1 files changed, 245 insertions, 0 deletions
diff --git a/core/realm.rs b/core/realm.rs
new file mode 100644
index 000000000..e3c7a5641
--- /dev/null
+++ b/core/realm.rs
@@ -0,0 +1,245 @@
+// Copyright 2018-2023 the Deno authors. All rights reserved. MIT license.
+
+use crate::bindings;
+use crate::modules::ModuleCode;
+use crate::ops::OpCtx;
+use crate::runtime::exception_to_err_result;
+use anyhow::Error;
+use std::cell::RefCell;
+use std::collections::HashMap;
+use std::collections::HashSet;
+use std::option::Option;
+use std::rc::Rc;
+use v8::HandleScope;
+use v8::Local;
+
+#[derive(Default)]
+pub(crate) struct ContextState {
+  pub(crate) js_recv_cb: Option<v8::Global<v8::Function>>,
+  pub(crate) js_build_custom_error_cb: Option<v8::Global<v8::Function>>,
+  pub(crate) js_promise_reject_cb: Option<v8::Global<v8::Function>>,
+  pub(crate) js_format_exception_cb: Option<v8::Global<v8::Function>>,
+  pub(crate) js_wasm_streaming_cb: Option<v8::Global<v8::Function>>,
+  pub(crate) pending_promise_rejections:
+    HashMap<v8::Global<v8::Promise>, v8::Global<v8::Value>>,
+  pub(crate) unrefed_ops: HashSet<i32>,
+  // We don't explicitly re-read this prop but need the slice to live alongside
+  // the context
+  pub(crate) op_ctxs: Box<[OpCtx]>,
+}
+
+/// A representation of a JavaScript realm tied to a [`JsRuntime`], that allows
+/// execution in the realm's context.
+///
+/// A [`JsRealm`] instance is a reference to an already existing realm, which
+/// does not hold ownership of it, so instances can be created and dropped as
+/// needed. As such, calling [`JsRealm::new`] doesn't create a new realm, and
+/// cloning a [`JsRealm`] only creates a new reference. See
+/// [`JsRuntime::create_realm`] to create new realms instead.
+///
+/// Despite [`JsRealm`] instances being references, multiple instances that
+/// point to the same realm won't overlap because every operation requires
+/// passing a mutable reference to the [`v8::Isolate`]. Therefore, no operation
+/// on two [`JsRealm`] instances tied to the same isolate can be run at the same
+/// time, regardless of whether they point to the same realm.
+///
+/// # Panics
+///
+/// Every method of [`JsRealm`] will panic if you call it with a reference to a
+/// [`v8::Isolate`] other than the one that corresponds to the current context.
+///
+/// In other words, the [`v8::Isolate`] parameter for all the related [`JsRealm`] methods
+/// must be extracted from the pre-existing [`JsRuntime`].
+///
+/// Example usage with the [`JsRealm::execute_script`] method:
+/// ```
+/// use deno_core::JsRuntime;
+/// use deno_core::RuntimeOptions;
+///
+/// let mut runtime = JsRuntime::new(RuntimeOptions::default());
+/// let new_realm = runtime
+///         .create_realm()
+///         .expect("Handle the error properly");
+/// let source_code = "var a = 0; a + 1";
+/// let result = new_realm
+///         .execute_script_static(runtime.v8_isolate(), "<anon>", source_code)
+///         .expect("Handle the error properly");
+/// # drop(result);
+/// ```
+///
+/// # Lifetime of the realm
+///
+/// As long as the corresponding isolate is alive, a [`JsRealm`] instance will
+/// keep the underlying V8 context alive even if it would have otherwise been
+/// garbage collected.
+#[derive(Clone)]
+pub struct JsRealm(v8::Global<v8::Context>);
+impl JsRealm {
+  pub fn new(context: v8::Global<v8::Context>) -> Self {
+    JsRealm(context)
+  }
+
+  pub fn context(&self) -> &v8::Global<v8::Context> {
+    &self.0
+  }
+
+  pub(crate) fn state(
+    &self,
+    isolate: &mut v8::Isolate,
+  ) -> Rc<RefCell<ContextState>> {
+    self
+      .context()
+      .open(isolate)
+      .get_slot::<Rc<RefCell<ContextState>>>(isolate)
+      .unwrap()
+      .clone()
+  }
+
+  pub(crate) fn state_from_scope(
+    scope: &mut v8::HandleScope,
+  ) -> Rc<RefCell<ContextState>> {
+    let context = scope.get_current_context();
+    context
+      .get_slot::<Rc<RefCell<ContextState>>>(scope)
+      .unwrap()
+      .clone()
+  }
+
+  /// For info on the [`v8::Isolate`] parameter, check [`JsRealm#panics`].
