Add comment closer to the TextFormat default recursion limit stressing that it is working as intended and will not be changed in the near term.

PiperOrigin-RevId: 908365390

Author: protobuf-github-bot

src/google/protobuf/text_format.cc

@@ -1926,6 +1926,20 @@ MessageFactory* TextFormat::Finder::FindExtensionFactory(
 
 // ===========================================================================
 
+// Note: this value is intentionally unbounded by default. This is due to the
+// use-cases of TextProto primarily being to parse trusted inputs, alongside a
+// strong need to avoid breaking long-standing and working as intended usages
+// parsing messages which exceed depth 100. Use-cases which need to limit this
+// (e.g. anything parsing of untrusted TextProto inputs) must explicitly opt
+// into a limit.
+//
+// At a future date we may consider reducing this default, but we have
+// no concrete plans to do so. PRs proposing to reduce this value to 100
+// unfortunately will not be accepted at this time.
+//
+// See comment on TextFormat class in text_format.h for more info.
+static constexpr int kDefaultRecursionLimit = std::numeric_limits<int>::max();
+
 TextFormat::Parser::Parser()
     : error_collector_(nullptr),
       finder_(nullptr),
@@ -1938,7 +1952,7 @@ TextFormat::Parser::Parser()
       allow_field_number_(false),
       allow_relaxed_whitespace_(false),
       allow_singular_overwrites_(false),
-      recursion_limit_(std::numeric_limits<int>::max()) {}
+      recursion_limit_(kDefaultRecursionLimit) {}
 
 namespace {