From 4c86d3fe5930b123375c96c479a0d41526e63d03 Mon Sep 17 00:00:00 2001
From: Christian Krause <christian.krause@mailbox.org>
Date: Mon, 5 Jul 2021 09:46:09 +0200
Subject: [PATCH] [document-start] adds min/max empty lines after document
 start/end

---
 tests/rules/test_document_start.py | 62 ++++++++++++++++++++++++++++++
 yamllint/rules/document_start.py   | 28 +++++++++++++-
 2 files changed, 88 insertions(+), 2 deletions(-)

diff --git a/tests/rules/test_document_start.py b/tests/rules/test_document_start.py
index 20de9ad03..843813108 100644
--- a/tests/rules/test_document_start.py
+++ b/tests/rules/test_document_start.py
@@ -102,3 +102,65 @@ def test_directives(self):
                    '---\n'
                    'doc: 2\n'
                    '...\n', conf)
+
+    def test_empty_lines(self):
+        conf = ('document-start:\n'
+                '  present: true\n'
+                '  max-empty-lines-after: 0\n')
+
+        self.check('%YAML 1.2\n'
+                   '---\n'
+                   'doc: ument\n', conf)
+
+        self.check('%YAML 1.2\n'
+                   '---\n'
+                   '\n'
+                   'doc: ument\n', conf, problem=(4, 1))
+
+        conf = ('document-start:\n'
+                '  present: true\n'
+                '  max-empty-lines-after: 1\n')
+
+        self.check('%YAML 1.2\n'
+                   '---\n'
+                   '\n'
+                   'doc: ument\n', conf)
+
+        self.check('%YAML 1.2\n'
+                   '---\n'
+                   '\n'
+                   '\n'
+                   'doc: ument\n', conf, problem=(5, 1))
+
+        conf = ('document-start:\n'
+                '  present: true\n'
+                '  min-empty-lines-after: 1\n')
+
+        self.check('%YAML 1.2\n'
+                   '---\n'
+                   '\n'
+                   'doc: ument\n', conf)
+
+        self.check('%YAML 1.2\n'
+                   '---\n'
+                   'doc: ument\n', conf, problem=(3, 1))
+
+        conf = ('document-start:\n'
+                '  present: true\n'
+                '  max-empty-lines-after: 1\n'
+                '  min-empty-lines-after: 1\n')
+
+        self.check('%YAML 1.2\n'
+                   '---\n'
+                   '\n'
+                   'doc: ument\n', conf)
+
+        self.check('%YAML 1.2\n'
+                   '---\n'
+                   'doc: ument\n', conf, problem=(3, 1))
+
+        self.check('%YAML 1.2\n'
+                   '---\n'
+                   '\n'
+                   '\n'
+                   'doc: ument\n', conf, problem=(5, 1))
diff --git a/yamllint/rules/document_start.py b/yamllint/rules/document_start.py
index 9bab4b40b..da0cee056 100644
--- a/yamllint/rules/document_start.py
+++ b/yamllint/rules/document_start.py
@@ -79,8 +79,12 @@
 
 ID = 'document-start'
 TYPE = 'token'
-CONF = {'present': bool}
-DEFAULT = {'present': True}
+CONF = {'present': bool,
+        'max-empty-lines-after': (int, -1),
+        'min-empty-lines-after': (int, 0)}
+DEFAULT = {'present': True,
+           'max-empty-lines-after': -1,
+           'min-empty-lines-after': 0}
 
 
 def check(conf, token, prev, next, nextnext, context):
@@ -94,6 +98,26 @@ def check(conf, token, prev, next, nextnext, context):
             yield LintProblem(token.start_mark.line + 1, 1,
                               'missing document start "---"')
 
+        if (conf['max-empty-lines-after'] >= 0 and
+                isinstance(prev, yaml.DocumentStartToken)):
+
+            empty_lines = token.start_mark.line - prev.start_mark.line - 1
+
+            if empty_lines > conf['max-empty-lines-after']:
+                yield LintProblem(token.start_mark.line + 1,
+                                  token.start_mark.column + 1,
+                                  'too many empty lines after document start')
+
+        if (conf['min-empty-lines-after'] > 0 and
+                isinstance(prev, yaml.DocumentStartToken)):
+
+            empty_lines = token.start_mark.line - prev.start_mark.line - 1
+
+            if empty_lines < conf['min-empty-lines-after']:
+                yield LintProblem(token.start_mark.line + 1,
+                                  token.start_mark.column + 1,
+                                  'too few empty lines after document start')
+
     else:
         if isinstance(token, yaml.DocumentStartToken):
             yield LintProblem(token.start_mark.line + 1,