SERVER-32736: Add "onError" and "onNull" options to $dateFromString

3 files changed, 355 insertions, 45 deletions

diff --git a/src/mongo/db/pipeline/expression.cpp b/src/mongo/db/pipeline/expression.cpp
index 3db514b5222..f679616e720 100644
--- a/src/mongo/db/pipeline/expression.cpp
+++ b/src/mongo/db/pipeline/expression.cpp
@@ -1279,9 +1279,7 @@ intrusive_ptr<Expression> ExpressionDateFromString::parse(
                           << typeName(expr.type()),
             expr.type() == BSONType::Object);
 
-    BSONElement dateStringElem;
-    BSONElement timeZoneElem;
-    BSONElement formatElem;
+    BSONElement dateStringElem, timeZoneElem, formatElem, onNullElem, onErrorElem;
 
     const BSONObj args = expr.embeddedObject();
     for (auto&& arg : args) {
@@ -1293,6 +1291,10 @@ intrusive_ptr<Expression> ExpressionDateFromString::parse(
             dateStringElem = arg;
         } else if (field == "timezone"_sd) {
             timeZoneElem = arg;
+        } else if (field == "onNull"_sd) {
+            onNullElem = arg;
+        } else if (field == "onError"_sd) {
+            onErrorElem = arg;
         } else {
             uasserted(40541,
                       str::stream() << "Unrecognized argument to $dateFromString: "
@@ -1306,29 +1308,45 @@ intrusive_ptr<Expression> ExpressionDateFromString::parse(
         expCtx,
         parseOperand(expCtx, dateStringElem, vps),
         timeZoneElem ? parseOperand(expCtx, timeZoneElem, vps) : nullptr,
-        formatElem ? parseOperand(expCtx, formatElem, vps) : nullptr);
+        formatElem ? parseOperand(expCtx, formatElem, vps) : nullptr,
+        onNullElem ? parseOperand(expCtx, onNullElem, vps) : nullptr,
+        onErrorElem ? parseOperand(expCtx, onErrorElem, vps) : nullptr);
 }
 
 ExpressionDateFromString::ExpressionDateFromString(
     const boost::intrusive_ptr<ExpressionContext>& expCtx,
     intrusive_ptr<Expression> dateString,
     intrusive_ptr<Expression> timeZone,
-    intrusive_ptr<Expression> format)
+    intrusive_ptr<Expression> format,
+    intrusive_ptr<Expression> onNull,
+    intrusive_ptr<Expression> onError)
     : Expression(expCtx),
       _dateString(std::move(dateString)),
       _timeZone(std::move(timeZone)),
-      _format(std::move(format)) {}
+      _format(std::move(format)),
+      _onNull(std::move(onNull)),
+      _onError(std::move(onError)) {}
 
 intrusive_ptr<Expression> ExpressionDateFromString::optimize() {
     _dateString = _dateString->optimize();
     if (_timeZone) {
         _timeZone = _timeZone->optimize();
     }
+
     if (_format) {
         _format = _format->optimize();
     }
 
-    if (ExpressionConstant::allNullOrConstant({_dateString, _timeZone, _format})) {
+    if (_onNull) {
+        _onNull = _onNull->optimize();
+    }
+
+    if (_onError) {
+        _onError = _onError->optimize();
+    }
+
+    if (ExpressionConstant::allNullOrConstant(
+            {_dateString, _timeZone, _format, _onNull, _onError})) {
         // Everything is a constant, so we can turn into a constant.
         return ExpressionConstant::create(getExpressionContext(), evaluate(Document{}));
     }
@@ -1340,48 +1358,71 @@ Value ExpressionDateFromString::serialize(bool explain) const {
         Document{{"$dateFromString",
                   Document{{"dateString", _dateString->serialize(explain)},
                            {"timezone", _timeZone ? _timeZone->serialize(explain) : Value()},
-                           {"format", _format ? _format->serialize(explain) : Value()}}}});
+                           {"format", _format ? _format->serialize(explain) : Value()},
+                           {"onNull", _onNull ? _onNull->serialize(explain) : Value()},
+                           {"onError", _onError ? _onError->serialize(explain) : Value()}}}});
 }
 
