[clang] [clang-tools-extra] [llvm] [clang] Introduce diagnostics suppression mappings (PR #112517)

[Boaz Brickner via cfe-commits]

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@@ -477,6 +485,100 @@ void DiagnosticsEngine::setSeverityForAll(diag::Flavor Flavor,
       setSeverity(Diag, Map, Loc);
 }
 
+namespace {
+class WarningsSpecialCaseList : public llvm::SpecialCaseList {
+public:
+  static std::unique_ptr<WarningsSpecialCaseList>
+  create(const llvm::MemoryBuffer &MB, std::string &Err) {
+    auto SCL = std::make_unique<WarningsSpecialCaseList>();
+    if (SCL->createInternal(&MB, Err))
+      return SCL;
+    return nullptr;
+  }
+
+  // Section names refer to diagnostic groups, which cover multiple individual
+  // diagnostics. Expand diagnostic groups here to individual diagnostics.
+  // A diagnostic can have multiple diagnostic groups associated with it, we let
+  // the last section take precedence in such cases.
+  void processSections(DiagnosticsEngine &Diags) {
+    // Drop the default section introduced by special case list, we only support
+    // exact diagnostic group names.
+    Sections.erase("*");
+    // Make sure we iterate sections by their line numbers.
+    std::vector<std::pair<unsigned, const llvm::StringMapEntry<Section> *>>
+        LineAndSection;
+    for (const auto &Entry : Sections) {
+      LineAndSection.emplace_back(
+          Entry.second.SectionMatcher->Globs.at(Entry.first()).second, &Entry);
+    }
+    llvm::sort(LineAndSection);
+    static constexpr auto kFlavor = clang::diag::Flavor::WarningOrError;
+    for (const auto &[_, Entry] : LineAndSection) {
+      SmallVector<diag::kind, 256> GroupDiags;
+      if (Diags.getDiagnosticIDs()->getDiagnosticsInGroup(
+              kFlavor, Entry->first(), GroupDiags)) {
+        StringRef Suggestion =
+            DiagnosticIDs::getNearestOption(kFlavor, Entry->first());
+        Diags.Report(diag::warn_unknown_diag_option)
+            << static_cast<unsigned>(kFlavor) << Entry->first()
+            << !Suggestion.empty() << Suggestion;
+        continue;
+      }
+      for (auto D : GroupDiags)
+        DiagToSection[D] = &Entry->getValue();
+    }
+  }
+
+  bool isDiagSuppressed(diag::kind D, llvm::StringRef FilePath) const {
+    auto Section = DiagToSection.find(D);
+    if (Section == DiagToSection.end())
+      return false;
+    auto SrcEntries = Section->second->Entries.find("src");
+    if (SrcEntries == Section->second->Entries.end())
+      return false;
+    // Find the longest glob pattern that matches FilePath. A positive match
+    // implies D should be suppressed for FilePath.
+    llvm::StringRef LongestMatch;
+    bool LongestWasNegative;
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bricknerb wrote:

Initialize.

https://github.com/llvm/llvm-project/pull/112517