view mercurial/hgweb/wsgiheaders.py @ 46335:25be21ec6c65

share: rework config options to be much clearer and easier

Recently I implemented various boolean configs which control how to behave when
there is a share-safe mismatch between source and share repository. Mismatch
means that source supports share-safe where as share does not or vice versa.

However, while discussion and documentation we realized that it's too
complicated and there are some combinations of values which makes no sense.

We decided to introduce a config option with 4 possible values which
makes controlling and understanding things easier.

The config option `share.safe-mismatch.source-{not-}safe` can have
following 4 values:

* abort (default): error out if there is mismatch
* allow: allow to work with respecting share source configuration
* {up|down}grade-abort: try to {up|down}grade, if it fails, abort
* {up|down}grade-allow: try to {up|down}grade, if it fails, continue in allow
mode


I am not sure if I can explain 3 config options which I deleted right now in
just 5 lines which is a sign of how complex they became.

No test changes demonstrate that functionality is same, only names have changed.

Differential Revision: https://phab.mercurial-scm.org/D9785

"""This was forked from cpython's wsgiref.headers module to work on bytes.

Header from old file showing copyright is below.

Much of this module is red-handedly pilfered from email.message in the stdlib,
so portions are Copyright (C) 2001,2002 Python Software Foundation, and were
written by Barry Warsaw.
"""

# Regular expression that matches `special' characters in parameters, the
# existence of which force quoting of the parameter value.
from __future__ import absolute_import, print_function

import re

tspecials = re.compile(br'[ ()<>@,;:\\"/\[\]?=]')


def _formatparam(param, value=None, quote=1):
    """Convenience function to format and return a key=value pair.
    This will quote the value if needed or if quote is true.
    """
    if value is not None and len(value) > 0:
        if quote or tspecials.search(value):
            value = value.replace(b'\\', b'\\\\').replace(b'"', r'\"')
            return b'%s="%s"' % (param, value)
        else:
            return b'%s=%s' % (param, value)
    else:
        return param


class Headers(object):
    """Manage a collection of HTTP response headers"""

    def __init__(self, headers=None):
        headers = headers if headers is not None else []
        if type(headers) is not list:
            raise TypeError(b"Headers must be a list of name/value tuples")
        self._headers = headers
        if __debug__:
            for k, v in headers:
                self._convert_string_type(k)
                self._convert_string_type(v)

    def _convert_string_type(self, value):
        """Convert/check value type."""
        if type(value) is bytes:
            return value
        raise AssertionError(
            u"Header names/values must be"
            u" of type bytes (got %s)" % repr(value)
        )

    def __len__(self):
        """Return the total number of headers, including duplicates."""
        return len(self._headers)

    def __setitem__(self, name, val):
        """Set the value of a header."""
        del self[name]
        self._headers.append(
            (self._convert_string_type(name), self._convert_string_type(val))
        )

    def __delitem__(self, name):
        """Delete all occurrences of a header, if present.
        Does *not* raise an exception if the header is missing.
        """
        name = self._convert_string_type(name.lower())
        self._headers[:] = [kv for kv in self._headers if kv[0].lower() != name]

    def __getitem__(self, name):
        """Get the first header value for 'name'
        Return None if the header is missing instead of raising an exception.
        Note that if the header appeared multiple times, the first exactly which
        occurrence gets returned is undefined.  Use getall() to get all
        the values matching a header field name.
        """
        return self.get(name)

    def __contains__(self, name):
        """Return true if the message contains the header."""
        return self.get(name) is not None

    def get_all(self, name):
        """Return a list of all the values for the named field.
        These will be sorted in the order they appeared in the original header
        list or were added to this instance, and may contain duplicates.  Any
        fields deleted and re-inserted are always appended to the header list.
        If no fields exist with the given name, returns an empty list.
        """
        name = self._convert_string_type(name.lower())
        return [kv[1] for kv in self._headers if kv[0].lower() == name]

    def get(self, name, default=None):
        """Get the first header value for 'name', or return 'default'"""
        name = self._convert_string_type(name.lower())
        for k, v in self._headers:
            if k.lower() == name:
                return v
        return default

    def keys(self):
        """Return a list of all the header field names.
        These will be sorted in the order they appeared in the original header
        list, or were added to this instance, and may contain duplicates.
        Any fields deleted and re-inserted are always appended to the header
        list.
        """
        return [k for k, v in self._headers]

    def values(self):
        """Return a list of all header values.
        These will be sorted in the order they appeared in the original header
        list, or were added to this instance, and may contain duplicates.
        Any fields deleted and re-inserted are always appended to the header
        list.
        """
        return [v for k, v in self._headers]

    def items(self):
        """Get all the header fields and values.
        These will be sorted in the order they were in the original header
        list, or were added to this instance, and may contain duplicates.
        Any fields deleted and re-inserted are always appended to the header
        list.
        """
        return self._headers[:]

    def __repr__(self):
        return "%s(%r)" % (self.__class__.__name__, self._headers)

    def __str__(self):
        """str() returns the formatted headers, complete with end line,
        suitable for direct HTTP transmission."""
        return b'\r\n'.join(
            [b"%s: %s" % kv for kv in self._headers] + [b'', b'']
        )

    def __bytes__(self):
        return str(self).encode('iso-8859-1')

    def setdefault(self, name, value):
        """Return first matching header value for 'name', or 'value'
        If there is no header named 'name', add a new header with name 'name'
        and value 'value'."""
        result = self.get(name)
        if result is None:
            self._headers.append(
                (
                    self._convert_string_type(name),
                    self._convert_string_type(value),
                )
            )
            return value
        else:
            return result

    def add_header(self, _name, _value, **_params):
        """Extended header setting.
        _name is the header field to add.  keyword arguments can be used to set
        additional parameters for the header field, with underscores converted
        to dashes.  Normally the parameter will be added as key="value" unless
        value is None, in which case only the key will be added.
        Example:
        h.add_header('content-disposition', 'attachment', filename='bud.gif')
        Note that unlike the corresponding 'email.message' method, this does
        *not* handle '(charset, language, value)' tuples: all values must be
        strings or None.
        """
        parts = []
        if _value is not None:
            _value = self._convert_string_type(_value)
            parts.append(_value)
        for k, v in _params.items():
            k = self._convert_string_type(k)
            if v is None:
                parts.append(k.replace(b'_', b'-'))
            else:
                v = self._convert_string_type(v)
                parts.append(_formatparam(k.replace(b'_', b'-'), v))
        self._headers.append(
            (self._convert_string_type(_name), b"; ".join(parts))
        )