[clang] [Format] Fix detection of languages when reading from stdin (PR #79051)

[Ben Hamilton via cfe-commits]

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@@ -547,18 +547,20 @@ static void PrintVersion(raw_ostream &OS) {
 // Dump the configuration.
 static int dumpConfig(bool IsSTDIN) {
   std::unique_ptr<llvm::MemoryBuffer> Code;
-  // We can't read the code to detect the language if there's no file name.
-  if (!IsSTDIN) {
-    // Read in the code in case the filename alone isn't enough to detect the
-    // language.
-    ErrorOr<std::unique_ptr<MemoryBuffer>> CodeOrErr =
-        MemoryBuffer::getFileOrSTDIN(FileNames[0]);
-    if (std::error_code EC = CodeOrErr.getError()) {
-      llvm::errs() << EC.message() << "\n";
-      return 1;
-    }
-    Code = std::move(CodeOrErr.get());
+
+  // FileNames should have at least "-" in it even if no file was specified.
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bhamiltoncx wrote:

OK, changed to "must".

https://github.com/llvm/llvm-project/pull/79051