(Closes #505) by removing blank line comments being generated as Comment objects.

example/test_files/make_public_correct.f90

@@ -1,31 +1,23 @@
 MODULE a_mod
-
   ! Access_Stmt private will be removed:
-
   ! Attr_Spec with 0 and 1 additional attribute, the protected will be remobed
   REAL :: planet_radius = 123
   REAL, PARAMETER :: planet_radius_constant = 123
-
   LOGICAL :: public_protected = .FALSE.
   LOGICAL :: only_protected = .FALSE.
   LOGICAL :: private_protected = .FALSE.
-
   ! Access_stmt with public, this will be unmodified
   PUBLIC :: public_protected
   ! Protected_Stmt - the whole statement will be removed
   ! Access_stmt with private - the whole statement will be removed
-
   TYPE :: my_type
     ! Private_Components_Stmt in a type will be removed
     INTEGER :: a, b
     CONTAINS
     ! This private will also be removed.
-
   END TYPE my_type
-
   ! Access_Spec - the `private` will be removed
   TYPE(my_type), PUBLIC :: my_var
-
   CONTAINS
   SUBROUTINE sub_a
   END SUBROUTINE sub_a

src/fparser/two/Fortran2003.py

@@ -238,6 +238,12 @@ def __new__(cls, string, parent_cls=None):
         from fparser.common import readfortran
 
         if isinstance(string, readfortran.Comment):
+            # We can reach this with false readfortran.Comment nodes
+            # that represent empty lines in the original input. These
+            # have no syntactic relevance, and so are not kept by
+            # fparser.
+            if string.comment == "":
+                return
             # We were after a comment and we got a comment. Construct
             # one manually to avoid recursively calling this __new__
             # method again...

src/fparser/two/tests/test_comments_and_directives.py

@@ -35,7 +35,7 @@
 
 import pytest
 from fparser.two.Fortran2003 import Program, Comment, Directive, Subroutine_Subprogram
-from fparser.two.utils import walk
+from fparser.two.utils import walk, FortranSyntaxError
 from fparser.api import get_reader
 
 from fparser.two.parser import ParserFactory
@@ -92,7 +92,7 @@ def test_simple_prog():
         "  ! A full line comment\n"
         '  PRINT *, "Hello"\n'
         "  ! This block gets executed\n"
-        "END PROGRAM a_prog\n"
+        "END PROGRAM a_prog"
     )
 
 
@@ -120,7 +120,7 @@ def test_ifthen():
         '    PRINT *, "Hello"\n'
         "    ! Another full line comment\n"
         "  END IF\n"
-        "END PROGRAM a_prog\n"
+        "END PROGRAM a_prog"
     )
 
 
@@ -147,7 +147,7 @@ def test_inline_ifthen():
         "    ! An in-line comment here\n"
         "  END IF\n"
         "  ! A comment after a block\n"
-        "END PROGRAM a_prog\n"
+        "END PROGRAM a_prog"
     )
 
 
@@ -441,15 +441,11 @@ def test_directive_stmts():
     old = reader.get_item()
     assert old is not None
 
-    out = walk(program, Comment)
-    comments = 0
-    for comment in out:
-        if comment.items[0] != "":
-            comments = comments + 1
-    assert comments == 3
-    assert str(out[1]) == "!$dir inline"
-    assert str(out[3]) == "! A comment!"
-    assert str(out[4]) == "!!$ Another comment"
+    comments = walk(program, Comment)
+    assert len(comments) == 3
+    assert str(comments[0]) == "!$dir inline"
+    assert str(comments[1]) == "! A comment!"
+    assert str(comments[2]) == "!!$ Another comment"
 
     # Check that passing something that isn't a comment into a Directive
     # __new__ call doesn't create a Directive.
@@ -606,3 +602,47 @@ def test_inline_directive_is_comment():
     program = Program(reader)
     out = walk(program, Directive)
     assert len(out) == 0
+
+
+def test_syntax_error_with_comments():
+    """Test that when we keep comments we still correctly give syntax errors
+    when the first line of the file is a blank line."""
+    source = """
+
+
+! This is module m
+
+
+module m
+  integer :: x
+contains
+  subroutine foo()
+    if (.true.)
+      x = 0
+    end if
+  end subroutine
+end module"""
+    reader = get_reader(source, ignore_comments=False)
+    with pytest.raises(FortranSyntaxError) as err:
+        program = Program(reader)
+    assert "at line 11\n" in str(err.value)
+    assert ">>>    if (.true.)\n" in str(err.value)
+
+
+def test_base_to_fortran_empty_comment():
+    """Test that if we have an empty comment we get the correct
+    to_fortran from the base class implementation (i.e. no tab)"""
+    source = """
+    !Comment
+    program test
+    end program
+    """
+    reader = get_reader(source, ignore_comments=False)
+    program = Program(reader)
+    out = walk(program, Comment)
+    comment = out[0]
+    assert comment.tofortran(tab="    ") == "    !Comment"
+    # Change the comment to be an empty comment.
+    comment.items = [""]
+    comment.item = ""
+    assert comment.tofortran(tab="    ") == ""