Clear diagnostics between processing of source files

src/libdredd/src/new_mutate_frontend_action_factory.cc

@@ -19,6 +19,7 @@
 #include <string>
 
 #include "clang/AST/ASTConsumer.h"
+#include "clang/Basic/Diagnostic.h"
 #include "clang/Frontend/CompilerInstance.h"
 #include "clang/Frontend/FrontendAction.h"
 #include "clang/Frontend/FrontendOptions.h"
@@ -45,15 +46,23 @@ class MutateFrontendAction : public clang::ASTFrontendAction {
       llvm::StringRef file) override;
 
   bool BeginInvocation(clang::CompilerInstance& compiler_instance) override {
-    (void)compiler_instance;  // Unused.
+    // Clear any diagnostics generated when operating on previous source files.
+    compiler_instance.getDiagnostics().getClient()->clear();
+
+    // Sanity check to confirm that there is a current input file.
     const bool input_exists = !getCurrentInput().isEmpty();
     (void)input_exists;  // Keep release-mode compilers happy.
     assert(input_exists && "No current file.");
+
+    // Check whether this file has already been processed.
     if (processed_files_->contains(getCurrentFile().str())) {
       llvm::errs() << "Warning: already processed " << getCurrentFile()
                    << "; skipping repeat occurrence.\n";
       return false;
     }
+
+    // Record that this file has been processed so that duplicate processing
+    // will be detected in the future.
     processed_files_->insert(getCurrentFile().str());
     return true;
   }

test/bespoke/one_bad_file_one_good_file/bad.c

@@ -0,0 +1,3 @@
+void foo() error {
+
+}

test/bespoke/one_bad_file_one_good_file/good.c

@@ -0,0 +1,3 @@
+void bar() {
+
+}

test/bespoke/one_bad_file_one_good_file/test.py

@@ -0,0 +1,23 @@
+import os
+import re
+import shutil
+import subprocess
+import sys
+from pathlib import Path
+
+DREDD_REPO_ROOT = os.environ['DREDD_REPO_ROOT']
+DREDD_INSTALLED_EXECUTABLE = Path(DREDD_REPO_ROOT, 'third_party', 'clang+llvm', 'bin', 'dredd')
+
+
+def main():
+    # Run Dredd
+    cmd = [DREDD_INSTALLED_EXECUTABLE, 'bad.c', 'good.c', '--']
+    result = subprocess.run(cmd, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
+    assert result.returncode != 0
+    error_output = result.stderr.decode('utf-8')
+    pattern = r"Error while processing .*good\.c"
+    assert re.search(pattern, error_output) is None
+
+
+if __name__ == '__main__':
+    sys.exit(main())