Validate configs for all inputs files up front

And make ClangTidyContext::getOptionsForFile resilient to errors at that
point.

Author: galenelias

clang-tools-extra/clang-tidy/ClangTidyDiagnosticConsumer.cpp

@@ -265,8 +265,16 @@ const ClangTidyOptions &ClangTidyContext::getOptions() const {
 ClangTidyOptions ClangTidyContext::getOptionsForFile(StringRef File) const {
   // Merge options on top of getDefaults() as a safeguard against options with
   // unset values.
-  return ClangTidyOptions::getDefaults().merge(
-      *OptionsProvider->getOptions(File), 0);
+  ClangTidyOptions defaultOptions = ClangTidyOptions::getDefaults();
+  llvm::ErrorOr<ClangTidyOptions> fileOptions =
+      OptionsProvider->getOptions(File);
+
+  // If there was an error parsing the options, just use the default options.
+  // Ideally, the options for each file should be validated before this point.
+  if (!fileOptions)
+    return defaultOptions;
+
+  return defaultOptions.merge(*fileOptions, 0);
 }
 
 void ClangTidyContext::setEnableProfiling(bool P) { Profile = P; }

clang-tools-extra/clang-tidy/tool/ClangTidyMain.cpp

@@ -630,6 +630,17 @@ int clangTidyMain(int argc, const char **argv) {
   if (!EffectiveOptions)
     return 1;
 
+  // Validate the configuration files associated with all input files so we can
+  // return an error up front.
+  if (PathList.size() > 1) {
+    for (auto iter = PathList.begin() + 1; iter != PathList.end(); ++iter) {
+      llvm::ErrorOr<ClangTidyOptions> Options =
+          OptionsProvider->getOptions(*iter);
+      if (!Options)
+        return 1;
+    }
+  }
+
   std::vector<std::string> EnabledChecks =
       getCheckNames(*EffectiveOptions, AllowEnablingAnalyzerAlphaCheckers);