Fix line stripping edge case for %load magic command (#14495)

Closes:  #14494

IPython/core/magics/code.py

@@ -1,755 +1,757
 """Implementation of code management magic functions.
 """
 #-----------------------------------------------------------------------------
 #  Copyright (c) 2012 The IPython Development Team.
 #
 #  Distributed under the terms of the Modified BSD License.
 #
 #  The full license is in the file COPYING.txt, distributed with this software.
 #-----------------------------------------------------------------------------
 
 #-----------------------------------------------------------------------------
 # Imports
 #-----------------------------------------------------------------------------
 
 # Stdlib
 import inspect
 import io
 import os
 import re
 import sys
 import ast
 from itertools import chain
 from urllib.request import Request, urlopen
 from urllib.parse import urlencode
 from pathlib import Path
 
 # Our own packages
 from IPython.core.error import TryNext, StdinNotImplementedError, UsageError
 from IPython.core.macro import Macro
 from IPython.core.magic import Magics, magics_class, line_magic
 from IPython.core.oinspect import find_file, find_source_lines
 from IPython.core.release import version
 from IPython.testing.skipdoctest import skip_doctest
 from IPython.utils.contexts import preserve_keys
 from IPython.utils.path import get_py_filename
 from warnings import warn
 from logging import error
 from IPython.utils.text import get_text_list
 
 #-----------------------------------------------------------------------------
 # Magic implementation classes
 #-----------------------------------------------------------------------------
 
 # Used for exception handling in magic_edit
 class MacroToEdit(ValueError): pass
 
 ipython_input_pat = re.compile(r"<ipython\-input\-(\d+)-[a-z\d]+>$")
 
 # To match, e.g. 8-10 1:5 :10 3-
 range_re = re.compile(r"""
 (?P<start>\d+)?
 ((?P<sep>[\-:])
  (?P<end>\d+)?)?
 $""", re.VERBOSE)
 
 
 def extract_code_ranges(ranges_str):
     """Turn a string of range for %%load into 2-tuples of (start, stop)
     ready to use as a slice of the content split by lines.
 
     Examples
     --------
     list(extract_input_ranges("5-10 2"))
     [(4, 10), (1, 2)]
     """
     for range_str in ranges_str.split():
         rmatch = range_re.match(range_str)
         if not rmatch:
             continue
         sep = rmatch.group("sep")
         start = rmatch.group("start")
         end = rmatch.group("end")
 
         if sep == '-':
             start = int(start) - 1 if start else None
             end = int(end) if end else None
         elif sep == ':':
             start = int(start) - 1 if start else None
             end = int(end) - 1 if end else None
         else:
             end = int(start)
             start = int(start) - 1
         yield (start, end)
 
 
 def extract_symbols(code, symbols):
     """
     Return a tuple  (blocks, not_found)
     where ``blocks`` is a list of code fragments
     for each symbol parsed from code, and ``not_found`` are
     symbols not found in the code.
 
     For example::
 
         In [1]: code = '''a = 10
            ...: def b(): return 42
            ...: class A: pass'''
 
         In [2]: extract_symbols(code, 'A,b,z')
         Out[2]: (['class A: pass\\n', 'def b(): return 42\\n'], ['z'])
     """
     symbols = symbols.split(',')
 
     # this will raise SyntaxError if code isn't valid Python
     py_code = ast.parse(code)
 
     marks = [(getattr(s, 'name', None), s.lineno) for s in py_code.body]
     code = code.split('\n')
 
     symbols_lines = {}
     
     # we already know the start_lineno of each symbol (marks). 
     # To find each end_lineno, we traverse in reverse order until each 
     # non-blank line
     end = len(code)  
     for name, start in reversed(marks):
         while not code[end - 1].strip():
             end -= 1
         if name:
             symbols_lines[name] = (start - 1, end)
         end = start - 1
 
