Add symlinks for the legacy driver invocation (for emergency fallback invoked from 'swift-driver')

Author: artemcm

lib/Driver/Driver.cpp

@@ -99,6 +99,8 @@ void Driver::parseDriverKind(ArrayRef<const char *> Args) {
       llvm::StringSwitch<llvm::Optional<DriverKind>>(DriverName)
           .Case("swift", DriverKind::Interactive)
           .Case("swiftc", DriverKind::Batch)
+          .Case("swift-legacy-driver", DriverKind::Interactive)
+          .Case("swiftc-legacy-driver", DriverKind::Batch)
           .Case("sil-opt", DriverKind::SILOpt)
           .Case("sil-func-extractor", DriverKind::SILFuncExtractor)
           .Case("sil-nm", DriverKind::SILNM)

lib/DriverTool/driver.cpp

@@ -167,14 +167,25 @@ static bool shouldRunAsSubcommand(StringRef ExecName,
 static bool shouldDisallowNewDriver(DiagnosticEngine &diags,
                                     StringRef ExecName,
                                     const ArrayRef<const char *> argv) {
-  // We are not invoking the driver, so don't forward.
-  if (ExecName != "swift" && ExecName != "swiftc") {
-    return true;
-  }
   StringRef disableArg = "-disallow-use-new-driver";
   StringRef disableEnv = "SWIFT_USE_OLD_DRIVER";
   auto shouldWarn = !llvm::sys::Process::
     GetEnv("SWIFT_AVOID_WARNING_USING_OLD_DRIVER").has_value();
+
+  // We explicitly are on the fallback to the legacy driver from the new driver.
+  // Do not forward.
+  if (ExecName == "swift-legacy-driver" ||
+      ExecName == "swiftc-legacy-driver") {
+    if (shouldWarn)
+      diags.diagnose(SourceLoc(), diag::old_driver_deprecated, disableArg);
+    return true;
+  }
+
+  // We are not invoking the driver, so don't forward.
+  if (ExecName != "swift" && ExecName != "swiftc") {
+    return true;
+  }
+
   // If user specified using the old driver, don't forward.
   if (llvm::find_if(argv, [&](const char* arg) {
     return StringRef(arg) == disableArg;
@@ -345,6 +356,15 @@ static int run_driver(StringRef ExecName,
     }
   }
 
+  // We are in the fallback to legacy driver mode.
+  // Now that we have determined above that we are not going to
+  // forward the invocation to the new driver, ensure the rest of the
+  // downstream driver execution refers to itself by the appropriate name.
+  if (ExecName == "swift-legacy-driver")
+    ExecName = "swift";
+  else if (ExecName == "swiftc-legacy-driver")
+    ExecName = "swiftc";
+
   Driver TheDriver(Path, ExecName, argv, Diags);
   switch (TheDriver.getDriverKind()) {
   case Driver::DriverKind::SILOpt:

tools/driver/CMakeLists.txt

@@ -85,11 +85,20 @@ if(EXISTS "${SWIFT_RUNTIME_OUTPUT_INTDIR}/swift-driver${CMAKE_EXECUTABLE_SUFFIX}
     SOURCE "swift-driver${CMAKE_EXECUTABLE_SUFFIX}"
     DESTINATION "swift${CMAKE_EXECUTABLE_SUFFIX}"
     WORKING_DIRECTORY "${SWIFT_RUNTIME_OUTPUT_INTDIR}")
-
   swift_create_post_build_symlink(swift-frontend
     SOURCE "swift-driver${CMAKE_EXECUTABLE_SUFFIX}"
     DESTINATION "swiftc${CMAKE_EXECUTABLE_SUFFIX}"
     WORKING_DIRECTORY "${SWIFT_RUNTIME_OUTPUT_INTDIR}")
+
+  message(STATUS "Pointing 'swift-legacy-driver' and 'swiftc-legacy-driver' symlinks at 'swift-frontend'.")
+  swift_create_post_build_symlink(swift-frontend
+    SOURCE "swift-frontend${CMAKE_EXECUTABLE_SUFFIX}"
+    DESTINATION "swift-legacy-driver${CMAKE_EXECUTABLE_SUFFIX}"
+    WORKING_DIRECTORY "${SWIFT_RUNTIME_OUTPUT_INTDIR}")
+  swift_create_post_build_symlink(swift-frontend
+    SOURCE "swift-frontend${CMAKE_EXECUTABLE_SUFFIX}"
+    DESTINATION "swiftc-legacy-driver${CMAKE_EXECUTABLE_SUFFIX}"
+    WORKING_DIRECTORY "${SWIFT_RUNTIME_OUTPUT_INTDIR}")
 else()
   message(STATUS "Pointing 'swift' and 'swiftc' symlinks at 'swift-frontend' - no early SwiftDriver build found.")
   swift_create_post_build_symlink(swift-frontend
@@ -207,4 +216,10 @@ if(EXISTS "${SWIFT_RUNTIME_OUTPUT_INTDIR}/swift-driver${CMAKE_EXECUTABLE_SUFFIX}
   swift_install_in_component(PROGRAMS "${SWIFT_RUNTIME_OUTPUT_INTDIR}/swift-help${CMAKE_EXECUTABLE_SUFFIX}"
                              DESTINATION "bin"
                              COMPONENT compiler)
+  swift_install_in_component(FILES "${SWIFT_RUNTIME_OUTPUT_INTDIR}/swiftc-legacy-driver${CMAKE_EXECUTABLE_SUFFIX}"
+                             DESTINATION "bin"
+                             COMPONENT compiler)
+  swift_install_in_component(FILES "${SWIFT_RUNTIME_OUTPUT_INTDIR}/swift-legacy-driver${CMAKE_EXECUTABLE_SUFFIX}"
+                             DESTINATION "bin"
+                             COMPONENT compiler)
 endif()