vscode package.json String does not match the pattern

This behavior is by design to enforce NPM conventions for the package.json file (to paraphrase, "lower-case only"). I agree it is a nuisance, especially since the project name is often pre-filled, e.g. by "create-react-app". As you point out, it is possible to create a custom schema to ignore this, but it's really not recommended. There isn't any alternative at this time. Myself, I just change the value to lower-case.

Use name field value in lowercase separated by hyphen (-).

In this case, you want to use your custom name without VSCode warning you about the name, unfortunately there is not much to do but to write your custom Schema and use it in your package.json.

For example, you can take the package.json schema in https://json.schemastore.org/package.json and see this part of code that specifies a pattern to follow for the name of packages:

        "name": {
            "description": "The name of the package.",
            "type": "string",
            "maxLength": 214,
            "minLength": 1,
            "pattern": "^(?:(?:@(?:[a-z0-9-*~][a-z0-9-*._~]*)?/[a-z0-9-._~])|[a-z0-9-~])[a-z0-9-._~]*$"
        },

This is the Schema that Visual Studio Code uses by default in a package.json.

You'll need to write your own schema in a JSON file, for example MyOwnSchema.json.

Now, I want to suppress the pattern warning, then I do the follow, just remove the pattern property:

        "name": {
            "description": "The name of the package.",
            "type": "string",
            "maxLength": 214,
            "minLength": 1
        },

Or if you want, you can use your custom pattern...

        "name": {
            "description": "The name of the package.",
            "type": "string",
            "maxLength": 214,
            "minLength": 1,
            "pattern": "^MyOwnCustomName$"
        },

Now, in your package.json you need to specify the schema you modified to use it in your file like this:

{
    "$schema": "./MyOwnSchema.json",
    "name": "MyOwnCustomName",
}

This will suppress the warning... Just consider some things, you're using a custom schema and not the official provided by Node.js or NPM packages, so you need to be sure of what you are doing... Check that everything is correct, this will change the behaviour of the name but not of the other properties, you can change it too if you want... Also consider that if the official schema is updated, you will not have the recent changes.

Or if you don't want to complicate the things too much, just rename the package as it says with the pattern that they want (my-package).