     # Now symbols_lines is a map
     # {'symbol_name': (start_lineno, end_lineno), ...}
     
     # fill a list with chunks of codes for each requested symbol
     blocks = []
     not_found = []
     for symbol in symbols:
         if symbol in symbols_lines:
             start, end = symbols_lines[symbol]
             blocks.append('\n'.join(code[start:end]) + '\n')
         else:
             not_found.append(symbol)
 
     return blocks, not_found
 
 def strip_initial_indent(lines):
     """For %load, strip indent from lines until finding an unindented line.
 
     https://github.com/ipython/ipython/issues/9775
     """
     indent_re = re.compile(r'\s+')
 
     it = iter(lines)
     first_line = next(it)
     indent_match = indent_re.match(first_line)
 
     if indent_match:
         # First line was indented
         indent = indent_match.group()
         yield first_line[len(indent):]
 
         for line in it:
             if line.startswith(indent):
-                yield line[len(indent):]
+                yield line[len(indent) :]
+            elif line in ("\n", "\r\n") or len(line) == 0:
+                yield line
             else:
                 # Less indented than the first line - stop dedenting
                 yield line
                 break
     else:
         yield first_line
 
     # Pass the remaining lines through without dedenting
     for line in it:
         yield line
 
 
 class InteractivelyDefined(Exception):
     """Exception for interactively defined variable in magic_edit"""
     def __init__(self, index):
         self.index = index
 
 
 @magics_class
 class CodeMagics(Magics):
     """Magics related to code management (loading, saving, editing, ...)."""
 
     def __init__(self, *args, **kwargs):
         self._knowntemps = set()
         super(CodeMagics, self).__init__(*args, **kwargs)
 
     @line_magic
     def save(self, parameter_s=''):
         """Save a set of lines or a macro to a given filename.
 
         Usage:\\
           %save [options] filename [history]
 
         Options:
 
           -r: use 'raw' input.  By default, the 'processed' history is used,
           so that magics are loaded in their transformed version to valid
           Python.  If this option is given, the raw input as typed as the
           command line is used instead.
           
           -f: force overwrite.  If file exists, %save will prompt for overwrite
           unless -f is given.
 
           -a: append to the file instead of overwriting it.
 
         The history argument uses the same syntax as %history for input ranges,
         then saves the lines to the filename you specify.
 
         If no ranges are specified, saves history of the current session up to
         this point.
 
         It adds a '.py' extension to the file if you don't do so yourself, and
         it asks for confirmation before overwriting existing files.
 
         If `-r` option is used, the default extension is `.ipy`.
         """
 
         opts,args = self.parse_options(parameter_s,'fra',mode='list')
         if not args:
             raise UsageError('Missing filename.')
         raw = 'r' in opts
         force = 'f' in opts
         append = 'a' in opts
         mode = 'a' if append else 'w'
         ext = '.ipy' if raw else '.py'
         fname, codefrom = args[0], " ".join(args[1:])
         if not fname.endswith(('.py','.ipy')):
             fname += ext
         fname = os.path.expanduser(fname)
         file_exists = os.path.isfile(fname)
         if file_exists and not force and not append:
             try:
                 overwrite = self.shell.ask_yes_no('File `%s` exists. Overwrite (y/[N])? ' % fname, default='n')
             except StdinNotImplementedError:
                 print("File `%s` exists. Use `%%save -f %s` to force overwrite" % (fname, parameter_s))
                 return
             if not overwrite :
                 print('Operation cancelled.')
                 return
         try:
             cmds = self.shell.find_user_code(codefrom,raw)
         except (TypeError, ValueError) as e:
             print(e.args[0])
             return
         with io.open(fname, mode, encoding="utf-8") as f:
             if not file_exists or not append:
                 f.write("# coding: utf-8\n")
             f.write(cmds)
             # make sure we end on a newline
             if not cmds.endswith('\n'):
                 f.write('\n')
         print('The following commands were written to file `%s`:' % fname)
         print(cmds)
 
     @line_magic
     def pastebin(self, parameter_s=''):
         """Upload code to dpaste.com, returning the URL.
 
