Bug 280912 – Can't build WebKit's clang module on watchOS/tvOS due to availability errors

• Component: Tools / Tests
• Status: NEW

[Elliott Williams]

As part of merging WebKit's Swift overlay into the main framework <https://bugs.webkit.org/show_bug.cgi?id=280734>, I've experimented with building the overlay APIs for all Apple platforms. Presently the overlay is only built for platforms where WebKit is a public framework.

When I try to build for watchOS/tvOS, I get errors emitting WebKit's underlying clang module, due to availability. For example:

    WebKit SwiftEmitModule normal arm64 Emitting\ module\ for\ WebKit 
    Source/WebKit/UIProcess/API/Cocoa/NSAttributedString.h:30:9: note: while building module 'UIKit' imported from Source/WebKit/UIProcess/API/Cocoa/NSAttributedString.h:30:
    #import <UIKit/NSAttributedString.h>                                 
    <module-includes>:1:9: note: in file included from <module-includes>:1:
    #import "Headers/UIKit.h"                               
    WebKitBuild/Release-appletvsimulator/SDKAdditions/System/Library/Frameworks/UIKit.framework/Headers/UIKit.h:20:9: note: in file included from WebKitBuild/Release-appletvsimulator/SDKAdditions/System/Library/Frameworks/UIKit.framewor
    k/Headers/UIKit.h:20:                                          
    #import <UIKit/ShareSheet.h>           
    WebKitBuild/Release-appletvsimulator/SDKAdditions/System/Library/Frameworks/UIKit.framework/Headers/ShareSheet.h:12:9: note: in file included from WebKitBuild/Release-appletvsimulator/SDKAdditions/System/Library/Frameworks/UIKit.fra
    mework/Headers/ShareSheet.h:12:                                 
    #import <UIKit/UIDocumentInteractionController.h>
    WebKitBuild/Release-appletvsimulator/SDKAdditions/System/Library/Frameworks/UIKit.framework/Headers/UIDocumentInteractionController.h:20:98: error: 'UIActionSheetDelegate' is unavailable: not available on tvOS
    API_AVAILABLE(ios(3.2)) __TVOS_PROHIBITED @interface UIDocumentInteractionController : NSObject <UIActionSheetDelegate>
    WebKitBuild/Release-appletvsimulator/SDKAdditions/System/Library/Frameworks/UIKit.framework/Headers/UIActionSheet.h:63:11: note: 'UIActionSheetDelegate' has been explicitly marked unavailable here
    @protocol UIActionSheetDelegate <NSObject>             
    <module-includes>:1:9: note: in file included from <module-includes>:1:
    #import "Headers/WebKit.h"                         
    WebKitBuild/Release-appletvsimulator/WebKit.framework/Headers/WebKit.h:26:9: note: in file included from WebKitBuild/Release-appletvsimulator/WebKit.framework/Headers/WebKit.h:26:
    #import <WebKit/NSAttributedString.h>                     
    Source/WebKit/UIProcess/API/Cocoa/NSAttributedString.h:30:9: error: could not build module 'UIKit'
    #import <UIKit/NSAttributedString.h>        
    <unknown>:0: error: could not build Objective-C module 'WebKit'

The problem is "__TVOS_PROHIBITED" indicates that UIDocumentInteractionController is SPI on tvOS. Normally, our <AvailabilityProhibitedInternal.h> header in the appropriate additions SDK in WebKitLibraries/SDKs would suppress this availability marker, but I think it's being ignored entirely because clang is looking at the `availability` modulemap in the SDK, not importing headers textually. Perhaps we need a new way to suppress availability info for building with modules.

In the meantime, I don't think this blocks merging the Swift overlay. It just means we cannot bring the overlay API to these two platforms.

[Radar WebKit Bug Importer]

<rdar://problem/137312444>