 Value ExpressionDateFromString::evaluate(const Document& root) const {
     const Value dateString = _dateString->evaluate(root);
+    Value formatValue;
+
+    // Eagerly validate the format parameter, ignoring if nullish since the input string nullish
+    // behavior takes precedence.
+    if (_format) {
+        formatValue = _format->evaluate(root);
+        if (!formatValue.nullish()) {
+            uassert(40684,
+                    str::stream() << "$dateFromString requires that 'format' be a string, found: "
+                                  << typeName(formatValue.getType())
+                                  << " with value "
+                                  << formatValue.toString(),
+                    formatValue.getType() == BSONType::String);
+
+            TimeZone::validateFromStringFormat(formatValue.getStringData());
+        }
+    }
 
+    // Evaluate the timezone parameter before checking for nullish input, as this will throw an
+    // exception for an invalid timezone string.
     auto timeZone = makeTimeZone(getExpressionContext()->timeZoneDatabase, root, _timeZone.get());
 
-    if (!timeZone || dateString.nullish()) {
-        return Value(BSONNULL);
+    // Behavior for nullish input takes precedence over other nullish elements.
+    if (dateString.nullish()) {
+        return _onNull ? _onNull->evaluate(root) : Value(BSONNULL);
     }
 
-    uassert(40543,
-            str::stream() << "$dateFromString requires that 'dateString' be a string, found: "
-                          << typeName(dateString.getType())
-                          << " with value "
-                          << dateString.toString(),
-            dateString.getType() == BSONType::String);
-    const auto& dateTimeString = dateString.getStringData();
+    try {
+        uassert(ErrorCodes::ConversionFailure,
+                str::stream() << "$dateFromString requires that 'dateString' be a string, found: "
+                              << typeName(dateString.getType())
+                              << " with value "
+                              << dateString.toString(),
+                dateString.getType() == BSONType::String);
 
-    if (_format) {
-        const Value format = _format->evaluate(root);
+        const auto dateTimeString = dateString.getStringData();
 
-        if (format.nullish()) {
+        if (!timeZone) {
             return Value(BSONNULL);
         }
 
-        uassert(40684,
-                str::stream() << "$dateFromString requires that 'format' be a string, found: "
-                              << typeName(format.getType())
-                              << " with value "
-                              << format.toString(),
-                format.getType() == BSONType::String);
-        const auto& formatString = format.getStringData();
+        if (_format) {
+            if (formatValue.nullish()) {
+                return Value(BSONNULL);
+            }
 
-        TimeZone::validateFromStringFormat(formatString);
+            return Value(getExpressionContext()->timeZoneDatabase->fromString(
+                dateTimeString, timeZone, formatValue.getStringData()));
+        }
 
-        return Value(getExpressionContext()->timeZoneDatabase->fromString(
-            dateTimeString, timeZone, formatString));
+        return Value(
+            getExpressionContext()->timeZoneDatabase->fromString(dateTimeString, timeZone));
+    } catch (const ExceptionFor<ErrorCodes::ConversionFailure>&) {
+        if (_onError) {
+            return _onError->evaluate(root);
+        }
+        throw;
     }
-
-    return Value(getExpressionContext()->timeZoneDatabase->fromString(dateTimeString, timeZone));
 }
 
 void ExpressionDateFromString::_doAddDependencies(DepsTracker* deps) const {
@@ -1389,9 +1430,18 @@ void ExpressionDateFromString::_doAddDependencies(DepsTracker* deps) const {
     if (_timeZone) {
         _timeZone->addDependencies(deps);
     }
+
     if (_format) {
         _format->addDependencies(deps);
     }
+
+    if (_onNull) {
+        _onNull->addDependencies(deps);
+    }
+
+    if (_onError) {
+        _onError->addDependencies(deps);
+    }
 }
 