         Usage:\\
           %pastebin [-d "Custom description"][-e 24] 1-7
 
         The argument can be an input history range, a filename, or the name of a
         string or macro.
 
         If no arguments are given, uploads the history of this session up to
         this point.
 
         Options:
 
           -d: Pass a custom description. The default will say
               "Pasted from IPython".
           -e: Pass number of days for the link to be expired.
               The default will be 7 days.
         """
         opts, args = self.parse_options(parameter_s, "d:e:")
 
         try:
             code = self.shell.find_user_code(args)
         except (ValueError, TypeError) as e:
             print(e.args[0])
             return
 
         expiry_days = 7
         try:
             expiry_days = int(opts.get("e", 7))
         except ValueError as e:
             print(e.args[0].capitalize())
             return
         if expiry_days < 1 or expiry_days > 365:
             print("Expiry days should be in range of 1 to 365")
             return
 
         post_data = urlencode(
             {
                 "title": opts.get("d", "Pasted from IPython"),
                 "syntax": "python",
                 "content": code,
                 "expiry_days": expiry_days,
             }
         ).encode("utf-8")
 
         request = Request(
             "https://dpaste.com/api/v2/",
             headers={"User-Agent": "IPython v{}".format(version)},
         )
         response = urlopen(request, post_data)
         return response.headers.get('Location')
 
     @line_magic
     def loadpy(self, arg_s):
         """Alias of `%load`
 
         `%loadpy` has gained some flexibility and dropped the requirement of a `.py`
         extension. So it has been renamed simply into %load. You can look at
         `%load`'s docstring for more info.
         """
         self.load(arg_s)
 
     @line_magic
     def load(self, arg_s):
         """Load code into the current frontend.
 
         Usage:\\
           %load [options] source
 
           where source can be a filename, URL, input history range, macro, or
           element in the user namespace
 
         If no arguments are given, loads the history of this session up to this
         point.
 
         Options:
 
           -r <lines>: Specify lines or ranges of lines to load from the source.
           Ranges could be specified as x-y (x..y) or in python-style x:y 
           (x..(y-1)). Both limits x and y can be left blank (meaning the 
           beginning and end of the file, respectively).
 
           -s <symbols>: Specify function or classes to load from python source. 
 
           -y : Don't ask confirmation for loading source above 200 000 characters.
 
           -n : Include the user's namespace when searching for source code.
 
         This magic command can either take a local filename, a URL, an history
         range (see %history) or a macro as argument, it will prompt for
         confirmation before loading source with more than 200 000 characters, unless
         -y flag is passed or if the frontend does not support raw_input::
 
         %load
         %load myscript.py
         %load 7-27
         %load myMacro
         %load http://www.example.com/myscript.py
         %load -r 5-10 myscript.py
         %load -r 10-20,30,40: foo.py
         %load -s MyClass,wonder_function myscript.py
         %load -n MyClass
         %load -n my_module.wonder_function
         """
         opts,args = self.parse_options(arg_s,'yns:r:')
         search_ns = 'n' in opts
         contents = self.shell.find_user_code(args, search_ns=search_ns)
 
         if 's' in opts:
             try:
                 blocks, not_found = extract_symbols(contents, opts['s'])
             except SyntaxError:
                 # non python code
                 error("Unable to parse the input as valid Python code")
                 return
 
             if len(not_found) == 1:
                 warn('The symbol `%s` was not found' % not_found[0])
             elif len(not_found) > 1:
                 warn('The symbols %s were not found' % get_text_list(not_found,
                                                                      wrap_item_with='`')
                 )
 
             contents = '\n'.join(blocks)
 
         if 'r' in opts:
             ranges = opts['r'].replace(',', ' ')
             lines = contents.split('\n')
             slices = extract_code_ranges(ranges)
             contents = [lines[slice(*slc)] for slc in slices]
             contents = '\n'.join(strip_initial_indent(chain.from_iterable(contents)))
 
         l = len(contents)
 
