Changes in iOS 12.3 may break builds

[rajivshah3]

Description

(please don't kill me for not following the template 😄- this is more of a "heads up" than a bug report)

In iOS 12.3, it looks like Apple is introducing a new type called symbol to the JavaScriptCore API:
(from /Applications/Xcode-beta.app/Contents/Developer/Platforms/iPhoneSimulator.platform/Developer/SDKs/iPhoneSimulator.sdk/System/Library/Frameworks/JavaScriptCore.framework/Headers/JSValueRef.h)

/*!
@enum JSType
@abstract     A constant identifying the type of a JSValue.
@constant     kJSTypeUndefined  The unique undefined value.
@constant     kJSTypeNull       The unique null value.
@constant     kJSTypeBoolean    A primitive boolean value, one of true or false.
@constant     kJSTypeNumber     A primitive number value.
@constant     kJSTypeString     A primitive string value.
@constant     kJSTypeObject     An object value (meaning that this JSValueRef is a JSObjectRef).
@constant     kJSTypeSymbol     A primitive symbol value.
*/
typedef enum {
    kJSTypeUndefined,
    kJSTypeNull,
    kJSTypeBoolean,
    kJSTypeNumber,
    kJSTypeString,
    kJSTypeObject,
    kJSTypeSymbol API_AVAILABLE(macosx(10.14.4), ios(12.3))
} JSType;

This has certain consequences for Realm:

realm-js/src/jsc/jsc_value.hpp

Lines 44 to 54 in 91d87fe

	template<>
	inline const char *jsc::Value::typeof(JSContextRef ctx, const JSValueRef &value) {
	switch (JSValueGetType(ctx, value)) {
	case kJSTypeNull: return "null";
	case kJSTypeNumber: return "number";
	case kJSTypeObject: return "object";
	case kJSTypeString: return "string";
	case kJSTypeBoolean: return "boolean";
	case kJSTypeUndefined: return "undefined";
	}
	}

Since the kJSTypeSymbol enum value is not handled in the above switch statement, builds on Xcode 10.2 Beta (10P82s) will fail with this error:

I was able to resolve the error by adding this:

case kJSTypeSymbol: return "symbol";

I'm not sure what side effects that change has so I haven't made a PR yet.

Version of Realm and Tooling

• Realm JS SDK Version: 2.21.1
• Node or React Native: React Native
• Client OS & Version: Building for iOS 12.2 (so I'm not sure why this issue is occuring with API_AVAILABLE(macosx(10.14.4), ios(12.3)))
• Which debugger for React Native: None

[kneth]

@rajivshah3 Thanks for the update. We are in the process of updating and preparing our CI system with the latest Apple releases (still waiting for next Xcode version).

[yurnery]

it builds failure after i upgrade to XCode 10.2, should i fix it myself?

[reyalpsirc]

Indeed, the builds are failing with latest XCode 10.2 with the error of "control may reach end of non-void function"

[majirosstefan]

same here, Enumeration value 'kJSTypeSymbol' not handled in switch ==> "control may reach end of non-void function" leads to Realm build fail

Quick workaround is to use xcode 10.1 (build is passing in 10.1), can be downloaded here https://developer.apple.com/downloads/more/

[APSRaphael]

Got the same problem, it looks like surely upgrade XCode to 10.2 cause the error.

[rajivshah3]

@kneth it looks like Xcode 10.2 was released to the public today. Should I do a PR adding case kJSTypeSymbol: return "symbol"; or a default case as suggested in #2305 (comment)?

Edit: Looks like someone beat me to it 😄 #2303

[rajivshah3]

Fixed in #2303

[shivkrishnashah]

Fixed By Adding

case kJSTypeSymbol: return "symbol";

Example

switch (JSValueGetType(ctx, value)) {
    case kJSTypeNull: return "null";
    case kJSTypeNumber: return "number";
    case kJSTypeObject: return "object";
    case kJSTypeString: return "string";
    case kJSTypeBoolean: return "boolean";
    case kJSTypeUndefined: return "undefined";
    case kJSTypeSymbol: return "symbol";
}

[quangcanh2975]

Fixed By Adding

case kJSTypeSymbol: return "symbol";

Example

switch (JSValueGetType(ctx, value)) {
    case kJSTypeNull: return "null";
    case kJSTypeNumber: return "number";
    case kJSTypeObject: return "object";
    case kJSTypeString: return "string";
    case kJSTypeBoolean: return "boolean";
    case kJSTypeUndefined: return "undefined";
    case kJSTypeSymbol: return "symbol";
}

@shivkrishnashah Thank you so much! It worked for me