Redflare

Experimental early work-in-progress JavaScript static analyzer tool.

Design goals:

• Full program analyzer Tool should work with the entire program codebase to produce the best results. This allows to track every call site of each function and highlight all the dead code.
• No extra syntax It shouldn't introduce any custom type definitions or annotations. Platform or library APIs should be defined using standard JavaScript.
• Static assertions Adds static assertions to JavaScript, a way to ensure conditions are always true without running the program.

Installation

The fastest way to get started is to install Redflare CLI globally.

npm install redflare -g

Usage

First, make sure you use modern version of Node like v4 or newer. Redflare needs program entry point as an input (for now there is no support for require() so all code needs to be in one file):

redflare index.js

Example:

function foo(x) {
  return x / 5;
}

foo('string');

outputs:

index.js:2:9
 1| function foo(x) {
 2|   return x / 5;
  |          ^^^^^
  |          error: division of string by number
 3| }
 4|

Static assertions

Redflare adds global static assertion function __STATIC_ASSERT(expr[, message]). Expression needs to evaluate into known at analysis-time truthy value or error will be reported. It's also useful to add type checks to the code.

__STATIC_ASSERT(true);
__STATIC_ASSERT(true === true, 'this should be true');
__STATIC_ASSERT(typeof value === 'string', 'value should be a string');
__STATIC_ASSERT(typeof value === 'number' && value > 0, 'value should be a positive number');

How does it work?

Redflare is an abstract interpreter JavaScript VM that operates on abstract values instead of an actual values. For example, <any number>, <positive number>, <any boolean> or just <any> are all valid abstract values. JavaScript operators can be defined in terms of abstract values, like expression (<any number> + <any number>) results in another <any number>, so we can easily infer result values or types of expressions. As another example, typeof <any number> results in actual value number.

Todo

• Add all the missing operators
• Loops (for, for-of, for-in, do-while, while)
• Objects/arrays/tuples
• More builtin functions
• require() / import
• Function side-effect analysis
• Event loop, setTimeout etc
• More consistent and configurable errors
• ES2015 support

License

MIT