         # 200 000 is ~ 2500 full 80 character lines
         # so in average, more than 5000 lines
         if l > 200000 and 'y' not in opts:
             try:
                 ans = self.shell.ask_yes_no(("The text you're trying to load seems pretty big"\
                 " (%d characters). Continue (y/[N]) ?" % l), default='n' )
             except StdinNotImplementedError:
                 #assume yes if raw input not implemented
                 ans = True
 
             if ans is False :
                 print('Operation cancelled.')
                 return
 
         contents = "# %load {}\n".format(arg_s) + contents
 
         self.shell.set_next_input(contents, replace=True)
 
     @staticmethod
     def _find_edit_target(shell, args, opts, last_call):
         """Utility method used by magic_edit to find what to edit."""
 
         def make_filename(arg):
             "Make a filename from the given args"
             try:
                 filename = get_py_filename(arg)
             except IOError:
                 # If it ends with .py but doesn't already exist, assume we want
                 # a new file.
                 if arg.endswith('.py'):
                     filename = arg
                 else:
                     filename = None
             return filename
 
         # Set a few locals from the options for convenience:
         opts_prev = 'p' in opts
         opts_raw = 'r' in opts
 
         # custom exceptions
         class DataIsObject(Exception): pass
 
         # Default line number value
         lineno = opts.get('n',None)
 
         if opts_prev:
             args = '_%s' % last_call[0]
             if args not in shell.user_ns:
                 args = last_call[1]
 
         # by default this is done with temp files, except when the given
         # arg is a filename
         use_temp = True
 
         data = ''
 
         # First, see if the arguments should be a filename.
         filename = make_filename(args)
         if filename:
             use_temp = False
         elif args:
             # Mode where user specifies ranges of lines, like in %macro.
             data = shell.extract_input_lines(args, opts_raw)
             if not data:
                 try:
                     # Load the parameter given as a variable. If not a string,
                     # process it as an object instead (below)
 
                     # print('*** args',args,'type',type(args))  # dbg
                     data = eval(args, shell.user_ns)
                     if not isinstance(data, str):
                         raise DataIsObject
 
                 except (NameError,SyntaxError):
                     # given argument is not a variable, try as a filename
                     filename = make_filename(args)
                     if filename is None:
                         warn("Argument given (%s) can't be found as a variable "
                              "or as a filename." % args)
                         return (None, None, None)
                     use_temp = False
 
                 except DataIsObject as e:
                     # macros have a special edit function
                     if isinstance(data, Macro):
                         raise MacroToEdit(data) from e
 
                     # For objects, try to edit the file where they are defined
                     filename = find_file(data)
                     if filename:
                         if 'fakemodule' in filename.lower() and \
                             inspect.isclass(data):
                             # class created by %edit? Try to find source
                             # by looking for method definitions instead, the
                             # __module__ in those classes is FakeModule.
                             attrs = [getattr(data, aname) for aname in dir(data)]
                             for attr in attrs:
                                 if not inspect.ismethod(attr):
                                     continue
                                 filename = find_file(attr)
                                 if filename and \
                                   'fakemodule' not in filename.lower():
                                     # change the attribute to be the edit
                                     # target instead
                                     data = attr
                                     break
                         
                         m = ipython_input_pat.match(os.path.basename(filename))
                         if m:
                             raise InteractivelyDefined(int(m.groups()[0])) from e
 
                         datafile = 1
                     if filename is None:
                         filename = make_filename(args)
                         datafile = 1
                         if filename is not None:
                             # only warn about this if we get a real name
                             warn('Could not find file where `%s` is defined.\n'
                              'Opening a file named `%s`' % (args, filename))
                     # Now, make sure we can actually read the source (if it was
                     # in a temp file it's gone by now).
                     if datafile:
                         if lineno is None:
                             lineno = find_source_lines(data)
                         if lineno is None:
                             filename = make_filename(args)
                             if filename is None:
                                 warn('The file where `%s` was defined '
                                      'cannot be read or found.' % data)
                                 return (None, None, None)
                     use_temp = False
 
         if use_temp:
             filename = shell.mktempfile(data)
             print('IPython will make a temporary file named:',filename)
 
