Merge branch 'master' into feature/2093-docs-revampfeature/2093-docs-revamp

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diff --git a/setuptools/_distutils/text_file.py b/setuptools/_distutils/text_file.py
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+"""text_file
+
+provides the TextFile class, which gives an interface to text files
+that (optionally) takes care of stripping comments, ignoring blank
+lines, and joining lines with backslashes."""
+
+import sys, io
+
+
+class TextFile:
+    """Provides a file-like object that takes care of all the things you
+       commonly want to do when processing a text file that has some
+       line-by-line syntax: strip comments (as long as "#" is your
+       comment character), skip blank lines, join adjacent lines by
+       escaping the newline (ie. backslash at end of line), strip
+       leading and/or trailing whitespace.  All of these are optional
+       and independently controllable.
+
+       Provides a 'warn()' method so you can generate warning messages that
+       report physical line number, even if the logical line in question
+       spans multiple physical lines.  Also provides 'unreadline()' for
+       implementing line-at-a-time lookahead.
+
+       Constructor is called as:
+
+           TextFile (filename=None, file=None, **options)
+
+       It bombs (RuntimeError) if both 'filename' and 'file' are None;
+       'filename' should be a string, and 'file' a file object (or
+       something that provides 'readline()' and 'close()' methods).  It is
+       recommended that you supply at least 'filename', so that TextFile
+       can include it in warning messages.  If 'file' is not supplied,
+       TextFile creates its own using 'io.open()'.
+
+       The options are all boolean, and affect the value returned by
+       'readline()':
+         strip_comments [default: true]
+           strip from "#" to end-of-line, as well as any whitespace
+           leading up to the "#" -- unless it is escaped by a backslash
+         lstrip_ws [default: false]
+           strip leading whitespace from each line before returning it
+         rstrip_ws [default: true]
+           strip trailing whitespace (including line terminator!) from
+           each line before returning it
+         skip_blanks [default: true}
+           skip lines that are empty *after* stripping comments and
+           whitespace.  (If both lstrip_ws and rstrip_ws are false,
+           then some lines may consist of solely whitespace: these will
+           *not* be skipped, even if 'skip_blanks' is true.)
+         join_lines [default: false]
+           if a backslash is the last non-newline character on a line
+           after stripping comments and whitespace, join the following line
+           to it to form one "logical line"; if N consecutive lines end
+           with a backslash, then N+1 physical lines will be joined to
+           form one logical line.
+         collapse_join [default: false]
+           strip leading whitespace from lines that are joined to their
+           predecessor; only matters if (join_lines and not lstrip_ws)
+         errors [default: 'strict']
+           error handler used to decode the file content
+
+       Note that since 'rstrip_ws' can strip the trailing newline, the
+       semantics of 'readline()' must differ from those of the builtin file
+       object's 'readline()' method!  In particular, 'readline()' returns
+       None for end-of-file: an empty string might just be a blank line (or
+       an all-whitespace line), if 'rstrip_ws' is true but 'skip_blanks' is
+       not."""
+
+    default_options = { 'strip_comments': 1,
+                        'skip_blanks':    1,
+                        'lstrip_ws':      0,
+                        'rstrip_ws':      1,
+                        'join_lines':     0,
+                        'collapse_join':  0,
+                        'errors':         'strict',
+                      }
+
+    def __init__(self, filename=None, file=None, **options):
+        """Construct a new TextFile object.  At least one of 'filename'
+           (a string) and 'file' (a file-like object) must be supplied.
+           They keyword argument options are described above and affect
+           the values returned by 'readline()'."""
+        if filename is None and file is None:
+            raise RuntimeError("you must supply either or both of 'filename' and 'file'")
+
+        # set values for all options -- either from client option hash
+        # or fallback to default_options
+        for opt in self.default_options.keys():
+            if opt in options:
+                setattr(self, opt, options[opt])
+            else:
+                setattr(self, opt, self.default_options[opt])
+
+        # sanity check client option hash
+        for opt in options.keys():
+            if opt not in self.default_options:
+                raise KeyError("invalid TextFile option '%s'" % opt)
+
+        if file is None:
+            self.open(filename)
+        else:
+            self.filename = filename
+            self.file = file
+            self.current_line = 0       # assuming that file is at BOF!
+
+        # 'linebuf' is a stack of lines that will be emptied before we
+        # actually read from the file; it's only populated by an
+        # 'unreadline()' operation
+        self.linebuf = []
+
+    def open(self, filename):
+        """Open a new file named 'filename'.  This overrides both the
+           'filename' and 'file' arguments to the constructor."""
+        self.filename = filename
+        self.file = io.open(self.filename, 'r', errors=self.errors)
+        self.current_line = 0
+
+    def close(self):
+        """Close the current file and forget everything we know about it
+           (filename, current line number)."""
