migrator: emit error messages when migration scripts are missing.

include/swift/AST/DiagnosticsDriver.def

@@ -161,6 +161,9 @@ WARNING(warn_emit_public_type_metadata_accessors_deprecated, none,
 
 REMARK(remark_using_batch_mode,none, "using batch mode", ())
 
+ERROR(cannot_find_migration_script, none,
+      "missing migration script from path '%0'", (StringRef))
+
 #ifndef DIAG_NO_UNDEF
 # if defined(DIAG)
 #  undef DIAG

include/swift/IDE/APIDigesterData.h

@@ -22,6 +22,8 @@
 #include "llvm/Support/raw_ostream.h"
 
 namespace swift {
+class DiagnosticEngine;
+
 namespace ide {
 namespace api {
 
@@ -370,7 +372,7 @@ struct APIDiffItemStore {
   static void serialize(llvm::raw_ostream &os, ArrayRef<APIDiffItem*> Items);
   static void serialize(llvm::raw_ostream &os, ArrayRef<NameCorrectionInfo> Items);
   APIDiffItemStore(const APIDiffItemStore& that) = delete;
-  APIDiffItemStore();
+  APIDiffItemStore(DiagnosticEngine &Diags);
   ~APIDiffItemStore();
   ArrayRef<APIDiffItem*> getDiffItems(StringRef Key) const;
   ArrayRef<APIDiffItem*> getAllDiffItems() const;

include/swift/Migrator/ASTMigratorPass.h

@@ -24,6 +24,7 @@
 namespace swift {
 class SourceManager;
 struct MigratorOptions;
+class DiagnosticEngine;
 
 namespace migrator {
 class ASTMigratorPass {
@@ -34,12 +35,13 @@ class ASTMigratorPass {
   const StringRef Filename;
   const unsigned BufferID;
   SourceManager &SM;
+  DiagnosticEngine &Diags;
 
   ASTMigratorPass(EditorAdapter &Editor, SourceFile *SF,
                   const MigratorOptions &Opts)
     : Editor(Editor), SF(SF), Opts(Opts), Filename(SF->getFilename()),
       BufferID(SF->getBufferID().getValue()),
-      SM(SF->getASTContext().SourceMgr) {}
+      SM(SF->getASTContext().SourceMgr), Diags(SF->getASTContext().Diags) {}
 };
 
 /// Run a general pass to migrate code based on SDK differences in the previous

lib/IDE/APIDigesterData.cpp

@@ -16,6 +16,8 @@
 #include "llvm/Support/MemoryBuffer.h"
 #include "swift/Basic/JSONSerialization.h"
 #include "swift/IDE/APIDigesterData.h"
+#include "swift/AST/DiagnosticEngine.h"
+#include "swift/AST/DiagnosticsDriver.h"
 
 using namespace swift;
 using namespace ide;
@@ -481,6 +483,7 @@ serialize(llvm::raw_ostream &os, ArrayRef<NameCorrectionInfo> Items) {
 
 struct swift::ide::api::APIDiffItemStore::Implementation {
 private:
+  DiagnosticEngine &Diags;
   llvm::SmallVector<std::unique_ptr<llvm::MemoryBuffer>, 2> AllBuffer;
   llvm::BumpPtrAllocator Allocator;
 
@@ -500,6 +503,7 @@ struct swift::ide::api::APIDiffItemStore::Implementation {
   }
 
 public:
+  Implementation(DiagnosticEngine &Diags): Diags(Diags) {}
   llvm::StringMap<std::vector<APIDiffItem*>> Data;
   bool PrintUsr;
   std::vector<APIDiffItem*> AllItems;
@@ -509,7 +513,9 @@ struct swift::ide::api::APIDiffItemStore::Implementation {
     {
       auto FileBufOrErr = llvm::MemoryBuffer::getFileOrSTDIN(FileName);
       if (!FileBufOrErr) {
-        llvm_unreachable("Failed to read JSON file");
+        Diags.diagnose(SourceLoc(), diag::cannot_find_migration_script,
+          FileName);
+        return;
       }
       pMemBuffer = FileBufOrErr->get();
       AllBuffer.push_back(std::move(FileBufOrErr.get()));
@@ -546,8 +552,8 @@ getDiffItems(StringRef Key) const {
 ArrayRef<APIDiffItem*> swift::ide::api::APIDiffItemStore::
 getAllDiffItems() const { return Impl.AllItems; }
 
