fix(inspector): Preserve floating point precision from inspector response (#1141)

Fixes denoland/deno#29059

Messages from the inspector that hold a number value can result in the
loss of floating point precision when deserialized.

When a user sends `0.9999999999999999` in the REPL, V8 returns a
[RemoteObject](https://chromedevtools.github.io/devtools-protocol/tot/Runtime/#type-RemoteObject)
that contains the field `"value": 0.9999999999999999`. However, when
it's deserialized into `serde_json::Value` here:


https://github.com/denoland/deno_core/blob/fc1ef37491950e82d2fb2e5e426a55723e730ce1/core/inspector.rs#L883-L884

`value` becomes `serde_json::Number(1.0)`, causing the REPL to print
`1`. Enabling the `float_roundtrip` feature flag of serde json resolves
this.

Author: Tango992

core/Cargo.toml

@@ -44,7 +44,7 @@ parking_lot.workspace = true
 percent-encoding.workspace = true
 pin-project.workspace = true
 serde.workspace = true
-serde_json = { workspace = true, features = ["preserve_order"] }
+serde_json = { workspace = true, features = ["float_roundtrip", "preserve_order"] }
 serde_v8.workspace = true
 smallvec.workspace = true
 sourcemap.workspace = true

core/runtime/tests/misc.rs

@@ -11,10 +11,13 @@ use cooked_waker::WakeRef;
 use deno_error::JsErrorBox;
 use parking_lot::Mutex;
 use rstest::rstest;
+use serde_json::Value;
+use serde_json::json;
 use std::borrow::Cow;
 use std::collections::HashMap;
 use std::collections::HashSet;
 use std::future::poll_fn;
+use std::pin::pin;
 use std::rc::Rc;
 use std::sync::Arc;
 use std::sync::atomic::AtomicBool;
@@ -437,6 +440,66 @@ fn inspector() {
   runtime.execute_script("check.js", "null").unwrap();
 }
 
+#[rstest]
+// https://github.com/denoland/deno/issues/29059
+#[case(0.9999999999999999)]
+#[case(31.245270191439438)]
+#[case(117.63331139400017)]
+#[tokio::test]
+async fn test_preserve_float_precision_from_local_inspector_evaluate(
+  #[case] input: f64,
+) {
+  let mut runtime = JsRuntime::new(RuntimeOptions {
+    inspector: true,
+    ..Default::default()
+  });
+
+  let result = local_inspector_evaluate(&mut runtime, &format!("{}", input))
+    .await
+    .unwrap();
+
+  assert_eq!(
+    result["result"]["value"],
+    Value::Number(serde_json::Number::from_f64(input).unwrap()),
+  );
+}
+
+async fn local_inspector_evaluate(
+  runtime: &mut JsRuntime,
+  expression: &str,
+) -> Result<Value, CoreError> {
+  let session_options = inspector::InspectorSessionOptions {
+    kind: inspector::InspectorSessionKind::NonBlocking {
+      wait_for_disconnect: true,
+    },
+  };
+
+  let mut local_inspector_session = runtime
+    .inspector()
+    .borrow()
+    .create_local_session(session_options);
+
+  let post_message_future = pin!(local_inspector_session.post_message(
+    "Runtime.evaluate",
+    Some(json!({
+      "expression": expression,
+    })),
+  ));
+
+  // https://chromedevtools.github.io/devtools-protocol/tot/Runtime/#type-RemoteObject
+  let remote_object_result = runtime
+    .with_event_loop_future(
+      post_message_future,
+      PollEventLoopOptions {
+        pump_v8_message_loop: false,
+        ..Default::default()
+      },
+    )
+    .await?;
+
+  Ok(remote_object_result)
+}
+
 #[test]
 fn test_get_module_namespace() {
   let mut runtime = JsRuntime::new(RuntimeOptions {