Fix issue with strip_comments causing a syntax error (fixes #425)

2 files changed, 20 insertions, 0 deletions

diff --git a/sqlparse/filters/others.py b/sqlparse/filters/others.py
index df4d861..b0bb898 100644
--- a/sqlparse/filters/others.py
+++ b/sqlparse/filters/others.py
@@ -26,6 +26,13 @@ class StripCommentsFilter(object):
             if (prev_ is None or next_ is None or
                     prev_.is_whitespace or prev_.match(T.Punctuation, '(') or
                     next_.is_whitespace or next_.match(T.Punctuation, ')')):
+                # Insert a whitespace to ensure the following SQL produces
+                # a valid SQL. For example:
+                #
+                # Before: select a--comment\nfrom foo
+                # After: select a from foo
+                if prev_ is not None and next_ is None:
+                    tlist.tokens.insert(tidx, sql.Token(T.Whitespace, ' '))
                 tlist.tokens.remove(token)
             else:
                 tlist.tokens[tidx] = sql.Token(T.Whitespace, ' ')
diff --git a/tests/test_format.py b/tests/test_format.py
index 72af62e..aff07c1 100644
--- a/tests/test_format.py
+++ b/tests/test_format.py
@@ -50,6 +50,19 @@ class TestFormat(object):
         sql = 'select-- foo\nfrom -- bar\nwhere'
         res = sqlparse.format(sql, strip_comments=True)
         assert res == 'select from where'
+        sql = 'select *-- statement starts here\n\nfrom foo'
+        res = sqlparse.format(sql, strip_comments=True)
+        assert res == 'select * from foo'
+        sql = 'select * from foo-- statement starts here\nwhere'
+        res = sqlparse.format(sql, strip_comments=True)
+        assert res == 'select * from foo where'
+        sql = 'select a-- statement starts here\nfrom foo'
+        res = sqlparse.format(sql, strip_comments=True)
+        assert res == 'select a from foo'
+        sql = '--comment\nselect a-- statement starts here\n' \
+              'from foo--comment\nf'
+        res = sqlparse.format(sql, strip_comments=True)
+        assert res == 'select a from foo f'
 
     def test_strip_comments_invalid_option(self):
         sql = 'select-- foo\nfrom -- bar\nwhere'