Fixed serializeJson(doc, String) when allocation fails (fixes #1572)

extras/tests/Misc/StringWriter.cpp

@@ -11,95 +11,121 @@
 using namespace ARDUINOJSON_NAMESPACE;
 
 template <typename StringWriter>
-static size_t print(StringWriter& sb, const char* s) {
-  return sb.write(reinterpret_cast<const uint8_t*>(s), strlen(s));
+static size_t print(StringWriter& writer, const char* s) {
+  return writer.write(reinterpret_cast<const uint8_t*>(s), strlen(s));
 }
 
 template <typename StringWriter, typename String>
-void common_tests(StringWriter& sb, const String& output) {
+void common_tests(StringWriter& writer, const String& output) {
   SECTION("InitialState") {
     REQUIRE(std::string("") == output);
   }
 
   SECTION("EmptyString") {
-    REQUIRE(0 == print(sb, ""));
+    REQUIRE(0 == print(writer, ""));
     REQUIRE(std::string("") == output);
   }
 
   SECTION("OneString") {
-    REQUIRE(4 == print(sb, "ABCD"));
+    REQUIRE(4 == print(writer, "ABCD"));
     REQUIRE(std::string("ABCD") == output);
   }
 
   SECTION("TwoStrings") {
-    REQUIRE(4 == print(sb, "ABCD"));
-    REQUIRE(4 == print(sb, "EFGH"));
+    REQUIRE(4 == print(writer, "ABCD"));
+    REQUIRE(4 == print(writer, "EFGH"));
     REQUIRE(std::string("ABCDEFGH") == output);
   }
 }
 
 TEST_CASE("StaticStringWriter") {
   char output[20] = {0};
-  StaticStringWriter sb(output, sizeof(output));
+  StaticStringWriter writer(output, sizeof(output));
 
-  common_tests(sb, static_cast<const char*>(output));
+  common_tests(writer, static_cast<const char*>(output));
 
   SECTION("OverCapacity") {
-    REQUIRE(20 == print(sb, "ABCDEFGHIJKLMNOPQRSTUVWXYZ"));
-    REQUIRE(0 == print(sb, "ABC"));
+    REQUIRE(20 == print(writer, "ABCDEFGHIJKLMNOPQRSTUVWXYZ"));
+    REQUIRE(0 == print(writer, "ABC"));
     REQUIRE("ABCDEFGHIJKLMNOPQRST" == std::string(output, 20));
   }
 }
 
 TEST_CASE("Writer<std::string>") {
   std::string output;
-  Writer<std::string> sb(output);
-  common_tests(sb, output);
+  Writer<std::string> writer(output);
+  common_tests(writer, output);
 }
 
 TEST_CASE("Writer<String>") {
   ::String output;
-  Writer< ::String> sb(output);
+  Writer< ::String> writer(output);
 
-  common_tests(sb, output);
+  SECTION("write(char)") {
+    SECTION("writes to temporary buffer") {
+      // accumulate in buffer
+      writer.write('a');
+      writer.write('b');
+      writer.write('c');
+      writer.write('d');
+      REQUIRE(output == "");
 
-  SECTION("Writes characters to temporary buffer") {
-    // accumulate in buffer
-    sb.write('a');
-    sb.write('b');
-    sb.write('c');
-    REQUIRE(output == "");
+      // flush when full
+      writer.write('e');
+      REQUIRE(output == "abcd");
 
-    // flush when full
-    sb.write('d');
-    REQUIRE(output == "abcd");
+      // flush on destruction
+      writer.write('f');
+      writer.~Writer();
+      REQUIRE(output == "abcdef");
+    }
 
-    // flush on destruction
-    sb.write('e');
-    sb.~Writer();
-    REQUIRE(output == "abcde");
+    SECTION("returns 1 on success") {
+      for (int i = 0; i < ARDUINOJSON_STRING_BUFFER_SIZE; i++) {
+        REQUIRE(writer.write('x') == 1);
+      }
+    }
+
+    SECTION("returns 0 on error") {
+      output.limitCapacityTo(1);
+
+      REQUIRE(writer.write('a') == 1);
+      REQUIRE(writer.write('b') == 1);
+      REQUIRE(writer.write('c') == 1);
+      REQUIRE(writer.write('d') == 1);
+      REQUIRE(writer.write('e') == 0);
+      REQUIRE(writer.write('f') == 0);
+    }
   }
 
-  SECTION("Writes strings to temporary buffer") {
-    // accumulate in buffer
-    print(sb, "abc");
-    REQUIRE(output == "");
+  SECTION("write(char*, size_t)") {
+    SECTION("empty string") {
+      REQUIRE(0 == print(writer, ""));
+      writer.flush();
+      REQUIRE(output == "");
+    }
 
-    // flush when full, and continue to accumulate
-    print(sb, "de");
-    REQUIRE(output == "abcd");
+    SECTION("writes to temporary buffer") {
+      // accumulate in buffer
+      print(writer, "abc");
+      REQUIRE(output == "");
 
-    // flush on destruction
-    sb.~Writer();
-    REQUIRE(output == "abcde");
+      // flush when full, and continue to accumulate
+      print(writer, "de");
+      REQUIRE(output == "abcd");
+
+      // flush on destruction
+      writer.~Writer();
+      REQUIRE(output == "abcde");
+    }
   }
 }
 
 TEST_CASE("Writer<custom_string>") {
   custom_string output;
-  Writer<custom_string> sb(output);
+  Writer<custom_string> writer(output);
 
-  REQUIRE(4 == print(sb, "ABCD"));
+  REQUIRE(4 == print(writer, "ABCD"));
   REQUIRE("ABCD" == output);
 }
 
@@ -116,3 +142,20 @@ TEST_CASE("IsWriteableString") {
     REQUIRE(IsWriteableString<std::basic_string<wchar_t> >::value == false);
   }
 }
+
+TEST_CASE("serializeJson(doc, String)") {
+  StaticJsonDocument<1024> doc;
+  doc["hello"] = "world";
+  ::String output;
+
+  SECTION("sufficient capacity") {
+    serializeJson(doc, output);
+    REQUIRE(output == "{\"hello\":\"world\"}");
+  }
+
+  SECTION("unsufficient capacity") {  // issue #1561
+    output.limitCapacityTo(10);
+    serializeJson(doc, output);
+    REQUIRE(output == "{\"hello\"");
+  }
+}