preserve directives, optional push root level scalar to own line

You need to set YAML().scalar_after_indicator = False to get a single scalar document
starting on its own line (instead of after the directives end indicator: --- abc")

fixes issue #304

*When this change indeed resolves your problem, please **Close** this issue*.
*(You can do so using the WorkFlow pull-down (close to the top right of this page))*

5 files changed, 78 insertions, 0 deletions

diff --git a/_test/roundtrip.py b/_test/roundtrip.py
index ee430a3..090b9e0 100644
--- a/_test/roundtrip.py
+++ b/_test/roundtrip.py
@@ -151,6 +151,55 @@ def round_trip(
     return data
 
 
+def na_round_trip(
+    inp,
+    outp=None,
+    extra=None,
+    intermediate=None,
+    indent=None,
+    top_level_colon_align=None,
+    prefix_colon=None,
+    preserve_quotes=None,
+    explicit_start=None,
+    explicit_end=None,
+    version=None,
+    dump_data=None,
+):
+    """
+    inp:    input string to parse
+    outp:   expected output (equals input if not specified)
+    """
+    if outp is None:
+        outp = inp
+    if version is not None:
+        version = version
+    doutp = dedent(outp)
+    if extra is not None:
+        doutp += extra
+    yaml = YAML()
+    yaml.preserve_quotes = preserve_quotes
+    yaml.scalar_after_indicator = False  # newline after every directives end
+    data = yaml.load(inp)
+    if dump_data:
+        print('data', data)
+    if intermediate is not None:
+        if isinstance(intermediate, dict):
+            for k, v in intermediate.items():
+                if data[k] != v:
+                    print('{0!r} <> {1!r}'.format(data[k], v))
+                    raise ValueError
+    yaml.indent = indent
+    yaml.top_level_colon_align = top_level_colon_align
+    yaml.prefix_colon = prefix_colon
+    yaml.explicit_start = explicit_start
+    yaml.explicit_end = explicit_end
+    res = yaml.dump(data, compare=doutp)
+    #if res != doutp:
+    #    diff(doutp, res, 'input string')
+    #print('\nroundtrip data:\n', res, sep="")
+    #assert res == doutp
+
+
 def YAML(**kw):
     import ruamel.yaml  # NOQA
 
diff --git a/_test/test_issues.py b/_test/test_issues.py
index 3692f61..9b301a9 100644
--- a/_test/test_issues.py
+++ b/_test/test_issues.py
@@ -8,6 +8,7 @@ import pytest  # NOQA
 
 from roundtrip import (
     round_trip,
+    na_round_trip,
     round_trip_load,
     round_trip_dump,
     dedent,
@@ -850,6 +851,16 @@ class TestIssues:
                            match='while scanning a directive'):
             yaml.load(inp)
 
+    def test_issue_304(self):
+        inp = """
+	%YAML 1.2
+	%TAG ! tag:example.com,2019:
+	---
+	!foo null
+	...
+        """
+        d = na_round_trip(inp)  # NOQA
+
 #    @pytest.mark.xfail(strict=True, reason='bla bla', raises=AssertionError)
 #    def test_issue_ xxx(self):
 #        inp = """
diff --git a/emitter.py b/emitter.py
index 14277fc..7cdebcd 100644
--- a/emitter.py
+++ b/emitter.py
@@ -204,6 +204,8 @@ class Emitter(object):
         self.analysis = None  # type: Any
         self.style = None  # type: Any
 
+        self.scalar_after_indicator = True  # write a scalar on the same line as `---`
+
     @property
     def stream(self):
         # type: () -> Any
@@ -408,6 +410,8 @@ class Emitter(object):
                 and self.sequence_context
             ):
                 self.sequence_context = False
+            if root and isinstance(self.event, ScalarEvent) and not self.scalar_after_indicator:
+                self.write_indent()
             self.process_tag()
             if isinstance(self.event, ScalarEvent):
                 # nprint('@', self.indention, self.no_newline, self.column)
diff --git a/main.py b/main.py
index 184c7ad..0785c95 100644
--- a/main.py
+++ b/main.py
@@ -161,6 +161,7 @@ class YAML(object):
         self.tags = None
         self.default_style = None
         self.top_level_block_style_scalar_no_indent_error_1_1 = False
+        self.scalar_after_indicator = None  # directives end indicator with single scalar document 
         # [a, b: 1, c: {d: 2}]  vs. [a, {b: 1}, {c: {d: 2}}]
         self.brace_single_entry_mapping_in_flow_sequence = False
 
@@ -518,12 +519,16 @@ class YAML(object):
                 self.Serializer = ruamel.yaml.serializer.Serializer
             self.emitter.stream = stream
             self.emitter.top_level_colon_align = tlca
+            if self.scalar_after_indicator is not None:
+                self.emitter.scalar_after_indicator = self.scalar_after_indicator
             return self.serializer, self.representer, self.emitter
         if self.Serializer is not None:
             # cannot set serializer with CEmitter
             self.Emitter = ruamel.yaml.emitter.Emitter
             self.emitter.stream = stream
             self.emitter.top_level_colon_align = tlca
+            if self.scalar_after_indicator is not None:
+                self.emitter.scalar_after_indicator = self.scalar_after_indicator
             return self.serializer, self.representer, self.emitter
         # C routines
 
diff --git a/parser.py b/parser.py
index 9793b42..566d13a 100644
--- a/parser.py
+++ b/parser.py
@@ -219,6 +219,9 @@ class Parser(object):
                 )
             token = self.scanner.get_token()
             end_mark = token.end_mark
+            # if self.loader is not None and \
+            #    end_mark.line != self.scanner.peek_token().start_mark.line:
+            #     self.loader.scalar_after_indicator = False
             event = DocumentStartEvent(
                 start_mark, end_mark, explicit=True, version=version, tags=tags
             )  # type: Any
@@ -295,6 +298,12 @@ class Parser(object):
             value = self.yaml_version, self.tag_handles.copy()  # type: Any
         else:
             value = self.yaml_version, None
+        if self.loader is not None and hasattr(self.loader, 'tags'):
+            self.loader.version = self.yaml_version
+            if self.loader.tags is None:
+                self.loader.tags = {}
+            for k in self.tag_handles:
+                self.loader.tags[k] = self.tag_handles[k]
         for key in self.DEFAULT_TAGS:
             if key not in self.tag_handles:
                 self.tag_handles[key] = self.DEFAULT_TAGS[key]