Clarify const-ness of JSI references

Summary:
Many operations on references in JS can modify the referent by
executing additional JS, including operations that we currently mark as
const such as `getProperty`. Because of this, the current distinction
between const and non-const operations on references like `jsi::Object`
is somewhat arbitrary.

A more consistent approach is to mark all operations as const, so that
it is clear that the const-ness applies to the reference and not the
referent. This is analogous to how smart pointers work, since something
like `const shared_ptr<T>` only makes the pointer const, as opposed to
`shared_ptr<const T>`.

This also gives users better guarantees and more flexibility in where
these references may be used.

Changelog:
[General][Changed] - Mark methods on JSI references as const.

Reviewed By: fbmal7

Differential Revision: D41599116

fbshipit-source-id: 40b1537581b09c5a34d0928ee04e7db2b50d26ea

API/hermes/TracingRuntime.cpp

@@ -402,7 +402,7 @@ bool TracingRuntime::hasProperty(
 }
 
 void TracingRuntime::setPropertyValue(
-    jsi::Object &obj,
+    const jsi::Object &obj,
     const jsi::String &name,
     const jsi::Value &value) {
   trace_.emplace_back<SynthTrace::SetPropertyRecord>(
@@ -417,7 +417,7 @@ void TracingRuntime::setPropertyValue(
 }
 
 void TracingRuntime::setPropertyValue(
-    jsi::Object &obj,
+    const jsi::Object &obj,
     const jsi::PropNameID &name,
     const jsi::Value &value) {
   trace_.emplace_back<SynthTrace::SetPropertyRecord>(
@@ -462,7 +462,7 @@ jsi::WeakObject TracingRuntime::createWeakObject(const jsi::Object &o) {
   return RD::createWeakObject(o);
 }
 
-jsi::Value TracingRuntime::lockWeakObject(jsi::WeakObject &wo) {
+jsi::Value TracingRuntime::lockWeakObject(const jsi::WeakObject &wo) {
   // See comment in TracingRuntime::createWeakObject for why this function isn't
   // traced.
   return RD::lockWeakObject(wo);
@@ -505,7 +505,7 @@ jsi::Value TracingRuntime::getValueAtIndex(const jsi::Array &arr, size_t i) {
 }
 
 void TracingRuntime::setValueAtIndexImpl(
-    jsi::Array &arr,
+    const jsi::Array &arr,
     size_t i,
     const jsi::Value &value) {
   trace_.emplace_back<SynthTrace::ArrayWriteRecord>(

API/hermes/TracingRuntime.h

@@ -75,19 +75,19 @@ class TracingRuntime : public jsi::RuntimeDecorator<jsi::Runtime> {
       override;
 
   void setPropertyValue(
-      jsi::Object &obj,
+      const jsi::Object &obj,
       const jsi::String &name,
       const jsi::Value &value) override;
   void setPropertyValue(
-      jsi::Object &obj,
+      const jsi::Object &obj,
       const jsi::PropNameID &name,
       const jsi::Value &value) override;
 
   jsi::Array getPropertyNames(const jsi::Object &o) override;
 
   jsi::WeakObject createWeakObject(const jsi::Object &o) override;
 
-  jsi::Value lockWeakObject(jsi::WeakObject &wo) override;
+  jsi::Value lockWeakObject(const jsi::WeakObject &wo) override;
 
   jsi::Array createArray(size_t length) override;
   jsi::ArrayBuffer createArrayBuffer(
@@ -100,8 +100,10 @@ class TracingRuntime : public jsi::RuntimeDecorator<jsi::Runtime> {
 
   jsi::Value getValueAtIndex(const jsi::Array &arr, size_t i) override;
 
-  void setValueAtIndexImpl(jsi::Array &arr, size_t i, const jsi::Value &value)
-      override;
+  void setValueAtIndexImpl(
+      const jsi::Array &arr,
+      size_t i,
+      const jsi::Value &value) override;
 
   jsi::Function createFunctionFromHostFunction(
       const jsi::PropNameID &name,

API/hermes/hermes.cpp

@@ -506,11 +506,12 @@ class HermesRuntimeImpl final : public HermesRuntime,
     return ::hermes::vm::Handle<::hermes::vm::JSArrayBuffer>::vmcast(&phv(arr));
   }
 
-  static ::hermes::vm::WeakRoot<vm::JSObject> &weakRoot(jsi::Pointer &pointer) {
+  static const ::hermes::vm::WeakRoot<vm::JSObject> &weakRoot(
+      const jsi::Pointer &pointer) {
     assert(
-        dynamic_cast<WeakRefPointerValue *>(getPointerValue(pointer)) &&
+        dynamic_cast<const WeakRefPointerValue *>(getPointerValue(pointer)) &&
         "Pointer does not contain a WeakRefPointerValue");
-    return static_cast<WeakRefPointerValue *>(getPointerValue(pointer))
+    return static_cast<const WeakRefPointerValue *>(getPointerValue(pointer))
         ->value();
   }
 
