Add error handling for compiler instance with context initialization and finalization.

Author: qiongsiwu

lib/DependencyScan/ScanDependencies.cpp

@@ -1413,9 +1413,14 @@ performModuleScanImpl(
       instance->getInvocation().getFrontendOptions().ParallelDependencyScan);
 
   auto initError = scanner.initializeWorkerClangScanningTool();
-  // TODO: fix error check!
-  if (initError)
-    llvm::consumeError(std::move(initError));
+  if (initError) {
+    llvm::handleAllErrors(
+        std::move(initError), [&](const llvm::StringError &E) {
+          instance->getDiags().diagnose(
+              SourceLoc(), diag::clang_dependency_scan_error, E.getMessage());
+        });
+    return std::make_error_code(std::errc::invalid_argument);
+  }
 
   // Identify imports of the main module and add an entry for it
   // to the dependency graph.
@@ -1432,8 +1437,15 @@ performModuleScanImpl(
     return std::make_error_code(std::errc::not_supported);
 
   auto finError = scanner.finalizeWorkerClangScanningTool();
-  if (finError)
-    llvm::consumeError(std::move(finError));
+  if (finError) {
+    llvm::handleAllErrors(std::move(finError), [&](const llvm::StringError &E) {
+      instance->getDiags().diagnose(
+          SourceLoc(), diag::clang_dependency_scan_error, E.getMessage());
+    });
+    // TODO:it is not expected that the finialization fails. Maybe we should
+    // turn this into an assert.
+    return std::make_error_code(std::errc::not_supported);
+  }
 
   auto topologicallySortedModuleList =
       computeTopologicalSortOfExplicitDependencies(allModules, cache);

unittests/DependencyScan/ModuleDeps.cpp

@@ -514,6 +514,6 @@ TEST_F(ScanTest, TestStressConcurrentDiagnostics) {
   ASSERT_FALSE(DependenciesOrErr.getError());
   auto Dependencies = DependenciesOrErr.get();
   auto Diagnostics = Dependencies->diagnostics;
-  ASSERT_TRUE(Diagnostics->count > 100);
+  ASSERT_TRUE(Diagnostics->count == 2);
   swiftscan_dependency_graph_dispose(Dependencies);
 }