[Frontend] Allow additional files for diagnostic verifier

This change adds a frontend flag, -verify-additional-file, which can be used to pass extra files directly to the diagnostic verifier. These files are not otherwise considered to be Swift source files; they are not compiled or even properly parsed.

This feature can be used to verify diagnostics emitted in non-source files, such as in module interfaces or header files.

include/swift/Basic/DiagnosticOptions.h

@@ -41,6 +41,10 @@ public:
   /// Indicates whether diagnostic passes should be skipped.
   bool SkipDiagnosticPasses = false;
 
+  /// Additional non-source files which will have diagnostics emitted in them,
+  /// and which should be scanned for expectations by the diagnostic verifier.
+  std::vector<std::string> AdditionalVerifierFiles;
+
   /// Keep emitting subsequent diagnostics after a fatal error.
   bool ShowDiagnosticsAfterFatalError = false;
 
@@ -54,22 +58,23 @@ public:
   /// Treat all warnings as errors
   bool WarningsAsErrors = false;
 
-  // When printing diagnostics, include the diagnostic name at the end
+  /// When printing diagnostics, include the diagnostic name (diag::whatever) at
+  /// the end.
   bool PrintDiagnosticNames = false;
 
   /// If set to true, include educational notes in printed output if available.
   /// Educational notes are documentation which supplement diagnostics.
   bool PrintEducationalNotes = false;
 
-  // If set to true, use the more descriptive experimental formatting style for
+  /// Whether to emit diagnostics in the terse LLVM style or in a more
-  // diagnostics.
+  /// descriptive style that's specific to Swift (currently experimental).
   FormattingStyle PrintedFormattingStyle = FormattingStyle::LLVM;
 
   std::string DiagnosticDocumentationPath = "";
 
   std::string LocalizationCode = "";
 
-  // Diagnostic messages directory path.
+  /// Path to a directory of diagnostic localization tables.
   std::string LocalizationPath = "";
 
   /// Return a hash code of any components from these options that should

include/swift/Frontend/DiagnosticVerifier.h

@@ -65,6 +65,7 @@ class DiagnosticVerifier : public DiagnosticConsumer {
   SourceManager &SM;
   std::vector<CapturedDiagnosticInfo> CapturedDiagnostics;
   ArrayRef<unsigned> BufferIDs;
+  SmallVector<unsigned, 4> AdditionalBufferIDs;
   bool AutoApplyFixes;
   bool IgnoreUnknown;
 
@@ -74,6 +75,10 @@ public:
       : SM(SM), BufferIDs(BufferIDs), AutoApplyFixes(AutoApplyFixes),
         IgnoreUnknown(IgnoreUnknown) {}
 
+  void appendAdditionalBufferID(unsigned bufferID) {
+    AdditionalBufferIDs.push_back(bufferID);
+  }
+
   virtual void handleDiagnostic(SourceManager &SM,
                                 const DiagnosticInfo &Info) override;
 

include/swift/Frontend/Frontend.h

@@ -560,8 +560,11 @@ private:
   bool setUpInputs();
   bool setUpASTContextIfNeeded();
   void setupStatsReporter();
-  void setupDiagnosticVerifierIfNeeded();
   void setupDependencyTrackerIfNeeded();
+
+  /// \return false if successsful, true on error.
+  bool setupDiagnosticVerifierIfNeeded();
+
   Optional<unsigned> setUpCodeCompletionBuffer();
 
   /// Find a buffer for a given input file and ensure it is recorded in

include/swift/Option/FrontendOptions.td

@@ -114,6 +114,8 @@ def tbd_is_installapi: Flag<["-"], "tbd-is-installapi">,
 def verify : Flag<["-"], "verify">,
   HelpText<"Verify diagnostics against expected-{error|warning|note} "
            "annotations">;
+def verify_additional_file : Separate<["-"], "verify-additional-file">,
+  HelpText<"Verify diagnostics in this file in addition to source files">;
 def verify_apply_fixes : Flag<["-"], "verify-apply-fixes">,
   HelpText<"Like -verify, but updates the original source file">;
 def verify_ignore_unknown: Flag<["-"], "verify-ignore-unknown">,

lib/Frontend/CompilerInvocation.cpp

@@ -957,6 +957,9 @@ static bool ParseDiagnosticArgs(DiagnosticOptions &Opts, ArgList &Args,
   Opts.ShowDiagnosticsAfterFatalError |=
     Args.hasArg(OPT_show_diagnostics_after_fatal);
 
+  for (Arg *A : Args.filtered(OPT_verify_additional_file))
+    Opts.AdditionalVerifierFiles.push_back(A->getValue());
+
   Opts.UseColor |=
       Args.hasFlag(OPT_color_diagnostics,
                    OPT_no_color_diagnostics,

lib/Frontend/DiagnosticVerifier.cpp

@@ -978,7 +978,9 @@ void DiagnosticVerifier::handleDiagnostic(SourceManager &SM,
 bool DiagnosticVerifier::finishProcessing() {
   DiagnosticVerifier::Result Result = {false, false};
 
-  for (auto &BufferID : BufferIDs) {
+  ArrayRef<unsigned> BufferIDLists[2] = { BufferIDs, AdditionalBufferIDs };
+  for (ArrayRef<unsigned> BufferIDList : BufferIDLists)
+    for (auto &BufferID : BufferIDList) {
       DiagnosticVerifier::Result FileResult = verifyFile(BufferID);
       Result.HadError |= FileResult.HadError;
       Result.HadUnexpectedDiag |= FileResult.HadUnexpectedDiag;

lib/Frontend/Frontend.cpp

@@ -290,15 +290,31 @@ void CompilerInstance::setupStatsReporter() {
   Stats = std::move(Reporter);
 }
 
-void CompilerInstance::setupDiagnosticVerifierIfNeeded() {
+bool CompilerInstance::setupDiagnosticVerifierIfNeeded() {
   auto &diagOpts = Invocation.getDiagnosticOptions();
+  bool hadError = false;
+
   if (diagOpts.VerifyMode != DiagnosticOptions::NoVerify) {
     DiagVerifier = std::make_unique<DiagnosticVerifier>(
         SourceMgr, InputSourceCodeBufferIDs,
         diagOpts.VerifyMode == DiagnosticOptions::VerifyAndApplyFixes,
         diagOpts.VerifyIgnoreUnknown);
+    for (const auto &filename : diagOpts.AdditionalVerifierFiles) {
+      auto result = getFileSystem().getBufferForFile(filename);
+      if (!result) {
+        Diagnostics.diagnose(SourceLoc(), diag::error_open_input_file,
+                             filename, result.getError().message());
+        hadError |= true;
+      }
+
+      auto bufferID = SourceMgr.addNewSourceBuffer(std::move(result.get()));
+      DiagVerifier->appendAdditionalBufferID(bufferID);
+    }
+
     addDiagnosticConsumer(DiagVerifier.get());
   }
+
+  return hadError;
 }
 
 void CompilerInstance::setupDependencyTrackerIfNeeded() {
@@ -347,7 +363,9 @@ bool CompilerInstance::setup(const CompilerInvocation &Invok) {
     return true;
 
   setupStatsReporter();
-  setupDiagnosticVerifierIfNeeded();
+
+  if (setupDiagnosticVerifierIfNeeded())
+    return true;
 
   return false;
 }