@@ -645,11 +646,11 @@ class HermesRuntimeImpl final : public HermesRuntime,
   bool hasProperty(const jsi::Object &, const jsi::PropNameID &name) override;
   bool hasProperty(const jsi::Object &, const jsi::String &name) override;
   void setPropertyValue(
-      jsi::Object &,
+      const jsi::Object &,
       const jsi::PropNameID &name,
       const jsi::Value &value) override;
   void setPropertyValue(
-      jsi::Object &,
+      const jsi::Object &,
       const jsi::String &name,
       const jsi::Value &value) override;
   bool isArray(const jsi::Object &) const override;
@@ -660,7 +661,7 @@ class HermesRuntimeImpl final : public HermesRuntime,
   jsi::Array getPropertyNames(const jsi::Object &) override;
 
   jsi::WeakObject createWeakObject(const jsi::Object &) override;
-  jsi::Value lockWeakObject(jsi::WeakObject &) override;
+  jsi::Value lockWeakObject(const jsi::WeakObject &) override;
 
   jsi::Array createArray(size_t length) override;
   jsi::ArrayBuffer createArrayBuffer(
@@ -669,8 +670,10 @@ class HermesRuntimeImpl final : public HermesRuntime,
   size_t size(const jsi::ArrayBuffer &) override;
   uint8_t *data(const jsi::ArrayBuffer &) override;
   jsi::Value getValueAtIndex(const jsi::Array &, size_t i) override;
-  void setValueAtIndexImpl(jsi::Array &, size_t i, const jsi::Value &value)
-      override;
+  void setValueAtIndexImpl(
+      const jsi::Array &,
+      size_t i,
+      const jsi::Value &value) override;
 
   jsi::Function createFunctionFromHostFunction(
       const jsi::PropNameID &name,
@@ -1916,7 +1919,7 @@ bool HermesRuntimeImpl::hasProperty(
 }
 
 void HermesRuntimeImpl::setPropertyValue(
-    jsi::Object &obj,
+    const jsi::Object &obj,
     const jsi::String &name,
     const jsi::Value &value) {
   vm::GCScope gcScope(runtime_);
@@ -1931,7 +1934,7 @@ void HermesRuntimeImpl::setPropertyValue(
 }
 
 void HermesRuntimeImpl::setPropertyValue(
-    jsi::Object &obj,
+    const jsi::Object &obj,
     const jsi::PropNameID &name,
     const jsi::Value &value) {
   vm::GCScope gcScope(runtime_);
@@ -2000,8 +2003,8 @@ jsi::WeakObject HermesRuntimeImpl::createWeakObject(const jsi::Object &obj) {
       static_cast<vm::JSObject *>(phv(obj).getObject()), runtime_));
 }
 
-jsi::Value HermesRuntimeImpl::lockWeakObject(jsi::WeakObject &wo) {
-  vm::WeakRoot<vm::JSObject> &wr = weakRoot(wo);
+jsi::Value HermesRuntimeImpl::lockWeakObject(const jsi::WeakObject &wo) {
+  const vm::WeakRoot<vm::JSObject> &wr = weakRoot(wo);
 
   if (const auto ptr = wr.get(runtime_, runtime_.getHeap()))
     return add<jsi::Object>(vm::HermesValue::encodeObjectValue(ptr));
@@ -2070,7 +2073,7 @@ jsi::Value HermesRuntimeImpl::getValueAtIndex(const jsi::Array &arr, size_t i) {
 }
 
 void HermesRuntimeImpl::setValueAtIndexImpl(
-    jsi::Array &arr,
+    const jsi::Array &arr,
     size_t i,
     const jsi::Value &value) {
   vm::GCScope gcScope(runtime_);

API/jsi/jsi/decorator.h

@@ -264,11 +264,13 @@ class RuntimeDecorator : public Base, private jsi::Instrumentation {
   bool hasProperty(const Object& o, const String& name) override {
     return plain_.hasProperty(o, name);
   };
-  void setPropertyValue(Object& o, const PropNameID& name, const Value& value)
-      override {
+  void setPropertyValue(
+      const Object& o,
+      const PropNameID& name,
+      const Value& value) override {
     plain_.setPropertyValue(o, name, value);
   };
-  void setPropertyValue(Object& o, const String& name, const Value& value)
+  void setPropertyValue(const Object& o, const String& name, const Value& value)
       override {
     plain_.setPropertyValue(o, name, value);
   };
@@ -295,7 +297,7 @@ class RuntimeDecorator : public Base, private jsi::Instrumentation {
   WeakObject createWeakObject(const Object& o) override {
     return plain_.createWeakObject(o);
   };
-  Value lockWeakObject(WeakObject& wo) override {
+  Value lockWeakObject(const WeakObject& wo) override {
     return plain_.lockWeakObject(wo);
   };
 
