swift-api-digester: add an action to dump USRs for all decls in a header.

We need this for custom migration like rdar://39992329.

tools/swift-api-digester/swift-api-digester.cpp

@@ -71,6 +71,7 @@ namespace  {
     DeserializeDiffItems,
     DeserializeSDK,
     GenerateNameCorrectionTemplate,
+    FindUsr,
   };
 } // end anonymous namespace
 
@@ -143,6 +144,9 @@ Action(llvm::cl::desc("Mode:"), llvm::cl::init(ActionType::None),
           clEnumValN(ActionType::DeserializeSDK,
                      "deserialize-sdk",
                      "Deserialize sdk digester in a JSON file"),
+          clEnumValN(ActionType::FindUsr,
+                     "find-usr",
+                     "Find USR for decls by given condition"),
           clEnumValN(ActionType::GenerateNameCorrectionTemplate,
                      "generate-name-correction",
                      "Generate name correction template")));
@@ -171,6 +175,10 @@ OutputInJson("json", llvm::cl::desc("Print output in JSON format."));
 static llvm::cl::opt<bool>
 AvoidLocation("avoid-location",
               llvm::cl::desc("Avoid serializing the file paths of SDK nodes."));
+
+static llvm::cl::opt<std::string>
+LocationFilter("location",
+              llvm::cl::desc("Filter nodes with the given location."));
 } // namespace options
 
 namespace {
@@ -4018,6 +4026,34 @@ static int deserializeSDKDump(StringRef dumpPath, StringRef OutputPath) {
   return 0;
 }
 
+static int findDeclUsr(StringRef dumpPath) {
+  std::error_code EC;
+  if (!fs::exists(dumpPath)) {
+    llvm::errs() << dumpPath << " does not exist\n";
+    return 1;
+  }
+  SDKContext Ctx;
+  SwiftDeclCollector Collector(Ctx);
+  Collector.deSerialize(dumpPath);
+  struct FinderByLocation: SDKNodeVisitor {
+    StringRef Location;
+    FinderByLocation(StringRef Location): Location(Location) {}
+    void visit(SDKNode* Node) override {
+      if (auto *D = dyn_cast<SDKNodeDecl>(Node)) {
+        if (D->getLocation().find(Location) != StringRef::npos &&
+            !D->getUsr().empty()) {
+          llvm::outs() << D->getFullyQualifiedName() << ": " << D->getUsr() << "\n";
+        }
+      }
+    }
+  };
+  if (!options::LocationFilter.empty()) {
+    FinderByLocation Finder(options::LocationFilter);
+    Collector.visitAllRoots(Finder);
+  }
+  return 0;
+}
+
 int main(int argc, char *argv[]) {
   PROGRAM_START(argc, argv);
   INITIALIZE_LLVM();
@@ -4072,6 +4108,13 @@ int main(int argc, char *argv[]) {
       Store.addStorePath(Paths[I]);
     return deserializeNameCorrection(Store, options::OutputFile);
   }
+  case ActionType::FindUsr: {
+    if (options::SDKJsonPaths.size() != 1) {
+      llvm::cl::PrintHelpMessage();
+      return 1;
+    }
+    return findDeclUsr(options::SDKJsonPaths[0]);
+  }
   case ActionType::None:
     llvm::errs() << "Action required\n";
     llvm::cl::PrintHelpMessage();