CodeFill: Multi-token Code Completion by Jointly learning from Structure and Naming Sequences

by Izadi, Maliheh and Gismondi, Roberta and Gousios, Georgios

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Code completion is an essential feature of IDEs, yet current auto-completers are restricted to either grammar-based or NLP-based single token completions. Both approaches have significant draw-backs: grammar-based autocompletion is restricted in dynamically-typed language environments, whereas NLP-based autocompleters struggle to understand the semantics of the programming language and the developer’s code context. In this work, we present CodeFill, a language model for autocompletion that combines learned structure and naming information. Using a parallel Transformer architecture and multi-task learning, CodeFill consumes sequences of source code token names and their equivalent AST token types. Uniquely, CodeFill is trained both for single-token and multi-token (statement) prediction, which enables it to learn long-range dependencies among grammatical and naming elements. We train CodeFill on two datasets, consisting of 29M and 425M lines of code, respectively. To make the evaluation more realistic, we develop a method to automatically infer points in the source code at which completion matters. We compare CodeFill against four baselines and two state-of-the-art models, GPT-C and TravTrans+. CodeFill surpasses all baselines in single token prediction (MRR: 70.9% vs. 66.2% and 67.8%) and outperforms the state of the art for multi-token prediction (ROUGE-L: 63.7% vs. 52.4% and 59.2%, for n=4 tokens). We publicly release our source code and datasets.

Bibtex record

  author = {Izadi, Maliheh and Gismondi, Roberta and Gousios, Georgios},
  booktitle = {2022 IEEE/ACM 44th International Conference on Software Engineering (ICSE)},
  title = {CodeFill: Multi-token Code Completion by Jointly learning from Structure and Naming Sequences},
  year = {2022},
  volume = {},
  number = {},
  pages = {401-412},
  doi = {10.1145/3510003.3510172},
  url = {}

The paper