Cleaner handling of cases where action produces no output or where there are no inputs.

include/swift/Frontend/ArgsToFrontendOutputsConverter.h

@@ -124,10 +124,24 @@ public:
       const llvm::opt::ArgList &args, DiagnosticEngine &diags,
       const FrontendInputsAndOutputs &inputsAndOutputs,
       ArrayRef<std::string> outputFiles, StringRef moduleName);
-  Optional<SupplementaryOutputPaths> computeOutputPaths() const;
+  Optional<std::vector<SupplementaryOutputPaths>> computeOutputPaths() const;
 
 private:
-  /// \return None if error.
+  /// \Return a set of supplementary output paths for each input that might
+  /// produce supplementary outputs, or None to signal an error.
+  /// \note
+  /// At present, only one input can produce supplementary outputs, but
+  /// in the future, batch-mode will support multiple primary inputs and thus,
+  /// multiple sets of supplementary outputs. This function is written with that
+  /// future in mind.
+  /// \par
+  /// The paths are derived from arguments
+  /// such as -emit-module-path. These are not the final computed paths,
+  /// merely the ones passed in via the command line.
+  /// \note
+  /// In the future, these will also include those passed in via whatever
+  /// filelist scheme gets implemented to handle cases where the command line
+  /// arguments become burdensome.
   Optional<std::vector<SupplementaryOutputPaths>>
   getSupplementaryOutputPathsFromArguments() const;
 

lib/Frontend/ArgsToFrontendOptionsConverter.cpp

@@ -441,9 +441,6 @@ bool ArgsToFrontendOptionsConverter::
                             .convert(mainOutputs, supplementaryOutputs);
   if (hadError)
     return true;
-  assert(FrontendOptions::doesActionProduceOutput(Opts.RequestedAction) ||
-         mainOutputs.empty() &&
-             "Should be no main outputs if action does not produce them");
   Opts.InputsAndOutputs.setMainAndSupplementaryOutputs(mainOutputs,
                                                        supplementaryOutputs);
   return false;

lib/Frontend/ArgsToFrontendOutputsConverter.cpp

@@ -34,10 +34,6 @@ using namespace llvm::opt;
 bool ArgsToFrontendOutputsConverter::convert(
     std::vector<std::string> &mainOutputs,
     SupplementaryOutputPaths &supplementaryOutputs) {
-  const auto requestedAction =
-      ArgsToFrontendOptionsConverter::determineRequestedAction(Args);
-  if (!FrontendOptions::doesActionProduceOutput(requestedAction))
-    return false;
 
   Optional<OutputFilesComputer> ofc =
       OutputFilesComputer::create(Args, Diags, InputsAndOutputs);
@@ -47,7 +43,7 @@ bool ArgsToFrontendOutputsConverter::convert(
   if (!mains)
     return true;
 
-  Optional<SupplementaryOutputPaths> supplementaries =
+  Optional<std::vector<SupplementaryOutputPaths>> supplementaries =
       SupplementaryOutputPathsComputer(Args, Diags, InputsAndOutputs, *mains,
                                        ModuleName)
           .computeOutputPaths();
@@ -55,7 +51,10 @@ bool ArgsToFrontendOutputsConverter::convert(
     return true;
 
   mainOutputs = std::move(*mains);
-  supplementaryOutputs = std::move(*supplementaries);
+  assert(supplementaries->size() <= 1 &&
+         "Have not implemented multiple primaries yet");
+  if (!supplementaries->empty())
+    supplementaryOutputs = std::move(supplementaries->front());
   return false;
 }
 
@@ -166,6 +165,13 @@ OutputFilesComputer::computeOutputFiles() const {
 Optional<std::string>
 OutputFilesComputer::computeOutputFile(StringRef outputArg,
                                        const InputFile &input) const {
+  // Return an empty string to signify no output.
+  // The frontend does not currently produce a diagnostic
+  // if a -o argument is present for such an action
+  // for instance swiftc -frontend -o foo -interpret foo.swift
+  if (!FrontendOptions::doesActionProduceOutput(RequestedAction))
+    return std::string();
+
   if (!OutputDirectoryArgument.empty())
     return deriveOutputFileForDirectory(input);
 
@@ -228,16 +234,41 @@ SupplementaryOutputPathsComputer::SupplementaryOutputPathsComputer(
       RequestedAction(
           ArgsToFrontendOptionsConverter::determineRequestedAction(Args)) {}
 
