Factor out handling of line continuations

IPython/core/inputtransformer2.py

@@ -1,255 +1,258 b''
 import re
 from typing import List, Tuple
 from IPython.utils import tokenize2
 from IPython.utils.tokenutil import generate_tokens
 
 def leading_indent(lines):
     """Remove leading indentation.
     
     If the first line starts with a spaces or tabs, the same whitespace will be
     removed from each following line.
     """
     m = re.match(r'^[ \t]+', lines[0])
     if not m:
         return lines
     space = m.group(0)
     n = len(space)
     return [l[n:] if l.startswith(space) else l
             for l in lines]
 
 class PromptStripper:
     """Remove matching input prompts from a block of input.
     
     Parameters
     ----------
     prompt_re : regular expression
         A regular expression matching any input prompt (including continuation)
     initial_re : regular expression, optional
         A regular expression matching only the initial prompt, but not continuation.
         If no initial expression is given, prompt_re will be used everywhere.
         Used mainly for plain Python prompts, where the continuation prompt
         ``...`` is a valid Python expression in Python 3, so shouldn't be stripped.
     
     If initial_re and prompt_re differ,
     only initial_re will be tested against the first line.
     If any prompt is found on the first two lines,
     prompts will be stripped from the rest of the block.
     """
     def __init__(self, prompt_re, initial_re=None):
         self.prompt_re = prompt_re
         self.initial_re = initial_re or prompt_re
 
     def _strip(self, lines):
         return [self.prompt_re.sub('', l, count=1) for l in lines]
 
     def __call__(self, lines):
         if self.initial_re.match(lines[0]) or \
                 (len(lines) > 1 and self.prompt_re.match(lines[1])):
             return self._strip(lines)
         return lines
 
 classic_prompt = PromptStripper(
     prompt_re=re.compile(r'^(>>>|\.\.\.)( |$)'),
     initial_re=re.compile(r'^>>>( |$)')
 )
 
 ipython_prompt = PromptStripper(re.compile(r'^(In \[\d+\]: |\s*\.{3,}: ?)'))
 
 def cell_magic(lines):
     if not lines[0].startswith('%%'):
         return lines
     if re.match('%%\w+\?', lines[0]):
         # This case will be handled by help_end
         return lines
     magic_name, first_line = lines[0][2:].partition(' ')
     body = '\n'.join(lines[1:])
     return ['get_ipython().run_cell_magic(%r, %r, %r)' % (magic_name, first_line, body)]
 
 line_transforms = [
     leading_indent,
     classic_prompt,
     ipython_prompt,
     cell_magic,
 ]
 
 # -----
 
 def help_end(tokens_by_line):
     pass
 
 def escaped_command(tokens_by_line):
     pass
 
 def _find_assign_op(token_line):
     # Find the first assignment in the line ('=' not inside brackets)
     # We don't try to support multiple special assignment (a = b = %foo)
     paren_level = 0
     for i, ti in enumerate(token_line):
         s = ti.string
         if s == '=' and paren_level == 0:
             return i 
         if s in '([{':
             paren_level += 1
         elif s in ')]}':
             paren_level -= 1
 
+def find_end_of_continued_line(lines, start_line: int):
+    """Find the last line of a line explicitly extended using backslashes.
+
+    Uses 0-indexed line numbers.
+    """
+    end_line = start_line
+    while lines[end_line].endswith('\\\n'):
+        end_line += 1
+        if end_line >= len(lines):
+            break
+    return end_line
+
+def assemble_continued_line(lines, start: Tuple[int, int], end_line: int):
+    """Assemble pieces of a continued line into a single line.
+
+    Uses 0-indexed line numbers. *start* is (lineno, colno).
+    """
+    parts = [lines[start[0]][start[1]:]] + lines[start[0]+1:end_line+1]
+    return ' '.join([p[:-2] for p in parts[:-1]]  # Strip backslash+newline
+                    + [parts[-1][:-1]])         # Strip newline from last line
+
 class MagicAssign:
     @staticmethod
     def find(tokens_by_line):
         """Find the first magic assignment (a = %foo) in the cell.
         
