[lldb] Let languages see all SymbolContexts at once when filtering breakpoints (#129937)

This allows languages to make decisions based on the whole set of symbol
contexts, giving them strictly more power than when they are only
allowed to see one at a time.

Author: felipepiovezan

lldb/include/lldb/Target/Language.h

@@ -354,14 +354,13 @@ class Language : public PluginInterface {
 
   virtual llvm::StringRef GetInstanceVariableName() { return {}; }
 
-  /// Returns true if this SymbolContext should be ignored when setting
-  /// breakpoints by line (number or regex). Helpful for languages that create
-  /// artificial functions without meaningful user code associated with them
-  /// (e.g. code that gets expanded in late compilation stages, like by
-  /// CoroSplitter).
-  virtual bool IgnoreForLineBreakpoints(const SymbolContext &) const {
-    return false;
-  }
+  /// Given a symbol context list of matches which supposedly represent the
+  /// same file and line number in a CU, erases those that should be ignored
+  /// when setting breakpoints by line (number or regex). Helpful for languages
+  /// that create split a single source-line into many functions (e.g. call
+  /// sites transformed by CoroSplitter).
+  virtual void
+  FilterForLineBreakpoints(llvm::SmallVectorImpl<SymbolContext> &) const {}
 
   /// Returns a boolean indicating whether two symbol contexts are equal for the
   /// purposes of frame comparison. If the plugin has no opinion, it should

lldb/source/Breakpoint/BreakpointResolver.cpp

@@ -207,16 +207,15 @@ bool operator<(const SourceLoc lhs, const SourceLoc rhs) {
 void BreakpointResolver::SetSCMatchesByLine(
     SearchFilter &filter, SymbolContextList &sc_list, bool skip_prologue,
     llvm::StringRef log_ident, uint32_t line, std::optional<uint16_t> column) {
-  llvm::SmallVector<SymbolContext, 16> all_scs;
-
-  for (const auto &sc : sc_list) {
-    if (Language::GetGlobalLanguageProperties()
-            .GetEnableFilterForLineBreakpoints())
-      if (Language *lang = Language::FindPlugin(sc.GetLanguage());
-          lang && lang->IgnoreForLineBreakpoints(sc))
-        continue;
-    all_scs.push_back(sc);
-  }
+  llvm::SmallVector<SymbolContext, 16> all_scs(sc_list.begin(), sc_list.end());
+
+  // Let the language plugin filter `sc_list`. Because all symbol contexts in
+  // sc_list are assumed to belong to the same File, Line and CU, the code below
+  // assumes they have the same language.
+  if (!sc_list.IsEmpty() && Language::GetGlobalLanguageProperties()
+                                .GetEnableFilterForLineBreakpoints())
+    if (Language *lang = Language::FindPlugin(sc_list[0].GetLanguage()))
+      lang->FilterForLineBreakpoints(all_scs);
 
   while (all_scs.size()) {
     uint32_t closest_line = UINT32_MAX;