[Batch mode] Warn the user if -enable-batch-mode gets overridden by -whole-module-optimization or -index-file.

include/swift/AST/DiagnosticsDriver.def

@@ -141,6 +141,9 @@ WARNING(warn_opt_remark_disabled, none,
         "requires a single compiler invocation: consider enabling the "
         "-whole-module-optimization flag", ())
 
+WARNING(warn_ignoring_batch_mode,none,
+"ignoring '-enable-batch-mode' because '%0' was also specified", (StringRef))
+
 #ifndef DIAG_NO_UNDEF
 # if defined(DIAG)
 #  undef DIAG

include/swift/Driver/Driver.h

@@ -237,6 +237,8 @@ class Driver {
   ///
   /// \param TC The current tool chain.
   /// \param Args The input arguments.
+  /// \param BatchMode Whether the driver has been explicitly or implicitly
+  /// instructed to use batch mode.
   /// \param Inputs The inputs to the driver.
   /// \param[out] OI The OutputInfo in which to store the resulting output
   /// information.
@@ -382,6 +384,13 @@ class Driver {
   /// \param Args The arguments passed to the driver (excluding the path to the
   /// driver)
   void parseDriverKind(ArrayRef<const char *> Args);
+
+  /// Examine potentially conficting arguments and warn the user if
+  /// there is an actual conflict.
+  /// \param Args The input arguments.
+  /// \param Inputs The inputs to the driver.
+  OutputInfo::Mode computeCompilerMode(const llvm::opt::DerivedArgList &Args,
+                                       const InputFileList &Inputs) const;
 };
 
 } // end namespace driver

lib/Driver/Driver.cpp

@@ -1098,19 +1098,11 @@ void Driver::buildOutputInfo(const ToolChain &TC, const DerivedArgList &Args,
   // By default, the driver does not link its output; this will be updated
   // appropriately below if linking is required.
 
-  if (driverKind == DriverKind::Interactive) {
-    OI.CompilerMode = OutputInfo::Mode::Immediate;
-    if (Inputs.empty())
-      OI.CompilerMode = OutputInfo::Mode::REPL;
-    OI.CompilerOutputType = file_types::TY_Nothing;
+  OI.CompilerOutputType = driverKind == DriverKind::Interactive
+                              ? file_types::TY_Nothing
+                              : file_types::TY_Object;
 
-  } else { // DriverKind::Batch
-    OI.CompilerMode = OutputInfo::Mode::StandardCompile;
-    if (Args.hasArg(options::OPT_whole_module_optimization,
-                    options::OPT_index_file))
-      OI.CompilerMode = OutputInfo::Mode::SingleCompile;
-    OI.CompilerOutputType = file_types::TY_Object;
-  }
+  OI.CompilerMode = computeCompilerMode(Args, Inputs);
 
   if (const Arg *A = Args.getLastArg(options::OPT_num_threads)) {
     if (BatchMode) {
@@ -1379,6 +1371,31 @@ void Driver::buildOutputInfo(const ToolChain &TC, const DerivedArgList &Args,
 
 }
 
+OutputInfo::Mode
+Driver::computeCompilerMode(const DerivedArgList &Args,
+                            const InputFileList &Inputs) const {
+
+  if (driverKind == Driver::DriverKind::Interactive)
+    return Inputs.empty() ? OutputInfo::Mode::REPL
+                          : OutputInfo::Mode::Immediate;
+
+  const Arg *ArgRequiringWMO = Args.getLastArg(
+      options::OPT_whole_module_optimization, options::OPT_index_file);
+
+  if (!ArgRequiringWMO)
+    return OutputInfo::Mode::StandardCompile;
+
+  // Test for -enable-batch-mode, rather than the BatchMode flag that is
+  // passed into the caller because the diagnostic is intended to warn against
+  // overriding *explicit* batch mode. No warning should be given if in batch
+  // mode by default.
+  if (Args.hasArg(options::OPT_enable_batch_mode))
+    Diags.diagnose(SourceLoc(), diag::warn_ignoring_batch_mode,
+                   ArgRequiringWMO->getOption().getPrefixedName());
+
+  return OutputInfo::Mode::SingleCompile;
+}
+
 void Driver::buildActions(SmallVectorImpl<const Action *> &TopLevelActions,
                           const ToolChain &TC, const OutputInfo &OI,
                           const OutputFileMap *OFM,

test/Driver/batch_mode_with_WMO_or_index.swift

@@ -0,0 +1,14 @@
+// RUN: %empty-directory(%t)
+//
+// RUN: %swiftc_driver -whole-module-optimization -enable-batch-mode  %S/../Inputs/empty.swift -### 2>%t/stderr_WMO_batch | %FileCheck %s
+// RUN: %swiftc_driver -enable-batch-mode -whole-module-optimization  %S/../Inputs/empty.swift -### 2>%t/stderr_batch_WMO | %FileCheck %s
+// CHECK-NOT: -primary-file
+// RUN: %FileCheck -check-prefix CHECK-WMO %s <%t/stderr_WMO_batch
+// RUN: %FileCheck -check-prefix CHECK-WMO %s <%t/stderr_batch_WMO
+// CHECK-WMO: warning: ignoring '-enable-batch-mode' because '-whole-module-optimization' was also specified
+//
+// RUN: %swiftc_driver -index-file -enable-batch-mode  %S/../Inputs/empty.swift -### 2>%t/stderr_index_batch | %FileCheck %s
+// RUN: %swiftc_driver -enable-batch-mode -index-file  %S/../Inputs/empty.swift -### 2>%t/stderr_batch_index | %FileCheck %s
+// RUN: %FileCheck -check-prefix CHECK-INDEX %s <%t/stderr_index_batch
+// RUN: %FileCheck -check-prefix CHECK-INDEX %s <%t/stderr_batch_index
+// CHECK-INDEX: warning: ignoring '-enable-batch-mode' because '-index-file' was also specified