Bridging Developer Instructions and Code Completion Through Instruction-Aware Fill-in-the-Middle Paradigm

Fuente: arXiv
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Main Authors: Sun, Zhensu, Yang, Chengran, Peng, Chao, Gao, Pengfei, Du, Xiaoning, Li, Li, Lo, David
Format: Preprint
Published: 2025
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author Sun, Zhensu
Yang, Chengran
Peng, Chao
Gao, Pengfei
Du, Xiaoning
Li, Li
Lo, David
author_facet Sun, Zhensu
Yang, Chengran
Peng, Chao
Gao, Pengfei
Du, Xiaoning
Li, Li
Lo, David
contents Large Language Models (LLMs) have significantly advanced code completion, yet they often fail when the developer's intent is underspecified in the code context. To address this, developers usually add natural language instructions (e.g., comments) into the code context to clarify their intent. However, existing code LLMs applied for code completion systems merely undergo a fill-in-the-middle (FIM) pre-training, which struggles to leverage this information effectively due to the lack of instruction-like training data. Existing instruction-tuning techniques, improving instruction-following in general code generation, paradoxically degrades FIM performance, forcing a trade-off between instruction-following and infilling capabilities. To address this gap, we introduce Instruction-aware Fill-in-the-Middle (IFIM), an instruction-tuning method specifically designed to enhance FIM code completion models. IFIM extends the conventional FIM training objective by incorporating an explicit instruction section into the input, enabling the model to learn from (prefix, instruction, suffix) triplets. This approach allows the model to effectively leverage developer-provided directives while preserving its core completion abilities when no instructions are present. To facilitate this, we constructed a large-scale dataset by using GPT-4o to generate concise, intent-focused instructions for code infilling examples. We evaluated IFIM by applying it to two popular base models, Deepseek-Coder and Qwen2.5-Coder, on the benchmarks derived from HumanEval-infilling and RepoMasterEval. The results demonstrate that IFIM significantly improves instruction-following capabilities, boosting the Pass@1 score from 84.6% to 93.6%. Moreover, this enhancement does not compromise the models' original performance on FIM code completion tasks with no instructions provided.
format Preprint
id arxiv_https___arxiv_org_abs_2509_24637
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Bridging Developer Instructions and Code Completion Through Instruction-Aware Fill-in-the-Middle Paradigm
Sun, Zhensu
Yang, Chengran
Peng, Chao
Gao, Pengfei
Du, Xiaoning
Li, Li
Lo, David
Software Engineering
Large Language Models (LLMs) have significantly advanced code completion, yet they often fail when the developer's intent is underspecified in the code context. To address this, developers usually add natural language instructions (e.g., comments) into the code context to clarify their intent. However, existing code LLMs applied for code completion systems merely undergo a fill-in-the-middle (FIM) pre-training, which struggles to leverage this information effectively due to the lack of instruction-like training data. Existing instruction-tuning techniques, improving instruction-following in general code generation, paradoxically degrades FIM performance, forcing a trade-off between instruction-following and infilling capabilities. To address this gap, we introduce Instruction-aware Fill-in-the-Middle (IFIM), an instruction-tuning method specifically designed to enhance FIM code completion models. IFIM extends the conventional FIM training objective by incorporating an explicit instruction section into the input, enabling the model to learn from (prefix, instruction, suffix) triplets. This approach allows the model to effectively leverage developer-provided directives while preserving its core completion abilities when no instructions are present. To facilitate this, we constructed a large-scale dataset by using GPT-4o to generate concise, intent-focused instructions for code infilling examples. We evaluated IFIM by applying it to two popular base models, Deepseek-Coder and Qwen2.5-Coder, on the benchmarks derived from HumanEval-infilling and RepoMasterEval. The results demonstrate that IFIM significantly improves instruction-following capabilities, boosting the Pass@1 score from 84.6% to 93.6%. Moreover, this enhancement does not compromise the models' original performance on FIM code completion tasks with no instructions provided.
title Bridging Developer Instructions and Code Completion Through Instruction-Aware Fill-in-the-Middle Paradigm
topic Software Engineering
url https://arxiv.org/abs/2509.24637