From 32f80efe7e00a3a05d318f86ec9a06a94094c465 Mon Sep 17 00:00:00 2001
From: Benedikt Meurer <bmeurer@chromium.org>
Date: Wed, 12 May 2021 09:42:16 +0200
Subject: [PATCH] [inspector] Improve RemoteObject description for Wasm
 functions.

The WebAssembly specification requires the "name" property of (exported)
function wrappers to hold the index of the function within the module,
and the default ToString algorithm for Function instances thus generates
something along the lines of `function 42() { [native code] }`, which is
technically correct, but not very useful to developers to diagnose
(humans don't think of functions in a module in terms of their indices).
With this CL, we change the description returned for Wasm (exported)
functions to use the debug name of the Wasm function instead.

Screenshot: https://imgur.com/a/FVPeXDU.png
Doc: http://bit.ly/devtools-wasm-entities
Fixed: chromium:1206620
Bug: chromium:1164241
Change-Id: I096abc287ea077556c13c71f8d71f64452ab4831
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2891570
Commit-Queue: Benedikt Meurer <bmeurer@chromium.org>
Auto-Submit: Benedikt Meurer <bmeurer@chromium.org>
Reviewed-by: Kim-Anh Tran <kimanh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#74517}
---
 src/debug/debug-interface.cc                  | 25 +++++++++++++++++--
 .../wasm-evaluate-on-call-frame-expected.txt  | 24 +++++++++---------
 .../debugger/wasm-gc-breakpoints-expected.txt |  2 +-
 3 files changed, 36 insertions(+), 15 deletions(-)

diff --git a/src/debug/debug-interface.cc b/src/debug/debug-interface.cc
index 890ffb7b5b..0d56002e6e 100644
--- a/src/debug/debug-interface.cc
+++ b/src/debug/debug-interface.cc
@@ -14,6 +14,7 @@
 #include "src/objects/js-generator-inl.h"
 #include "src/objects/stack-frame-info-inl.h"
 #include "src/regexp/regexp-stack.h"
+#include "src/strings/string-builder-inl.h"
 
 #if V8_ENABLE_WEBASSEMBLY
 #include "src/debug/debug-wasm-objects-inl.h"
@@ -65,8 +66,28 @@ Local<String> GetFunctionDescription(Local<Function> function) {
         i::Handle<i::JSBoundFunction>::cast(receiver)));
   }
   if (receiver->IsJSFunction()) {
-    return Utils::ToLocal(
-        i::JSFunction::ToString(i::Handle<i::JSFunction>::cast(receiver)));
+    auto function = i::Handle<i::JSFunction>::cast(receiver);
+#if V8_ENABLE_WEBASSEMBLY
+    if (function->shared().HasWasmExportedFunctionData()) {
+      auto isolate = function->GetIsolate();
+      auto func_index =
+          function->shared().wasm_exported_function_data().function_index();
+      auto instance = i::handle(
+          function->shared().wasm_exported_function_data().instance(), isolate);
+      if (instance->module()->origin == i::wasm::kWasmOrigin) {
+        // For asm.js functions, we can still print the source
+        // code (hopefully), so don't bother with them here.
+        auto debug_name =
+            i::GetWasmFunctionDebugName(isolate, instance, func_index);
+        i::IncrementalStringBuilder builder(isolate);
+        builder.AppendCString("function ");
+        builder.AppendString(debug_name);
+        builder.AppendCString("() { [native code] }");
+        return Utils::ToLocal(builder.Finish().ToHandleChecked());
+      }
+    }
+#endif  // V8_ENABLE_WEBASSEMBLY
+    return Utils::ToLocal(i::JSFunction::ToString(function));
   }
   return Utils::ToLocal(
       receiver->GetIsolate()->factory()->function_native_code_string());
diff --git a/test/inspector/debugger/wasm-evaluate-on-call-frame-expected.txt b/test/inspector/debugger/wasm-evaluate-on-call-frame-expected.txt
index 11f9f20abc..2605342e0c 100644
--- a/test/inspector/debugger/wasm-evaluate-on-call-frame-expected.txt
+++ b/test/inspector/debugger/wasm-evaluate-on-call-frame-expected.txt
@@ -55,18 +55,18 @@ Debugger paused in $main.
 > functions = Functions
 > typeof functions = "object"
 > Object.keys(functions) = Array(4)
-> functions[0] = function 0() { [native code] }
-> functions[1] = function 1() { [native code] }
-> functions[2] = function 2() { [native code] }
-> functions[3] = function 3() { [native code] }
-> functions[4] = function 4() { [native code] }
-> functions["$foo.bar"] = function 0() { [native code] }
-> functions["$main"] = function 1() { [native code] }
-> $main = function 1() { [native code] }
-> functions["$func2"] = function 2() { [native code] }
-> $func2 = function 2() { [native code] }
-> functions["$func4"] = function 4() { [native code] }
-> $func4 = function 4() { [native code] }
+> functions[0] = function $foo.bar() { [native code] }
+> functions[1] = function $main() { [native code] }
+> functions[2] = function $func2() { [native code] }
+> functions[3] = function $func2() { [native code] }
+> functions[4] = function $func4() { [native code] }
+> functions["$foo.bar"] = function $foo.bar() { [native code] }
+> functions["$main"] = function $main() { [native code] }
+> $main = function $main() { [native code] }
+> functions["$func2"] = function $func2() { [native code] }
+> $func2 = function $func2() { [native code] }
+> functions["$func4"] = function $func4() { [native code] }
+> $func4 = function $func4() { [native code] }
 
 Running test: testLocals
 Compile module.
diff --git a/test/inspector/debugger/wasm-gc-breakpoints-expected.txt b/test/inspector/debugger/wasm-gc-breakpoints-expected.txt
index 68d938ed39..68f2801b6e 100644
--- a/test/inspector/debugger/wasm-gc-breakpoints-expected.txt
+++ b/test/inspector/debugger/wasm-gc-breakpoints-expected.txt
@@ -25,7 +25,7 @@ at $main (0:107):
    instance: exports: "main" (Function)
    module: Module
    functions: "$main": (Function)
-   globals: "$global0": function 0() { [native code] } ((ref null $type3))
+   globals: "$global0": function $main() { [native code] } ((ref null $type3))
 at (anonymous) (0:17):
    -- skipped
 exports.main returned!