feat(fixers): implement fixer for reraise no cause

src/tests/analyzers_exception_block_test.py

@@ -1,3 +1,4 @@
+import ast
 from functools import partial
 
 from tryceratops import analyzers
@@ -15,8 +16,11 @@ def test_reraise_no_cause():
 
     violations = analyzer.check(tree, "filename")
     assert len(violations) == 1
+    single = violations[0]
 
-    assert_no_cause(16, 8, violations[0])
+    assert_no_cause(16, 8, single)
+    assert single.exception_name is None
+    assert isinstance(single.except_node, ast.ExceptHandler)
 
 
 def test_verbose_reraise():

src/tests/fixers_test.py

@@ -1,8 +1,9 @@
 import ast
 from typing import List, Tuple
+from unittest.mock import MagicMock
 
-from tryceratops.fixers import VerboseReraiseFixer
-from tryceratops.violations import VerboseReraiseViolation, codes
+from tryceratops.fixers import RaiseWithoutCauseFixer, VerboseReraiseFixer
+from tryceratops.violations import RaiseWithoutCauseViolation, VerboseReraiseViolation, codes
 
 from .analyzer_helpers import read_sample_lines
 
@@ -11,16 +12,26 @@ def create_verbose_reraise_violation(code: Tuple[str, str], line: int):
     return VerboseReraiseViolation(code[0], line, 0, "", "", None, "ex")
 
 
+def create_raise_no_cause_violation(line: int, except_line: int):
+    code, _ = codes.RERAISE_NO_CAUSE
+    node_mock = MagicMock(spec=ast.Raise, lineno=line)
+    except_node_mock = MagicMock(spec=ast.ExceptHandler, lineno=except_line)
+    return RaiseWithoutCauseViolation(code, line, 0, "", "", node_mock, except_node_mock)
+
+
 def assert_ast_is_valid(results: List[str]):
     content = "\n".join(results)
     result = ast.parse(content)
     assert result is not None
 
 
-def assert_unmodified_lines(initial: List[str], results: List[str], modified_offset: int):
+def assert_unmodified_lines(initial: List[str], results: List[str], *modified_offsets: int):
     assert len(results) == len(initial)
-    assert results[:modified_offset] == initial[:modified_offset]
-    assert results[modified_offset + 1 :] == initial[modified_offset + 1 :]
+    for idx, initial_line in enumerate(initial):
+        if idx in modified_offsets:
+            continue
+
+        assert initial_line == results[idx], f"Line {idx+1} got modified"
 
 
 def test_verbose_fixer():
@@ -35,3 +46,18 @@ def test_verbose_fixer():
     assert_ast_is_valid(results)
     assert_unmodified_lines(lines, results, expected_modified_offset)
     assert results[expected_modified_offset].endswith("raise  # This is verbose\n")
+
+
+def test_raise_without_cause_fixer_without_exception_name():
+    fixer = RaiseWithoutCauseFixer()
+    lines = read_sample_lines("except_reraise_no_cause")
+    expected_modified_offsets = {14, 15}
+    dependent_offset, offending_offset = expected_modified_offsets
+    violation = create_raise_no_cause_violation(offending_offset + 1, dependent_offset + 1)
+
+    results = fixer.perform_fix(lines, violation)
+
+    assert_ast_is_valid(results)
+    assert_unmodified_lines(lines, results, *expected_modified_offsets)
+    assert results[dependent_offset].endswith("except Exception as ex:\n")
+    assert results[offending_offset].endswith("raise MyException() from ex\n")

src/tryceratops/analyzers/exception_block.py

@@ -1,14 +1,14 @@
 import ast
 from typing import Iterable, Optional
 
-from tryceratops.violations import codes
-from tryceratops.violations.violations import VerboseReraiseViolation
+from tryceratops.violations import RaiseWithoutCauseViolation, VerboseReraiseViolation, codes
 
 from .base import BaseAnalyzer, visit_error_handler
 
 
 class ExceptReraiseWithoutCauseAnalyzer(BaseAnalyzer):
     violation_code = codes.RERAISE_NO_CAUSE
+    violation_type = RaiseWithoutCauseViolation
 
