Merge pull request swiftlang#22199 from harlanhaskins/type-extensionality

[api-digester] Don’t synthesize type nodes with no public members or conformances

Author: Harlan Haskins

test/api-digester/Outputs/stability-stdlib-abi.swift.expected

@@ -1,6 +1,7 @@
 Func _SmallString.computeIsASCII() has been removed
 Func _SmallString.withMutableCapacity(_:) has been removed
 Struct _StringObject.Discriminator has been removed
+Struct __swift_stdlib_UErrorCode has been removed
 Var _SmallString.discriminator has been removed
 Var _StringObject.CountAndFlags._storage has declared type change from UInt to UInt64
 Var _StringObject.CountAndFlags.countMask has declared type change from UInt to UInt64

test/api-digester/internal-extension.swift

@@ -0,0 +1,37 @@
+// RUN: %empty-directory(%t.mod)
+// RUN: %empty-directory(%t.sdk)
+// RUN: %empty-directory(%t.module-cache)
+// RUN: %swift -emit-module -o %t.mod/cake.swiftmodule %S/Inputs/cake.swift -parse-as-library -I %S/Inputs/ClangCake %clang-importer-sdk-nosource
+// RUN: %swift -emit-module -o %t.mod/main.swiftmodule %s -parse-as-library -I %t.mod -I %S/Inputs/ClangCake %clang-importer-sdk-nosource
+// RUN: %api-digester -dump-sdk -module main -o %t.dump.json -module-cache-path %t.module-cache -swift-only -I %t.mod -I %S/Inputs/ClangCake %clang-importer-sdk-nosource
+// RUN: %FileCheck %s < %t.dump.json
+
+import cake
+
+// CHECK: publicSymbol
+public func publicSymbol() {}
+
+internal protocol InternalProto {}
+public protocol PublicProto {}
+
+// This internal extension doesn't declare any new members on S1, so it
+// shouldn't show up at all in the output.
+// CHECK-NOT: S1
+internal extension S1 {
+  var x: Int { return 4 }
+}
+
+// There should only be one conformance declared: the conformance of C0 to
+// PublicProto. InternalProto should not show up in the list.
+// CHECK:      "name": "C0",
+// CHECK:      "conformances": [
+// CHECK-NEXT:   {
+// CHECK-NEXT:     "kind": "Conformance",
+// CHECK-NEXT:     "name": "PublicProto",
+// CHECK-NEXT:     "printedName": "PublicProto"
+// CHECK-NEXT:   }
+// CHECK-NEXT: ]
+extension C0: InternalProto {
+}
+extension C0: PublicProto {
+}

tools/swift-api-digester/ModuleAnalyzerNodes.cpp

@@ -1368,11 +1368,31 @@ SwiftDeclCollector::constructExternalExtensionNode(NominalTypeDecl *NTD,
                                             ArrayRef<ExtensionDecl*> AllExts) {
   auto *TypeNode = SDKNodeInitInfo(Ctx, NTD).createSDKNode(SDKNodeKind::DeclType);
   addConformancesToTypeDecl(cast<SDKNodeDeclType>(TypeNode), NTD);
+
+  bool anyConformancesAdded = false;
   // The members of the extensions are the only members of this synthesized type.
   for (auto *Ext: AllExts) {
     HandledExtensions.insert(Ext);
     addMembersToRoot(TypeNode, Ext);
+
+    // Keep track if we've declared any conformances in this extension.
+    // FIXME: This is too conservative. We only _really_ care if this extension
+    //        declares a conformance to any public protocols outside the module
+    //        where the extended type originated. Eventually this should be
+    //        updated to filter extensions that declare conformances to internal
+    //        protocols that either don't inherit from any protocols or only
+    //        inherit from other internal protocols. It should also consider
+    //        conditional conformances with internal requirements that are still
+    //        part of the ABI.
+    if (!Ext->getInherited().empty())
+      anyConformancesAdded = true;
   }
+
+  // If none of the extensions added any public members or conformances, don't
+  // synthesize the type node.
+  if (TypeNode->getChildrenCount() == 0 && !anyConformancesAdded)
+    return nullptr;
+
   return TypeNode;
 }
 
@@ -1532,7 +1552,8 @@ void SwiftDeclCollector::lookupVisibleDecls(ArrayRef<ModuleDecl *> Modules) {
     }
   }
   for (auto Pair: ExtensionMap) {
-    RootNode->addChild(constructExternalExtensionNode(Pair.first, Pair.second));
+    if (auto child = constructExternalExtensionNode(Pair.first, Pair.second))
+      RootNode->addChild(child);
   }
 }
 

tools/swift-api-digester/ModuleAnalyzerNodes.h

@@ -648,6 +648,8 @@ class SwiftDeclCollector: public VisibleDeclConsumer {
 
   void printTopLevelNames();
 
+  /// Adds all conformances from the provided NominalTypeDecl to the provided
+  /// SDK node for that type decl.
   void addConformancesToTypeDecl(SDKNodeDeclType *Root, NominalTypeDecl* NTD);
   void addMembersToRoot(SDKNode *Root, IterableDeclContext *Context);