SERVER-40389 small tweaks to third_party/fmt & related.

    Add an option to scons: --use-system-fmt
    import.sh: use the upstream libfmt github repo.
    StringData fmt interop
    noexcept for to_string_view(StringData) hook
    noexcept for StringData's rawData() and size()
    add fmt to THIRD-PARTY-NOTICES + markdown tweaks
    import the fmt LICENSE.rst
    update fmt lib revision

2 files changed, 14 insertions, 2 deletions

diff --git a/src/mongo/base/string_data.h b/src/mongo/base/string_data.h
index ffb7941e7ac..4192ccd60f6 100644
--- a/src/mongo/base/string_data.h
+++ b/src/mongo/base/string_data.h
@@ -36,6 +36,8 @@
 #include <stdexcept>
 #include <string>
 
+#include <fmt/format.h>
+
 #include "mongo/stdx/type_traits.h"
 #define MONGO_INCLUDE_INVARIANT_H_WHITELISTED
 #include "mongo/util/invariant.h"
@@ -166,11 +168,11 @@ public:
      * null-terminated, so if using this without checking size(), you are likely doing
      * something wrong.
      */
-    constexpr const char* rawData() const {
+    constexpr const char* rawData() const noexcept {
         return _data;
     }
 
-    constexpr size_t size() const {
+    constexpr size_t size() const noexcept {
         return _size;
     }
     constexpr bool empty() const {
@@ -352,4 +354,8 @@ inline std::string operator+(StringData lhs, std::string rhs) {
     return rhs;
 }
 
+constexpr fmt::string_view to_string_view(StringData s) noexcept {
+    return fmt::string_view(s.rawData(), s.size());
+}
+
 }  // namespace mongo
diff --git a/src/mongo/base/string_data_test.cpp b/src/mongo/base/string_data_test.cpp
index 3e19a557d8e..a1d9d7d7773 100644
--- a/src/mongo/base/string_data_test.cpp
+++ b/src/mongo/base/string_data_test.cpp
@@ -319,4 +319,10 @@ TEST(ConstIterator, StdReplaceCopy) {
     }
 }
 
+TEST(StringDataFmt, Fmt) {
+    using namespace fmt::literals;
+    ASSERT_EQUALS(fmt::format("-{}-", "abc"_sd), "-abc-");
+    ASSERT_EQUALS("-{}-"_format("abc"_sd), "-abc-");
+}
+
 }  // namespace mongo