[RFC,v2,03/10] static-analyzer: Support adding tests to checks

diff --git a/static-analyzer.py b/static-analyzer.py
index 3ade422dbf..16e331000d 100755
--- a/static-analyzer.py
+++ b/static-analyzer.py
@@ -11,17 +11,26 @@ 
 import subprocess
 import sys
 import re
-from argparse import ArgumentParser, Namespace, RawDescriptionHelpFormatter
+from argparse import (
+    Action,
+    ArgumentParser,
+    Namespace,
+    RawDescriptionHelpFormatter,
+)
 from multiprocessing import Pool
 from pathlib import Path
+from tempfile import TemporaryDirectory
 import textwrap
 import time
+from traceback import print_exc
 from typing import (
+    Callable,
     Iterable,
     Iterator,
     List,
     Mapping,
     NoReturn,
+    Optional,
     Sequence,
     Union,
 )
@@ -37,7 +46,7 @@ 
 def parse_args() -> Namespace:
 
     available_checks = "\n".join(
-        f"  {name}   {' '.join((CHECKS[name].__doc__ or '').split())}"
+        f"  {name}   {' '.join((CHECKS[name].checker.__doc__ or '').split())}"
         for name in sorted(CHECKS)
     )
 
@@ -134,14 +143,37 @@  def parse_args() -> Namespace:
         help="Do everything except actually running the checks.",
     )
 
+    dev_options.add_argument(
+        "--test",
+        action=TestAction,
+        nargs=0,
+        help="Run tests for all checks and exit.",
+    )
+
     # parse arguments
 
-    args = parser.parse_args()
+    try:
+        args = parser.parse_args()
+    except TestSentinelError:
+        # --test was specified
+        if len(sys.argv) > 2:
+            parser.error("--test must be given alone")
+        return Namespace(test=True)
+
     args.check_names = sorted(set(args.check_names or CHECKS))
 
     return args
 
 
+class TestAction(Action):
+    def __call__(self, parser, namespace, values, option_string=None):
+        raise TestSentinelError
+
+
+class TestSentinelError(Exception):
+    pass
+
+
 # ---------------------------------------------------------------------------- #
 # Main
 
@@ -150,7 +182,11 @@  def main() -> int:
 
     args = parse_args()
 
-    if args.profile:
+    if args.test:
+
+        return test()
+
+    elif args.profile:
 
         import cProfile
         import pstats
@@ -170,6 +206,18 @@  def main() -> int:
         return analyze(args)
 
 
+def test() -> int:
+
+    for (check_name, check) in CHECKS.items():
+        for group in check.test_groups:
+            for input in group.inputs:
+                run_test(
+                    check_name, group.location, input, group.expected_output
+                )
+
+    return 0
+
+
 def analyze(args: Namespace) -> int:
 
     tr_units = get_translation_units(args)
@@ -247,6 +295,7 @@  class TranslationUnit:
     build_command: str
     system_include_paths: Sequence[str]
     check_names: Sequence[str]
+    custom_printer: Optional[Callable[[str], None]]
 
 
 def get_translation_units(args: Namespace) -> Sequence["TranslationUnit"]:
@@ -264,6 +313,7 @@  def get_translation_units(args: Namespace) -> Sequence["TranslationUnit"]:
             build_command=cmd["command"],
             system_include_paths=system_include_paths,
             check_names=args.check_names,
+            custom_printer=None,
         )
         for cmd in compile_commands
     )
@@ -380,7 +430,7 @@  def analyze_translation_unit(tr_unit: TranslationUnit) -> bool:
 
     try:
         for name in tr_unit.check_names:
-            CHECKS[name](check_context)
+            CHECKS[name].checker(check_context)
     except Exception as e:
         raise RuntimeError(f"Error analyzing {check_context._rel_path}") from e
 
@@ -428,7 +478,9 @@  def get_check_context(tr_unit: TranslationUnit) -> CheckContext:
         except clang.cindex.TranslationUnitLoadError as e:
             raise RuntimeError(f"Failed to load {rel_path}") from e
 