-        Returns (line, column) of the % if found, or None.
+        Returns (line, column) of the % if found, or None. *line* is 1-indexed.
         """
         for line in tokens_by_line:
             assign_ix = _find_assign_op(line)
             if (assign_ix is not None) \
                     and (len(line) >= assign_ix + 2) \
                     and (line[assign_ix+1].string == '%') \
                     and (line[assign_ix+2].type == tokenize2.NAME):
                 return line[assign_ix+1].start
     
     @staticmethod
     def transform(lines: List[str], start: Tuple[int, int]):
         """Transform a magic assignment found by find
         """
         start_line = start[0] - 1   # Shift from 1-index to 0-index
         start_col  = start[1]
-        
-        print("Start at", start_line, start_col)
-        print("Line", lines[start_line])
-    
-        lhs, rhs = lines[start_line][:start_col], lines[start_line][start_col:-1]
+
+        lhs = lines[start_line][:start_col]
+        end_line = find_end_of_continued_line(lines, start_line)
+        rhs = assemble_continued_line(lines, (start_line, start_col), end_line)
         assert rhs.startswith('%'), rhs
         magic_name, _, args = rhs[1:].partition(' ')
-        args_parts = [args]
-        end_line = start_line
-        # Follow explicit (backslash) line continuations
-        while end_line < len(lines) and args_parts[-1].endswith('\\'):
-            end_line += 1
-            args_parts[-1] = args_parts[-1][:-1]  # Trim backslash
-            args_parts.append(lines[end_line][:-1])  # Trim newline
-        args = ' '.join(args_parts)
         
         lines_before = lines[:start_line]
         call = "get_ipython().run_line_magic({!r}, {!r})".format(magic_name, args)
         new_line = lhs + call + '\n'
         lines_after = lines[end_line+1:]
         
         return lines_before + [new_line] + lines_after
 
 
 class SystemAssign:
     @staticmethod
     def find(tokens_by_line):
         """Find the first system assignment (a = !foo) in the cell.
 
-        Returns (line, column) of the ! if found, or None.
+        Returns (line, column) of the ! if found, or None. *line* is 1-indexed.
         """
         for line in tokens_by_line:
             assign_ix = _find_assign_op(line)
             if (assign_ix is not None) \
                     and (len(line) >= assign_ix + 2) \
                     and (line[assign_ix + 1].type == tokenize2.ERRORTOKEN):
                 ix = assign_ix + 1
 
                 while ix < len(line) and line[ix].type == tokenize2.ERRORTOKEN:
                     if line[ix].string == '!':
                         return line[ix].start
                     elif not line[ix].string.isspace():
                         break
                     ix += 1
 
     @staticmethod
     def transform(lines: List[str], start: Tuple[int, int]):
         """Transform a system assignment found by find
         """
         start_line = start[0] - 1  # Shift from 1-index to 0-index
         start_col = start[1]
 
-        print("Start at", start_line, start_col)
-        print("Line", lines[start_line])
-
-        lhs, rhs = lines[start_line][:start_col], lines[start_line][
-                                                  start_col:-1]
+        lhs = lines[start_line][:start_col]
+        end_line = find_end_of_continued_line(lines, start_line)
+        rhs = assemble_continued_line(lines, (start_line, start_col), end_line)
         assert rhs.startswith('!'), rhs
-        cmd_parts = [rhs[1:]]
-        end_line = start_line
-        # Follow explicit (backslash) line continuations
-        while end_line < len(lines) and cmd_parts[-1].endswith('\\'):
-            end_line += 1
-            cmd_parts[-1] = cmd_parts[-1][:-1]  # Trim backslash
-            cmd_parts.append(lines[end_line][:-1])  # Trim newline
-        cmd = ' '.join(cmd_parts)
+        cmd = rhs[1:]
 
         lines_before = lines[:start_line]
         call = "get_ipython().getoutput({!r})".format(cmd)
         new_line = lhs + call + '\n'
         lines_after = lines[end_line + 1:]
 
         return lines_before + [new_line] + lines_after
 
 def make_tokens_by_line(lines):
     tokens_by_line = [[]]
     for token in generate_tokens(iter(lines).__next__):
         tokens_by_line[-1].append(token)
         if token.type == tokenize2.NEWLINE:
             tokens_by_line.append([])
     
     return tokens_by_line
 
 class TokenTransformers:
     def __init__(self):
         self.transformers = [
             MagicAssign,
             SystemAssign,
         ]
     
     def do_one_transform(self, lines):
         """Find and run the transform earliest in the code.
         
