58 lines
2.2 KiB
Python
58 lines
2.2 KiB
Python
"""AST-level boundary error injection for Java using javalang."""
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from typing import Optional
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import javalang
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from app.dataset.rules.base import Mutation, MutationRule
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class JavaBoundaryErrorRule(MutationRule):
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"""Mutate array length boundary from `<` to `<=`.
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Uses `javalang` to locate a binary comparison against `.length` and flips
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the operator to introduce an off-by-one access.
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"""
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name = "java_boundary_error"
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language = "java"
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defect_type = "boundary_condition_error"
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def detect_and_mutate(self, source: str, filename: str = "") -> Optional[Mutation]:
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try:
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tree = javalang.parse.parse(source)
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except Exception:
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return None
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for path, node in tree:
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if not isinstance(node, javalang.tree.BinaryOperation):
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continue
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if node.operator != "<":
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continue
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right = node.operandr
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if isinstance(right, javalang.tree.MemberReference) and right.member == "length":
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# BinaryOperation itself may lack position; use enclosing statement
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if_statement = next((n for n in path if isinstance(n, javalang.tree.IfStatement)), None)
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pos = if_statement.position if if_statement else node.position
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if not pos:
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continue
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lines = source.splitlines(keepends=True)
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line_no = pos.line
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line = lines[line_no - 1]
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mutated_line = line.replace("< ", "<= ", 1)
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if mutated_line == line:
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mutated_line = line.replace("<", "<=", 1)
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if mutated_line == line:
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continue
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mutated = "".join(lines[:line_no - 1] + [mutated_line] + lines[line_no:])
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return Mutation(
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defect_type=self.defect_type,
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language=self.language,
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line_start=line_no,
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line_end=line_no,
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mutated_source=mutated,
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reference_fix="Use strict `< length` to avoid ArrayIndexOutOfBoundsException.",
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description="Changed array boundary check to off-by-one (<= length).",
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)
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return None
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