Fix env serialization for v1 configs (#1904)

Signed-off-by: Doug Walker <doug.walker@autodesk.com>

Author: doug-walker

src/OpenColorIO/OCIOYaml.cpp

@@ -4738,9 +4738,9 @@ inline void save(YAML::Emitter & out, const Config & config)
     out << YAML::Newline;
     out << YAML::Newline;
 
-    if (configMajorVersion >= 2)
+    if (configMajorVersion >= 2 || config.getNumEnvironmentVars() > 0)
     {
-        // Print the environment even if empty.
+        // For v2 configs, write the environment section, even if empty.
         out << YAML::Key << "environment";
         out << YAML::Value << YAML::BeginMap;
         for(int i = 0; i < config.getNumEnvironmentVars(); ++i)

tests/cpu/Config_tests.cpp

@@ -768,6 +768,55 @@ OCIO_ADD_TEST(Config, serialize_searchpath)
     }
 }
 
+OCIO_ADD_TEST(Config, serialize_environment)
+{
+    {
+        OCIO::ConfigRcPtr config = OCIO::Config::Create();
+        config->setMajorVersion(1);
+        config->setMinorVersion(0);
+
+        std::ostringstream os;
+        config->serialize(os);
+        StringUtils::StringVec osvec = StringUtils::SplitByLines(os.str());
+
+        // A v1 config does not write the environment section if it's empty.
+        const std::string expected{ "search_path: \"\"" };
+        OCIO_CHECK_EQUAL(osvec[2], expected);
+    }
+    {
+        OCIO::ConfigRcPtr config = OCIO::Config::Create();
+        config->setMajorVersion(2);
+        config->setMinorVersion(0);
+
+        std::ostringstream os;
+        config->serialize(os);
+        StringUtils::StringVec osvec = StringUtils::SplitByLines(os.str());
+
+        // A v2 config does write the environment section, even if it's empty.
+        const std::string expected1{ "environment:" };
+        const std::string expected2{ "  {}" };
+        OCIO_CHECK_EQUAL(osvec[2], expected1);
+        OCIO_CHECK_EQUAL(osvec[3], expected2);
+    }
+    {
+        OCIO::ConfigRcPtr config = OCIO::Config::Create();
+        config->setMajorVersion(1);
+        config->setMinorVersion(0);
+
+        config->addEnvironmentVar("SHOT", "0001");
+
+        std::ostringstream os;
+        config->serialize(os);
+        StringUtils::StringVec osvec = StringUtils::SplitByLines(os.str());
+
+        // A v1 config does write the environment section if it's not empty.
+        const std::string expected1{ "environment:" };
+        const std::string expected2{ "  SHOT: 0001" };
+        OCIO_CHECK_EQUAL(osvec[2], expected1);
+        OCIO_CHECK_EQUAL(osvec[3], expected2);
+    }
+}
+
 OCIO_ADD_TEST(Config, validation)
 {
     {