 /* ---------------------- ExpressionDateToParts ----------------------- */
diff --git a/src/mongo/db/pipeline/expression.h b/src/mongo/db/pipeline/expression.h
index 7f843caffcc..b70457cc06f 100644
--- a/src/mongo/db/pipeline/expression.h
+++ b/src/mongo/db/pipeline/expression.h
@@ -874,11 +874,15 @@ private:
     ExpressionDateFromString(const boost::intrusive_ptr<ExpressionContext>& expCtx,
                              boost::intrusive_ptr<Expression> dateString,
                              boost::intrusive_ptr<Expression> timeZone,
-                             boost::intrusive_ptr<Expression> format);
+                             boost::intrusive_ptr<Expression> format,
+                             boost::intrusive_ptr<Expression> onNull,
+                             boost::intrusive_ptr<Expression> onError);
 
     boost::intrusive_ptr<Expression> _dateString;
     boost::intrusive_ptr<Expression> _timeZone;
     boost::intrusive_ptr<Expression> _format;
+    boost::intrusive_ptr<Expression> _onNull;
+    boost::intrusive_ptr<Expression> _onError;
 };
 
 class ExpressionDateFromParts final : public Expression {
diff --git a/src/mongo/db/pipeline/expression_date_test.cpp b/src/mongo/db/pipeline/expression_date_test.cpp
index bfe72aefa3b..fbceb9c5349 100644
--- a/src/mongo/db/pipeline/expression_date_test.cpp
+++ b/src/mongo/db/pipeline/expression_date_test.cpp
@@ -772,11 +772,34 @@ TEST_F(ExpressionDateFromStringTest, SerializesToObjectSyntax) {
 
     ASSERT_VALUE_EQ(dateExp->serialize(true), expectedSerialization);
     ASSERT_VALUE_EQ(dateExp->serialize(false), expectedSerialization);
+
+    spec = BSON("$dateFromString" << BSON("dateString"
+                                          << "2017-07-04T13:06:44Z"
+                                          << "timezone"
+                                          << "Europe/London"
+                                          << "format"
+                                          << "%Y-%d-%mT%H:%M:%S"
+                                          << "onNull"
+                                          << "nullDefault"
+                                          << "onError"
+                                          << "errorDefault"));
+    dateExp = Expression::parseExpression(expCtx, spec, expCtx->variablesParseState);
+    expectedSerialization =
+        Value(Document{{"$dateFromString",
+                        Document{{"dateString", Document{{"$const", "2017-07-04T13:06:44Z"_sd}}},
+                                 {"timezone", Document{{"$const", "Europe/London"_sd}}},
+                                 {"format", Document{{"$const", "%Y-%d-%mT%H:%M:%S"_sd}}},
+                                 {"onNull", Document{{"$const", "nullDefault"_sd}}},
+                                 {"onError", Document{{"$const", "errorDefault"_sd}}}}}});
+
+    ASSERT_VALUE_EQ(dateExp->serialize(true), expectedSerialization);
+    ASSERT_VALUE_EQ(dateExp->serialize(false), expectedSerialization);
 }
 
 TEST_F(ExpressionDateFromStringTest, OptimizesToConstantIfAllInputsAreConstant) {
     auto expCtx = getExpCtx();
-    // Test that it becomes a constant with just the dateString.
+
+    // Test that it becomes a constant if all parameters evaluate to a constant value.
     auto spec = BSON("$dateFromString" << BSON("dateString"
                                                << "2017-07-04T13:09:57Z"));
     auto dateExp = Expression::parseExpression(expCtx, spec, expCtx->variablesParseState);
@@ -785,7 +808,6 @@ TEST_F(ExpressionDateFromStringTest, OptimizesToConstantIfAllInputsAreConstant)
     Date_t dateVal = Date_t::fromMillisSinceEpoch(1499173797000);
     ASSERT_VALUE_EQ(Value(dateVal), dateExp->evaluate(Document{}));
 
