[clang] [clang] Apply internal buffering to clang diagnostics printing (PR #113440)

[Aaron Ballman via cfe-commits]

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@@ -656,15 +656,19 @@ static bool printWordWrapped(raw_ostream &OS, StringRef Str, unsigned Columns,
 TextDiagnostic::TextDiagnostic(raw_ostream &OS, const LangOptions &LangOpts,
                                DiagnosticOptions *DiagOpts,
                                const Preprocessor *PP)
-    : DiagnosticRenderer(LangOpts, DiagOpts), OS(OS), PP(PP) {}
+    : DiagnosticRenderer(LangOpts, DiagOpts), Out(OS), PP(PP),
+      OS(InternalBuffer) {
+  this->OS.buffer().clear();
+  this->OS.enable_colors(true);
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AaronBallman wrote:

Shouldn't this be looking at `DiagOpts->ShowColors`?

https://github.com/llvm/llvm-project/pull/113440