[Support] Introduce formatv variant of createStringError (#80493)

Many times I have found myself wanting to create a StringError with the
ability to interpolate a StringRef into the error string. This can be
achieved with:

StringRef Foo("...");
auto Err = createStringError(..., "Something went wrong: %s",
Foo.str().c_str());

However, this requires us to construct a temporary std::string (which
may perform a memory allocation if large enough).

I propose a new variant of `createStringError` called
`createStringErrorV` which uses `formatv` under the hood. This allows
the above example to become:

StringRef Foo("...");
auto Err = createStringErrorV(..., "Something went wrong: {0}", Foo);

1 files changed, 17 insertions, 0 deletions

diff --git a/llvm/unittests/Support/ErrorTest.cpp b/llvm/unittests/Support/ErrorTest.cpp
index 11f9320..a700a50 100644
--- a/llvm/unittests/Support/ErrorTest.cpp
+++ b/llvm/unittests/Support/ErrorTest.cpp
@@ -472,6 +472,23 @@ TEST(Error, createStringError) {
     << "Failed to convert createStringError() result to error_code.";
 }
 
+TEST(Error, createStringErrorV) {
+  static llvm::StringRef Bar("bar");
+  static const std::error_code EC = errc::invalid_argument;
+  std::string Msg;
+  raw_string_ostream S(Msg);
+  logAllUnhandledErrors(createStringErrorV(EC, "foo{0}{1}{2:x}", Bar, 1, 0xff),
+                        S);
+  EXPECT_EQ(S.str(), "foobar10xff\n")
+      << "Unexpected createStringErrorV() log result";
+
+  S.flush();
+  Msg.clear();
+  auto Res = errorToErrorCode(createStringErrorV(EC, "foo{0}", Bar));
+  EXPECT_EQ(Res, EC)
+      << "Failed to convert createStringErrorV() result to error_code.";
+}
+
 // Test that the ExitOnError utility works as expected.
 TEST(ErrorDeathTest, ExitOnError) {
   ExitOnError ExitOnErr;