         # use last_call to remember the state of the previous call, but don't
         # let it be clobbered by successive '-p' calls.
         try:
             last_call[0] = shell.displayhook.prompt_count
             if not opts_prev:
                 last_call[1] = args
         except:
             pass
 
 
         return filename, lineno, use_temp
 
     def _edit_macro(self,mname,macro):
         """open an editor with the macro data in a file"""
         filename = self.shell.mktempfile(macro.value)
         self.shell.hooks.editor(filename)
 
         # and make a new macro object, to replace the old one
         mvalue = Path(filename).read_text(encoding="utf-8")
         self.shell.user_ns[mname] = Macro(mvalue)
 
     @skip_doctest
     @line_magic
     def edit(self, parameter_s='',last_call=['','']):
         """Bring up an editor and execute the resulting code.
 
         Usage:
           %edit [options] [args]
 
         %edit runs IPython's editor hook. The default version of this hook is
         set to call the editor specified by your $EDITOR environment variable.
         If this isn't found, it will default to vi under Linux/Unix and to
         notepad under Windows. See the end of this docstring for how to change
         the editor hook.
 
         You can also set the value of this editor via the
         ``TerminalInteractiveShell.editor`` option in your configuration file.
         This is useful if you wish to use a different editor from your typical
         default with IPython (and for Windows users who typically don't set
         environment variables).
 
         This command allows you to conveniently edit multi-line code right in
         your IPython session.
 
         If called without arguments, %edit opens up an empty editor with a
         temporary file and will execute the contents of this file when you
         close it (don't forget to save it!).
 
 
         Options:
 
         -n <number>: open the editor at a specified line number.  By default,
         the IPython editor hook uses the unix syntax 'editor +N filename', but
         you can configure this by providing your own modified hook if your
         favorite editor supports line-number specifications with a different
         syntax.
 
         -p: this will call the editor with the same data as the previous time
         it was used, regardless of how long ago (in your current session) it
         was.
 
         -r: use 'raw' input.  This option only applies to input taken from the
         user's history.  By default, the 'processed' history is used, so that
         magics are loaded in their transformed version to valid Python.  If
         this option is given, the raw input as typed as the command line is
         used instead.  When you exit the editor, it will be executed by
         IPython's own processor.
 
         -x: do not execute the edited code immediately upon exit. This is
         mainly useful if you are editing programs which need to be called with
         command line arguments, which you can then do using %run.
 
 
         Arguments:
 
         If arguments are given, the following possibilities exist:
 
         - If the argument is a filename, IPython will load that into the
           editor. It will execute its contents with execfile() when you exit,
           loading any code in the file into your interactive namespace.
 
         - The arguments are ranges of input history,  e.g. "7 ~1/4-6".
           The syntax is the same as in the %history magic.
 
         - If the argument is a string variable, its contents are loaded
           into the editor. You can thus edit any string which contains
           python code (including the result of previous edits).
 
         - If the argument is the name of an object (other than a string),
           IPython will try to locate the file where it was defined and open the
           editor at the point where it is defined. You can use `%edit function`
           to load an editor exactly at the point where 'function' is defined,
           edit it and have the file be executed automatically.
 
         - If the object is a macro (see %macro for details), this opens up your
           specified editor with a temporary file containing the macro's data.
           Upon exit, the macro is reloaded with the contents of the file.
 
         Note: opening at an exact line is only supported under Unix, and some
         editors (like kedit and gedit up to Gnome 2.8) do not understand the
         '+NUMBER' parameter necessary for this feature. Good editors like
         (X)Emacs, vi, jed, pico and joe all do.
 