-    if sys.stdout.isatty():
+    if tr_unit.custom_printer is not None:
+        printer = tr_unit.custom_printer
+    elif sys.stdout.isatty():
         # add padding to fully overwrite progress message
         printer = lambda s: print(s.ljust(50))
     else:
@@ -457,6 +509,75 @@  def get_check_context(tr_unit: TranslationUnit) -> CheckContext:
     return check_context
 
 
+# ---------------------------------------------------------------------------- #
+# Tests
+
+
+def run_test(
+    check_name: str, location: str, input: str, expected_output: str
+) -> None:
+
+    with TemporaryDirectory() as temp_dir:
+
+        os.chdir(temp_dir)
+
+        input_path = Path(temp_dir) / "file.c"
+        input_path.write_text(input)
+
+        actual_output_list = []
+
+        tu_context = TranslationUnit(
+            absolute_path=str(input_path),
+            build_working_dir=str(input_path.parent),
+            build_command=f"cc {shlex.quote(str(input_path))}",
+            system_include_paths=[],
+            check_names=[check_name],
+            custom_printer=lambda s: actual_output_list.append(s + "\n"),
+        )
+
+        check_context = get_check_context(tu_context)
+
+        # analyze translation unit
+
+        try:
+
+            for name in tu_context.check_names:
+                CHECKS[name].checker(check_context)
+
+        except Exception:
+
+            print(
+                f"\033[0;31mTest defined at {location} raised an"
+                f" exception.\033[0m"
+            )
+            print(f"\033[0;31mInput:\033[0m")
+            print(input, end="")
+            print(f"\033[0;31mExpected output:\033[0m")
+            print(expected_output, end="")
+            print(f"\033[0;31mException:\033[0m")
+            print_exc(file=sys.stdout)
+            print(f"\033[0;31mAST:\033[0m")
+            check_context.print_tree(check_context.translation_unit.cursor)
+
+            sys.exit(1)
+
+        actual_output = "".join(actual_output_list)
+
+        if actual_output != expected_output:
+
+            print(f"\033[0;33mTest defined at {location} failed.\033[0m")
+            print(f"\033[0;33mInput:\033[0m")
+            print(input, end="")
+            print(f"\033[0;33mExpected output:\033[0m")
+            print(expected_output, end="")
+            print(f"\033[0;33mActual output:\033[0m")
+            print(actual_output, end="")
+            print(f"\033[0;33mAST:\033[0m")
+            check_context.print_tree(check_context.translation_unit.cursor)
+
+            sys.exit(3)
+
+
 # ---------------------------------------------------------------------------- #
 # Utilities
 
diff --git a/static_analyzer/__init__.py b/static_analyzer/__init__.py
index e6ca48d714..36028724b1 100644
--- a/static_analyzer/__init__.py
+++ b/static_analyzer/__init__.py
@@ -3,16 +3,20 @@ 
 from ctypes import CFUNCTYPE, c_int, py_object
 from dataclasses import dataclass
 from enum import Enum
+import inspect
 import os
 import os.path
 from pathlib import Path
 from importlib import import_module
+import textwrap
 from typing import (
     Any,
     Callable,
     Dict,
+    Iterable,
     List,
     Optional,
+    Sequence,
     Union,
 )
 
@@ -218,18 +222,49 @@  def print_tree(
 
 Checker = Callable[[CheckContext], None]
 
