[clang-tidy] Add clang-additional-diagnostic-* checks that enable clang warnings

Prior to this change to enable additional clang diagnostics, one had to
specify extra arguments on either the command line, or in the config
file.

This meant invocations like `clang-tidy ... -- -Wall`, or `clang-tidy
--extra-arg=-Wall ...` as well as config files like the one below.

```
\# .clang-tidy
Checks: ...
ExtraArgs: ["-Wall"]
```

This patch merges this functionality with the commonly used checks
interface, so the invocation for enabling the `-Wall` flag will look
like `clang-tidy --checks="...,clang-additional-diagnostic-all" ...`.

Author: isuckatcs

clang-tools-extra/clang-tidy/ClangTidy.cpp

@@ -20,6 +20,7 @@
 #include "ClangTidyModuleRegistry.h"
 #include "ClangTidyProfiling.h"
 #include "ExpandModularHeadersPPCallbacks.h"
+#include "GlobList.h"
 #include "clang-tidy-config.h"
 #include "clang/AST/ASTConsumer.h"
 #include "clang/ASTMatchers/ASTMatchFinder.h"
@@ -581,7 +582,32 @@ runClangTidy(clang::tidy::ClangTidyContext &Context,
         return AdjustedArgs;
       };
 
+  // Add extra arguments required by clang-additional-diagnostic-* checks.
+  ArgumentsAdjuster ClangAdditionalDiagnosticArgumentsInserter =
+      [&Context](const CommandLineArguments &Args, StringRef Filename) {
+        ClangTidyOptions Opts = Context.getOptionsForFile(Filename);
+        if (!Opts.Checks)
+          return Args;
+
+        CommandLineArguments AdjustedArgs = Args;
+        CachedGlobList Filter(*Opts.Checks);
+
+        for (StringRef Flag : clang::DiagnosticIDs::getDiagnosticFlags()) {
+          if (Flag.starts_with("-Wno"))
+            continue;
+
+          std::string CheckName = "clang-additional-diagnostic-";
+          CheckName += Flag.drop_front(2);
+
+          if (Filter.contains(CheckName))
+            AdjustedArgs.insert(AdjustedArgs.end(), Flag.str());
+        }
+
+        return AdjustedArgs;
+      };
+
   Tool.appendArgumentsAdjuster(PerFileExtraArgumentsInserter);
+  Tool.appendArgumentsAdjuster(ClangAdditionalDiagnosticArgumentsInserter);
   Tool.appendArgumentsAdjuster(getStripPluginsAdjuster());
   Context.setEnableProfiling(EnableCheckProfile);
   Context.setProfileStoragePrefix(StoreCheckProfile);