test: Add an RAII class to manage the env.parseFailureExpected flag (#7669)

src/test/app/Batch_test.cpp

@@ -498,7 +498,7 @@ class Batch_test : public beast::unit_test::Suite
             auto const batchFee = batch::calcBatchFee(env, 0, 2);
             auto tx1 = batch::Inner(pay(alice, bob, XRP(1)), seq + 1);
             tx1[jss::Fee] = "1.5";
-            env.setParseFailureExpected(true);
+            auto const g = env.getParseFailureGuard(true);
             try
             {
                 env(batch::outer(alice, seq, batchFee, tfAllOrNothing),
@@ -510,7 +510,6 @@ class Batch_test : public beast::unit_test::Suite
             {
                 BEAST_EXPECT(true);
             }
-            env.setParseFailureExpected(false);
         }
 
         // temSEQ_AND_TICKET: Batch: inner txn cannot have both Sequence

src/test/app/Vault_test.cpp

@@ -5524,9 +5524,9 @@ class Vault_test : public beast::unit_test::Suite
             env.close();
 
             // 2. Mantissa larger than uint64 max
-            env.setParseFailureExpected(true);
             try
             {
+                auto const g = env.getParseFailureGuard(true);
                 tx[sfAssetsMaximum] = "18446744073709551617e5";  // uint64 max + 1
                 env(tx);
                 BEAST_EXPECTS(false, "Expected parse_error for mantissa larger than uint64 max");
@@ -5537,7 +5537,6 @@ class Vault_test : public beast::unit_test::Suite
                 BEAST_EXPECT(
                     e.what() == "invalidParamsField 'tx_json.AssetsMaximum' has invalid data."s);
             }
-            env.setParseFailureExpected(false);
         }
     }
 

src/test/jtx/Env.h

@@ -514,6 +514,49 @@ public:
         parseFailureExpected_ = b;
     }
 
+    /**
+     * RAII class to set and restore the parse failure flag (setParseFailureExpected).
+     *
+     * Can be created directly, or through the `getParseFailureGuard(bool)` function.
+     */
+    class ParseFailureGuard final
+    {
+        Env& self_;
+        bool const oldExpected_;
+
+    public:
+        ParseFailureGuard(Env& self, bool b)
+            : self_(self), oldExpected_(self_.parseFailureExpected_)
+        {
+            self_.setParseFailureExpected(b);
+        }
+
+        ~ParseFailureGuard()
+        {
+            self_.setParseFailureExpected(oldExpected_);
+        }
+
+        // No copy, no move
+        ParseFailureGuard(ParseFailureGuard const&) = delete;
+        ParseFailureGuard&
+        operator=(ParseFailureGuard const&) = delete;
+        ParseFailureGuard(ParseFailureGuard&& other) = delete;
+        ParseFailureGuard&
+        operator=(ParseFailureGuard&&) = delete;
+    };
+
+    /**
+     * Gets an RAII guard to set and restore the parse failure flag
+     *
+     * Usage:
+     * auto const guard = env.getParseFailureGuard(true/false);
+     */
+    [[nodiscard]] ParseFailureGuard
+    getParseFailureGuard(bool b)
+    {
+        return ParseFailureGuard{*this, b};
+    }
+
     /**
      * Turn off signature checks.
      */

src/test/jtx/impl/Env.cpp

@@ -629,7 +629,7 @@ Env::autofill(JTx& jt)
     catch (ParseError const&)
     {
         if (!parseFailureExpected_)
-            test.log << "parse failed:\n" << pretty(jv) << std::endl;
+            test.log << "parse failure:\n" << pretty(jv) << std::endl;
         rethrow();
     }
 }