+        file = self.file
+        self.file = None
+        self.filename = None
+        self.current_line = None
+        file.close()
+
+    def gen_error(self, msg, line=None):
+        outmsg = []
+        if line is None:
+            line = self.current_line
+        outmsg.append(self.filename + ", ")
+        if isinstance(line, (list, tuple)):
+            outmsg.append("lines %d-%d: " % tuple(line))
+        else:
+            outmsg.append("line %d: " % line)
+        outmsg.append(str(msg))
+        return "".join(outmsg)
+
+    def error(self, msg, line=None):
+        raise ValueError("error: " + self.gen_error(msg, line))
+
+    def warn(self, msg, line=None):
+        """Print (to stderr) a warning message tied to the current logical
+           line in the current file.  If the current logical line in the
+           file spans multiple physical lines, the warning refers to the
+           whole range, eg. "lines 3-5".  If 'line' supplied, it overrides
+           the current line number; it may be a list or tuple to indicate a
+           range of physical lines, or an integer for a single physical
+           line."""
+        sys.stderr.write("warning: " + self.gen_error(msg, line) + "\n")
+
+    def readline(self):
+        """Read and return a single logical line from the current file (or
+           from an internal buffer if lines have previously been "unread"
+           with 'unreadline()').  If the 'join_lines' option is true, this
+           may involve reading multiple physical lines concatenated into a
+           single string.  Updates the current line number, so calling
+           'warn()' after 'readline()' emits a warning about the physical
+           line(s) just read.  Returns None on end-of-file, since the empty
+           string can occur if 'rstrip_ws' is true but 'strip_blanks' is
+           not."""
+        # If any "unread" lines waiting in 'linebuf', return the top
+        # one.  (We don't actually buffer read-ahead data -- lines only
+        # get put in 'linebuf' if the client explicitly does an
+        # 'unreadline()'.
+        if self.linebuf:
+            line = self.linebuf[-1]
+            del self.linebuf[-1]
+            return line
+
+        buildup_line = ''
+
+        while True:
+            # read the line, make it None if EOF
+            line = self.file.readline()
+            if line == '':
+                line = None
+
+            if self.strip_comments and line:
+
+                # Look for the first "#" in the line.  If none, never
+                # mind.  If we find one and it's the first character, or
+                # is not preceded by "\", then it starts a comment --
+                # strip the comment, strip whitespace before it, and
+                # carry on.  Otherwise, it's just an escaped "#", so
+                # unescape it (and any other escaped "#"'s that might be
+                # lurking in there) and otherwise leave the line alone.
+
+                pos = line.find("#")
+                if pos == -1: # no "#" -- no comments
+                    pass
+
+                # It's definitely a comment -- either "#" is the first
+                # character, or it's elsewhere and unescaped.
+                elif pos == 0 or line[pos-1] != "\\":
+                    # Have to preserve the trailing newline, because it's
+                    # the job of a later step (rstrip_ws) to remove it --
+                    # and if rstrip_ws is false, we'd better preserve it!
+                    # (NB. this means that if the final line is all comment
+                    # and has no trailing newline, we will think that it's
+                    # EOF; I think that's OK.)
+                    eol = (line[-1] == '\n') and '\n' or ''
+                    line = line[0:pos] + eol
+
+                    # If all that's left is whitespace, then skip line
+                    # *now*, before we try to join it to 'buildup_line' --
+                    # that way constructs like
+                    #   hello \\
+                    #   # comment that should be ignored
+                    #   there
+                    # result in "hello there".
+                    if line.strip() == "":
+                        continue
+                else: # it's an escaped "#"
+                    line = line.replace("\\#", "#")
+
+            # did previous line end with a backslash? then accumulate
+            if self.join_lines and buildup_line:
+                # oops: end of file
+                if line is None:
+                    self.warn("continuation line immediately precedes "
+                              "end-of-file")
+                    return buildup_line
+
+                if self.collapse_join:
+                    line = line.lstrip()
+                line = buildup_line + line
+
+                # careful: pay attention to line number when incrementing it
+                if isinstance(self.current_line, list):
+                    self.current_line[1] = self.current_line[1] + 1
+                else:
+                    self.current_line = [self.current_line,
+                                         self.current_line + 1]
+            # just an ordinary line, read it as usual
+            else:
+                if line is None: # eof
+                    return None
+
+                # still have to be careful about incrementing the line number!
+                if isinstance(self.current_line, list):
+                    self.current_line = self.current_line[1] + 1
+                else:
+                    self.current_line = self.current_line + 1
+
+            # strip whitespace however the client wants (leading and
+            # trailing, or one or the other, or neither)
+            if self.lstrip_ws and self.rstrip_ws:
+                line = line.strip()
+            elif self.lstrip_ws:
+                line = line.lstrip()
+            elif self.rstrip_ws:
+                line = line.rstrip()
+
+            # blank line (whether we rstrip'ed or not)? skip to next line
+            # if appropriate
+            if (line == '' or line == '\n') and self.skip_blanks:
+                continue
+
+            if self.join_lines:
+                if line[-1] == '\\':
+                    buildup_line = line[:-1]
+                    continue
+
+                if line[-2:] == '\\\n':
+                    buildup_line = line[0:-2] + '\n'
+                    continue
+
+            # well, I guess there's some actual content there: return it
+            return line
+
+    def readlines(self):
+        """Read and return the list of all logical lines remaining in the
+           current file."""
+        lines = []
+        while True:
+            line = self.readline()
+            if line is None:
+                return lines
+            lines.append(line)
+
+    def unreadline(self, line):
+        """Push 'line' (a string) onto an internal buffer that will be
+           checked by future 'readline()' calls.  Handy for implementing
+           a parser with line-at-a-time lookahead."""
+        self.linebuf.append(line)