         Returns (changed, lines).
         
         This method is called repeatedly until changed is False, indicating
         that all available transformations are complete.
 
         The tokens following IPython special syntax might not be valid, so
         the transformed code is retokenised every time to identify the next
         piece of special syntax. Hopefully long code cells are mostly valid
         Python, not using lots of IPython special syntax, so this shouldn't be
         a performance issue. 
         """
         tokens_by_line = make_tokens_by_line(lines)
         candidates = []
         for transformer in self.transformers:
             locn = transformer.find(tokens_by_line)
             if locn:
                 candidates.append((locn, transformer))
         
         if not candidates:
             # Nothing to transform
             return False, lines
         
         first_locn, transformer = min(candidates)
         return True, transformer.transform(lines, first_locn)
 
     def __call__(self, lines):
         while True:
             changed, lines = self.do_one_transform(lines)
             if not changed:
                 return lines
 
 def assign_from_system(tokens_by_line, lines):
     pass
 
 
 def transform_cell(cell):
     if not cell.endswith('\n'):
         cell += '\n'  # Ensure every line has a newline
     lines = cell.splitlines(keepends=True)
     for transform in line_transforms:
         #print(transform, lines)
         lines = transform(lines)
     
     lines = TokenTransformers()(lines)
     for line in lines:
         print('~~', line)

IPython/core/tests/test_inputtransformer2.py

@@ -1,54 +1,60 b''
 import nose.tools as nt
 
 from IPython.core import inputtransformer2 as ipt2
 from IPython.core.inputtransformer2 import make_tokens_by_line
 
 MULTILINE_MAGIC_ASSIGN = ("""\
 a = f()
 b = %foo \\
   bar
 g()
 """.splitlines(keepends=True), """\
 a = f()
 b = get_ipython().run_line_magic('foo', '   bar')
 g()
 """.splitlines(keepends=True))
 
 MULTILINE_SYSTEM_ASSIGN = ("""\
 a = f()
 b = !foo \\
   bar
 g()
 """.splitlines(keepends=True), """\
 a = f()
 b = get_ipython().getoutput('foo    bar')
 g()
 """.splitlines(keepends=True))
 
+def test_continued_line():
+    lines = MULTILINE_MAGIC_ASSIGN[0]
+    nt.assert_equal(ipt2.find_end_of_continued_line(lines, 1), 2)
+
+    nt.assert_equal(ipt2.assemble_continued_line(lines, (1, 5), 2), "foo    bar")
+
 def test_find_assign_magic():
     tbl = make_tokens_by_line(MULTILINE_MAGIC_ASSIGN[0])
     nt.assert_equal(ipt2.MagicAssign.find(tbl), (2, 4))
 
     tbl = make_tokens_by_line(MULTILINE_SYSTEM_ASSIGN[0])  # Nothing to find
     nt.assert_equal(ipt2.MagicAssign.find(tbl), None)
 
 def test_transform_assign_magic():
     res = ipt2.MagicAssign.transform(MULTILINE_MAGIC_ASSIGN[0], (2, 4))
     nt.assert_equal(res, MULTILINE_MAGIC_ASSIGN[1])
 
 def test_find_assign_system():
     tbl = make_tokens_by_line(MULTILINE_SYSTEM_ASSIGN[0])
     nt.assert_equal(ipt2.SystemAssign.find(tbl), (2, 4))
 
     tbl = make_tokens_by_line(["a =  !ls\n"])
     nt.assert_equal(ipt2.SystemAssign.find(tbl), (1, 5))
 
     tbl = make_tokens_by_line(["a=!ls\n"])
     nt.assert_equal(ipt2.SystemAssign.find(tbl), (1, 2))
 
     tbl = make_tokens_by_line(MULTILINE_MAGIC_ASSIGN[0])  # Nothing to find
     nt.assert_equal(ipt2.SystemAssign.find(tbl), None)
 
 def test_transform_assign_system():
     res = ipt2.SystemAssign.transform(MULTILINE_SYSTEM_ASSIGN[0], (2, 4))
     nt.assert_equal(res, MULTILINE_SYSTEM_ASSIGN[1])