[lldb][NFC] Add unit test for persistent variable lookup with ClangExpressionDeclMap

This adds a unit test for looking up persistent declarations in the scratch AST
context. Also adds the `GetPersistentDecl` hook to the ClangExpressionDeclMap
that this unit test can emulate looking up persistent variables without having
a lldb_private::Target.

2 files changed, 26 insertions, 10 deletions

diff --git a/lldb/source/Plugins/ExpressionParser/Clang/ClangExpressionDeclMap.cpp b/lldb/source/Plugins/ExpressionParser/Clang/ClangExpressionDeclMap.cpp
index 33867fb4d45..23202766892 100644
--- a/lldb/source/Plugins/ExpressionParser/Clang/ClangExpressionDeclMap.cpp
+++ b/lldb/source/Plugins/ExpressionParser/Clang/ClangExpressionDeclMap.cpp
@@ -734,29 +734,33 @@ void ClangExpressionDeclMap::MaybeRegisterFunctionBody(
   }
 }
 
-void ClangExpressionDeclMap::SearchPersistenDecls(NameSearchContext &context,
-                                                  const ConstString name,
-                                                  unsigned int current_id) {
-  Log *log(lldb_private::GetLogIfAllCategoriesSet(LIBLLDB_LOG_EXPRESSIONS));
+clang::NamedDecl *ClangExpressionDeclMap::GetPersistentDecl(ConstString name) {
   if (!m_parser_vars)
-    return;
+    return nullptr;
   Target *target = m_parser_vars->m_exe_ctx.GetTargetPtr();
   if (!target)
-    return;
+    return nullptr;
 
   ClangASTContext *scratch_clang_ast_context =
       ClangASTContext::GetScratch(*target);
 
   if (!scratch_clang_ast_context)
-    return;
+    return nullptr;
 
   ASTContext *scratch_ast_context = scratch_clang_ast_context->getASTContext();
 
   if (!scratch_ast_context)
-    return;
+    return nullptr;
+
+  return m_parser_vars->m_persistent_vars->GetPersistentDecl(name);
+}
+
+void ClangExpressionDeclMap::SearchPersistenDecls(NameSearchContext &context,
+                                                  const ConstString name,
+                                                  unsigned int current_id) {
+  Log *log(lldb_private::GetLogIfAllCategoriesSet(LIBLLDB_LOG_EXPRESSIONS));
 
-  NamedDecl *persistent_decl =
-      m_parser_vars->m_persistent_vars->GetPersistentDecl(name);
+  NamedDecl *persistent_decl = GetPersistentDecl(name);
 
   if (!persistent_decl)
     return;
@@ -1409,6 +1413,10 @@ void ClangExpressionDeclMap::FindExternalVisibleDecls(
     if (name.GetStringRef().startswith("$__lldb"))
       return;
 
+    // No ParserVars means we can't do register or variable lookup.
+    if (!m_parser_vars)
+      return;
+
     ExpressionVariableSP pvar_sp(
         m_parser_vars->m_persistent_vars->GetVariable(name));
 
diff --git a/lldb/source/Plugins/ExpressionParser/Clang/ClangExpressionDeclMap.h b/lldb/source/Plugins/ExpressionParser/Clang/ClangExpressionDeclMap.h
index 223fd320109..41e41c1f1fe 100644
--- a/lldb/source/Plugins/ExpressionParser/Clang/ClangExpressionDeclMap.h
+++ b/lldb/source/Plugins/ExpressionParser/Clang/ClangExpressionDeclMap.h
@@ -283,6 +283,14 @@ public:
                                 CompilerDeclContext &namespace_decl,
                                 unsigned int current_id);
 
+protected:
+  /// Retrieves the declaration with the given name from the storage of
+  /// persistent declarations.
+  ///
+  /// \return
+  ///     A persistent decl with the given name or a nullptr.
+  virtual clang::NamedDecl *GetPersistentDecl(ConstString name);
+
 private:
   ExpressionVariableList
       m_found_entities; ///< All entities that were looked up for the parser.