From e38b20695788f2640ed01437f40817588e6516ce Mon Sep 17 00:00:00 2001
From: Jonne Ransijn <jonne@yyny.dev>
Date: Sat, 30 Nov 2024 16:29:25 +0100
Subject: [PATCH] AK: Print a more useful error message when a `MUST(...)`
 fails

```
VERIFICATION FAILED: !_temporary_result.is_error()
```

is not really a helpful error message.

When we are including `AK/Format.h`, which is most of the time,
we can easily print a much more useful error message:

```
UNEXPECTED ERROR: Cannot allocate memory (errno=12)
```
---
 AK/Assertions.cpp | 41 +++++++++++++++++++----------------------
 AK/Assertions.h   |  3 +++
 AK/Format.h       | 15 +++++++++++++++
 AK/Try.h          |  5 ++++-
 4 files changed, 41 insertions(+), 23 deletions(-)

diff --git a/AK/Assertions.cpp b/AK/Assertions.cpp
index 79d2de8c0ec..bc096d6a72a 100644
--- a/AK/Assertions.cpp
+++ b/AK/Assertions.cpp
@@ -81,45 +81,42 @@ ALWAYS_INLINE void dump_backtrace()
 
 extern "C" {
 
-void ak_verification_failed(char const* message)
+bool ak_colorize_output(void)
 {
 #if defined(AK_OS_SERENITY) || defined(AK_OS_ANDROID)
-    bool colorize_output = true;
+    return true;
 #elif defined(AK_OS_WINDOWS)
-    bool colorize_output = false;
+    return false;
 #else
-    bool colorize_output = isatty(STDERR_FILENO) == 1;
+    return isatty(STDERR_FILENO) == 1;
 #endif
+}
 
-    if (colorize_output)
+void ak_trap(void)
+{
+#if defined(AK_HAS_BACKTRACE_HEADER)
+    dump_backtrace();
+#endif
+    __builtin_trap();
+}
+
+void ak_verification_failed(char const* message)
+{
+    if (ak_colorize_output())
         ERRORLN("\033[31;1mVERIFICATION FAILED\033[0m: {}", message);
     else
         ERRORLN("VERIFICATION FAILED: {}", message);
 
-#if defined(AK_HAS_BACKTRACE_HEADER)
-    dump_backtrace();
-#endif
-    __builtin_trap();
+    ak_trap();
 }
 
 void ak_assertion_failed(char const* message)
 {
-#if defined(AK_OS_SERENITY) || defined(AK_OS_ANDROID)
-    bool colorize_output = true;
-#elif defined(AK_OS_WINDOWS)
-    bool colorize_output = false;
-#else
-    bool colorize_output = isatty(STDERR_FILENO) == 1;
-#endif
-
-    if (colorize_output)
+    if (ak_colorize_output())
         ERRORLN("\033[31;1mASSERTION FAILED\033[0m: {}", message);
     else
         ERRORLN("ASSERTION FAILED: {}", message);
 
-#if defined(AK_HAS_BACKTRACE_HEADER)
-    dump_backtrace();
-#endif
-    __builtin_trap();
+    ak_trap();
 }
 }
diff --git a/AK/Assertions.h b/AK/Assertions.h
index 58583dfc8a1..fb349ad4d11 100644
--- a/AK/Assertions.h
+++ b/AK/Assertions.h
@@ -6,6 +6,9 @@
 
 #pragma once
 
+extern "C" bool ak_colorize_output(void);
+extern "C" __attribute__((noreturn)) void ak_trap(void);
+
 extern "C" __attribute__((noreturn)) void ak_verification_failed(char const*);
 #define __stringify_helper(x) #x
 #define __stringify(x) __stringify_helper(x)
diff --git a/AK/Format.h b/AK/Format.h
index b4df3bb0e69..0c0d4fe7783 100644
--- a/AK/Format.h
+++ b/AK/Format.h
@@ -775,6 +775,21 @@ struct Formatter<Optional<T>> : Formatter<FormatString> {
 
 } // namespace AK
 
+#undef AK_HANDLE_UNEXPECTED_ERROR
+#define AK_HANDLE_UNEXPECTED_ERROR(result)                                    \
+    if (result.is_error()) [[unlikely]] {                                     \
+        if (ak_colorize_output()) {                                           \
+            ::AK::warn("\033[31;1mUNEXPECTED ERROR\033[0m");                  \
+        } else {                                                              \
+            ::AK::warn("UNEXPECTED ERROR");                                   \
+        }                                                                     \
+        if constexpr (::AK::HasFormatter<decltype(result.release_error())>) { \
+            ::AK::warn(": {}", result.release_error());                       \
+        }                                                                     \
+        ::AK::warnln(" at {}:{}", __FILE__, __LINE__);                        \
+        ak_trap();                                                            \
+    }
+
 #if USING_AK_GLOBALLY
 using AK::out;
 using AK::outln;
diff --git a/AK/Try.h b/AK/Try.h
index 14edb5c0676..09813597457 100644
--- a/AK/Try.h
+++ b/AK/Try.h
@@ -9,6 +9,9 @@
 #include <AK/Diagnostics.h>
 #include <AK/StdLibExtras.h>
 
+// This macro is redefined in `AK/Format.h` to give a nicer error message.
+#define AK_HANDLE_UNEXPECTED_ERROR(result) VERIFY(!result.is_error());
+
 // NOTE: This macro works with any result type that has the expected APIs.
 //       It's designed with AK::Result and AK::Error in mind.
 //
@@ -40,6 +43,6 @@
             auto&& _temporary_result = (expression));                                                \
         static_assert(!::AK::Detail::IsLvalueReference<decltype(_temporary_result.release_value())>, \
             "Do not return a reference from a fallible expression");                                 \
-        VERIFY(!_temporary_result.is_error());                                                       \
+        AK_HANDLE_UNEXPECTED_ERROR(_temporary_result)                                                \
         _temporary_result.release_value();                                                           \
     })