From dc29a28b632f164588b066959605666365cad8b5 Mon Sep 17 00:00:00 2001
From: "Andrew I. Christianson" <andy@andyic.org>
Date: Mon, 11 Jun 2018 09:28:53 -0400
Subject: [PATCH] MINIFICPP-535 Add support for nonexistent flow_file provided
 as param to an Expression

---
 extensions/expression-language/Expression.cpp | 29 ++++++++++++++-----
 .../ExpressionLanguageTests.cpp               |  6 ++++
 2 files changed, 28 insertions(+), 7 deletions(-)

diff --git a/extensions/expression-language/Expression.cpp b/extensions/expression-language/Expression.cpp
index 80c9440f7b..5681c0507a 100644
--- a/extensions/expression-language/Expression.cpp
+++ b/extensions/expression-language/Expression.cpp
@@ -64,7 +64,8 @@ Expression make_dynamic(const std::function<Value(const Parameters &params,
 Expression make_dynamic_attr(const std::string &attribute_id) {
   return make_dynamic([attribute_id](const Parameters &params, const std::vector<Expression> &sub_exprs) -> Value {
     std::string result;
-    if (params.flow_file.lock()->getAttribute(attribute_id, result)) {
+    const auto cur_flow_file = params.flow_file.lock();
+    if (cur_flow_file && cur_flow_file->getAttribute(attribute_id, result)) {
       return Value(result);
     } else {
       return Value();
@@ -1776,7 +1777,9 @@ Expression make_allAttributes(const std::string &function_name, const std::vecto
         attr_id = arg(params).asString();
         std::string attr_val;
 
-        if (params.flow_file.lock()->getAttribute(attr_id, attr_val)) {
+        const auto cur_flow_file = params.flow_file.lock();
+
+        if (cur_flow_file && cur_flow_file->getAttribute(attr_id, attr_val)) {
           return Value(attr_val);
         } else {
           return Value();
@@ -1825,7 +1828,9 @@ Expression make_anyAttribute(const std::string &function_name, const std::vector
         attr_id = arg(params).asString();
         std::string attr_val;
 
-        if (params.flow_file.lock()->getAttribute(attr_id, attr_val)) {
+        const auto cur_flow_file = params.flow_file.lock();
+
+        if (cur_flow_file && cur_flow_file->getAttribute(attr_id, attr_val)) {
           return Value(attr_val);
         } else {
           return Value();
@@ -1871,7 +1876,12 @@ Expression make_allMatchingAttributes(const std::string &function_name, const st
 
     for (const auto &arg : args) {
       const std::regex attr_regex = std::regex(arg(params).asString());
-      auto attrs = params.flow_file.lock()->getAttributes();
+      const auto cur_flow_file = params.flow_file.lock();
+      std::map<std::string, std::string> attrs;
+
+      if (cur_flow_file) {
+        attrs = cur_flow_file->getAttributes();
+      }
 
       for (const auto &attr : attrs) {
         if (std::regex_match(attr.first.begin(), attr.first.end(), attr_regex)) {
@@ -1879,7 +1889,7 @@ Expression make_allMatchingAttributes(const std::string &function_name, const st
                                                   const std::vector<Expression> &sub_exprs) -> Value {
             std::string attr_val;
 
-            if (params.flow_file.lock()->getAttribute(attr.first, attr_val)) {
+            if (cur_flow_file && cur_flow_file->getAttribute(attr.first, attr_val)) {
               return Value(attr_val);
             } else {
               return Value();
@@ -1925,7 +1935,12 @@ Expression make_anyMatchingAttribute(const std::string &function_name, const std
 
     for (const auto &arg : args) {
       const std::regex attr_regex = std::regex(arg(params).asString());
-      auto attrs = params.flow_file.lock()->getAttributes();
+      const auto cur_flow_file = params.flow_file.lock();
+      std::map<std::string, std::string> attrs;
+
+      if (cur_flow_file) {
+        attrs = cur_flow_file->getAttributes();
+      }
 
       for (const auto &attr : attrs) {
         if (std::regex_match(attr.first.begin(), attr.first.end(), attr_regex)) {
@@ -1933,7 +1948,7 @@ Expression make_anyMatchingAttribute(const std::string &function_name, const std
                                                   const std::vector<Expression> &sub_exprs) -> Value {
             std::string attr_val;
 
-            if (params.flow_file.lock()->getAttribute(attr.first, attr_val)) {
+            if (cur_flow_file && cur_flow_file->getAttribute(attr.first, attr_val)) {
               return Value(attr_val);
             } else {
               return Value();
diff --git a/libminifi/test/expression-language-tests/ExpressionLanguageTests.cpp b/libminifi/test/expression-language-tests/ExpressionLanguageTests.cpp
index f6e143eab2..4099636868 100644
--- a/libminifi/test/expression-language-tests/ExpressionLanguageTests.cpp
+++ b/libminifi/test/expression-language-tests/ExpressionLanguageTests.cpp
@@ -54,6 +54,12 @@ TEST_CASE("Attribute expression", "[expressionLanguageTestAttributeExpression]")
   REQUIRE("text_before__attr_value_a__text_after" == expr({flow_file}).asString());
 }
 
+TEST_CASE("Attribute expression (Null)", "[expressionLanguageTestAttributeExpressionNull]") {  // NOLINT
+  auto expr = expression::compile("text_before${attr_a}text_after");
+  std::shared_ptr<MockFlowFile> flow_file = nullptr;
+  REQUIRE("text_beforetext_after" == expr({flow_file}).asString());
+}
+
 TEST_CASE("Multi-attribute expression", "[expressionLanguageTestMultiAttributeExpression]") {  // NOLINT
   auto flow_file = std::make_shared<MockFlowFile>();
   flow_file->addAttribute("attr_a", "__attr_value_a__");