maybeWarn: try { var stackTraceLimit = Error.stackTraceLimit; Error.stackTraceLimit = Infinity; var stack = new Error().stack; Error.stackTraceLimit = stackTraceLimit; if (!stack.includes("babel-preset-react-app")) break maybeWarn; // Try this as a fallback, in case it's available in node_modules module.exports = require("@babel/plugin-transform-private-property-in-object"); setTimeout(console.warn, 2500, `\ \x1B[0;33mOne of your dependencies, babel-preset-react-app, is importing the "@babel/plugin-proposal-private-property-in-object" package without declaring it in its dependencies. This is currently working because "@babel/plugin-proposal-private-property-in-object" is already in your node_modules folder for unrelated reasons, but it \x1B[1mmay break at any time\x1B[0;33m. babel-preset-react-app is part of the create-react-app project, \x1B[1mwhich is not maintianed anymore\x1B[0;33m. It is thus unlikely that this bug will ever be fixed. Add "@babel/plugin-proposal-private-property-in-object" to your devDependencies to work around this error. This will make this message go away.\x1B[0m `); return; } catch (e) {} throw new Error(`\ --- PLACEHOLDER PACKAGE --- This @babel/plugin-proposal-private-property-in-object version is not meant to be imported. Something is importing @babel/plugin-proposal-private-property-in-object without declaring it in its dependencies (or devDependencies) in the package.json file. Add "@babel/plugin-proposal-private-property-in-object" to your devDependencies to work around this error. This will make this message go away. `);