-CHECKS: Dict[str, Checker] = {}
+
+class CheckTestGroup:
+
+    inputs: Sequence[str]
+    expected_output: str
+
+    location: str
+
+    def __init__(self, inputs: Iterable[str], expected_output: str) -> None:
+        def reformat_string(s: str) -> str:
+            return "".join(
+                line + "\n" for line in textwrap.dedent(s).strip().splitlines()
+            )
+
+        self.inputs = [reformat_string(input) for input in inputs]
+        self.expected_output = reformat_string(expected_output)
+
+        caller = inspect.stack()[1]
+        self.location = f"{os.path.relpath(caller.filename)}:{caller.lineno}"
+
+
+@dataclass
+class Check:
+    checker: Checker
+    test_groups: List[CheckTestGroup]
+
+
+CHECKS: Dict[str, Check] = {}
 
 
 def check(name: str) -> Callable[[Checker], Checker]:
     def decorator(checker: Checker) -> Checker:
         assert name not in CHECKS
-        CHECKS[name] = checker
+        CHECKS[name] = Check(checker=checker, test_groups=[])
         return checker
 
     return decorator
 
 
+def add_check_tests(check_name: str, *groups: CheckTestGroup) -> None:
+    CHECKS[check_name].test_groups.extend(groups)
+
+
 # ---------------------------------------------------------------------------- #
 # Import all checks
 
diff --git a/static_analyzer/return_value_never_used.py b/static_analyzer/return_value_never_used.py
index 05c06cd4c2..de1a6542d1 100644
--- a/static_analyzer/return_value_never_used.py
+++ b/static_analyzer/return_value_never_used.py
@@ -11,7 +11,9 @@ 
 
 from static_analyzer import (
     CheckContext,
+    CheckTestGroup,
     VisitorResult,
+    add_check_tests,
     check,
     might_have_attribute,
     visit,
@@ -115,3 +117,104 @@  def get_parent_if_unexposed_expr(node: Cursor) -> Cursor:
 
 
 # ---------------------------------------------------------------------------- #
+
+add_check_tests(
+    "return-value-never-used",
+    CheckTestGroup(
+        inputs=[
+            R"""
+                static void f(void) { }
+                """,
+            R"""
+                static __attribute__((unused)) int f(void) { }
+                """,
+            R"""
+                #define ATTR __attribute__((unused))
+                static __attribute__((unused)) int f(void) { }
+                """,
+            R"""
+                #define FUNC static __attribute__((unused)) int f(void) { }
+                FUNC
+                """,
+            R"""
+                static __attribute__((unused, constructor)) int f(void) { }
+                """,
+            R"""
+                static __attribute__((constructor, unused)) int f(void) { }
+                """,
+            R"""
+                static int f(void) { return 42; }
+                static void g(void) {
+                    int x = f();
+                }
+                """,
+            R"""
+                static int f(void) { return 42; }
+                static void g(void) {
+                    for (0; f(); 0) { }
+                }
+                """,
+            R"""
+                static int f(void) { return 42; }
+                static void g(void) {
+                    for (f(); ; ) { }
+                }
+                """,
+            R"""
+                static int f(void) { return 42; }
+                static void g(void) {
+                    for ( ; f(); ) { }
+                }
+                """,
+            R"""
+                static int f(void) { return 42; }
+                static void g(void) {
+                    for ( ; ; f()) { }
+                }
+                """,
+            R"""
+                static int f(void) { return 42; }
+                static void g(void) {
+                    int (*ptr)(void) = 0;
+                    __atomic_store_n(&ptr, f, __ATOMIC_RELAXED);
+                }
+                """,
+        ],
+        expected_output=R"""
+            """,
+    ),
+    CheckTestGroup(
+        inputs=[
+            R"""
+                static int f(void) { return 42; }
+                """,
+            R"""
+                static int f(void) { return 42; }
+                static void g(void) {
+                    f();
+                }
+                """,
+            R"""
+                static int f(void) { return 42; }
+                static void g(void) {
+                    for (f(); 0; f()) { }
+                }
+                """,
+        ],
+        expected_output=R"""
+            file.c:1:12: f() return value is never used
+            """,
+    ),
+    CheckTestGroup(
+        inputs=[
+            R"""
+                static __attribute__((constructor)) int f(void) { }
+                """,
+        ],
+        expected_output=R"""
+            file.c:1:41: f() return value is never used
+            """,
+    ),
+)
+
+# ---------------------------------------------------------------------------- #