[pylint] Re-implement unreachable (PLW0101)

crates/ruff_linter/Cargo.toml

@@ -15,6 +15,7 @@ license = { workspace = true }
 [dependencies]
 ruff_cache = { workspace = true }
 ruff_diagnostics = { workspace = true, features = ["serde"] }
+ruff_index = { workspace = true }
 ruff_notebook = { workspace = true }
 ruff_macros = { workspace = true }
 ruff_python_ast = { workspace = true, features = ["serde", "cache"] }

crates/ruff_linter/resources/test/fixtures/control-flow-graph/assert.py

@@ -9,3 +9,29 @@ def func():
 
 def func():
     assert False, "oops"
+
+def func():
+    y = 2
+    assert y == 2
+    assert y > 1
+    assert y < 3
+
+def func():
+    for i in range(3):
+        assert i < x
+
+def func():
+    for j in range(3):
+        x = 2
+    else:
+        assert False
+    return 1
+
+def func():
+    for j in range(3):
+        if j == 2:
+            print('yay')
+            break
+    else:
+        assert False
+    return 1

crates/ruff_linter/resources/test/fixtures/control-flow-graph/for.py

@@ -40,8 +40,6 @@ def func():
         if True:
             break
 
-# TODO(charlie): The `pass` here does not get properly redirected to the top of the
-# loop, unlike below.
 def func():
     for i in range(5):
         pass
@@ -54,3 +52,59 @@ def func():
     else:
         return 1
     x = 1
+
+def func():
+    for i in range(5):
+        pass
+    else:
+        pass
+
+def func():
+    for i in range(3):
+        if i == 2:
+            assert i is not None
+            break
+    else:
+        raise Exception()
+    x = 0
+
+def func():
+    for i in range(13):
+        for i in range(12):
+            x = 2
+            if True:
+                break
+
+        x = 3
+        if True:
+            break
+
+    print('hello')
+
+
+def func():
+    for i in range(13):
+        for i in range(12):
+            x = 2
+            if True:
+                continue
+
+        x = 3
+        if True:
+            break
+
+    print('hello')
+
+
+def func():
+    for i in range(13):
+        for i in range(12):
+            x = 2
+            if True:
+                break
+
+        x = 3
+        if True:
+            continue
+
+    print('hello')

crates/ruff_linter/resources/test/fixtures/control-flow-graph/if.py

@@ -106,3 +106,25 @@ def func(self, obj: BytesRep) -> bytes:
             self.error(f"can't resolve buffer '{id}'")
 
     return buffer.data
+
+def func(x):
+    if x == 1:
+        return 1
+    elif False:
+        return 2
+    elif x == 3:
+        return 3
+    elif True:
+        return 4
+    elif x == 5:
+        return 5
+    elif x == 6:
+        return 6
+
+def func():
+    if x:
+        return
+    else:
+        assert x
+
+    print('pop')

crates/ruff_linter/resources/test/fixtures/control-flow-graph/simple.py

@@ -21,3 +21,14 @@ def func():
     i = 0
     i += 2
     return i
+
+def func():
+    with x:
+        i = 0
+    i = 1
+
+def func():
+    with x:
+        i = 0
+        return 1
+    i = 1

crates/ruff_linter/resources/test/fixtures/control-flow-graph/try.py

@@ -1,41 +1,118 @@
 def func():
     try:
-       ...
+        print("try")
     except Exception:
-       ...
+        print("Exception")
     except OtherException as e:
-       ...
+        print("OtherException")
     else:
-       ...
+        print("else")
     finally:
-       ...
+        print("finally")
 
 def func():
     try:
-       ...
-    except Exception:
-       ...
+        print("try")
+    except:
+        print("Exception")
+
+def func():
+    try:
+        print("try")
+    except:
+        print("Exception")
+    except OtherException as e:
+        print("OtherException")
 
 def func():
     try:
-       ...
+        print("try")
     except Exception:
-       ...
+        print("Exception")
     except OtherException as e:
-       ...
+        print("OtherException")
 
 def func():
     try:
-       ...
+        print("try")
     except Exception:
-       ...
+        print("Exception")
     except OtherException as e:
-       ...
+        print("OtherException")
     else:
-       ...
+        print("else")
+
+def func():
+    try:
+        print("try")
+    finally:
+        print("finally")
 
 def func():
     try:
-       ...
+        return 0
+    except:
+        return 1
+    finally:
+        return 2
+
+def func():
+    try:
+        raise Exception()
+    except:
+        print("reached")
+
+def func():
+    try:
+        assert False
+        print("unreachable")
+    except:
+        print("reached")
+
+def func():
+    try:
+        raise Exception()
+    finally:
+        print('reached')
+        return 2
+
+def func():
+    try:
+        assert False
+        print("unreachable")
+    finally:
+        print("reached")
+
+# Test case from ibis caused overflow
+def func():
+    try:
+        if catalog is not None:
+            try:
+                x = 0
+            except PySparkParseException:
+                x = 1
+        try:
+            x = 2
+        except PySparkParseException:
+            x = 3
+        x = 8
+    finally:
+        if catalog is not None:
+            try:
+                x = 4
+            except PySparkParseException:
+                x = 5
+        try:
+            x = 6
+        except PySparkParseException:
+            x = 7
+
+
+def func():
+    try:
+        assert False
+    except ex:
+        raise ex
+
     finally:
-       ...
+        raise Exception("other")

crates/ruff_linter/resources/test/fixtures/control-flow-graph/while.py

@@ -99,12 +99,39 @@ def func():
         if True:
             break
 
-'''
-TODO: because `try` statements aren't handled this triggers a false positive as
-the last statement is reached, but the rules thinks it isn't (it doesn't
-see/process the break statement).
+def func():
+    while True:
+        x = 0
+        x = 1
+        break
+        x = 2
+    x = 3
+
+def func():
+    while True:
+        x = 0
+        x = 1
+        continue
+        x = 2
+    x = 3
+
+def func():
+    while True:
+        x = 0
+        x = 1
+        return
+        x = 2
+    x = 3
+
+def func():
+    while True:
+        x = 0
+        x = 1
+        raise Exception
+        x = 2
+    x = 3
 
-# Test case found in the Bokeh repository that trigger a false positive.
+# Test case found in the Bokeh repository that triggered a false positive.
 def bokeh2(self, host: str = DEFAULT_HOST, port: int = DEFAULT_PORT) -> None:
     self.stop_serving = False
     while True:
@@ -118,4 +145,3 @@ def bokeh2(self, host: str = DEFAULT_HOST, port: int = DEFAULT_PORT) -> None:
             port += 1
 
     self.thread = threading.Thread(target=self._run_web_server)
-'''