-    // Test that it becomes a constant with the dateString and timezone being a constant.
     spec = BSON("$dateFromString" << BSON("dateString"
                                           << "2017-07-04T13:09:57"
                                           << "timezone"
@@ -806,6 +828,29 @@ TEST_F(ExpressionDateFromStringTest, OptimizesToConstantIfAllInputsAreConstant)
     dateVal = Date_t::fromMillisSinceEpoch(1499170197000);
     ASSERT_VALUE_EQ(Value(dateVal), dateExp->evaluate(Document{}));
 
+    spec = BSON("$dateFromString" << BSON("dateString"
+                                          << "2017-07-04T13:09:57"
+                                          << "onNull"
+                                          << "Null default"));
+    dateExp = Expression::parseExpression(expCtx, spec, expCtx->variablesParseState);
+    ASSERT(dynamic_cast<ExpressionConstant*>(dateExp->optimize().get()));
+
+    spec = BSON("$dateFromString" << BSON("dateString"
+                                          << "2017-07-04T13:09:57"
+                                          << "onError"
+                                          << "Error default"));
+    dateExp = Expression::parseExpression(expCtx, spec, expCtx->variablesParseState);
+    ASSERT(dynamic_cast<ExpressionConstant*>(dateExp->optimize().get()));
+
+    spec = BSON("$dateFromString" << BSON("dateString"
+                                          << "2017-07-04T13:09:57"
+                                          << "onError"
+                                          << "Error default"
+                                          << "onNull"
+                                          << "null default"));
+    dateExp = Expression::parseExpression(expCtx, spec, expCtx->variablesParseState);
+    ASSERT(dynamic_cast<ExpressionConstant*>(dateExp->optimize().get()));
+
     // Test that it does *not* become a constant if dateString is not a constant.
     spec = BSON("$dateFromString" << BSON("dateString"
                                           << "$date"));
@@ -829,6 +874,22 @@ TEST_F(ExpressionDateFromStringTest, OptimizesToConstantIfAllInputsAreConstant)
                                           << "$format"));
     dateExp = Expression::parseExpression(expCtx, spec, expCtx->variablesParseState);
     ASSERT_FALSE(dynamic_cast<ExpressionConstant*>(dateExp->optimize().get()));
+
+    // Test that it does *not* become a constant if onNull is not a constant.
+    spec = BSON("$dateFromString" << BSON("dateString"
+                                          << "2017-07-04T13:09:57Z"
+                                          << "onNull"
+                                          << "$onNull"));
+    dateExp = Expression::parseExpression(expCtx, spec, expCtx->variablesParseState);
+    ASSERT_FALSE(dynamic_cast<ExpressionConstant*>(dateExp->optimize().get()));
+
+    // Test that it does *not* become a constant if onError is not a constant.
+    spec = BSON("$dateFromString" << BSON("dateString"
+                                          << "2017-07-04T13:09:57Z"
+                                          << "onError"
+                                          << "$onError"));
+    dateExp = Expression::parseExpression(expCtx, spec, expCtx->variablesParseState);
+    ASSERT_FALSE(dynamic_cast<ExpressionConstant*>(dateExp->optimize().get()));
 }
 
 TEST_F(ExpressionDateFromStringTest, RejectsUnparsableString) {
@@ -837,7 +898,7 @@ TEST_F(ExpressionDateFromStringTest, RejectsUnparsableString) {
     auto spec = BSON("$dateFromString" << BSON("dateString"
                                                << "60.Monday1770/06:59"));
     auto dateExp = Expression::parseExpression(expCtx, spec, expCtx->variablesParseState);
-    ASSERT_THROWS_CODE(dateExp->evaluate({}), AssertionException, 40553);
+    ASSERT_THROWS_CODE(dateExp->evaluate({}), AssertionException, ErrorCodes::ConversionFailure);
 }
 
