Improve unreachable code analysis (#302)

Fixes #270 and catches additional unreachable code.

---------

Co-authored-by: Jendrik Seipp <[email protected]>

CHANGELOG.md

@@ -1,5 +1,6 @@
 # next (unreleased)
 
+* Improve reachability analysis (kreathon, #270, #302).
 * Add type hints for `get_unused_code` and the fields of the `Item` class (John Doknjas, #361).
 
 # 2.13 (2024-10-02)

tests/__init__.py

@@ -39,6 +39,14 @@ def check_unreachable(v, lineno, size, name):
     assert item.name == name
 
 
+def check_multiple_unreachable(v, checks):
+    assert len(v.unreachable_code) == len(checks)
+    for item, (lineno, size, name) in zip(v.unreachable_code, checks):
+        assert item.first_lineno == lineno
+        assert item.size == size
+        assert item.name == name
+
+
 @pytest.fixture
 def v():
     return core.Vulture(verbose=True)

tests/test_conditions.py

@@ -2,7 +2,6 @@
 
 from vulture import utils
 
-from . import check_unreachable
 from . import v
 
 assert v  # Silence pyflakes
@@ -73,147 +72,3 @@ def test_errors():
         condition = ast.parse(condition, mode="eval").body
         assert not utils.condition_is_always_false(condition)
         assert not utils.condition_is_always_true(condition)
-
-
-def test_while(v):
-    v.scan(
-        """\
-while False:
-    pass
-"""
-    )
-    check_unreachable(v, 1, 2, "while")
-
-
-def test_while_nested(v):
-    v.scan(
-        """\
-while True:
-    while False:
-        pass
-"""
-    )
-    check_unreachable(v, 2, 2, "while")
-
-
-def test_if_false(v):
-    v.scan(
-        """\
-if False:
-    pass
-"""
-    )
-    check_unreachable(v, 1, 2, "if")
-
-
-def test_elif_false(v):
-    v.scan(
-        """\
-if bar():
-    pass
-elif False:
-    print("Unreachable")
-"""
-    )
-    check_unreachable(v, 3, 2, "if")
-
-
-def test_nested_if_statements_false(v):
-    v.scan(
-        """\
-if foo():
-    if bar():
-        pass
-    elif False:
-        print("Unreachable")
-        pass
-    elif something():
-        print("Reachable")
-    else:
-        pass
-else:
-    pass
-"""
-    )
-    check_unreachable(v, 4, 3, "if")
-
-
-def test_if_false_same_line(v):
-    v.scan(
-        """\
-if False: a = 1
-else: c = 3
-"""
-    )
-    check_unreachable(v, 1, 1, "if")
-
-
-def test_if_true(v):
-    v.scan(
-        """\
-if True:
-    a = 1
-    b = 2
-else:
-    c = 3
-    d = 3
-"""
-    )
-    # For simplicity, we don't report the "else" line as dead code.
-    check_unreachable(v, 5, 2, "else")
-
-
-def test_if_true_same_line(v):
-    v.scan(
-        """\
-if True:
-    a = 1
-    b = 2
-else: c = 3
-d = 3
-"""
-    )
-    check_unreachable(v, 4, 1, "else")
-
-
-def test_nested_if_statements_true(v):
-    v.scan(
-        """\
-if foo():
-    if bar():
-        pass
-    elif True:
-        if something():
-            pass
-        else:
-            pass
-    elif something_else():
-        print("foo")
-    else:
-        print("bar")
-else:
-    pass
-"""
-    )
-    check_unreachable(v, 9, 4, "else")
-
-
-def test_redundant_if(v):
-    v.scan(
-        """\
-if [5]:
-    pass
-"""
-    )
-    print(v.unreachable_code[0].size)
-    check_unreachable(v, 1, 2, "if")
-
-
-def test_if_exp_true(v):
-    v.scan("foo if True else bar")
-    check_unreachable(v, 1, 1, "ternary")
-
-
-def test_if_exp_false(v):
-    v.scan("foo if False else bar")
-    check_unreachable(v, 1, 1, "ternary")