include cross-import overlay information in the symbol graph itself

Author: QuietMisdreavus

lib/SymbolGraphGen/FormatVersion.h

@@ -15,6 +15,6 @@
 
 #define SWIFT_SYMBOLGRAPH_FORMAT_MAJOR 0
 #define SWIFT_SYMBOLGRAPH_FORMAT_MINOR 5
-#define SWIFT_SYMBOLGRAPH_FORMAT_PATCH 0
+#define SWIFT_SYMBOLGRAPH_FORMAT_PATCH 1
 
 #endif // SWIFT_SYMBOLGRAPHGEN_FORMATVERSION_H

lib/SymbolGraphGen/SymbolGraph.cpp

@@ -39,7 +39,15 @@ SymbolGraph::SymbolGraph(SymbolGraphASTWalker &Walker,
   M(M),
   ExtendedModule(ExtendedModule),
   Ctx(Ctx),
-  ModuleVersion(ModuleVersion) {}
+  ModuleVersion(ModuleVersion) {
+    if (auto *DM = M.getDeclaringModuleIfCrossImportOverlay()) {
+      DeclaringModule = DM;
+      SmallVector<Identifier, 1> Bystanders;
+      if (M.getRequiredBystandersIfCrossImportOverlay(DM, Bystanders)) {
+        BystanderModules = Bystanders;
+      }
+    }
+  }
 
 // MARK: - Utilities
 
@@ -499,7 +507,17 @@ void SymbolGraph::serialize(llvm::json::OStream &OS) {
     }); // end metadata:
 
     OS.attributeObject("module", [&](){
-      OS.attribute("name", M.getNameStr());
+      if (DeclaringModule) {
+        // A cross-import overlay can be considered part of its declaring module
+        OS.attribute("name", (*DeclaringModule)->getNameStr());
+        std::vector<StringRef> B;
+        for (auto BModule : BystanderModules) {
+          B.push_back(BModule.str());
+        }
+        OS.attribute("bystanders", B);
+      } else {
+        OS.attribute("name", M.getNameStr());
+      }
       AttributeRAII Platform("platform", OS);
 
       auto *MainFile = M.getFiles().front();

lib/SymbolGraphGen/SymbolGraph.h

@@ -42,6 +42,16 @@ struct SymbolGraph {
    The module whose types were extended in `M`.
    */
   Optional<ModuleDecl *> ExtendedModule;
+  
+  /**
+   The module declaring `M`, if `M` is a cross-import overlay.
+   */
+  Optional<ModuleDecl *> DeclaringModule;
+  
+  /**
+   The modules that must be imported alongside `DeclaringModule` for `M` to be imported, if `M` is a cross-import overlay.
+   */
+  SmallVector<Identifier, 1> BystanderModules;
 
   /**
    A context for allocations.

lib/SymbolGraphGen/SymbolGraphGen.cpp

@@ -22,10 +22,21 @@ using namespace symbolgraphgen;
 namespace {
 int serializeSymbolGraph(SymbolGraph &SG,
                          const SymbolGraphOptions &Options) {
-  SmallString<256> FileName(SG.M.getNameStr());
-  if (SG.ExtendedModule.hasValue()) {
-    FileName.push_back('@');
-    FileName.append(SG.ExtendedModule.getValue()->getNameStr());
+  SmallString<256> FileName;
+  if (SG.DeclaringModule.hasValue()) {
+    // Save a cross-import overlay symbol graph as `MainModule@BystandingModule[@BystandingModule...].symbols.json`
+    FileName.append(SG.DeclaringModule.getValue()->getNameStr());
+    for (auto BystanderModule : SG.BystanderModules) {
+      FileName.push_back('@');
+      FileName.append(BystanderModule.str());
+    }
+  } else {
+    FileName.append(SG.M.getNameStr());
+    
+    if (SG.ExtendedModule.hasValue()) {
+      FileName.push_back('@');
+      FileName.append(SG.ExtendedModule.getValue()->getNameStr());
+    }
   }
   FileName.append(".symbols.json");