Guard

This is the home of a java plugin I want to work on. Currently, this is still in early concept stages, but I wrote out this README because I thought it would be fun. The current state of the project is only as far as having the toolchain set up (ty @lea89 for the help there!) and writing a basic proof-of-concept annotation parser.

RoadMap:

• Implement a basic @Guard.Null annotation for variable declaration that null checks the resolved value of that line.
• Expand that system to check each step along the way (see usages, this is psuedo optional chaining)
• Implement safe returns out of Expression statements with null checks at each step along the way
• Implement error handling for improper annotation usage
• See if It's possible to supply a consumer as an annotation argument?!? Would be cool to modify the early exit code.
• Implement some other types of annotations, such as Guard.Empty, Guard.Exception, etc. A lot of this is still pretty loose as I'll need to know how much I can abuse the parameters.

Example Developer Facing Usages

Variable nullability:

private void foo() {
    @Guard.Null String idString = this.id;
    ...
}
// Maps to...
private void foo() {
    String idString = this.id;
    if (idString == null) {
        return;
    }
}

Chaining, and functions:

private void foo() {
    @Guard.Null char firstIdChar = this.id.charAt(0);
    ...
}
// Maps to...
private void foo() {
    String idString = this.id; // likely some other generated, less helpful name
    if (idString == null) {
        return;
    }
    char firstIdChar = idString.charAt(0);
    if (firstIdChar == null) {
        return;
    }
    ...
}

Chaining, functions, and emptiness:

private void foo() {
    @Guard.Empty
    @Guard.Null 
    char firstIdChar = this.id.charAt(0);
    ...
}
// Maps to...
private void foo() {
    String idString = this.id; // likely some other generated, less helpful name
    if (idString == null) {
        return;
    }
    if (idString.isEmpty()) {
        return;
    }
    char firstIdChar = idString.charAt(0);
    if (firstIdChar == null) {
        return;
    }
    ...
}

And hopefully more! This project will probably take some time, considering I'm new to compiler plugins, and I'm only able to do this when I have free time outside of work. However, I think it would be a novel (and useful) idea to bring optional chaining out of kotlin and into java. Considering that projects like Lombok have gotten so popular as well, I feel like there might be some people who also would appreciate the boiler-plate reduction that this would bring?

There is probably some valid criticism to this idea in that it's a bit silly to use a verbose language if you don't want to be verbose. However, I counter this with the super thought out "choice is cool" argument.