Insert default text into newly created files using vscod extension api - visual-studio-code

Question

I'm trying to create a simple vscode extension that will insert some default text into a newly created file. What I want is for the vscode.workspace.createFileSystemWatcher to call a function that gets the activeTextEditor and writes to the new file. Here is what I've tried:
import * as vscode from "vscode";
export function activate(context: vscode.ExtensionContext) {
let disposable = vscode.commands.registerCommand(
"default-text-generator.generate",
() => {
function _watcherChangeApplied(editor?: vscode.TextEditor) {
if (editor) {
editor.edit((editBuilder) => {
editBuilder.insert(editor.selection.active, "Hello World");
});
}
}
const editor = vscode.window.activeTextEditor;
let uri: vscode.Uri | undefined = editor?.document.uri;
if (uri) {
let watcher = vscode.workspace.createFileSystemWatcher(
new vscode.RelativePattern(
vscode.workspace.getWorkspaceFolder(uri)!,
"**/*.ts"
),
false,
false,
false
);
watcher.onDidCreate(() => _watcherChangeApplied(editor));
}
}
);
context.subscriptions.push(disposable);
}
// this method is called when your extension is deactivated
export function deactivate(): void {
//deactivate
}
Here's what's happening. The editor seems to insert the text, then immediately gets overwritten back to a blank page. I can't seem to figure out why.

Answer 1

The problem happens because the editor you are referring to is not what you think to be. It is not the newly created editor but instead, the editor that you are focused/active when the new .ts file is created.
The FileSystemWatcher.onDidCreate event provides you a Uri to the newly created file inside your workspace, but not necessarily opened in VS Code. Try creating a file via terminal and you will see what I mean. The file is created, the event is fired, but no editor is opened in VS Code.
So, you won't be able to use the editor.edit API to manipulate the file. Instead, you should edit the file using RAW/Node functions. But, in this case, maybe/probably you will clash with the external tool that is creating the .ts file (which may not be VS Code, if you use the FileWatcher). If only files created via VS Code must be detected, you should change to the workspace.onDidCreateFiles event instead. But yet, it also only provides you the Uri, not the Editor.
Hope this helps

Answer 2

This works:
let disposable2 = vscode.commands.registerCommand('yourCommand.here', async (...file) => {
async function _watcherChangeApplied(uri) {
if (uri) {
const editor = await vscode.window.showTextDocument(uri);
editor.edit((editBuilder) => {
editBuilder.insert(editor.selection.active, "Hello World");
});
await editor.document.save();
}
}
const editor = vscode.window.activeTextEditor;
let uri = editor?.document.uri;
if (uri) {
let watcher = vscode.workspace.createFileSystemWatcher(
new vscode.RelativePattern(
vscode.workspace.getWorkspaceFolder(uri),
"**/*.ts"
),
false,
false,
false
);
// watcher.onDidCreate(() => _watcherChangeApplied(editor));
watcher.onDidCreate((uri) => _watcherChangeApplied(uri));
}
}
The key point is that watcher.onDidCreate() will return the uri of the newly created file. You can pass that to your _watcherChangeApplied(uri) function.
In _watcherChangeApplied(uri) you can show the created file via await vscode.window.showTextDocument(uri) and that function returns an editor that you can use with its edit functions.
The code works whether you create the file within vscode (like the New File... icon button at the top of the explorer) or via the terminal (like touch test.ts).
If you want to enable creating new files through the terminal, for example, and NOT open them, try this _watcherChangeApplied(uri):
async function _watcherChangeApplied(uri) {
if (uri) {
const document = await vscode.workspace.openTextDocument(uri);
const strToAdd = "Hello World";
const wse = new vscode.WorkspaceEdit();
wse.insert(uri, new vscode.Position(0,0), strToAdd);
await vscode.workspace.applyEdit(wse);
await document.save();
}
}