feat(new option): added option to attempt to keep blank lines in templates

--preser-blank-lines option can be used to try and keep existing blank lines during formatting.

closes #261

docs/src/docs/configuration.md

@@ -393,3 +393,28 @@ preserve_leading_space=true
 }
 ```
 
+## preserve_blank_lines
+
+Preserve blank where possible. Ideal for non-html template files where blank lines are intentional.
+
+Usage:
+
+**flag**
+
+```bash
+--preserve-blank-lines
+```
+
+**pyproject.toml**
+
+```ini
+preserve_blank_lines=true
+```
+
+**.djlintrc**
+
+```json
+{
+  "preserve_blank_lines": true
+}
+```

docs/src/fr/docs/configuration.md

@@ -392,3 +392,30 @@ preserve_leading_space=true
   "preserve_leading_space": true
 }
 ```
+
+
+## preserve_blank_lines
+
+Préserve les blancs lorsque cela est possible. Idéal pour les fichiers de modèles non-html où les lignes vides sont intentionnelles.
+
+Utilisation:
+
+**flag**
+
+```bash
+--preserve-blank-lines
+```
+
+**pyproject.toml**
+
+```ini
+preserve_blank_lines=true
+```
+
+**.djlintrc**
+
+```json
+{
+  "preserve_blank_lines": true
+}
+```

docs/src/ru/docs/configuration.md

@@ -388,3 +388,30 @@ preserve_leading_space=true
   "preserve_leading_space": true
 }
 ```
+
+
+## preserve_blank_lines
+
+Сохраняйте пробелы там, где это возможно. Идеально подходит для не-html файлов шаблонов, где пустые строки являются намеренными.
+
+Использование:
+
+**flag**
+
+```bash
+--preserve-blank-lines
+```
+
+**pyproject.toml**
+
+```ini
+preserve_blank_lines=true
+```
+
+**.djlintrc**
+
+```json
+{
+  "preserve_blank_lines": true
+}
+```

src/djlint/__init__.py

@@ -99,6 +99,11 @@ from .src import get_src
     is_flag=True,
     help="Attempt to preserve leading space on text.",
 )
+@click.option(
+    "--preserve-blank-lines",
+    is_flag=True,
+    help="Attempt to preserve blank lines.",
+)
 @colorama_text(autoreset=True)
 def main(
     src: List[str],
@@ -114,6 +119,7 @@ def main(
     use_gitignore: bool,
     warn: bool,
     preserve_leading_space: bool,
+    preserve_blank_lines: bool,
 ) -> None:
     """djLint · HTML template linter and formatter."""
     config = Config(
@@ -130,6 +136,7 @@ def main(
         use_gitignore=use_gitignore,
         warn=warn,
         preserve_leading_space=preserve_leading_space,
+        preserve_blank_lines=preserve_blank_lines,
     )
 
     temp_file = None

src/djlint/formatter/condense.py

@@ -25,16 +25,35 @@ def condense_html(html: str, config: Config) -> str:
 
     func = partial(strip_space, config, html)
 
+    line_contents = r"(.*?)"
+    trailing_contents = r"\n \t"
+
+    if config.preserve_blank_lines:
+        line_contents = r"([^\n]+?)"
+        trailing_contents = r" \t"
+
     if not config.preserve_leading_space:
         # remove any leading/trailing space
-        html = re.sub(re.compile(r"^[ \t]*(.*?)[\n \t]*$", re.M), func, html)
+
+        html = re.sub(
+            re.compile(rf"^[ \t]*{line_contents}[{trailing_contents}]*$", re.M),
+            func,
+            html,
+        )
+
     else:
         # only remove leading space in front of tags
         # <, {%, {#, {{
         html = re.sub(
-            re.compile(r"^[ \t]*((?:<|{%|{#|{{).*?)[\n \t]*$", re.M), func, html
+            re.compile(
+                rf"^[ \t]*((?:<|{{%|{{\#|{{{{).*?)[{trailing_contents}]*$", re.M
+            ),
+            func,
+            html,
+        )
+        html = re.sub(
+            re.compile(rf"^{line_contents}[{trailing_contents}]*$", re.M), func, html
         )
-        html = re.sub(re.compile(r"^(.*?)[\n \t]*$", re.M), func, html)
 
     def if_blank_line_after_match(config: Config, html: str) -> bool:
         """Check if there should be a blank line after."""

src/djlint/formatter/indent.py

@@ -248,4 +248,7 @@ def indent_html(rawcode: str, config: Config) -> str:
         # handlebars templates
         beautified_code = re.sub(r"({{#(?:each|if).+?[^ ])(}})", func, beautified_code)
 
-    return beautified_code.strip() + "\n"
+    if not config.preserve_blank_lines:
+        beautified_code = beautified_code.lstrip()
+
+    return beautified_code.rstrip() + "\n"

src/djlint/settings.py

@@ -192,6 +192,7 @@ class Config:
         use_gitignore: bool = False,
         warn: bool = False,
         preserve_leading_space: bool = False,
+        preserve_blank_lines: bool = False,
     ):
 
         self.reformat = reformat
@@ -234,6 +235,10 @@ class Config:
             or djlint_settings.get("preserve_leading_space", False)
         )
 
+        self.preserve_blank_lines: bool = preserve_blank_lines or djlint_settings.get(
+            "preserve_blank_lines", False
+        )
+
         # ignore is based on input and also profile
         self.ignore: str = str(ignore or djlint_settings.get("ignore", ""))
 

tests/test_config/test_preserve_blank_lines/html.html

@@ -0,0 +1,28 @@
+ 
+{% if   abc == 101 %}
+ interface Ethernet1/2
+   description // Connected to leaf-2
+   no switchport
+   ip address 10.1.2.1/30
+   ip router ospf 1 area 0.0.0.0
+   no shutdown
+{% endif %}
+
+
+{% if abc == 102 %}
+ interface Ethernet1/2
+   description // Connected to leaf-2
+   no switchport
+   ip address 10.1.2.1/30
+   ip router ospf 1 area 0.0.0.0
+   no shutdown
+{% endif %}
+
+{% if abc == 103 %}
+ interface Ethernet1/2
+   description // Connected to leaf-2
+   no switchport
+   ip address 10.1.2.1/30
+   ip router ospf 1 area 0.0.0.0
+   no shutdown
+{% endif %}

tests/test_config/test_preserve_blank_lines/test_config.py

@@ -0,0 +1,29 @@
+"""Djlint tests specific to --preserve-leading-space option.
+
+run::
+
+   pytest tests/test_config/test_preserve_blank_lines/test_config.py --cov=src/djlint --cov-branch \
+          --cov-report xml:coverage.xml --cov-report term-missing
+
+   pytest tests/test_config/test_preserve_blank_lines/test_config.py::test_config
+
+"""
+# pylint: disable=C0116
+from click.testing import CliRunner
+
+from src.djlint import main as djlint
+
+
+def test_config(runner: CliRunner) -> None:
+
+    result = runner.invoke(
+        djlint,
+        [
+            "tests/test_config/test_preserve_blank_lines/html.html",
+            "--check",
+            "--preserve-leading-space",
+            "--preserve-blank-lines",
+        ],
+    )
+
+    assert result.exit_code == 0