Fixed comparison of JsonVariant with mixed strings (closes #1051)

Author: bblanchon

CHANGELOG.md

@@ -5,6 +5,7 @@ HEAD
 ----
 
 * Added operators `==` and `!=` for `JsonDocument`, `ElementProxy`, and `MemberProxy`
+* Fixed comparison of `JsonVariant` when one contains a linked string and the other contains an owned string (issue #1051)
 
 v6.11.2 (2019-07-08)
 -------

src/ArduinoJson/Variant/VariantContent.hpp

@@ -16,15 +16,18 @@ namespace ARDUINOJSON_NAMESPACE {
 enum {
   VALUE_MASK = 0x7F,
 
+  OWNERSHIP_BIT = 0x01,
   VALUE_IS_NULL = 0,
-  VALUE_IS_LINKED_RAW = 0x01,
-  VALUE_IS_OWNED_RAW = 0x02,
-  VALUE_IS_LINKED_STRING = 0x03,
-  VALUE_IS_OWNED_STRING = 0x04,
-  VALUE_IS_BOOLEAN = 0x05,
-  VALUE_IS_POSITIVE_INTEGER = 0x06,
-  VALUE_IS_NEGATIVE_INTEGER = 0x07,
-  VALUE_IS_FLOAT = 0x08,
+  VALUE_IS_LINKED_RAW = 0x02,
+  VALUE_IS_OWNED_RAW = 0x03,
+  VALUE_IS_LINKED_STRING = 0x04,
+  VALUE_IS_OWNED_STRING = 0x05,
+
+  // CAUTION: no OWNERSHIP_BIT below
+  VALUE_IS_BOOLEAN = 0x06,
+  VALUE_IS_POSITIVE_INTEGER = 0x08,
+  VALUE_IS_NEGATIVE_INTEGER = 0x0A,
+  VALUE_IS_FLOAT = 0x0C,
 
   COLLECTION_MASK = 0x60,
   VALUE_IS_OBJECT = 0x20,

src/ArduinoJson/Variant/VariantData.hpp

@@ -101,7 +101,9 @@ class VariantData {
   }
 
   bool equals(const VariantData &other) const {
-    if (type() != other.type()) return false;
+    // Check that variant have the same type, but ignore string ownership
+    if ((type() | OWNERSHIP_BIT) != (other.type() | OWNERSHIP_BIT))
+      return false;
 
     switch (type()) {
       case VALUE_IS_LINKED_STRING:

test/JsonVariant/compare.cpp

@@ -286,6 +286,17 @@ TEST_CASE("JsonVariant comparisons") {
     REQUIRE_FALSE(variant1 == variant3);
   }
 
+  SECTION("Variants containing mixed strings (issue #1051)") {
+    variant1.set("hello");
+    variant2.set(std::string("hello"));
+
+    REQUIRE(variant1 == variant2);
+    REQUIRE_FALSE(variant1 != variant2);
+
+    REQUIRE(variant2 == variant1);
+    REQUIRE_FALSE(variant2 != variant1);
+  }
+
   SECTION("Variants containing double") {
     variant1.set(42.0);
     variant2.set(42.0);