         After executing your code, %edit will return as output the code you
         typed in the editor (except when it was an existing file). This way
         you can reload the code in further invocations of %edit as a variable,
         via _<NUMBER> or Out[<NUMBER>], where <NUMBER> is the prompt number of
         the output.
 
         Note that %edit is also available through the alias %ed.
 
         This is an example of creating a simple function inside the editor and
         then modifying it. First, start up the editor::
 
           In [1]: edit
           Editing... done. Executing edited code...
           Out[1]: 'def foo():\\n    print("foo() was defined in an editing
           session")\\n'
 
         We can then call the function foo()::
 
           In [2]: foo()
           foo() was defined in an editing session
 
         Now we edit foo.  IPython automatically loads the editor with the
         (temporary) file where foo() was previously defined::
 
           In [3]: edit foo
           Editing... done. Executing edited code...
 
         And if we call foo() again we get the modified version::
 
           In [4]: foo()
           foo() has now been changed!
 
         Here is an example of how to edit a code snippet successive
         times. First we call the editor::
 
           In [5]: edit
           Editing... done. Executing edited code...
           hello
           Out[5]: "print('hello')\\n"
 
         Now we call it again with the previous output (stored in _)::
 
           In [6]: edit _
           Editing... done. Executing edited code...
           hello world
           Out[6]: "print('hello world')\\n"
 
         Now we call it with the output #8 (stored in _8, also as Out[8])::
 
           In [7]: edit _8
           Editing... done. Executing edited code...
           hello again
           Out[7]: "print('hello again')\\n"
 
 
         Changing the default editor hook:
 
         If you wish to write your own editor hook, you can put it in a
         configuration file which you load at startup time.  The default hook
         is defined in the IPython.core.hooks module, and you can use that as a
         starting example for further modifications.  That file also has
         general instructions on how to set a new hook for use once you've
         defined it."""
         opts,args = self.parse_options(parameter_s,'prxn:')
 
         try:
             filename, lineno, is_temp = self._find_edit_target(self.shell, 
                                                        args, opts, last_call)
         except MacroToEdit as e:
             self._edit_macro(args, e.args[0])
             return
         except InteractivelyDefined as e:
             print("Editing In[%i]" % e.index)
             args = str(e.index)
             filename, lineno, is_temp = self._find_edit_target(self.shell, 
                                                        args, opts, last_call)
         if filename is None:
             # nothing was found, warnings have already been issued,
             # just give up.
             return
 
         if is_temp:
             self._knowntemps.add(filename)
         elif (filename in self._knowntemps):
             is_temp = True
 
 
         # do actual editing here
         print('Editing...', end=' ')
         sys.stdout.flush()
         filepath = Path(filename)
         try:
             # Quote filenames that may have spaces in them when opening
             # the editor
             quoted = filename = str(filepath.absolute())
             if " " in quoted:
                 quoted = "'%s'" % quoted
             self.shell.hooks.editor(quoted, lineno)
         except TryNext:
             warn('Could not open editor')
             return
 
         # XXX TODO: should this be generalized for all string vars?
         # For now, this is special-cased to blocks created by cpaste
         if args.strip() == "pasted_block":
             self.shell.user_ns["pasted_block"] = filepath.read_text(encoding="utf-8")
 
         if 'x' in opts:  # -x prevents actual execution
             print()
         else:
             print('done. Executing edited code...')
             with preserve_keys(self.shell.user_ns, '__file__'):
                 if not is_temp:
                     self.shell.user_ns["__file__"] = filename
                 if "r" in opts:  # Untranslated IPython code
                     source = filepath.read_text(encoding="utf-8")
                     self.shell.run_cell(source, store_history=False)
                 else:
                     self.shell.safe_execfile(filename, self.shell.user_ns,
                                              self.shell.user_ns)
 
         if is_temp:
             try:
                 return filepath.read_text(encoding="utf-8")
             except IOError as msg:
                 if Path(msg.filename) == filepath:
                     warn('File not found. Did you forget to save?')
                     return
                 else:
                     self.shell.showtraceback()