@@ -318,7 +320,8 @@ class RuntimeDecorator : public Base, private jsi::Instrumentation {
   Value getValueAtIndex(const Array& a, size_t i) override {
     return plain_.getValueAtIndex(a, i);
   };
-  void setValueAtIndexImpl(Array& a, size_t i, const Value& value) override {
+  void setValueAtIndexImpl(const Array& a, size_t i, const Value& value)
+      override {
     plain_.setValueAtIndexImpl(a, i, value);
   };
 
@@ -656,12 +659,14 @@ class WithRuntimeDecorator : public RuntimeDecorator<Plain, Base> {
     Around around{with_};
     return RD::hasProperty(o, name);
   };
-  void setPropertyValue(Object& o, const PropNameID& name, const Value& value)
-      override {
+  void setPropertyValue(
+      const Object& o,
+      const PropNameID& name,
+      const Value& value) override {
     Around around{with_};
     RD::setPropertyValue(o, name, value);
   };
-  void setPropertyValue(Object& o, const String& name, const Value& value)
+  void setPropertyValue(const Object& o, const String& name, const Value& value)
       override {
     Around around{with_};
     RD::setPropertyValue(o, name, value);
@@ -696,7 +701,7 @@ class WithRuntimeDecorator : public RuntimeDecorator<Plain, Base> {
     Around around{with_};
     return RD::createWeakObject(o);
   };
-  Value lockWeakObject(WeakObject& wo) override {
+  Value lockWeakObject(const WeakObject& wo) override {
     Around around{with_};
     return RD::lockWeakObject(wo);
   };
@@ -725,7 +730,8 @@ class WithRuntimeDecorator : public RuntimeDecorator<Plain, Base> {
     Around around{with_};
     return RD::getValueAtIndex(a, i);
   };
-  void setValueAtIndexImpl(Array& a, size_t i, const Value& value) override {
+  void setValueAtIndexImpl(const Array& a, size_t i, const Value& value)
+      override {
     Around around{with_};
     RD::setValueAtIndexImpl(a, i, value);
   };

API/jsi/jsi/jsi-inl.h

@@ -111,19 +111,21 @@ inline bool Object::hasProperty(Runtime& runtime, const PropNameID& name)
 }
 
 template <typename T>
-void Object::setProperty(Runtime& runtime, const char* name, T&& value) {
+void Object::setProperty(Runtime& runtime, const char* name, T&& value) const {
   setProperty(
       runtime, String::createFromAscii(runtime, name), std::forward<T>(value));
 }
 
 template <typename T>
-void Object::setProperty(Runtime& runtime, const String& name, T&& value) {
+void Object::setProperty(Runtime& runtime, const String& name, T&& value)
+    const {
   setPropertyValue(
       runtime, name, detail::toValue(runtime, std::forward<T>(value)));
 }
 
 template <typename T>
-void Object::setProperty(Runtime& runtime, const PropNameID& name, T&& value) {
+void Object::setProperty(Runtime& runtime, const PropNameID& name, T&& value)
+    const {
   setPropertyValue(
       runtime, name, detail::toValue(runtime, std::forward<T>(value)));
 }
@@ -229,12 +231,12 @@ inline Array Object::getPropertyNames(Runtime& runtime) const {
   return runtime.getPropertyNames(*this);
 }
 
-inline Value WeakObject::lock(Runtime& runtime) {
+inline Value WeakObject::lock(Runtime& runtime) const {
   return runtime.lockWeakObject(*this);
 }
 
 template <typename T>
-void Array::setValueAtIndex(Runtime& runtime, size_t i, T&& value) {
+void Array::setValueAtIndex(Runtime& runtime, size_t i, T&& value) const {
   setValueAtIndexImpl(
       runtime, i, detail::toValue(runtime, std::forward<T>(value)));
 }

API/jsi/jsi/jsi.h

@@ -336,10 +336,12 @@ class JSI_EXPORT Runtime {
   virtual Value getProperty(const Object&, const String& name) = 0;
   virtual bool hasProperty(const Object&, const PropNameID& name) = 0;
   virtual bool hasProperty(const Object&, const String& name) = 0;
+  virtual void setPropertyValue(
+      const Object&,
+      const PropNameID& name,
+      const Value& value) = 0;
   virtual void
-  setPropertyValue(Object&, const PropNameID& name, const Value& value) = 0;
-  virtual void
-  setPropertyValue(Object&, const String& name, const Value& value) = 0;
+  setPropertyValue(const Object&, const String& name, const Value& value) = 0;
 