-swift::ide::api::APIDiffItemStore::APIDiffItemStore() :
-  Impl(*new Implementation()) {}
+swift::ide::api::APIDiffItemStore::APIDiffItemStore(DiagnosticEngine &Diags) :
+  Impl(*new Implementation(Diags)) {}
 
 swift::ide::api::APIDiffItemStore::~APIDiffItemStore() { delete &Impl; }
 

lib/Migrator/APIDiffMigratorPass.cpp

@@ -332,7 +332,7 @@ struct APIDiffMigratorPass : public ASTMigratorPass, public SourceEntityWalker {
   SourceLoc FileEndLoc;
   APIDiffMigratorPass(EditorAdapter &Editor, SourceFile *SF,
                       const MigratorOptions &Opts):
-    ASTMigratorPass(Editor, SF, Opts),
+    ASTMigratorPass(Editor, SF, Opts), DiffStore(Diags),
     FileEndLoc(SM.getRangeForBuffer(BufferID).getEnd()) {
       SmallVector<Decl*, 16> TopDecls;
       SF->getTopLevelDecls(TopDecls);

test/Migrator/missing_script.swift

@@ -0,0 +1,3 @@
+// RUN: %empty-directory(%t) && not %target-swift-frontend -c -update-code -primary-file %s -F %S/mock-sdk -api-diff-data-file %S/Inputs/NoSuchFile.json -emit-migrated-file-path %t/missing_script.swift.result -emit-remap-file-path %t/missing_script.swift.remap -o /dev/null &> %t.diag
+// RUN: %FileCheck %s < %t.diag
+// CHECK: missing migration script from path

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

@@ -4104,8 +4104,8 @@ static void readIgnoredUsrs(llvm::StringSet<> &IgnoredUsrs) {
   readFileLineByLine(Path, IgnoredUsrs);
 }
 
-static int deserializeDiffItems(StringRef DiffPath, StringRef OutputPath) {
-  APIDiffItemStore Store;
+static int deserializeDiffItems(APIDiffItemStore &Store, StringRef DiffPath,
+    StringRef OutputPath) {
   Store.addStorePath(DiffPath);
   std::error_code EC;
   llvm::raw_fd_ostream FS(OutputPath, EC, llvm::sys::fs::F_None);
@@ -4222,13 +4222,18 @@ int main(int argc, char *argv[]) {
       llvm::cl::PrintHelpMessage();
       return 1;
     }
-    if (options::Action == ActionType::DeserializeDiffItems)
-      return deserializeDiffItems(options::SDKJsonPaths[0], options::OutputFile);
-    else
+    if (options::Action == ActionType::DeserializeDiffItems) {
+      CompilerInstance CI;
+      APIDiffItemStore Store(CI.getDiags());
+      return deserializeDiffItems(Store, options::SDKJsonPaths[0],
+        options::OutputFile);
+    } else {
       return deserializeSDKDump(options::SDKJsonPaths[0], options::OutputFile);
+    }
   }
   case ActionType::GenerateNameCorrectionTemplate: {
-    APIDiffItemStore Store;
+    CompilerInstance CI;
+    APIDiffItemStore Store(CI.getDiags());
     auto &Paths = options::SDKJsonPaths;
     for (unsigned I = 0; I < Paths.size(); I ++)
       Store.addStorePath(Paths[I]);