NBFBaselines

[PAPER | ARTIFACT]

Neural baselines for finding and fixing single token bugs in Python

Software bugs can interrupt our workflow and finding them can often be very time-consuming. Especially smaller bugs are often hard to spot since they affect only a few lines of code out of thousands. For example, recognizing that a variable was not renamed after refactoring or that a loop will run in an out-of-bounds error because of the comparison operator is often difficult.

NBFBaselines collects baseline algorithm for learning to localize and repair software bugs. These algorihtms are designed to assist a developer in finding and fixing simple software bugs. They learn from millionth of bugs and their fixes to detect and repair new bugs in unseen code. Currently, bug finders often support a wide range of simple bugs such as:

• Variable Misuses: The developer uses a variable although another was meant

def compare(x1, x2):
    s1 = str(x1)
    s2 = str(x1) # Bug: x2 instead of x1
    return s1 == s2

• Binary Operator Bugs: The wrong binary operator was used

def add_one(L):
    i = 0
    while i <= len(L): 
        L[i] = L[i] + 1
        i += 1

• Unary Operator Bugs: A unary operator was used mistakenly or was forgotten

if namespace: # Bug: not namespace instead of namespace
    self.namespacesFilter = [ "prymatex", "user" ] 
else:
    self.namespacesFilter = namespace.split()

• Wrong Literal Bugs: The wrong literal was used

def add_one(L):
    i = 0
    while i < len(L): 
        L[i] = L[i] + 1
        i += 2 # Bug: 1 instead of 2

RealiT: Training on mutants and real bugs

RealiT is a neural bug localization and repair model trained on mutants and real bug fixes obtained from open source Python projects. Due to this combined training RealiT achieves a high performance in the localization and repair of real bugs. RealiT currently support the localization and repair of the four types of single statement bugs discussed before. You can try RealiT yourself by following our quick start guide.

Quick start

You can try RealiT with only a few lines of code:

from nbfbaselines import NBFModel

realit_model = NBFModel.from_pretrained("realit")

realit_model("""

def f(x, y):
    return x + x

""")

# Output:
# [{'text': 'def f ( x , y ) :\n    return x + y\n    ',
#  'before': 'x', 'after': 'y',
#  'prob': 0.981337789216316}]

RealiT is mostly trained on function implementation written in Python 3. Therefore, it will work best if provided with a complete function implementation. It will likely also work on partial code snippets (e.g. partial function implementation or statement outside of a function).

You can also test RealiT in your browser without cloning this project. For this, open the following Colab link.

Models

We trained and publish several baseline models for neural bug detection. All models were evaluated on PyPIBugs and on the test portion of ETH Py150k. We used PyPIBugs to estimate the localization (Loc), repair (Rep) and Joint localization and repair performance (Joint). ETH Py150k was used to estimate the false positive rate (FPR).

RealiT models:

model_id	FPR	Joint	Loc	Rep	description
realit5x-noreal	25.2	21.4	25.8	59.9	RealiT without fine-tuning on real bugs and 5x mutants injected during pre-training
realit-noreal	30.0	24.9	30.4	65.6	RealiT without fine-tuning on real bugs
realit	22.0	36.7	41.9	73.5	Base RealiT model (Transformer) trained on 100x mutants and fine-tuned on real bugs.
csnrealit	16.5	38.7	42.7	76.7	RealiT further pre-trained on the Python corpus of CodeSearchNet.

You can try these models easily yourself:

from nbfbaselines import NBFModel

nbf_model = NBFModel.from_pretrained([model_id])

Evaluation

The models were evaluated with the following Python script:

$ python run_eval.py [model_id] [test_file] [output_file] [options...]

For model_id, you can use any of the model ids specified before. The format of the test file is described below. The script accepts further options:

option	description	default
--topk	Activates beam search over the topk most likely repairs	1
--cpu	The script tries to run the code on an Nvidia GPU if availale. This forces the script to run on CPU.	False
--max_length	The maximal number of tokens to be accepted by the model. If an example has more token, we assume that no bug is detected. Tune this if the model exceeds the available memory.	5000
--ignore_error	The script stops if the evaluation runs into an error (e.g. because the code contains a syntax error). This ignores the error and continues the evaluation.	False

Test file format: As a test file, we expect a file in json lines format where each JSON object has the following format:

{
    "input_text": [buggy_code_or_correct_code],
    "error_marker": [sl, sc, el, ec],
    "repair": [repair_text]
}

Note that input_text is required. The fields error_marker and repair are required if the code contains a bug. error_marker specifies the start line (sl), start char in that line (sc), end line (el) and the end char in that line (ec). The repair can be any string. The JSON object can contain further meta data. An example for a test_file is given in data/real_bugs_dummy.jsonl.

Status of Graph Models

The graph models will be published soon. Until then, please refer to our artifact containing the complete implementation of the graph models.

Project info

Cedric Richter - @cedrichter - cedric.richter@uol.de

Distributed under the MIT license. See LICENSE for more information.

If you find this project or our artifact useful, please cite our work:

@inproceedings{richter2023how,
  title={How to Train Your Neural Bug Detector: Artificial vs Real Bugs},
  author={Cedric Richter, Heike Wehrheim},
  booktitle={ASE},
  year={2023}
}

This project is currently incomplete and mainly designed to showcase RealiT. However, we plan to release the full code base including further pre-trained models, training script and evaluation code.

For more information on RealiT specifically, please check our preprint.

Feel free to open an issue if anything unexpected happens.