Preserve newlines before comments

Closes #62.

tests/test_formatting.py

@@ -5,6 +5,7 @@
 import pathlib
 import sys
 import unittest
+import textwrap
 
 # Sets up sys.path and provides helpers
 import testutils as tu
@@ -62,6 +63,34 @@ def test_index_slice(self):
         self.assertEqual(self._format(b"data[1 :1-1];").rstrip(), b"data[1 : 1 - 1];")
         self.assertEqual(self._format(b"data[f(): ];").rstrip(), b"data[f() :];")
 
+    def test_format_comment_separator(self):
+        """Validates that we preserve the separator before a comment. This is a
+        regression test for #62."""
+
+        self.assertEqual(
+            self._format(b"global x = 42;   # Inline.\n"), b"global x = 42; # Inline.\n"
+        )
+
+        code = textwrap.dedent(
+            """\
+               event zeek_init() {}
+               # Comment on next line.
+            """
+        )
+
+        expected = textwrap.dedent(
+            """\
+            event zeek_init()
+            \t{ }
+            # Comment on next line.
+            """
+        )
+
+        # We split out lines here to work around different line endings on Windows.
+        self.assertEqual(
+            self._format(code.encode()).decode().splitlines(), expected.splitlines()
+        )
+
 
 class TestFormattingErrors(unittest.TestCase):
     def _format(self, content):

zeekscript/formatter.py

@@ -1336,10 +1336,15 @@ def __init__(self, script, node, ostream, indent=0, hints=None):
 class MinorCommentFormatter(CommentFormatter):
     def format(self):
         node = self.node
-        # There's something before us and it's not a newline, then
-        # separate this comment from it with a space:
-        if node.prev_cst_sibling and not node.prev_cst_sibling.is_nl():
-            self._write_sp()
+
+        # Preserve separator to previous node if any.
+        if node.prev_cst_sibling:
+            if node.prev_cst_sibling.is_nl():
+                # Keep newlines verbatim.
+                self._write_nl()
+            else:
+                # If we are on the same line, normalize to exactly one space.
+                self._write_sp()
 
         self._format_token()  # Write comment itself