Firestore: Add more details to the assertion failure in OrderBy::Compare() (#9305)

Author: dconeybe

Firestore/CHANGELOG.md

@@ -1,3 +1,7 @@
+# Unreleased
+- [changed] Add more details to the assertion failure in OrderBy::Compare() to
+  help with future debugging (#9258).
+
 # v8.12.0
 - [fixed] Fixed an AppCheck issue that caused Firestore listeners to stop
 working and receive a "Permission Denied" error. This issue only occurred for

Firestore/core/src/core/order_by.cc

@@ -17,6 +17,7 @@
 #include "Firestore/core/src/core/order_by.h"
 
 #include <ostream>
+#include <sstream>
 
 #include "Firestore/core/src/model/document.h"
 #include "Firestore/core/src/model/value_util.h"
@@ -31,6 +32,38 @@ using model::Document;
 using model::FieldPath;
 using util::ComparisonResult;
 
+namespace {
+
+void AssertBothOptionalsHaveValues(
+    const model::FieldPath& field_path,
+    const absl::optional<google_firestore_v1_Value>& value1,
+    const absl::optional<google_firestore_v1_Value>& value2,
+    const Document& lhs,
+    const Document& rhs) {
+  if (value1.has_value() && value2.has_value()) {
+    return;
+  }
+
+  std::ostringstream ss;
+  ss << "Trying to compare documents on fields that don't exist;"
+     << " field_path=" << field_path.CanonicalString()
+     << ", lhs=" << lhs->key().ToString() << ", rhs=" << rhs->key().ToString()
+     << ", value1.has_value()=" << (value1.has_value() ? "true" : "false")
+     << ", value2.has_value()=" << (value2.has_value() ? "true" : "false");
+
+  if (value1.has_value()) {
+    ss << ", value1=" << value1->ToString();
+  }
+  if (value2.has_value()) {
+    ss << ", value2=" << value2->ToString();
+  }
+
+  std::string message = ss.str();
+  HARD_FAIL(message.c_str());
+}
+
+}  // namespace
+
 ComparisonResult OrderBy::Compare(const Document& lhs,
                                   const Document& rhs) const {
   ComparisonResult result;
@@ -39,8 +72,7 @@ ComparisonResult OrderBy::Compare(const Document& lhs,
   } else {
     absl::optional<google_firestore_v1_Value> value1 = lhs->field(field_);
     absl::optional<google_firestore_v1_Value> value2 = rhs->field(field_);
-    HARD_ASSERT(value1.has_value() && value2.has_value(),
-                "Trying to compare documents on fields that don't exist.");
+    AssertBothOptionalsHaveValues(field_, value1, value2, lhs, rhs);
     result = model::Compare(*value1, *value2);
   }