From 16cfc5e55318d424dc434f931469f7f8a6f29689 Mon Sep 17 00:00:00 2001
From: Martin Curlej <mcurlej@redhat.com>
Date: Sep 27 2017 19:34:39 +0000
Subject: Added custom types for yaml fields to preserve newlines


added test, bugfix

improved test

---

diff --git a/modulemd/__init__.py b/modulemd/__init__.py
index a841c71..47a4212 100644
--- a/modulemd/__init__.py
+++ b/modulemd/__init__.py
@@ -57,6 +57,7 @@ from modulemd.components.module import ModuleComponentModule
 from modulemd.components.rpm import ModuleComponentRPM
 from modulemd.filter import ModuleFilter
 from modulemd.profile import ModuleProfile
+from modulemd.util import PreservedDesc, PreservedMacros
 
 supported_mdversions = ( 1, )
 
@@ -458,7 +459,28 @@ class ModuleMetadata(object):
 
         :rtype: str
         """
-        return yaml.safe_dump(self.dumpd(), default_flow_style=False)
+
+        # we need to extend the macros and description property of the dict
+        # so we can preserve the correct newlines when dumping the dict to YAML
+        # PyYAML requires that each of those properties has a unique type so
+        # they can be identified by the Dumper.
+        mmd = self.dumpd()
+        if "buildopts" in mmd["data"]:
+            macros_string = mmd["data"]["buildopts"]["rpms"]["macros"]
+            yaml.add_representer(PreservedMacros, PreservedMacros.representer)
+            pmacros = PreservedMacros(macros_string)
+            mmd["data"]["buildopts"]["rpms"]["macros"] = pmacros
+
+        if "description" in mmd["data"]:
+            desc_string = mmd["data"]["description"]
+            yaml.add_representer(PreservedDesc, PreservedDesc.representer)
+            pdesc = PreservedDesc(desc_string)
+            mmd["data"]["description"] = pdesc
+
+        return yaml.dump_all([mmd],
+                                None,
+                                Dumper=yaml.Dumper,
+                                default_flow_style=False)
 
     @property
     def mdversion(self):
diff --git a/modulemd/tests/test_io.py b/modulemd/tests/test_io.py
index c420eb9..c77ba93 100644
--- a/modulemd/tests/test_io.py
+++ b/modulemd/tests/test_io.py
@@ -29,6 +29,7 @@ import unittest
 import os
 import sys
 import datetime
+import yaml
 
 DIR = os.path.dirname(__file__)
 sys.path.insert(0, os.path.join(DIR, ".."))
@@ -149,3 +150,16 @@ class TestIO(unittest.TestCase):
         self.assertEqual(arepr, repr(a))
         self.assertEqual(brepr, repr(b))
         os.remove("testdumpall.yaml")
+
+    def test_dumps_correct_num_newlines(self):
+        mmd = ModuleMetadata()
+        mmd.buildopts.rpms.macros = "1\n2\n3\n"
+        mmd.description = "test test test test test test\n"
+
+        data = mmd.dumpd()
+        bad_yaml_str = yaml.safe_dump(data, default_flow_style=False)
+        correct_yaml_str = mmd.dumps()
+        self.assertNotEqual(
+            bad_yaml_str.count('\n'),
+            correct_yaml_str.count('\n')
+        )
diff --git a/modulemd/util.py b/modulemd/util.py
new file mode 100644
index 0000000..318a301
--- /dev/null
+++ b/modulemd/util.py
@@ -0,0 +1,27 @@
+
+class PreservedMacros(str):
+    """
+    Extended string type used for preserving newlines in strings used by
+    PyYAML package when dumping dicts to yaml files. This type defines
+    the macros field from the YAML metadata.
+    """
+    @staticmethod
+    def representer(dumper, data):
+        """
+        Representer method which defines the YAML field we want to preserve.
+        """
+        return dumper.represent_scalar("tag:yaml.org,2002:str", data, style="|")
+
+
+class PreservedDesc(str):
+    """
+    Extended string type used for preserving newlines in strings used by
+    PyYAML package when dumping dicts to yaml files. This type defines
+    the Description field from the YAML metadata.
+    """
+    @staticmethod
+    def representer(dumper, data):
+        """
+        Representer method which defines the YAML field we want to preserve.
+        """
+        return dumper.represent_scalar("tag:yaml.org,2002:str", data, style=">")