[SymbolGraph] Completely filter unavailable/obsoleted symbols

Symbol graph files are processed per platform--documentation for symbols that
are unconditionally unavailable or obsoleted on a platform shouldn't be shown
for that same platform.

Also, removes `isUnconditionallyUnavailable` from the JSON format. If it's
unconditionally unavailable, it won't show up at all.

rdar://60193675

Author: bitjammer

lib/SymbolGraphGen/FormatVersion.h

@@ -15,6 +15,6 @@
 
 #define SWIFT_SYMBOLGRAPH_FORMAT_MAJOR 0
 #define SWIFT_SYMBOLGRAPH_FORMAT_MINOR 4
-#define SWIFT_SYMBOLGRAPH_FORMAT_PATCH 0
+#define SWIFT_SYMBOLGRAPH_FORMAT_PATCH 1
 
 #endif // SWIFT_SYMBOLGRAPHGEN_FORMATVERSION_H

lib/SymbolGraphGen/Symbol.cpp

@@ -396,9 +396,6 @@ void Symbol::serializeAvailabilityMixin(llvm::json::OStream &OS) const {
         if (AvAttr->isUnconditionallyDeprecated()) {
           OS.attribute("isUnconditionallyDeprecated", true);
         }
-        if (AvAttr->isUnconditionallyUnavailable()) {
-          OS.attribute("isUnconditionallyUnavailable", true);
-        }
       }); // end availability object
     }
   }); // end availability: []

lib/SymbolGraphGen/SymbolGraphASTWalker.cpp

@@ -46,7 +46,26 @@ SymbolGraph *SymbolGraphASTWalker::getModuleSymbolGraph(ModuleDecl *M) {
   return SG;
 }
 
+namespace {
+bool isUnavailableOrObsoleted(const Decl *D) {
+  if (const auto *Avail =
+        D->getAttrs().getUnavailable(D->getASTContext())) {
+    switch (Avail->getVersionAvailability(D->getASTContext())) {
+      case AvailableVersionComparison::Unavailable:
+      case AvailableVersionComparison::Obsoleted:
+        return true;
+      default:
+        break;
+    }
+  }
+  return false;
+}
+} // end anonymous namespace
+
 bool SymbolGraphASTWalker::walkToDeclPre(Decl *D, CharSourceRange Range) {
+    if (isUnavailableOrObsoleted(D)) {
+      return false;
+    }
 
     switch (D->getKind()) {
     // We'll record nodes for the following kinds of declarations.
@@ -80,6 +99,10 @@ bool SymbolGraphASTWalker::walkToDeclPre(Decl *D, CharSourceRange Range) {
       return false;
     }
 
+    if (isUnavailableOrObsoleted(ExtendedNominal)) {
+      return false;
+    }
+
     // If there are some protocol conformances on this extension, we'll
     // grab them for some new conformsTo relationships.
     if (!Extension->getInherited().empty()) {

test/SymbolGraph/Symbols/Mixins/Availability/UnconditionallyUnavailable.swift

@@ -0,0 +1,37 @@
+// RUN: %empty-directory(%t)
+// RUN: %target-build-swift %s -module-name Unavailable -emit-module -emit-module-path %t/
+// RUN: %target-swift-symbolgraph-extract -module-name Unavailable -I %t -pretty-print -output-dir %t
+// RUN: %FileCheck %s --input-file %t/Unavailable.symbols.json
+
+// REQUIRES: OS=macosx
+
+public struct ShouldAppear {}
+
+// CHECK-NOT: OSXUnavailable
+@available(OSX, unavailable)
+public struct OSXUnavailable {}
+
+@available(OSX, unavailable)
+extension ShouldAppear {
+  public func shouldntAppear1() {}
+}
+
+// CHECK-NOT: OSXObsoleted
+@available(OSX, obsoleted: 10.9)
+public struct OSXObsoleted {}
+
+@available(OSX, obsoleted: 10.9)
+extension ShouldAppear {
+  public func shouldntAppear2() {}
+}
+
+// CHECK-NOT: SwiftObsoleted
+@available(swift, obsoleted: 1.0)
+public struct SwiftObsoleted {}
+
+@available(swift, obsoleted: 1.0)
+extension ShouldAppear {
+  public func shouldntAppear3() {}
+}
+
+// CHECK-NOT: shouldntAppear