CRAQL: A Composable Language for Querying Source Code

TL;DR

CRAQL is a new, SQL-like query language designed for source code analysis that leverages abstract syntax trees to enable complex, composable queries across parsed code structures, improving clarity and efficiency.

Contribution

The paper introduces CRAQL, a novel query language for source code that supports composable queries on ASTs, enhancing expressiveness and applicability across programming languages.

Findings

CRAQL can query complex code structures with high clarity.

CRAQL demonstrates efficient analysis on millions of Java files.

The language offers advantages over existing code querying tools.

Abstract

This paper describes the design and implementation of CRAQL (Composable Repository Analysis and Query Language), a new query language for source code. The growth of source code mining and its applications suggest the need for a query language that can fully utilize and correlate across the unique structure and metadata of parsed source code. CRAQL is built on an underlying abstraction analogous to the underpinnings of SQL, but aimed at parsed source code. Thus, while SQL queries' inputs and outputs are sets of tuples, CRAQL queries' inputs and outputs are sets of abstract syntax trees (ASTs). This abstraction makes CRAQL queries composable (the output of one query can become the input to another) and improves the power of the language by allowing for querying of the tree structure and metadata, as well as raw text. Furthermore, the abstraction enables tree-specific language optimizations and allows CRAQL to be easily applied to any language that is parsable into ASTs. These attributes, along with a familiar syntax similar to SQL, allow complex queries to be expressed in a compact, straightforward manner. Questions such as "find the longest series of statements without any loops," "find methods that are never called," "find getters (0-parameter methods with a single statement that returns a member variable)," or "find the percentage of variables declared at the top of a block" all translate to simple, understandable queries in CRAQL. In this paper we describe the language, its features and capabilities. We compare CRAQL to other languages for querying source code and find that it has potential advantages in clarity and compactness. We discuss the features and optimizations added to support searching parse tree collections effectively and efficiently. Finally, we summarize the application of the language to millions of Java source files, the details of which are in a companion paper.