Control #file behavior with a command line option

Author: beccadax

include/swift/Basic/LangOptions.h

@@ -94,6 +94,10 @@ namespace swift {
     /// when using RequireExplicitAvailability.
     std::string RequireExplicitAvailabilityTarget;
 
+    /// If true, '#file' evaluates to the full path rather than a
+    /// human-readable string.
+    bool MagicFileIdentifierEvaluatesToPath = false;
+
     ///
     /// Support for alternate usage modes
     ///

include/swift/Option/Options.td

@@ -267,6 +267,14 @@ def output_file_map_EQ : Joined<["-"], "output-file-map=">,
   Flags<[NoInteractiveOption, ArgumentIsPath]>,
   Alias<output_file_map>;
 
+def pound_file : Separate<["-"], "pound-file">,
+  Flags<[FrontendOption]>,
+  HelpText<"Specifies whether '#file' evaluates to a full path or a compact human-readable string">,
+  MetaVarName<"compact|path">;
+def pound_file_EQ : Joined<["-"], "pound-file=">,
+  Flags<[FrontendOption]>,
+  Alias<pound_file>;
+
 def save_temps : Flag<["-"], "save-temps">,
   Flags<[NoInteractiveOption,DoesNotAffectIncrementalBuild]>,
   HelpText<"Save intermediate compilation results">;

lib/Driver/ToolChains.cpp

@@ -238,6 +238,7 @@ static void addCommonFrontendArgs(const ToolChain &TC, const OutputInfo &OI,
   inputArgs.AddLastArg(arguments, options::OPT_enable_astscope_lookup);
   inputArgs.AddLastArg(arguments, options::OPT_disable_astscope_lookup);
   inputArgs.AddLastArg(arguments, options::OPT_disable_parser_lookup);
+  inputArgs.AddLastArg(arguments, options::OPT_pound_file);
 
   // Pass on any build config options
   inputArgs.AddAllArgs(arguments, options::OPT_D);

lib/Frontend/CompilerInvocation.cpp

@@ -453,6 +453,17 @@ static bool ParseLangArgs(LangOptions &Opts, ArgList &Args,
     Opts.OptimizationRemarkMissedPattern =
         generateOptimizationRemarkRegex(Diags, Args, A);
 
+  if (Arg *A = Args.getLastArg(OPT_pound_file)) {
+    StringRef value = A->getValue();
+    if (value == "path")
+      Opts.MagicFileIdentifierEvaluatesToPath = true;
+    else if (value == "compact")
+      Opts.MagicFileIdentifierEvaluatesToPath = false;
+    else
+      Diags.diagnose(SourceLoc(), diag::error_invalid_arg_value,
+                     A->getSpelling(), value);
+  }
+
   llvm::Triple Target = Opts.Target;
   StringRef TargetArg;
   if (const Arg *A = Args.getLastArg(OPT_target)) {

lib/SILGen/SILGenApply.cpp

@@ -4881,7 +4881,7 @@ static std::string getMagicFileString(SILGenFunction &SGF, SourceLoc loc) {
     return "";
 
   auto path = SGF.getASTContext().SourceMgr.getDisplayNameForLoc(loc);
-  if (false /* FIXME: Add a command line flag for this */)
+  if (SGF.getASTContext().LangOpts.MagicFileIdentifierEvaluatesToPath)
     return path;
 
   auto value = llvm::sys::path::filename(path).str();