 TEST_F(ExpressionDateFromStringTest, RejectsTimeZoneInString) {
@@ -846,12 +907,12 @@ TEST_F(ExpressionDateFromStringTest, RejectsTimeZoneInString) {
     auto spec = BSON("$dateFromString" << BSON("dateString"
                                                << "2017-07-13T10:02:57 Europe/London"));
     auto dateExp = Expression::parseExpression(expCtx, spec, expCtx->variablesParseState);
-    ASSERT_THROWS_CODE(dateExp->evaluate({}), AssertionException, 40553);
+    ASSERT_THROWS_CODE(dateExp->evaluate({}), AssertionException, ErrorCodes::ConversionFailure);
 
     spec = BSON("$dateFromString" << BSON("dateString"
                                           << "July 4, 2017 Europe/London"));
     dateExp = Expression::parseExpression(expCtx, spec, expCtx->variablesParseState);
-    ASSERT_THROWS_CODE(dateExp->evaluate({}), AssertionException, 40553);
+    ASSERT_THROWS_CODE(dateExp->evaluate({}), AssertionException, ErrorCodes::ConversionFailure);
 }
 
 TEST_F(ExpressionDateFromStringTest, RejectsTimeZoneInStringAndArgument) {
@@ -863,7 +924,7 @@ TEST_F(ExpressionDateFromStringTest, RejectsTimeZoneInStringAndArgument) {
                                                << "timezone"
                                                << "Europe/London"));
     auto dateExp = Expression::parseExpression(expCtx, spec, expCtx->variablesParseState);
-    ASSERT_THROWS_CODE(dateExp->evaluate({}), AssertionException, 40551);
+    ASSERT_THROWS_CODE(dateExp->evaluate({}), AssertionException, ErrorCodes::ConversionFailure);
 
     // Test with timezone abbreviation and timezone
     spec = BSON("$dateFromString" << BSON("dateString"
@@ -871,7 +932,7 @@ TEST_F(ExpressionDateFromStringTest, RejectsTimeZoneInStringAndArgument) {
                                           << "timezone"
                                           << "Europe/London"));
     dateExp = Expression::parseExpression(expCtx, spec, expCtx->variablesParseState);
-    ASSERT_THROWS_CODE(dateExp->evaluate({}), AssertionException, 40551);
+    ASSERT_THROWS_CODE(dateExp->evaluate({}), AssertionException, ErrorCodes::ConversionFailure);
 
     // Test with GMT offset and timezone
     spec = BSON("$dateFromString" << BSON("dateString"
@@ -879,7 +940,7 @@ TEST_F(ExpressionDateFromStringTest, RejectsTimeZoneInStringAndArgument) {
                                           << "timezone"
                                           << "Europe/London"));
     dateExp = Expression::parseExpression(expCtx, spec, expCtx->variablesParseState);
-    ASSERT_THROWS_CODE(dateExp->evaluate({}), AssertionException, 40554);
+    ASSERT_THROWS_CODE(dateExp->evaluate({}), AssertionException, ErrorCodes::ConversionFailure);
 
     // Test with GMT offset and GMT timezone
     spec = BSON("$dateFromString" << BSON("dateString"
@@ -887,7 +948,7 @@ TEST_F(ExpressionDateFromStringTest, RejectsTimeZoneInStringAndArgument) {
                                           << "timezone"
                                           << "GMT"));
     dateExp = Expression::parseExpression(expCtx, spec, expCtx->variablesParseState);
-    ASSERT_THROWS_CODE(dateExp->evaluate({}), AssertionException, 40554);
+    ASSERT_THROWS_CODE(dateExp->evaluate({}), AssertionException, ErrorCodes::ConversionFailure);
 }
 
