Generated code is not compilated on Unix implementation of JDK

[EgorkaKulikov]

Description

Create tests for project in Intellij Idea 2021.1 with JDK 11 for the following class

Actual behavior

Generate code contains the following line that is not appropriate for Unix related JDKs and leads to ClassNotFoundException

Object fs = createInstance("java.io.WinNTFileSystem");

Additional context

Bug was found by Dmitry Fedrushkov wx1076228

[dvfedrush]

import java.io.File;

public class Solution {
    /**
     * check if a file exists
     */
    public boolean func_1(String filePathString) {
        File f = new File(filePathString);
        return f.exists() && !f.isDirectory();
    }
}

[denis-fokin]

As I remember, JDK uses a list of system packages to prohibit users’ classes in system packages. So, the idea to keep a list of dangerous APIs is already implemented in JDK.

Java API is not changed inside major releases. We can keep a list of classes in JDK library that are supposed to be mocked always.

The question is how to collect the list. OpenJDK repositories follow a couple of simple principles one of them is to keep 'operating system'–dependent packages in a subfolder with the OS id.

For example:

Win32GraphicsDevice.java is for sure a class that should not be instantiated through reflection on our own. In Java 11 the class is placed in a subfolder of windows folder.
openjdk-jdk11/src/java.desktop/windows/classes/sun/awt/Win32GraphicsDevice.java

The idea is to collect all such classes for different versions of JDK and check them before generate code that instantiates an object of class from the list. In that case we should mock the object or, if possible, mock the code that uses the object.