-Optional<SupplementaryOutputPaths>
+Optional<std::vector<SupplementaryOutputPaths>>
 SupplementaryOutputPathsComputer::computeOutputPaths() const {
   Optional<std::vector<SupplementaryOutputPaths>> pathsFromUser =
       getSupplementaryOutputPathsFromArguments();
   if (!pathsFromUser)
     return None;
 
-  return computeOutputPathsForOneInput(
-      OutputFiles[0], (*pathsFromUser)[0],
-      InputsAndOutputs.firstInputProducingOutput());
+  if (InputsAndOutputs.hasPrimaryInputs())
+    assert(OutputFiles.size() == pathsFromUser->size());
+  else if (InputsAndOutputs.isSingleThreadedWMO())
+    assert(OutputFiles.size() == pathsFromUser->size() &&
+           pathsFromUser->size() == 1);
+  else {
+    // Multi-threaded WMO is the exception
+    assert(OutputFiles.size() == InputsAndOutputs.inputCount() &&
+                   pathsFromUser->size() == InputsAndOutputs.hasInputs()
+               ? 1
+               : 0);
+  }
+
+  std::vector<SupplementaryOutputPaths> outputPaths;
+  unsigned i = 0;
+  bool hadError = false;
+  InputsAndOutputs.forEachInputProducingSupplementaryOutput(
+      [&](const InputFile &input) -> void {
+        if (auto suppPaths = computeOutputPathsForOneInput(
+                OutputFiles[i], (*pathsFromUser)[i], input))
+          outputPaths.push_back(*suppPaths);
+        else
+          hadError = true;
+        ++i;
+      });
+  if (hadError)
+    return None;
+  return outputPaths;
 }
 
 Optional<std::vector<SupplementaryOutputPaths>>
@@ -302,7 +333,7 @@ SupplementaryOutputPathsComputer::getSupplementaryFilenamesFromArguments(
     return std::vector<std::string>(N, std::string());
 
   Diags.diagnose(SourceLoc(), diag::error_wrong_number_of_arguments,
-                 Args.getLastArg(pathID)->getOption().getName(), N,
+                 Args.getLastArg(pathID)->getOption().getPrefixedName(), N,
                  paths.size());
   return None;
 }
@@ -387,7 +418,6 @@ SupplementaryOutputPathsComputer::determineSupplementaryOutputFilename(
     options::ID emitOpt, std::string pathFromArguments, StringRef extension,
     StringRef mainOutputIfUsable,
     StringRef defaultSupplementaryOutputPathExcludingExtension) const {
-  using namespace options;
 
   if (!pathFromArguments.empty())
     return pathFromArguments;

lib/Frontend/FrontendInputsAndOutputs.cpp

@@ -289,9 +289,7 @@ void FrontendInputsAndOutputs::forEachInputProducingAMainOutputFile(
 void FrontendInputsAndOutputs::setMainAndSupplementaryOutputs(
     ArrayRef<std::string> outputFiles,
     SupplementaryOutputPaths supplementaryOutputs) {
-  if (outputFiles.empty())
-    ;
-  else if (hasPrimaryInputs()) {
+  if (hasPrimaryInputs()) {
     unsigned i = 0;
     for (auto index : indices(AllInputs)) {
       InputFile &f = AllInputs[index];
@@ -344,15 +342,14 @@ bool FrontendInputsAndOutputs::hasNamedOutputFile() const {
 
 unsigned
 FrontendInputsAndOutputs::countOfFilesProducingSupplementaryOutput() const {
-  assertMustNotBeMoreThanOnePrimaryInput();
-  return 1; // will be extended when batch mode is implemented
+  return hasPrimaryInputs() ? primaryInputCount() : hasInputs() ? 1 : 0;
 }
 
 void FrontendInputsAndOutputs::forEachInputProducingSupplementaryOutput(
     llvm::function_ref<void(const InputFile &)> fn) const {
   if (hasPrimaryInputs())
     forEachPrimaryInput(fn);
-  else
+  else if (hasInputs())
     fn(firstInput());
 }
 

test/Frontend/wrong-number-of-arguments.swift

@@ -1,2 +1,2 @@
 // RUN: not %swift  -c -primary-file a.swift b.swift -emit-module-path one -emit-module-path two 2>&1 | %FileCheck %s -check-prefix=CHECK1
-// CHECK1: <unknown>:0: error: wrong number of 'emit-module-path' arguments (expected 1, got 2)
+// CHECK1: <unknown>:0: error: wrong number of '-emit-module-path' arguments (expected 1, got 2)