Non composer extension insight composer mode TYPO3

composer autoload custom extension

1.  Copy your extension to `[web/]typo3conf/ext/` of your composer mode TYPO3 (or kickstart one with extension_builder).
2.  Add autoload entry to your root composer.json (that one which requires "typo3/cms")
```json
"autoload": {
	"psr-4": {
		"T3easy\\MyExt\\": "web/typo3conf/ext/my_ext/Classes/"
	}
}
```
3.  Run `composer dump-autoload -a` to update the autoloader.
    https://getcomposer.org/doc/03-cli.md#dump-autoload
4.  Install the extension with the `Extension Manager` / `cli_dispatch.phpsh` / `typo3_console`

composer.json

{
	"repositories": [
		{ "type": "composer", "url": "https://composer.typo3.org/" },
		{ "type": "vcs", "url": "https://github.com/FriendsOfTYPO3/extension_builder.git"}
	],
	"name": "typo3/cms-base-distribution",
	"description" : "TYPO3 CMS Base Distribution",
	"license": "GPL-2.0+",
	"require": {
		"typo3/cms": "^8.6",

		"typo3/cms-belog": "^8.6",
		"typo3/cms-beuser": "^8.6",
		"typo3/cms-context-help": "^8.6",
		"typo3/cms-fluid-styled-content": "^8.6",
		"typo3/cms-felogin": "^8.6",
		"typo3/cms-filelist": "^8.6",
		"typo3/cms-impexp": "^8.6",
		"typo3/cms-info": "^8.6",
		"typo3/cms-info-pagetsconfig": "^8.6",
		"typo3/cms-lowlevel": "^8.6",
		"typo3/cms-reports": "^8.6",
		"typo3/cms-rsaauth": "^8.6",
		"typo3/cms-rte-ckeditor": "^8.6",
		"typo3/cms-setup": "^8.6",
		"typo3/cms-tstemplate": "^8.6",
		"typo3/cms-viewpage": "^8.6",

		"helhum/typo3-console": "^4.3",
		"ebt/extension-builder": "8.6.x-dev"
	},
	"extra": {
		"helhum/typo3-console": {
			"install-extension-dummy": false
		},
		"typo3/cms": {
			"cms-package-dir": "{$vendor-dir}/typo3/cms",
			"web-dir": "web"
		}
	},
	"autoload": {
		"psr-4": {
			"T3easy\\MyExt\\": "web/typo3conf/ext/my_ext/Classes/"
		}
	}
}

https://gist.github.com/stigfaerch/a8fcaee98f43798b17eaebf9e9fee14c#file-composer-json-L4
For requiring extension from git repository.