[clang] [analyzer][NFC] Introduce framework for checker families (PR #139256)

[Balazs Benics via cfe-commits]

================
@@ -484,83 +484,87 @@ class Call {
 
 } // end eval namespace
 
-class CheckerBase : public ProgramPointTag {
-  /// A single checker class (i.e. a subclass of `CheckerBase`) can implement
-  /// multiple user-facing checkers that have separate names and can be enabled
-  /// separately, but are backed by the same singleton checker object.
-  SmallVector<std::optional<CheckerNameRef>, 1> RegisteredNames;
-
-  friend class ::clang::ento::CheckerManager;
+/// A `CheckerFrontend` instance is what the user recognizes as "one checker":
+/// it has a public canonical name (injected from the `CheckerManager`), can be
+/// enabled or disabled, can have associated checker options and can be printed
+/// as the "source" of bug reports.
+/// The singleton instance of a simple `Checker<...>` is-a `CheckerFrontend`
+/// (for historical reasons, to preserve old straightforward code), while the
+/// singleton instance of a `CheckerFamily<...>` class owns multiple
+/// `CheckerFrontend` instances as data members.
+/// Modeling checkers that are hidden from the user but can be enabled or
+/// disabled separately (as dependencies of other checkers) are also considered
+/// to be `CheckerFrontend`s.
+class CheckerFrontend {
+  /// The `Name` is nullopt if and only if the checker is disabled.
+  std::optional<CheckerNameRef> Name;
 
 public:
-  CheckerNameRef getName(CheckerPartIdx Idx = DefaultPart) const {
-    assert(Idx < RegisteredNames.size() && "Checker part index is too large!");
-    std::optional<CheckerNameRef> Name = RegisteredNames[Idx];
-    assert(Name && "Requested checker part is not registered!");
-    return *Name;
-  }
-
-  bool isPartEnabled(CheckerPartIdx Idx) const {
-    return Idx < RegisteredNames.size() && RegisteredNames[Idx].has_value();
-  }
-
-  void registerCheckerPart(CheckerPartIdx Idx, CheckerNameRef Name) {
-    // Paranoia: notice if e.g. UINT_MAX is passed as a checker part index.
-    assert(Idx < 256 && "Checker part identifiers should be small integers.");
-
-    if (Idx >= RegisteredNames.size())
-      RegisteredNames.resize(Idx + 1, std::nullopt);
-
-    assert(!RegisteredNames[Idx] && "Repeated registration of checker a part!");
-    RegisteredNames[Idx] = Name;
-  }
-
-  StringRef getTagDescription() const override {
-    // When the ExplodedGraph is dumped for debugging (in DOT format), this
-    // method is called to attach a description to nodes created by this
-    // checker _class_. Ideally this should be recognizable identifier of the
-    // whole class, but for this debugging purpose it's sufficient to use the
-    // name of the first registered checker part.
-    for (const auto &OptName : RegisteredNames)
-      if (OptName)
-        return *OptName;
-
-    return "Unregistered checker";
+  void enable(CheckerManager &Mgr) {
+    assert(!Name && "Checker part registered twice!");
+    Name = Mgr.getCurrentCheckerName();
   }
+  bool isEnabled() const { return static_cast<bool>(Name); }
----------------
steakhal wrote:

```suggestion
  bool isEnabled() const { return Name.has_value(); }
```

https://github.com/llvm/llvm-project/pull/139256