   virtual bool isArray(const Object&) const = 0;
   virtual bool isArrayBuffer(const Object&) const = 0;
@@ -349,7 +351,7 @@ class JSI_EXPORT Runtime {
   virtual Array getPropertyNames(const Object&) = 0;
 
   virtual WeakObject createWeakObject(const Object&) = 0;
-  virtual Value lockWeakObject(WeakObject&) = 0;
+  virtual Value lockWeakObject(const WeakObject&) = 0;
 
   virtual Array createArray(size_t length) = 0;
   virtual ArrayBuffer createArrayBuffer(
@@ -358,7 +360,8 @@ class JSI_EXPORT Runtime {
   virtual size_t size(const ArrayBuffer&) = 0;
   virtual uint8_t* data(const ArrayBuffer&) = 0;
   virtual Value getValueAtIndex(const Array&, size_t i) = 0;
-  virtual void setValueAtIndexImpl(Array&, size_t i, const Value& value) = 0;
+  virtual void
+  setValueAtIndexImpl(const Array&, size_t i, const Value& value) = 0;
 
   virtual Function createFunctionFromHostFunction(
       const PropNameID& name,
@@ -666,7 +669,7 @@ class JSI_EXPORT Object : public Pointer {
   }
 
   /// \return the result of `this instanceOf ctor` in JS.
-  bool instanceOf(Runtime& rt, const Function& ctor) {
+  bool instanceOf(Runtime& rt, const Function& ctor) const {
     return rt.instanceOf(*this, ctor);
   }
 
@@ -701,19 +704,19 @@ class JSI_EXPORT Object : public Pointer {
   /// used to make one: nullptr_t, bool, double, int, const char*,
   /// String, or Object.
   template <typename T>
-  void setProperty(Runtime& runtime, const char* name, T&& value);
+  void setProperty(Runtime& runtime, const char* name, T&& value) const;
 
   /// Sets the property value from a Value or anything which can be
   /// used to make one: nullptr_t, bool, double, int, const char*,
   /// String, or Object.
   template <typename T>
-  void setProperty(Runtime& runtime, const String& name, T&& value);
+  void setProperty(Runtime& runtime, const String& name, T&& value) const;
 
   /// Sets the property value from a Value or anything which can be
   /// used to make one: nullptr_t, bool, double, int, const char*,
   /// String, or Object.
   template <typename T>
-  void setProperty(Runtime& runtime, const PropNameID& name, T&& value);
+  void setProperty(Runtime& runtime, const PropNameID& name, T&& value) const;
 
   /// \return true iff JS \c Array.isArray() would return \c true.  If
   /// so, then \c getArray() will succeed.
@@ -832,15 +835,17 @@ class JSI_EXPORT Object : public Pointer {
   Array getPropertyNames(Runtime& runtime) const;
 
  protected:
-  void
-  setPropertyValue(Runtime& runtime, const String& name, const Value& value) {
+  void setPropertyValue(
+      Runtime& runtime,
+      const String& name,
+      const Value& value) const {
     return runtime.setPropertyValue(*this, name, value);
   }
 
   void setPropertyValue(
       Runtime& runtime,
       const PropNameID& name,
-      const Value& value) {
+      const Value& value) const {
     return runtime.setPropertyValue(*this, name, value);
   }
 
@@ -866,7 +871,7 @@ class JSI_EXPORT WeakObject : public Pointer {
   /// otherwise returns \c undefined.  Note that this method has nothing to do
   /// with threads or concurrency.  The name is based on std::weak_ptr::lock()
   /// which serves a similar purpose.
-  Value lock(Runtime& runtime);
+  Value lock(Runtime& runtime) const;
 
   friend class Runtime;
 };
@@ -902,7 +907,7 @@ class JSI_EXPORT Array : public Object {
   /// value behaves as with Object::setProperty().  If \c i is out of
   /// range [ 0..\c length ] throws a JSIException.
   template <typename T>
-  void setValueAtIndex(Runtime& runtime, size_t i, T&& value);
+  void setValueAtIndex(Runtime& runtime, size_t i, T&& value) const;
 
   /// There is no current API for changing the size of an array once
   /// created.  We'll probably need that eventually.
@@ -920,7 +925,8 @@ class JSI_EXPORT Array : public Object {
   friend class Object;
   friend class Value;
 
-  void setValueAtIndexImpl(Runtime& runtime, size_t i, const Value& value) {
+  void setValueAtIndexImpl(Runtime& runtime, size_t i, const Value& value)
+      const {
     return runtime.setValueAtIndexImpl(*this, i, value);
   }
 
@@ -946,7 +952,7 @@ class JSI_EXPORT ArrayBuffer : public Object {
     return runtime.size(*this);
   }
 
-  uint8_t* data(Runtime& runtime) {
+  uint8_t* data(Runtime& runtime) const {
     return runtime.data(*this);
   }