unformatted
  content and reporting success
- acode.format() now returns null (not a failure) when no formatter is
  configured, so format-on-save keeps working for unformatted file types;
  the format command propagates the tri-state result

Fixes #2900

Author: xaniexane

src/lib/acode.js

@@ -826,6 +826,13 @@ class Acode {
 		appSettings.update(false);
 	}
 
+	/**
+	 * Formats the active file with the configured formatter.
+	 * @param {boolean} [selectIfNull] open the formatter picker when no formatter is configured
+	 * @returns {Promise<boolean|null>} `true` when formatting ran, `false`
+	 * when the formatter failed, `null` when no formatter is configured
+	 * (not a failure; callers should not treat it as one)
+	 */
 	async format(selectIfNull = true) {
 		const file = editorManager.activeFile;
 		if (!file || file.type !== "editor") return false;
@@ -858,7 +865,9 @@ class Acode {
 			} else {
 				toast(strings["please select a formatter"]);
 			}
-			return false;
+			// No formatter configured: not a failure, so report `null`
+			// instead of `false` (both are falsy for existing callers).
+			return null;
 		}
 
 		try {

src/lib/commands.js

@@ -727,6 +727,7 @@ export default {
 			// Restore cursor position after formatting (pos.row is now 1-based)
 			editor.gotoLine(pos.row, pos.column);
 		}
+		return didFormat;
 	},
 	async eol() {
 		if (editorManager.activeFile?.type !== "editor") return;

src/lib/saveFile.js

@@ -172,11 +172,22 @@ async function saveFile(
 		}
 
 		if (appSettings.value.formatOnSave) {
-			editorManager.activeFile.markChanged = false;
+			// Formatters operate on the active editor document. If the user
+			// switched tabs while an async save step was pending, formatting
+			// here would rewrite the wrong file, so only format when the file
+			// being saved is the active one.
+			file.markChanged = false;
 			try {
-				acode.exec("format", false);
+				if (editorManager.activeFile === file) {
+					// Await the formatter so the write below captures the
+					// formatted document. A failed format aborts the save;
+					// `null` means no formatter is configured, which is not
+					// a failure.
+					const formatted = await acode.exec("format", false);
+					if (formatted === false) return false;
+				}
 			} finally {
-				editorManager.activeFile.markChanged = true;
+				file.markChanged = true;
 			}
 		}