     @visit_error_handler
     def visit_ExceptHandler(self, node: ast.ExceptHandler) -> None:
@@ -18,7 +18,7 @@ def is_raise_without_cause(node: ast.AST):
             return False
 
         reraises_no_cause = [stm for stm in ast.walk(node) if is_raise_without_cause(stm)]
-        self._mark_violation(*reraises_no_cause)
+        self._mark_violation(*reraises_no_cause, exception_name=node.name, except_node=node)
 
         self.generic_visit(node)
 

src/tryceratops/fixers/__init__.py

@@ -1 +1 @@
-from .exception_block import VerboseReraiseFixer
+from .exception_block import RaiseWithoutCauseFixer, VerboseReraiseFixer

src/tryceratops/fixers/exception_block.py

@@ -4,7 +4,7 @@
 from typing import Generic, Iterable, List, Tuple, TypeVar
 
 from tryceratops.violations import Violation, codes
-from tryceratops.violations.violations import VerboseReraiseViolation
+from tryceratops.violations.violations import RaiseWithoutCauseViolation, VerboseReraiseViolation
 
 
 class FileFixerHandler:
@@ -79,3 +79,32 @@ def perform_fix(self, lines: List[str], violation: VerboseReraiseViolation) -> L
         all_lines[violation.line - 1] = new_line
 
         return all_lines
+
+
+class RaiseWithoutCauseFixer(BaseFixer[RaiseWithoutCauseViolation]):
+    violation_code = codes.RERAISE_NO_CAUSE
+    exception_name_to_create = "ex"
+
+    def _add_name_to_except_handler(self, line: str) -> str:
+        # TODO: refactor function name
+        new_line = re.sub(r"except (.*):", rf"except \1 as {self.exception_name_to_create}:", line)
+        return new_line
+
+    def perform_fix(self, lines: List[str], violation: RaiseWithoutCauseViolation) -> List[str]:
+        all_lines = lines[:]
+        exception_name = violation.exception_name
+
+        if violation.except_node and exception_name is None:
+            # TODO: refactor: calc line, get line, modify line, write line
+            dependent_line_offset = violation.except_node.lineno - 1
+            dependent_line = all_lines[dependent_line_offset]
+            dependent_fixed_line = self._add_name_to_except_handler(dependent_line)
+            all_lines[dependent_line_offset] = dependent_fixed_line
+            exception_name = self.exception_name_to_create
+
+        guilty_line = all_lines[violation.line - 1]
+        # TODO: What if this raise is multi-line?
+        new_line = re.sub(r"raise (.*)", rf"raise \1 from {exception_name}", guilty_line)
+        all_lines[violation.line - 1] = new_line
+
+        return all_lines

src/tryceratops/violations/__init__.py

@@ -1,2 +1,2 @@
 from .codes import *
-from .violations import VerboseReraiseViolation, Violation
+from .violations import RaiseWithoutCauseViolation, VerboseReraiseViolation, Violation

src/tryceratops/violations/violations.py

@@ -33,3 +33,24 @@ def build(
     ):
         code, msg = vio_details
         return cls(code, node.lineno, node.col_offset, msg, filename, node, exception_name)
+
+
+@dataclass
+class RaiseWithoutCauseViolation(Violation):
+    except_node: Optional[ast.AST] = None
+    exception_name: Optional[str] = None
+
+    @classmethod
+    def build(
+        cls,
+        filename: str,
+        vio_details: Tuple[str, str],
+        node: ast.AST,
+        except_node: Optional[ast.AST] = None,
+        exception_name: Optional[str] = None,
+        **kwargs
+    ):
+        code, msg = vio_details
+        return cls(
+            code, node.lineno, node.col_offset, msg, filename, node, except_node, exception_name
+        )