[lldb] Check if language is supported before creating a REPL instance

[JDevlieghere]

Summary

Currently, we'll try to instantiate a ClangREPL for every known language. The plugin manager already knows what languages are supported, so rely on that to only instantiate a REPL when we know the requested language in supported.

rdar://86439474

lldb/include/lldb/Core/PluginManager.h

public:
   static bool RegisterPlugin(llvm::StringRef name, llvm::StringRef description,
                              REPLCreateInstance create_callback,
                              LanguageSet supported_languages);
 
   static bool UnregisterPlugin(REPLCreateInstance create_callback);
 
   static REPLCreateInstance GetREPLCreateCallbackAtIndex(uint32_t idx);
 
+  static LanguageSet GetREPLSupportedLanguagesAtIndex(uint32_t idx);
+
   static LanguageSet GetREPLAllTypeSystemSupportedLanguages();
 
   // Some plug-ins might register a DebuggerInitializeCallback callback when
   // registering the plug-in. After a new Debugger instance is created, this
   // DebuggerInitialize function will get called. This allows plug-ins to
   // install Properties and do any other initialization that requires a
   // debugger instance.
   static void DebuggerInitialize(Debugger &debugger);

lldb/source/Core/PluginManager.cpp

 bool PluginManager::UnregisterPlugin(REPLCreateInstance create_callback) {
   return GetREPLInstances().UnregisterPlugin(create_callback);
 }
 
 REPLCreateInstance PluginManager::GetREPLCreateCallbackAtIndex(uint32_t idx) {
   return GetREPLInstances().GetCallbackAtIndex(idx);
 }
 
+LanguageSet PluginManager::GetREPLSupportedLanguagesAtIndex(uint32_t idx) {
+  const auto &instances = GetREPLInstances().GetInstances();
+  return idx < instances.size() ? instances[idx].supported_languages
+                                : LanguageSet();
+}
+
 LanguageSet PluginManager::GetREPLAllTypeSystemSupportedLanguages() {
   const auto &instances = GetREPLInstances().GetInstances();
   LanguageSet all;
   for (unsigned i = 0; i < instances.size(); ++i)
     all.bitvector |= instances[i].supported_languages.bitvector;
   return all;
 }
 

lldb/source/Expression/REPL.cpp

 
 lldb::REPLSP REPL::Create(Status &err, lldb::LanguageType language,
                           Debugger *debugger, Target *target,
                           const char *repl_options) {
   uint32_t idx = 0;
   lldb::REPLSP ret;
 
   while (REPLCreateInstance create_instance =
-             PluginManager::GetREPLCreateCallbackAtIndex(idx++)) {
+             PluginManager::GetREPLCreateCallbackAtIndex(idx)) {
+    LanguageSet supported_languages =
+        PluginManager::GetREPLSupportedLanguagesAtIndex(idx++);
+    if (!supported_languages[language])
+      continue;
     ret = (*create_instance)(err, language, debugger, target, repl_options);
     if (ret) {
       break;
     }
   }
 
   return ret;
 }

lldb/test/Shell/REPL/Basic.test

+// Basic sanity checking of the REPL.
+
+// RUN: %lldb --repl --repl-language c++ 2>&1 | FileCheck %s --check-prefix=CPP
+// CPP: error: must have a target to create a REPL
+
+// RUN: %lldb --repl --repl-language python 2>&1 | FileCheck %s --check-prefix=PYTHON
+// PYTHON: error: couldn't find a REPL for python
+
+// RUN: not %lldb --repl --repl-language bogus 2>&1 | FileCheck %s --check-prefix=BOGUS
+// BOGUS: error: Unrecognized language name: "bogus"