+  pub fn handle_scope<'s>(
+    &self,
+    isolate: &'s mut v8::Isolate,
+  ) -> v8::HandleScope<'s> {
+    v8::HandleScope::with_context(isolate, &self.0)
+  }
+
+  /// For info on the [`v8::Isolate`] parameter, check [`JsRealm#panics`].
+  pub fn global_object<'s>(
+    &self,
+    isolate: &'s mut v8::Isolate,
+  ) -> v8::Local<'s, v8::Object> {
+    let scope = &mut self.handle_scope(isolate);
+    self.0.open(scope).global(scope)
+  }
+
+  fn string_from_code<'a>(
+    scope: &mut HandleScope<'a>,
+    code: &ModuleCode,
+  ) -> Option<Local<'a, v8::String>> {
+    if let Some(code) = code.try_static_ascii() {
+      v8::String::new_external_onebyte_static(scope, code)
+    } else {
+      v8::String::new_from_utf8(
+        scope,
+        code.as_bytes(),
+        v8::NewStringType::Normal,
+      )
+    }
+  }
+
+  /// Executes traditional JavaScript code (traditional = not ES modules) in the
+  /// realm's context.
+  ///
+  /// For info on the [`v8::Isolate`] parameter, check [`JsRealm#panics`].
+  ///
+  /// The `name` parameter can be a filepath or any other string. E.g.:
+  ///
+  ///   - "/some/file/path.js"
+  ///   - "<anon>"
+  ///   - "[native code]"
+  ///
+  /// The same `name` value can be used for multiple executions.
+  ///
+  /// `Error` can usually be downcast to `JsError`.
+  pub fn execute_script_static(
+    &self,
+    isolate: &mut v8::Isolate,
+    name: &'static str,
+    source_code: &'static str,
+  ) -> Result<v8::Global<v8::Value>, Error> {
+    self.execute_script(isolate, name, ModuleCode::from_static(source_code))
+  }
+
+  /// Executes traditional JavaScript code (traditional = not ES modules) in the
+  /// realm's context.
+  ///
+  /// For info on the [`v8::Isolate`] parameter, check [`JsRealm#panics`].
+  ///
+  /// The `name` parameter can be a filepath or any other string. E.g.:
+  ///
+  ///   - "/some/file/path.js"
+  ///   - "<anon>"
+  ///   - "[native code]"
+  ///
+  /// The same `name` value can be used for multiple executions.
+  ///
+  /// `Error` can usually be downcast to `JsError`.
+  pub fn execute_script(
+    &self,
+    isolate: &mut v8::Isolate,
+    name: &'static str,
+    source_code: ModuleCode,
+  ) -> Result<v8::Global<v8::Value>, Error> {
+    let scope = &mut self.handle_scope(isolate);
+
+    let source = Self::string_from_code(scope, &source_code).unwrap();
+    debug_assert!(name.is_ascii());
+    let name =
+      v8::String::new_external_onebyte_static(scope, name.as_bytes()).unwrap();
+    let origin = bindings::script_origin(scope, name);
+
+    let tc_scope = &mut v8::TryCatch::new(scope);
+
+    let script = match v8::Script::compile(tc_scope, source, Some(&origin)) {
+      Some(script) => script,
+      None => {
+        let exception = tc_scope.exception().unwrap();
+        return exception_to_err_result(tc_scope, exception, false);
+      }
+    };
+
+    match script.run(tc_scope) {
+      Some(value) => {
+        let value_handle = v8::Global::new(tc_scope, value);
+        Ok(value_handle)
+      }
+      None => {
+        assert!(tc_scope.has_caught());
+        let exception = tc_scope.exception().unwrap();
+        exception_to_err_result(tc_scope, exception, false)
+      }
+    }
+  }
+
+  // TODO(andreubotella): `mod_evaluate`, `load_main_module`, `load_side_module`
+
+  pub(crate) fn check_promise_rejections(
+    &self,
+    isolate: &mut v8::Isolate,
+  ) -> Result<(), Error> {
+    let context_state_rc = self.state(isolate);
+    let mut context_state = context_state_rc.borrow_mut();
+
+    if context_state.pending_promise_rejections.is_empty() {
+      return Ok(());
+    }
+
+    let key = {
+      context_state
+        .pending_promise_rejections
+        .keys()
+        .next()
+        .unwrap()
+        .clone()
+    };
+    let handle = context_state
+      .pending_promise_rejections
+      .remove(&key)
+      .unwrap();
+    drop(context_state);
+
+    let scope = &mut self.handle_scope(isolate);
+    let exception = v8::Local::new(scope, handle);
+    exception_to_err_result(scope, exception, true)
+  }
+}