Don't crash if a -filelist file doesn't exist or doesn't contain the primary file.

I know this is the frontend and not the driver, but c'mon.

Author: rjmccall

include/swift/AST/DiagnosticsFrontend.def

@@ -128,6 +128,10 @@ ERROR(error_implicit_output_file_is_directory,none,
   "the implicit output file '%0' is a directory; explicitly specify a filename "
   "using -o", (StringRef))
 
+ERROR(error_primary_file_not_found,none,
+      "primary file '%0' was not found in file list '%1'",
+      (StringRef, StringRef))
+
 ERROR(repl_must_be_initialized,none,
       "variables currently must have an initial value when entered at the "
       "top level of the REPL", ())

lib/Frontend/CompilerInvocation.cpp

@@ -112,32 +112,46 @@ static void debugFailWithCrash() {
   LLVM_BUILTIN_TRAP;
 }
 
-static unsigned readFileList(std::vector<std::string> &inputFiles,
-                             const llvm::opt::Arg *filelistPath,
-                             const llvm::opt::Arg *primaryFileArg = nullptr) {
-  bool foundPrimaryFile = false;
-  unsigned primaryFileIndex = 0;
-  StringRef primaryFile;
-  if (primaryFileArg)
-    primaryFile = primaryFileArg->getValue();
+/// Try to read a file list file.
+///
+/// Returns false on error.
+static bool readFileList(DiagnosticEngine &diags,
+                         std::vector<std::string> &inputFiles,
+                         const llvm::opt::Arg *filelistPath,
+                         const llvm::opt::Arg *primaryFileArg = nullptr,
+                         unsigned *primaryFileIndex = nullptr) {
+  assert((primaryFileArg == nullptr) || (primaryFileIndex != nullptr) &&
+         "did not provide argument for primary file index");
 
   llvm::ErrorOr<std::unique_ptr<llvm::MemoryBuffer>> buffer =
       llvm::MemoryBuffer::getFile(filelistPath->getValue());
-  assert(buffer && "can't read filelist; unrecoverable");
+  if (!buffer) {
+    diags.diagnose(SourceLoc(), diag::cannot_open_file,
+                   filelistPath->getValue(), buffer.getError().message());
+    return false;
+  }
+
+  bool foundPrimaryFile = false;
+  if (primaryFileIndex) *primaryFileIndex = 0;
 
   for (StringRef line : make_range(llvm::line_iterator(*buffer.get()), {})) {
     inputFiles.push_back(line);
-    if (foundPrimaryFile)
+
+    if (foundPrimaryFile || primaryFileArg == nullptr)
       continue;
-    if (line == primaryFile)
+    if (line == primaryFileArg->getValue())
       foundPrimaryFile = true;
     else
-      ++primaryFileIndex;
+      ++*primaryFileIndex;
   }
 
-  if (primaryFileArg)
-    assert(foundPrimaryFile && "primary file not found in filelist");
-  return primaryFileIndex;
+  if (primaryFileArg && !foundPrimaryFile) {
+    diags.diagnose(SourceLoc(), diag::error_primary_file_not_found,
+                   primaryFileArg->getValue(), filelistPath->getValue());
+    return false;
+  }
+
+  return true;
 }
 
 static bool ParseFrontendArgs(FrontendOptions &Opts, ArgList &Args,
@@ -199,11 +213,13 @@ static bool ParseFrontendArgs(FrontendOptions &Opts, ArgList &Args,
 
   if (const Arg *A = Args.getLastArg(OPT_filelist)) {
     const Arg *primaryFileArg = Args.getLastArg(OPT_primary_file);
-    auto primaryFileIndex = readFileList(Opts.InputFilenames, A,
-                                         primaryFileArg);
-    if (primaryFileArg)
-      Opts.PrimaryInput = SelectedInput(primaryFileIndex);
-    assert(!Args.hasArg(OPT_INPUT) && "mixing -filelist with inputs");
+    unsigned primaryFileIndex = 0;
+    if (readFileList(Diags, Opts.InputFilenames, A,
+                     primaryFileArg, &primaryFileIndex)) {
+      if (primaryFileArg)
+        Opts.PrimaryInput = SelectedInput(primaryFileIndex);
+      assert(!Args.hasArg(OPT_INPUT) && "mixing -filelist with inputs");
+    }
   } else {
     for (const Arg *A : make_range(Args.filtered_begin(OPT_INPUT,
                                                        OPT_primary_file),
@@ -355,7 +371,7 @@ static bool ParseFrontendArgs(FrontendOptions &Opts, ArgList &Args,
     Opts.InputKind = InputFileKind::IFK_Swift;
 
   if (const Arg *A = Args.getLastArg(OPT_output_filelist)) {
-    readFileList(Opts.OutputFilenames, A);
+    readFileList(Diags, Opts.OutputFilenames, A);
     assert(!Args.hasArg(OPT_o) && "don't use -o with -output-filelist");
   } else {
     Opts.OutputFilenames = Args.getAllArgValues(OPT_o);

test/Frontend/filelist.swift

@@ -5,6 +5,12 @@
 // RUN: not %target-swift-frontend -parse -filelist %t/input.txt -primary-file %s 2>&1 | FileCheck %s
 // RUN: not %target-swift-frontend -parse -filelist %t/input.txt 2>&1 | FileCheck %s
 
+// RUN: not %target-swift-frontend -emit-bc -filelist %t/nonexistent-input.txt 2>&1 | FileCheck -check-prefix=CHECK-BADFILE %s
+// CHECK-BADFILE: error: cannot open file
+
+// RUN: not %target-swift-frontend -emit-bc -filelist %t/input.txt -primary-file nonexistent.swift 2>&1 | FileCheck -check-prefix=CHECK-BADPRIMARYFILE %s
+// CHECK-BADPRIMARYFILE: error: primary file 'nonexistent.swift' was not found in file list
+
 // RUN: echo '%t/filelist-other.bc' >> %t/output.txt
 // RUN: echo '%t/filelist.bc' >> %t/output.txt
 // RUN: echo '%t/filelist-other.bc' >> %t/output.txt