Indent block sequences in emitted files

[mudpy.git] / mudpy / data.py

diff --git a/mudpy/data.py b/mudpy/data.py
index 5233da2..d9eb8eb 100644 (file)
--- a/mudpy/data.py
+++ b/mudpy/data.py
@@ -12,6 +12,26 @@ import mudpy
 import yaml
 
 
+class _IBSEmitter(yaml.emitter.Emitter):
+
+    """Override the default YAML Emitter to indent block sequences."""
+
+    def expect_block_sequence(self):
+        """Match the expectations of the ``yamllint`` style checker."""
+
+        # TODO(fungi) Get an option for this implemented upstream in
+        # the pyyaml library
+        self.increase_indent(flow=False, indentless=False)
+        self.state = self.expect_first_block_sequence_item
+
+
+class _IBSDumper(yaml.SafeDumper, _IBSEmitter):
+
+    """Use our _IBSEmitter instead of the default implementation."""
+
+    pass
+
+
 class Data:
 
     """A file containing universe elements and their facets."""
@@ -144,8 +164,9 @@ class Data:
             os.umask(old_umask)
 
             # write and close the file
-            yaml.safe_dump(self.data, allow_unicode=True,
-                           default_flow_style=False, stream=file_descriptor)
+            yaml.dump(self.data, Dumper=_IBSDumper, allow_unicode=True,
+                      default_flow_style=False, explicit_start=True, indent=4,
+                      stream=file_descriptor)
             file_descriptor.close()
 
             # unset the modified flag