Emit error diagnostic for a primary if all errors suppressed

include/swift/AST/DiagnosticConsumer.h

@@ -101,6 +101,8 @@ public:
 
   /// \returns true if an error occurred while finishing-up.
   virtual bool finishProcessing() { return false; }
+
+  virtual bool hadOnlySuppressedFatalErrors() const { return false; }
 };
   
 /// \brief DiagnosticConsumer that discards all diagnostics.
@@ -165,6 +167,9 @@ private:
   /// If null, diagnostics are suppressed.
   Optional<DiagnosticConsumer *> ConsumerForSubsequentNotes = None;
 
+  bool WasAFatalDiagnosticSuppressed = false;
+  bool WasAFatalDiagnosticEmitted = false;
+
 public:
   /// Takes ownership of the DiagnosticConsumers specified in \p consumers.
   ///
@@ -181,6 +186,8 @@ public:
 
   bool finishProcessing() override;
 
+  bool hadOnlySuppressedFatalErrors() const override;
+
 private:
   void computeConsumersOrderedByRange(SourceManager &SM);
 

include/swift/AST/DiagnosticEngine.h

@@ -768,6 +768,8 @@ namespace swift {
         ArrayRef<DiagnosticArgument> FormatArgs,
         DiagnosticFormatOptions FormatOpts = DiagnosticFormatOptions());
 
+    bool hadOnlySuppressedFatalErrors() const;
+
   private:
     /// \brief Flush the active diagnostic.
     void flushActiveDiagnostic();

include/swift/AST/DiagnosticsFrontend.def

@@ -235,6 +235,8 @@ WARNING(cannot_assign_value_to_conditional_compilation_flag,none,
 ERROR(error_optimization_remark_pattern, none, "%0 in '%1'",
       (StringRef, StringRef))
 
+ERROR(error_compilation_failed,none, "compilation failed", ())
+
 #ifndef DIAG_NO_UNDEF
 # if defined(DIAG)
 #  undef DIAG

lib/AST/DiagnosticConsumer.cpp

@@ -176,17 +176,25 @@ void FileSpecificDiagnosticConsumer::handleDiagnostic(
     break;
   }
 
+  const bool isErrorFatal = Kind == DiagnosticKind::Error;
   if (!specificConsumer.hasValue()) {
     for (auto &subConsumer : SubConsumers) {
       if (subConsumer.second) {
         subConsumer.second->handleDiagnostic(SM, Loc, Kind, FormatString,
                                              FormatArgs, Info);
+        WasAFatalDiagnosticEmitted |= isErrorFatal;
       }
     }
-  } else if (DiagnosticConsumer *c = specificConsumer.getValue())
+  } else if (DiagnosticConsumer *c = specificConsumer.getValue()) {
     c->handleDiagnostic(SM, Loc, Kind, FormatString, FormatArgs, Info);
-  else
-    ; // Suppress non-primary diagnostic in batch mode.
+    WasAFatalDiagnosticEmitted |= isErrorFatal;
+  } else { // Suppress non-primary diagnostic in batch mode.
+    WasAFatalDiagnosticSuppressed |= isErrorFatal;
+  }
+}
+
+bool FileSpecificDiagnosticConsumer::hadOnlySuppressedFatalErrors() const {
+  return WasAFatalDiagnosticSuppressed && !WasAFatalDiagnosticEmitted;
 }
 
 bool FileSpecificDiagnosticConsumer::finishProcessing() {

lib/AST/DiagnosticEngine.cpp

@@ -259,6 +259,14 @@ bool DiagnosticEngine::finishProcessing() {
   return hadError;
 }
 
+bool DiagnosticEngine::hadOnlySuppressedFatalErrors() const {
+  for (auto &Consumer : Consumers) {
+    if (Consumer->hadOnlySuppressedFatalErrors())
+      return true;
+  }
+  return false;
+}
+
 /// \brief Skip forward to one of the given delimiters.
 ///
 /// \param Text The text to search through, which will be updated to point

lib/FrontendTool/FrontendTool.cpp

@@ -1651,6 +1651,9 @@ int swift::performFrontend(ArrayRef<const char *> Args,
 
   auto finishDiagProcessing = [&](int retValue) -> int {
     FinishDiagProcessingCheckRAII.CalledFinishDiagProcessing = true;
+    if (Instance->getDiags().hadOnlySuppressedFatalErrors())
+      Instance->getDiags().diagnose(SourceLoc(),
+                                    diag::error_compilation_failed);
     bool err = Instance->getDiags().finishProcessing();
     return retValue ? retValue : err;
   };

test/Misc/serialized-diagnostics-batch-mode-compilation-failed.swift

@@ -0,0 +1,24 @@
+// To avoid redundant diagnostics showing up in Xcode, batch-mode must suppress diagnostics in
+// non-primary files.
+// But if the only fatal errors are suppressed ones, a "compilation failed" error must be emitted
+// for the primary files so Xcode knows something happened.
+//
+// RUN: rm -f %t.*
+
+// RUN: not %target-swift-frontend -typecheck  -primary-file %s  -serialize-diagnostics-path %t.main.dia -primary-file %S/../Inputs/empty.swift  -serialize-diagnostics-path %t.empty.dia %S/Inputs/serialized-diagnostics-batch-mode-suppression-helper.swift 2> %t.stderr.txt
+// RUN: c-index-test -read-diagnostics %t.main.dia 2> %t.main.txt
+// RUN: c-index-test -read-diagnostics %t.empty.dia 2> %t.empty.txt
+
+// Ensure there was an error:
+
+// RUN: %FileCheck -check-prefix=ERROR %s <%t.stderr.txt
+// ERROR: error:
+
+// Ensure the error is in the serialized diagnostics:
+
+// RUN: %FileCheck -check-prefix=COMPILATION-FAILED %s <%t.main.txt
+// RUN: %FileCheck -check-prefix=COMPILATION-FAILED %s <%t.empty.txt
+// COMPILATION-FAILED: compilation failed
+
+func test(x: SomeType) {
+}

test/Misc/serialized-diagnostics-batch-mode-nonprimary-suppression.swift

@@ -7,20 +7,11 @@
 // RUN: c-index-test -read-diagnostics %t.main.dia 2> %t.main.txt
 // RUN: c-index-test -read-diagnostics %t.empty.dia 2> %t.empty.txt
 
-// Ensure there was an error:
+// RUN: %FileCheck -check-prefix=NO-COMPILATION-FAILED %s <%t.main.txt
+// RUN: %FileCheck -check-prefix=NO-COMPILATION-FAILED %s <%t.empty.txt
+// NO-COMPILATION-FAILED-NOT: compilation failed
 
-// RUN: %FileCheck -check-prefix=ERROR %s <%t.stderr.txt
-// ERROR: error:
-
-// Ensure the error is not in the serialized diagnostics:
-
-// RUN: %FileCheck -check-prefix=NO-DIAGNOSTICS %s <%t.main.txt
-// RUN: %FileCheck -check-prefix=NO-DIAGNOSTICS %s <%t.empty.txt
-// NO-DIAGNOSTICS: Number of diagnostics: 0
-
-// RUN: %FileCheck -check-prefix=NO-ERROR %s <%t.main.txt
-// RUN: %FileCheck -check-prefix=NO-ERROR %s <%t.empty.txt
-// NO-ERROR-NOT: error:
 
 func test(x: SomeType) {
+  nonexistant(); // create a fatal error here
 }