Lokale TYPO3 Extension mit Composer installieren

https://stackoverflow.com/questions/53453110/try-to-install-my-own-extension-via-composer-in-typo3

I assume you want to use your extension only on one installation as local extension. So that's the way to go:

Create a directory, e.g. packages in your project's root directory.

Move your extension into this directory and name the folder stsa-hellotypo3. The part before the dash is your namespace, the part behind the package name.

Add to your composer.json of your extension the following entry:

"extra": {
    "typo3/cms": {
        "extension-key": "stsa_hellotypo3"
    }
}

Now TYPO3 will use stsa_hellotypo3 as extension key.

Change into your composer.json file in your TYPO3 project root the repositories entry:

"repositories": [
    {
        "type": "path",
        "url": "packages/*"
    },
    {
        "type": "composer",
        "url": "https://composer.typo3.org/"
    }
],

composer will look now into the packages folder for packages to install.

Now you can add your extension to the project:

composer require stsa/hellotypo3:@dev

The extension is symlink'ed as stsa_hellotypo3 in typo3conf/ext/ directory. With the @dev the development version is installed (which you have). you can also add a version entry into your extension's composer.json file, then you can omit the @dev.

If you do it that way you don't have to add your extension's autoloading information to the root composer.json file.