Add module aliasing option to swift-ide-test

Add module aliasing handling in code complete
Resolves rdar://86294338

lib/Frontend/CompilerInvocation.cpp

@@ -262,6 +262,33 @@ void CompilerInvocation::setSDKPath(const std::string &Path) {
   updateRuntimeLibraryPaths(SearchPathOpts, LangOpts.Target);
 }
 
+// This assumes the param args contains valid strings for module
+// aliasing. The full validation of input for aliasing is done at
+// ArgsToFrontendOptionsConverter::computeModulealiases.
+void CompilerInvocation::setModuleAliasMap(std::vector<std::string> args) {
+  // ModuleAliasMap should initially be empty as setting
+  // it should be called only once
+  FrontendOpts.ModuleAliasMap.clear();
+  for (auto item: args) {
+    auto str = StringRef(item);
+    // splits to an alias and the underlying name
+    auto pair = str.split('=');
+    auto lhs = pair.first;
+    auto rhs = pair.second;
+    if (rhs.empty()) // bad format, so skip to the next
+        continue;
+    if (!FrontendOpts.ModuleAliasMap.insert({rhs, StringRef()}).second) {
+      // the underlying name was already added, so skip
+      continue;
+    }
+    auto underlyingName = FrontendOpts.ModuleAliasMap.find(rhs)->first();
+    if (!FrontendOpts.ModuleAliasMap.insert({lhs, underlyingName}).second) {
+      // the alias was already added, so skip
+      continue;
+    }
+  }
+}
+
 static bool ParseFrontendArgs(
     FrontendOptions &opts, ArgList &args, DiagnosticEngine &diags,
     SmallVectorImpl<std::unique_ptr<llvm::MemoryBuffer>> *buffers) {