[clang] [clang] [diagnostics] Add `-fdiagnostics-add-output` switch for SARIF (PR #185201)

[Balázs Benics via cfe-commits]

================
@@ -439,10 +439,26 @@ json::Object SarifDocumentWriter::createDocument() {
   endRun();
 
   json::Object Doc{
-      {"$schema", SchemaURI},
-      {"version", SchemaVersion},
+      {"$schema", Version.SchemaURI},
+      {"version", Version.SchemaVersion},
   };
   if (!Runs.empty())
     Doc["runs"] = json::Array(Runs);
   return Doc;
 }
+
+ArrayRef<SarifVersion> SarifDocumentWriter::getSupportedVersions() {
+  static const SarifVersion Versions[] = {
+      {"2.1.0", "2.1",
+       "https://docs.oasis-open.org/sarif/sarif/v2.1.0/cos02/schemas/"
+       "sarif-schema-2.1.0.json",
+       true}};
+
+  return Versions;
+}
+
+const SarifVersion &SarifDocumentWriter::getDefaultVersion() {
+  const auto Versions = getSupportedVersions();
+  return *std::find_if(Versions.begin(), Versions.end(),
+                       [](const SarifVersion &V) { return V.IsDefault; });
+}
----------------
steakhal wrote:

For a moment I was thinking if we should enforce that only a single entry can have IsDefault=true;
That could be achieved by using:
```c++
const SarifVersion &getDefaultVersion() {
  return *llvm::find_singleton<SarifVersion>(
      getSupportedVersions(), std::mem_fn(&SarifVersion::IsDefault));
}
```

https://github.com/llvm/llvm-project/pull/185201