76 lines
3.0 KiB
Python
76 lines
3.0 KiB
Python
"""AST-level null-pointer 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 JavaNoneReferenceRule(MutationRule):
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"""Remove a null-check guard in Java source.
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Uses the pure-Python `javalang` parser to locate an `if (x != null)` guard
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and remove it, leaving the dereference unprotected. This keeps mutation
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semantics precise without regex/text replacement.
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"""
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name = "java_none_reference"
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language = "java"
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defect_type = "null_pointer"
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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.IfStatement):
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continue
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cond = node.condition
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# Match: x != null
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if (
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isinstance(cond, javalang.tree.BinaryOperation)
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and cond.operator == "!="
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and isinstance(cond.operandr, javalang.tree.Literal)
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and cond.operandr.value == "null"
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):
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var_name = getattr(cond.operandl, "member", str(cond.operandl))
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lines = source.splitlines(keepends=True)
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start = node.position.line if node.position else 1
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# Estimate end line by finding matching brace (simplistic)
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end = start
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depth = 0
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for idx in range(start - 1, len(lines)):
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depth += lines[idx].count("{") - lines[idx].count("}")
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if depth > 0:
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end = idx + 1
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if depth <= 0 and idx > start - 1:
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end = idx + 1
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break
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body_lines = lines[start - 1:end]
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# keep body lines between header and closing brace, dedent one level
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inner = body_lines[1:-1] if len(body_lines) > 2 else []
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dedented = []
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for line in inner:
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if line.startswith(" "):
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dedented.append(" " + line[12:])
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elif line.startswith(" "):
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dedented.append(" " + line[8:])
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elif line.startswith(" "):
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dedented.append(line[4:])
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else:
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dedented.append(line)
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mutated = "".join(lines[: start - 1] + dedented + lines[end:])
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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=start,
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line_end=end,
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mutated_source=mutated,
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reference_fix=f"Add `if ({var_name} != null)` guard before dereferencing.",
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description=f"Removed null-check guard for '{var_name}'.",
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)
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return None
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