Complexity & Travis-CI Lab

In this lab, you'll be implementing simple algorithms for checking basic properties of code complexity, and working with Travis-CI for Continuous Integration.

Two design patterns are of importance here:

• A Builder pattern, which is used to build up state and then finally emit.
• A Visitor pattern, which is used to abstract the process of visiting a data structure such as abstract syntax tree (AST). The only input you have to provide is what action to perform at each node.

Esprima

Writing programs to do static code analysis on Javascript is easier now than ever, thanks to esprima - the Javascript parser library. We will practice how to use esprima to do something fairly simple – measure basic code complexity metrics of JavaScript programs.

Video

This video provides more background about esprima: Watch 5:00-14:30,28:00-34:00.

Interactive Abstract Syntax Tree (AST)

Use the demo page to see what a code snippet looks like, in order to help you navigate the data structure. Better to open in a separate browser tab, as you will need to work with it for coding inspiration.

For example, the following snippet:

function functionName( node )
{
	if( node.id )
	{
		return node.id.name;
	}
	return "anon function @" + node.loc.start.line;
}

Will appear as following, and:

Can be interacted with here.

Lab activities:

The repository contains a stub that parses a javascript file and visits each function.

1. Run the program and print all the tokens in an ast.

      npm install
      node analysis.js
   

2. Do a simple calculation (2 Points Each)

   a) ParameterCount: The number of parameters for functions (FunctionBuilder) b) String Usage: How many string literals are used in file? (FileBuilder)

3. Using multiple visitors (2 Points Each)

   a) SimpleCyclomaticComplexity: The number of if statements/loops + 1. b) MaxConditions: The max number of condition predicates (expressions seperated by ||, &&) in an if statement.

4. Check build status on Travis-CI when committing each new function. Submit a screenshot of the final build. (2 Points)

5. Advanced (2 Extra Points)

   a) MaxNestingDepth: The max depth of scopes (nested ifs, loops, etc) -- this one is hard, only expect a few to get to do finish this one (using parents/etc).