From cda2ff0b180d311a24cf545c0339ba8977437db3 Mon Sep 17 00:00:00 2001
From: Peter Pentchev <roam@ringlet.net>
Date: Fri, 10 Feb 2023 16:28:34 +0200
Subject: [PATCH] Handle functions that never return in RET503 (#2701)

---
 .../test/fixtures/flake8_return/RET503.py     | 71 +++++++++++++++++++
 crates/ruff/src/rules/flake8_return/rules.rs  | 30 ++++++++
 ...lake8_return__tests__RET503_RET503.py.snap | 70 +++++++++++++-----
 3 files changed, 155 insertions(+), 16 deletions(-)

diff --git a/crates/ruff/resources/test/fixtures/flake8_return/RET503.py b/crates/ruff/resources/test/fixtures/flake8_return/RET503.py
index 0cf189612f..e708d7d3e5 100644
--- a/crates/ruff/resources/test/fixtures/flake8_return/RET503.py
+++ b/crates/ruff/resources/test/fixtures/flake8_return/RET503.py
@@ -1,3 +1,11 @@
+import os
+import posix
+from posix import abort
+import sys as std_sys
+
+import pytest
+from pytest import xfail as py_xfail
+
 ###
 # Errors
 ###
@@ -39,6 +47,20 @@ def x(y):
         print()  # error
 
 
+# A nonexistent function
+def func_unknown(x):
+    if x > 0:
+        return False
+    no_such_function()  # error
+
+
+# A function that does return the control
+def func_no_noreturn(x):
+    if x > 0:
+        return False
+    print("", end="")  # error
+
+
 ###
 # Non-errors
 ###
@@ -123,3 +145,52 @@ def prompts(self, foo):
     for x in foo:
         yield x
         yield x + 1
+
+
+# Functions that never return
+def noreturn__exit(x):
+    if x > 0:
+        return 1
+    os._exit(0)
+
+
+def noreturn_abort(x):
+    if x > 0:
+        return 1
+    os.abort()
+
+
+def noreturn_abort_2():
+    if x > 0:
+        return 1
+    abort()
+
+
+def noreturn_exit():
+    if x > 0:
+        return 1
+    std_sys.exit(0)
+
+
+def noreturn_pytest_exit():
+    if x > 0:
+        return 1
+    pytest.exit("oof")
+
+
+def noreturn_pytest_fail():
+    if x > 0:
+        return 1
+    pytest.fail("oof")
+
+
+def noreturn_pytest_skip():
+    if x > 0:
+        return 1
+    pytest.skip("oof")
+
+
+def noreturn_pytest_xfail():
+    if x > 0:
+        return 1
+    py_xfail("oof")
diff --git a/crates/ruff/src/rules/flake8_return/rules.rs b/crates/ruff/src/rules/flake8_return/rules.rs
index b406eb74b9..f2703beaa8 100644
--- a/crates/ruff/src/rules/flake8_return/rules.rs
+++ b/crates/ruff/src/rules/flake8_return/rules.rs
@@ -165,6 +165,30 @@ fn implicit_return_value(checker: &mut Checker, stack: &Stack) {
     }
 }
 
+const NORETURN_FUNCS: &[&[&str]] = &[
+    // builtins
+    &["", "exit"],
+    // stdlib
+    &["os", "_exit"],
+    &["os", "abort"],
+    &["posix", "abort"],
+    &["sys", "exit"],
+    // third-party modules
+    &["pytest", "exit"],
+    &["pytest", "fail"],
+    &["pytest", "skip"],
+    &["pytest", "xfail"],
+];
+
+/// Return `true` if the `func` is a known function that never returns.
+fn is_noreturn_func(checker: &Checker, func: &Expr) -> bool {
+    checker.resolve_call_path(func).map_or(false, |call_path| {
+        NORETURN_FUNCS
+            .iter()
+            .any(|target| call_path.as_slice() == *target)
+    })
+}
+
 /// RET503
 fn implicit_return(checker: &mut Checker, last_stmt: &Stmt) {
     match &last_stmt.node {
@@ -208,6 +232,12 @@ fn implicit_return(checker: &mut Checker, last_stmt: &Stmt) {
         | StmtKind::While { .. }
         | StmtKind::Raise { .. }
         | StmtKind::Try { .. } => {}
+        StmtKind::Expr { value, .. }
+            if matches!(
+                &value.node,
+                ExprKind::Call { func, ..  }
+                    if is_noreturn_func(checker, func)
+            ) => {}
         _ => {
             let mut diagnostic = Diagnostic::new(ImplicitReturn, Range::from_located(last_stmt));
             if checker.patch(diagnostic.kind.rule()) {
diff --git a/crates/ruff/src/rules/flake8_return/snapshots/ruff__rules__flake8_return__tests__RET503_RET503.py.snap b/crates/ruff/src/rules/flake8_return/snapshots/ruff__rules__flake8_return__tests__RET503_RET503.py.snap
index 7b2ce1e456..1398784d1c 100644
--- a/crates/ruff/src/rules/flake8_return/snapshots/ruff__rules__flake8_return__tests__RET503_RET503.py.snap
+++ b/crates/ruff/src/rules/flake8_return/snapshots/ruff__rules__flake8_return__tests__RET503_RET503.py.snap
@@ -5,78 +5,116 @@ expression: diagnostics
 - kind:
     ImplicitReturn: ~
   location:
-    row: 7
+    row: 15
     column: 4
   end_location:
-    row: 8
+    row: 16
     column: 16
   fix: ~
   parent: ~
 - kind:
     ImplicitReturn: ~
   location:
-    row: 14
+    row: 22
     column: 8
   end_location:
-    row: 14
+    row: 22
     column: 15
   fix:
     content:
       - "        return None"
       - ""
     location:
-      row: 15
+      row: 23
       column: 0
     end_location:
-      row: 15
+      row: 23
       column: 0
   parent: ~
 - kind:
     ImplicitReturn: ~
   location:
-    row: 23
+    row: 31
     column: 4
   end_location:
-    row: 23
+    row: 31
     column: 11
   fix:
     content:
       - "    return None"
       - ""
     location:
-      row: 24
+      row: 32
       column: 0
     end_location:
-      row: 24
+      row: 32
       column: 0
   parent: ~
 - kind:
     ImplicitReturn: ~
   location:
-    row: 29
+    row: 37
     column: 8
   end_location:
-    row: 30
+    row: 38
     column: 20
   fix: ~
   parent: ~
 - kind:
     ImplicitReturn: ~
   location:
-    row: 39
+    row: 47
     column: 8
   end_location:
-    row: 39
+    row: 47
     column: 15
   fix:
     content:
       - "        return None"
       - ""
     location:
-      row: 40
+      row: 48
       column: 0
     end_location:
-      row: 40
+      row: 48
+      column: 0
+  parent: ~
+- kind:
+    ImplicitReturn: ~
+  location:
+    row: 54
+    column: 4
+  end_location:
+    row: 54
+    column: 22
+  fix:
+    content:
+      - "    return None"
+      - ""
+    location:
+      row: 55
+      column: 0
+    end_location:
+      row: 55
+      column: 0
+  parent: ~
+- kind:
+    ImplicitReturn: ~
+  location:
+    row: 61
+    column: 4
+  end_location:
+    row: 61
+    column: 21
+  fix:
+    content:
+      - "    return None"
+      - ""
+    location:
+      row: 62
+      column: 0
+    end_location:
+      row: 62
       column: 0
   parent: ~