Line statement and leading empty lines

[bertwesarg]

Following up #52, I'm wondering while Jinja does not also keep leading empty lines after a line statement.

---

Expected Behavior

== No empty lines
0
1
2
== Leading empty line

0

1

2
== Trailing empty line
0

1

2

== Leading and trailing empty lines

0


1


2

Actual Behavior

== No empty lines
0
1
2
== Leading empty line
0
1
2
== Trailing empty line
0

1

2

== Leading and trailing empty lines
0

1

2

Template Code

env = Environment(line_statement_prefix='%%')

print('== No empty lines')
print(env.from_string("""%% for item in seq
{{item}}
%% endfor""").render(seq=list(range(3))), end='')

print('== Leading empty line')
print(env.from_string("""%% for item in seq

{{item}}
%% endfor""").render(seq=list(range(3))), end='')

print('== Trailing empty line')
print(env.from_string("""%% for item in seq
{{item}}

%% endfor""").render(seq=list(range(3))), end='')

print('== Leading and trailing empty lines')
print(env.from_string("""%% for item in seq

{{item}}

%% endfor""").render(seq=list(range(3))), end='')

Your Environment

• Python version: 2.7.17
• Jinja version: 2.11.2

Proposed Fix

The fix for #52 only handled the trailing empty lines. Here is a fix to also handle the leading empty lines:

diff --git a/src/jinja2/lexer.py b/src/jinja2/lexer.py
index 552356a..f8fb7f5 100644 src/jinja2/lexer.py
--- a/src/jinja2/lexer.py
+++ b/src/jinja2/lexer.py
@@ -593,7 +593,7 @@ class Lexer(object):
             ],
             # line statements
             TOKEN_LINESTATEMENT_BEGIN: [
-                (c(r"\s*(\n|$)"), TOKEN_LINESTATEMENT_END, "#pop")
+                (c(r"[ \t\v]*(\n|$)"), TOKEN_LINESTATEMENT_END, "#pop")
             ]
             + tag_rules,
             # line comments

[bertwesarg]

@davidism any comments?

[davidism]

Working on other things right now. Please don't ping maintainers for updates, we'll get to it when we can. Don't have an idea for this yet, given other space-related issues right now.

[bertwesarg]

@mvolfik could you try to explain me, what is the difference between my proposal and yours? Thanks.