From 642adc7547023ec17f9c912e631790fa508c9818 Mon Sep 17 00:00:00 2001
From: Mark Benvenuto <mark.benvenuto@mongodb.com>
Date: Fri, 11 Sep 2020 11:33:33 -0400
Subject: SERVER-50036 logd() fails with invalid format string

---
 src/mongo/logv2/logv2_test.cpp      | 12 ++++++++++++
 src/mongo/logv2/plain_formatter.cpp |  9 +++++++++
 2 files changed, 21 insertions(+)

diff --git a/src/mongo/logv2/logv2_test.cpp b/src/mongo/logv2/logv2_test.cpp
index f863c7db555..e6139d964be 100644
--- a/src/mongo/logv2/logv2_test.cpp
+++ b/src/mongo/logv2/logv2_test.cpp
@@ -1769,6 +1769,18 @@ TEST_F(UnstructuredLoggingTest, Args) {
     });
 }
 
+TEST_F(UnstructuredLoggingTest, ArgsLikeFormatSpecifier) {
+    // Ensure the plain formatter does not process the formatted string
+    startCapturingLogMessages();
+
+    std::string format_str = "format {} str {} fields";
+    logd(format_str, 1, "{ x : 1}");  // NOLINT
+    validate([&format_str](const BSONObj& obj) {
+        ASSERT_EQUALS(obj.getField(kMessageFieldName).String(),
+                      fmt::format(format_str, 1, "{ x : 1}"));
+    });
+}
+
 TEST_F(UnstructuredLoggingTest, ManyArgs) {
     std::string format_str = "{}{}{}{}{}{}{}{}{}{}{}";
     logd(format_str, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11);  // NOLINT
diff --git a/src/mongo/logv2/plain_formatter.cpp b/src/mongo/logv2/plain_formatter.cpp
index 0fad5d46b84..de83f01667e 100644
--- a/src/mongo/logv2/plain_formatter.cpp
+++ b/src/mongo/logv2/plain_formatter.cpp
@@ -152,6 +152,15 @@ void PlainFormatter::operator()(boost::log::record_view const& rec,
     StringData message = extract<StringData>(attributes::message(), rec).get();
     const auto& attrs = extract<TypeErasedAttributeStorage>(attributes::attributes(), rec).get();
 
+    // Log messages logged via logd are already formatted and have the id == 0
+    if (attrs.empty()) {
+        if (extract<int32_t>(attributes::id(), rec).get() == 0) {
+            buffer.append(message.rawData(), message.rawData() + message.size());
+
+            return;
+        }
+    }
+
     TextValueExtractor extractor;
     extractor.args.reserve(attrs.size());
     attrs.apply(extractor);
-- 
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