 TEST_F(ExpressionDateFromStringTest, RejectsNonStringFormat) {
@@ -916,14 +977,14 @@ TEST_F(ExpressionDateFromStringTest, RejectsStringsThatDoNotMatchFormat) {
                                                << "format"
                                                << "%Y-%m-%d"));
     auto dateExp = Expression::parseExpression(expCtx, spec, expCtx->variablesParseState);
-    ASSERT_THROWS_CODE(dateExp->evaluate({}), AssertionException, 40553);
+    ASSERT_THROWS_CODE(dateExp->evaluate({}), AssertionException, ErrorCodes::ConversionFailure);
 
     spec = BSON("$dateFromString" << BSON("dateString"
                                           << "2017-07"
                                           << "format"
                                           << "%m-%Y"));
     dateExp = Expression::parseExpression(expCtx, spec, expCtx->variablesParseState);
-    ASSERT_THROWS_CODE(dateExp->evaluate({}), AssertionException, 40553);
+    ASSERT_THROWS_CODE(dateExp->evaluate({}), AssertionException, ErrorCodes::ConversionFailure);
 }
 
 TEST_F(ExpressionDateFromStringTest, EscapeCharacterAllowsPrefixUsage) {
@@ -1050,6 +1111,201 @@ TEST_F(ExpressionDateFromStringTest, ConvertStringWithISODateFormat) {
     ASSERT_EQ("2017-01-08T00:00:00.000Z", dateExp->evaluate(Document{}).toString());
 }
 
-}  // namespace ExpressionDateFromStringTest
+TEST_F(ExpressionDateFromStringTest, ReturnsOnNullForNullishInput) {
+    auto expCtx = getExpCtx();
+
+    auto spec = BSON("$dateFromString" << BSON("dateString" << BSONNULL << "onNull"
+                                                            << "Null default"));
+    auto dateExp = Expression::parseExpression(expCtx, spec, expCtx->variablesParseState);
+    ASSERT_VALUE_EQ(Value("Null default"_sd), dateExp->evaluate(Document{}));
+
+    spec = BSON("$dateFromString" << BSON("dateString"
+                                          << "$missing"
+                                          << "onNull"
+                                          << "Null default"));
+    dateExp = Expression::parseExpression(expCtx, spec, expCtx->variablesParseState);
+    ASSERT_VALUE_EQ(Value("Null default"_sd), dateExp->evaluate(Document{}));
+
+    spec = BSON("$dateFromString" << BSON("dateString"
+                                          << "$missing"
+                                          << "onNull"
+                                          << "$alsoMissing"));
+    dateExp = Expression::parseExpression(expCtx, spec, expCtx->variablesParseState);
+    ASSERT_VALUE_EQ(Value(), dateExp->evaluate(Document{}));
+
+    spec = BSON("$dateFromString" << BSON("dateString" << BSONNULL << "onNull" << BSONNULL));
+    dateExp = Expression::parseExpression(expCtx, spec, expCtx->variablesParseState);
+    ASSERT_VALUE_EQ(Value(BSONNULL), dateExp->evaluate(Document{}));
+}
+
+TEST_F(ExpressionDateFromStringTest, InvalidFormatTakesPrecedenceOverOnNull) {
+    auto expCtx = getExpCtx();
+
+    auto spec = BSON("$dateFromString" << BSON("dateString" << BSONNULL << "onNull"
+                                                            << "Null default"
+                                                            << "format"
+                                                            << 5));
+    auto dateExp = Expression::parseExpression(expCtx, spec, expCtx->variablesParseState);
+    ASSERT_THROWS_CODE(dateExp->evaluate({}), AssertionException, 40684);
+
+    spec = BSON("$dateFromString" << BSON("dateString" << BSONNULL << "onNull"
+                                                       << "Null default"
+                                                       << "format"
+                                                       << "%"));
+    dateExp = Expression::parseExpression(expCtx, spec, expCtx->variablesParseState);
+    ASSERT_THROWS_CODE(dateExp->evaluate({}), AssertionException, 18535);
+}
+
+TEST_F(ExpressionDateFromStringTest, InvalidFormatTakesPrecedenceOverOnError) {
+    auto expCtx = getExpCtx();
+
+    auto spec = BSON("$dateFromString" << BSON("dateString"
+                                               << "Invalid dateString"
+                                               << "onError"
+                                               << "Not used default"
+                                               << "format"
+                                               << 5));
+    auto dateExp = Expression::parseExpression(expCtx, spec, expCtx->variablesParseState);
+    ASSERT_THROWS_CODE(dateExp->evaluate({}), AssertionException, 40684);
+
+    spec = BSON("$dateFromString" << BSON("dateString" << 5 << "onError"
+                                                       << "Not used default"
+                                                       << "format"
+                                                       << "%"));
+    dateExp = Expression::parseExpression(expCtx, spec, expCtx->variablesParseState);
+    ASSERT_THROWS_CODE(dateExp->evaluate({}), AssertionException, 18535);
+}
+
+TEST_F(ExpressionDateFromStringTest, InvalidTimezoneTakesPrecedenceOverOnNull) {
+    auto expCtx = getExpCtx();
+
+    auto spec = BSON("$dateFromString" << BSON("dateString" << BSONNULL << "onNull"
+                                                            << "Null default"
+                                                            << "timezone"
+                                                            << 5));
+    auto dateExp = Expression::parseExpression(expCtx, spec, expCtx->variablesParseState);
+    ASSERT_THROWS_CODE(dateExp->evaluate({}), AssertionException, 40517);
 
