https://github.com/calvin-l/lightweight-typestate-checker

An easy-to-use typestate checker
https://github.com/calvin-l/lightweight-typestate-checker

Last synced: 23 days ago
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An easy-to-use typestate checker

• Host: GitHub
• URL: https://github.com/calvin-l/lightweight-typestate-checker
• Owner: Calvin-L
• License: mit
• Created: 2023-06-02T05:30:57.000Z (over 1 year ago)
• Default Branch: main
• Last Pushed: 2023-09-22T01:48:33.000Z (over 1 year ago)
• Last Synced: 2024-10-16T08:10:43.469Z (2 months ago)
• Language: Java
• Size: 35.2 KB
• Stars: 0
• Watchers: 2
• Forks: 0
• Open Issues: 0
• Metadata Files:
  • Readme: README.md
  • License: LICENSE

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README

        
# Lightweight Typestate Checker

An easy-to-use typestate checker for Java.

Features:

 - Lightweight: no complicated alias analysis or ownership annotations.

   (Instead, certain annotations have to be "stable"---more on this when I get

   around to writing it up.)

 - Easy-to-use: no need to learn a new language.  Typestate transitions are

   specified using simple annotations: `@RequiresState`, `@NewStateOnReturn`,

   `@NewStateOnReturnIf`, and `@NewStateOnException`.

 - Sound: you are never allowed to call a method when an object could be in the

   wrong state.

## Example

```java

public class Example {

  public static void main(String[] args) throws IOException {

    try (Conn c = new Conn()) {

      // Attempting to use `c` before calling `connect()` is bad!

      //   > error: [contracts.precondition] precondition of c.use is not satisfied.

      //   >   found   : c is @State("idle")

      //   >   required: c is @State("connected")

      c.use();

    }

  }

  static class Conn implements AutoCloseable {

    @NewStateOnReturn("idle")

    public Conn() {

    }

    @RequiresState(value="this", state="idle")

    @NewStateOnReturn("connected")

    public void connect() {

    }

    @RequiresState(value="this", state="connected")

    public void use() {

    }

    @Override

    @NewStateOnReturn("closed")

    @NewStateOnException(exception=Throwable.class, state="closed")

    public void close() {

    }

  }

}

```

## Quickstart

Add `-processor org.lwtsc.LightWeightTypeStateChecker` to your `javac` flags.

(More on adding this to your existing build system when I get around to writing

it up---but you can start by reading

[the official Checker Framework docs](https://checkerframework.org/manual/#external-tools)

and studying

[the example project](/example/)).