fix: UserErrors leave json_parse in an invalid state

Summary:
When json_parse throws a user error and it's not wrapped in a try, if that exception is caught
outside expression evaluation and the ExprSet attempts to be reused, the json_parse function
may be in an invalid state and will throw a runtime exception.

This was exposed in ExpressionFuzzer after 
facebookincubator#12281 was landed.

This fix is to clear the state whenever we see a UserException after calling parse whether or not 
the function is wrapped in a try.

Differential Revision: D69473523

velox/functions/prestosql/JsonFunctions.cpp

@@ -171,12 +171,15 @@ class JsonParseFunction : public exec::VectorFunction {
 
         if (auto error = parse(size, needNormalize)) {
           context.setErrors(rows, errors_[error]);
+          clearState();
           return;
         }
         auto* output = buffer->asMutable<char>();
         auto outputSize = concatViews(views_, output);
         rawStringViews[0] = StringView(output, outputSize);
       } catch (const VeloxException& e) {
+        clearState();
+
         if (!e.isUserError()) {
           throw;
         }
@@ -256,6 +259,8 @@ class JsonParseFunction : public exec::VectorFunction {
             output += outputSize;
           }
         } catch (const VeloxException& e) {
+          clearState();
+
           if (!e.isUserError()) {
             throw;
           }
@@ -264,8 +269,6 @@ class JsonParseFunction : public exec::VectorFunction {
 
           FB_LOG_EVERY_MS(WARNING, 1000)
               << "Caught user error in json_parse: " << e.message();
-
-          clearState();
         }
       });
 

velox/functions/prestosql/tests/JsonFunctionsTest.cpp

@@ -376,17 +376,17 @@ TEST_F(JsonFunctionsTest, jsonParse) {
 
   // Test try with invalid escape sequence.
   {
-    auto data = makeRowVector({makeFlatVector<StringView>({
+    data = makeRowVector({makeFlatVector<StringView>({
         // The logic for sorting keys checks the validity of escape sequences
         // and will throw a user error in this case.
         "{\"k\\i\":\"abc\",\"k2\":\"xyz\"}", // invalid json
         // Add a second value to ensure the state is cleared.
         R"([{"k1": "v1" }, {"k2": "v2" }])" // valid json
     })});
 
-    auto result = evaluate("try(json_parse(c0))", data);
+    result = evaluate("try(json_parse(c0))", data);
 
-    auto expected = makeNullableFlatVector<StringView>(
+    expected = makeNullableFlatVector<StringView>(
         {std::nullopt, R"([{"k1":"v1"},{"k2":"v2"}])"}, JSON());
 
     velox::test::assertEqualVectors(expected, result);
@@ -395,16 +395,70 @@ TEST_F(JsonFunctionsTest, jsonParse) {
   // Test try with invalid escape sequence going through fast path for
   // constants.
   {
-    auto data =
+    data =
         makeRowVector({makeConstant("{\"k\\i\":\"abc\",\"k2\":\"xyz\"}", 3)});
 
-    auto result = evaluate("try(json_parse(c0))", data);
+    result = evaluate("try(json_parse(c0))", data);
 
-    auto expected = makeNullableFlatVector<StringView>(
+    expected = makeNullableFlatVector<StringView>(
         {std::nullopt, std::nullopt, std::nullopt}, JSON());
 
     velox::test::assertEqualVectors(expected, result);
   }
+
+  // Test reusing ExprSet after user exception thrown.
+  {
+    // A batch with an invalid value that will throw a user error.
+    auto data1 = makeRowVector(
+        {makeConstant(R"({\"k\\i\":\"abc\",\"k2\":\"xyz\u4FE\"})", 3)});
+
+    // A batch with valid values.
+    auto data2 = makeRowVector({makeFlatVector<StringView>(
+        {R"([{"k1": "v1" }, {"k2": "v2" }])",
+         R"([{"k3": "v3" }, {"k4": "v4" }])"})});
+
+    auto typedExpr = makeTypedExpr("json_parse(c0)", asRowType(data1->type()));
+    exec::ExprSet exprSet({typedExpr}, &execCtx_);
+
+    VELOX_ASSERT_USER_THROW(evaluate(exprSet, data1), "Invalid escape digit");
+
+    expected = makeNullableFlatVector<StringView>(
+        {R"([{"k1":"v1"},{"k2":"v2"}])", R"([{"k3":"v3"},{"k4":"v4"}])"},
+        JSON());
+
+    result = evaluate(exprSet, data2);
+    velox::test::assertEqualVectors(expected, result);
+  }
+
+  // Test reusing ExprSet after user exception thrown in fast path for
+  // constants.
+  {
+    // A batch with an invalid value that will throw a user error.
+    auto data1 = makeRowVector({makeFlatVector<StringView>({
+        // The logic for sorting keys checks the validity of escape sequences
+        // and will throw a user error if unicode sequences are invalid.
+        R"({"k\\i":"abc","k2":"xyz\u4FE"})", // invalid json
+        // Add a second value to ensure the state is cleared.
+        R"([{"k1": "v1" }, {"k2": "v2" }])" // valid json
+    })});
+
+    // A batch with valid values.
+    auto data2 = makeRowVector({makeFlatVector<StringView>(
+        {R"([{"k1": "v1" }, {"k2": "v2" }])",
+         R"([{"k3": "v3" }, {"k4": "v4" }])"})});
+
+    auto typedExpr = makeTypedExpr("json_parse(c0)", asRowType(data1->type()));
+    exec::ExprSet exprSet({typedExpr}, &execCtx_);
+
+    VELOX_ASSERT_USER_THROW(evaluate(exprSet, data1), "Invalid escape digit");
+
+    expected = makeNullableFlatVector<StringView>(
+        {R"([{"k1":"v1"},{"k2":"v2"}])", R"([{"k3":"v3"},{"k4":"v4"}])"},
+        JSON());
+
+    result = evaluate(exprSet, data2);
+    velox::test::assertEqualVectors(expected, result);
+  }
 }
 
 TEST_F(JsonFunctionsTest, canonicalization) {