LibWasm+LibWeb: Sneak a JS::Completion into Wasm::Result

Imported functions in Wasm may throw JS exceptions, and we need to
preserve these exceptions so we can pass them to the calling JS code.

This also adds a `assert_wasm_result()` API to Result for cases where
only Wasm traps or values are expected (e.g. internal uses) to avoid
making LibWasm (pointlessly) handle JS exceptions that will never show
up in reality.

1 files changed, 10 insertions, 8 deletions

diff --git a/Userland/Utilities/wasm.cpp b/Userland/Utilities/wasm.cpp
index 00652bbd57..38c061095a 100644
--- a/Userland/Utilities/wasm.cpp
+++ b/Userland/Utilities/wasm.cpp
@@ -206,15 +206,17 @@ static bool pre_interpret_hook(Wasm::Configuration& config, Wasm::InstructionPoi
             Wasm::Result result { Wasm::Trap {} };
             {
                 Wasm::BytecodeInterpreter::CallFrameHandle handle { g_interpreter, config };
-                result = config.call(g_interpreter, *address, move(values));
+                result = config.call(g_interpreter, *address, move(values)).assert_wasm_result();
             }
-            if (result.is_trap())
+            if (result.is_trap()) {
                 warnln("Execution trapped: {}", result.trap().reason);
-            if (!result.values().is_empty())
-                warnln("Returned:");
-            for (auto& value : result.values()) {
-                g_stdout->write("  -> "sv.bytes()).release_value_but_fixme_should_propagate_errors();
-                g_printer->print(value);
+            } else {
+                if (!result.values().is_empty())
+                    warnln("Returned:");
+                for (auto& value : result.values()) {
+                    g_stdout->write("  -> "sv.bytes()).release_value_but_fixme_should_propagate_errors();
+                    g_printer->print(value);
+                }
             }
             continue;
         }
@@ -513,7 +515,7 @@ ErrorOr<int> serenity_main(Main::Arguments arguments)
                 outln();
             }
 
-            auto result = machine.invoke(g_interpreter, run_address.value(), move(values));
+            auto result = machine.invoke(g_interpreter, run_address.value(), move(values)).assert_wasm_result();
 
             if (debug)
                 launch_repl();