+    spec = BSON("$dateFromString" << BSON("dateString" << BSONNULL << "onNull"
+                                                       << "Null default"
+                                                       << "timezone"
+                                                       << "invalid timezone string"));
+    dateExp = Expression::parseExpression(expCtx, spec, expCtx->variablesParseState);
+    ASSERT_THROWS_CODE(dateExp->evaluate({}), AssertionException, 40485);
+}
+
+TEST_F(ExpressionDateFromStringTest, InvalidTimezoneTakesPrecedenceOverOnError) {
+    auto expCtx = getExpCtx();
+
+    auto spec = BSON("$dateFromString" << BSON("dateString"
+                                               << "Invalid dateString"
+                                               << "onError"
+                                               << "On error default"
+                                               << "timezone"
+                                               << 5));
+    auto dateExp = Expression::parseExpression(expCtx, spec, expCtx->variablesParseState);
+    ASSERT_THROWS_CODE(dateExp->evaluate({}), AssertionException, 40517);
+
+    spec = BSON("$dateFromString" << BSON("dateString" << 5 << "onError"
+                                                       << "On error default"
+                                                       << "timezone"
+                                                       << "invalid timezone string"));
+    dateExp = Expression::parseExpression(expCtx, spec, expCtx->variablesParseState);
+    ASSERT_THROWS_CODE(dateExp->evaluate({}), AssertionException, 40485);
+}
+
+TEST_F(ExpressionDateFromStringTest, OnNullTakesPrecedenceOverOtherNullishParameters) {
+    auto expCtx = getExpCtx();
+
+    auto spec = BSON("$dateFromString" << BSON("dateString" << BSONNULL << "onNull"
+                                                            << "Null default"
+                                                            << "timezone"
+                                                            << BSONNULL));
+    auto dateExp = Expression::parseExpression(expCtx, spec, expCtx->variablesParseState);
+    ASSERT_VALUE_EQ(Value("Null default"_sd), dateExp->evaluate(Document{}));
+
+    spec = BSON("$dateFromString" << BSON("dateString" << BSONNULL << "onNull"
+                                                       << "Null default"
+                                                       << "format"
+                                                       << BSONNULL));
+    dateExp = Expression::parseExpression(expCtx, spec, expCtx->variablesParseState);
+    ASSERT_VALUE_EQ(Value("Null default"_sd), dateExp->evaluate(Document{}));
+}
+
+TEST_F(ExpressionDateFromStringTest, OnNullOnlyUsedIfInputStringIsNullish) {
+    auto expCtx = getExpCtx();
+
+    auto spec = BSON("$dateFromString" << BSON("dateString"
+                                               << "2018-02-14"
+                                               << "onNull"
+                                               << "Null default"
+                                               << "timezone"
+                                               << BSONNULL));
+    auto dateExp = Expression::parseExpression(expCtx, spec, expCtx->variablesParseState);
