Example of composer.json for Drupal 8 patches

composer.json

{
    "name": "drupal/recommended-project",
    "description": "Project template for Drupal 9 projects with a relocated document root",
    "type": "project",
    "license": "GPL-2.0-or-later",
    "homepage": "https://www.drupal.org/project/drupal",
    "support": {
        "docs": "https://www.drupal.org/docs/user_guide/en/index.html",
        "chat": "https://www.drupal.org/node/314178"
    },
    "repositories": [
        {
            "type": "composer",
            "url": "https://packages.drupal.org/8"
        },
        {
            "type": "composer",
            "url": "https://asset-packagist.org"
        }
    ],
    "require": {
        "bower-asset/jquery-simple-color": "^1.2",
        "bower-asset/spectrum": "^1.8",
        "composer/installers": "^1.9",
        "cweagans/composer-patches": "~1.0",
        "drupal/admin_toolbar": "^2.4",
        "drupal/color_field": "^2.4",
        "drupal/commerce": "^2.21",
        "drupal/commerce_agree_terms": "1.x-dev@dev",
        "drupal/commerce_shipping": "2.x-dev@dev",
        "drupal/commerce_stock": "^1.0@alpha",
        "drupal/commerce_stripe": "^1.0@RC",
        "drupal/core-composer-scaffold": "^8.8",
        "drupal/core-project-message": "^8.8",
        "drupal/core-recommended": "^8.8",
        "drupal/email_registration": "^1.1",
        "drupal/eu_cookie_compliance": "^1.14",
        "drupal/extlink": "^1.5",
        "drupal/google_analytics": "^3.1",
        "drupal/inline_entity_form": "^1.0@RC",
        "drupal/mailgun": "^1.0",
        "drupal/menu_link_attributes": "^1.1",
        "drupal/metatag": "^1.15",
        "drupal/paragraphs": "^1.12",
        "drupal/pathauto": "^1.8",
        "drupal/rabbit_hole": "^1.0@beta",
        "drupal/redirect": "^1.6",
        "drupal/redirect_after_login": "^2.6",
        "drupal/twig_field_value": "^2.0",
        "drupal/twig_tweak": "^2.8",
        "drupal/xmlsitemap": "^1.0",
        "drush/drush": "^10.3",
        "oomphinc/composer-installers-extender": "^2.0"
    },
    "conflict": {
        "drupal/drupal": "*"
    },
    "minimum-stability": "stable",
    "prefer-stable": true,
    "config": {
        "sort-packages": true
    },
    "extra": {
        "composer-exit-on-patch-failure": true,
        "enable-patching": true,
        "patchLevel": {
            "drupal/core": "-p2"
        },
        "drupal-scaffold": {
            "locations": {
                "web-root": "web/"
            },
            "file-mapping": {
              "[web-root]/sites/default/default.services.yml": false,
              "[web-root]/sites/default/default.settings.php": false
            }
        },
        "installer-types": [
            "npm-asset",
            "bower-asset"
        ],
        "installer-paths": {
            "web/core": [
                "type:drupal-core"
            ],
            "web/libraries/{$name}": [
                "type:bower-asset",
                "type:npm-asset",
                "type:drupal-library"
            ],
            "web/modules/contrib/{$name}": [
                "type:drupal-module"
            ],
            "web/profiles/contrib/{$name}": [
                "type:drupal-profile"
            ],
            "web/themes/contrib/{$name}": [
                "type:drupal-theme"
            ],
            "drush/Commands/contrib/{$name}": [
                "type:drupal-drush"
            ],
            "web/modules/custom/{$name}": [
                "type:drupal-custom-module"
            ],
            "web/profiles/custom/{$name}": [
                "type:drupal-custom-profile"
            ],
            "web/themes/custom/{$name}": [
                "type:drupal-custom-theme"
            ]
        },
        "drupal-core-project-message": {
            "include-keys": [
                "homepage",
                "support"
            ],
            "post-create-project-cmd-message": [
                "<bg=blue;fg=white>                                                         </>",
                "<bg=blue;fg=white>  Congratulations, you’ve installed the Drupal codebase  </>",
                "<bg=blue;fg=white>  from the drupal/recommended-project template!          </>",
                "<bg=blue;fg=white>                                                         </>",
                "",
                "<bg=yellow;fg=black>Next steps</>:",
                "  * Install the site: https://www.drupal.org/docs/8/install",
                "  * Read the user guide: https://www.drupal.org/docs/user_guide/en/index.html",
                "  * Get support: https://www.drupal.org/support",
                "  * Get involved with the Drupal community:",
                "      https://www.drupal.org/getting-involved",
                "  * Remove the plugin that prints this message:",
                "      composer remove drupal/core-project-message"
            ]
        },
        "patches": {
            "drupal/commerce_stripe": {
                "PaymentMethodAddForm needs to implement TrustedCallbackInterface for Drupal 9 => https://www.drupal.org/project/commerce_stripe/issues/3168822": "https://www.drupal.org/files/issues/2020-10-09/PaymentMethodAddForm%20needs%20to%20implement%20TrustedCallbackInterface%20for%20Drupal%209-3168822-14.patch",
                "Fixes for D9 compatability => https://www.drupal.org/project/commerce_stripe/issues/3141622": "https://www.drupal.org/files/issues/2020-05-23/fixes_for_d9_compata-3141622-6.patch"
            },
            "drupal/email_registration": {
                "Commerce 2 Completion Registration checkout pane => https://www.drupal.org/project/email_registration/issues/2987060": "https://www.drupal.org/files/issues/2019-04-30/2987060-17.patch"
            },
            "drupal/commerce_agree_terms": {
                "Drupal 9 support => https://www.drupal.org/project/commerce_agree_terms/issues/3197344": "https://www.drupal.org/files/issues/2021-02-08/drupal9-support.patch"
            }
        }
    }
}