+    ASSERT_VALUE_EQ(Value(BSONNULL), dateExp->evaluate(Document{}));
+
+    spec = BSON("$dateFromString" << BSON("dateString"
+                                          << "2018-02-14"
+                                          << "onNull"
+                                          << "Null default"
+                                          << "format"
+                                          << BSONNULL));
+    dateExp = Expression::parseExpression(expCtx, spec, expCtx->variablesParseState);
+    ASSERT_VALUE_EQ(Value(BSONNULL), dateExp->evaluate(Document{}));
+}
+
+TEST_F(ExpressionDateFromStringTest, ReturnsOnErrorForParseFailures) {
+    auto expCtx = getExpCtx();
+
+    std::vector<std::string> invalidDates = {
+        "60.Monday1770/06:59", "July 4th", "12:50:53", "2017, 12:50:53"};
+    for (auto date : invalidDates) {
+        auto spec = BSON("$dateFromString" << BSON("dateString" << date << "onError"
+                                                                << "Error default"));
+        auto dateExp = Expression::parseExpression(expCtx, spec, expCtx->variablesParseState);
+        ASSERT_VALUE_EQ(Value("Error default"_sd), dateExp->evaluate(Document{}));
+    }
+}
+
+TEST_F(ExpressionDateFromStringTest, ReturnsOnErrorForFormatMismatch) {
+    auto expCtx = getExpCtx();
+
+    const std::string date = "2018/02/06";
+    std::vector<std::string> unmatchedFormats = {"%Y", "%Y/%m/%d:%H", "Y/m/d"};
+    for (auto format : unmatchedFormats) {
+        auto spec =
+            BSON("$dateFromString" << BSON("dateString" << date << "format" << format << "onError"
+                                                        << "Error default"));
+        auto dateExp = Expression::parseExpression(expCtx, spec, expCtx->variablesParseState);
+        ASSERT_VALUE_EQ(Value("Error default"_sd), dateExp->evaluate(Document{}));
+    }
+}
+
+TEST_F(ExpressionDateFromStringTest, OnNullEvaluatedLazily) {
+    auto expCtx = getExpCtx();
+
+    auto spec = BSON("$dateFromString" << BSON("dateString"
+                                               << "$date"
+                                               << "onNull"
+                                               << BSON("$divide" << BSON_ARRAY(1 << 0))));
+    auto dateExp = Expression::parseExpression(expCtx, spec, expCtx->variablesParseState);
+    ASSERT_EQ("2018-02-14T00:00:00.000Z",
+              dateExp->evaluate(Document{{"date", "2018-02-14"_sd}}).toString());
+    ASSERT_THROWS_CODE(dateExp->evaluate(Document{}), AssertionException, 16608);
+}
+
+TEST_F(ExpressionDateFromStringTest, OnErrorEvaluatedLazily) {
+    auto expCtx = getExpCtx();
+
+    auto spec = BSON("$dateFromString" << BSON("dateString"
+                                               << "$date"
+                                               << "onError"
+                                               << BSON("$divide" << BSON_ARRAY(1 << 0))));
+    auto dateExp = Expression::parseExpression(expCtx, spec, expCtx->variablesParseState);
+    ASSERT_EQ("2018-02-14T00:00:00.000Z",
+              dateExp->evaluate(Document{{"date", "2018-02-14"_sd}}).toString());
+    ASSERT_THROWS_CODE(dateExp->evaluate(Document{{"date", 5}}), AssertionException, 16608);
+}
+
+}  // namespace ExpressionDateFromStringTest
 }  // namespace mongo