[PATCH RFC] configoptions: introduce registrar for config options
Ryan McElroy
rm at fb.com
Tue Apr 11 09:47:55 UTC 2017
Thanks for sending this out and sorry for not paying attention to it for
so long.
The relevant parts of the sprint discussion, I think, are in the
sections "Friendly HG Breakout" and " Experimental as a Tag instead of a
Name" (those are the two places where "registry" came up. There's also
some related discussion in the " Flags and defaults breakout" breakout,
but that stuff has mostly been sent in patches by Rodrigo and myself
already.
I have to take a closer look at this patch and at Jun's immutable config
stuff to see if these interact at all. I also think that David SP was
thinking about some config registry stuff as well. I may play with this
idea during the freeze to see if I can come up with a nice incremental
conversion as well.
Again, thanks for the RFC. I'll try to dive in deeper soon.
~Ryan
On 3/24/17 5:41 PM, Gregory Szorc wrote:
> On Fri, Mar 24, 2017 at 10:24 AM, Martin von Zweigbergk
> <martinvonz at google.com <mailto:martinvonz at google.com>> wrote:
>
> On Sun, Mar 12, 2017 at 12:18 PM, Gregory Szorc
> <gregory.szorc at gmail.com <mailto:gregory.szorc at gmail.com>> wrote:
> > # HG changeset patch
> > # User Gregory Szorc <gregory.szorc at gmail.com
> <mailto:gregory.szorc at gmail.com>>
> > # Date 1489346234 25200
> > # Sun Mar 12 12:17:14 2017 -0700
> > # Node ID dd26bc2a3056879181851aaa3ff4accbfc42e1ad
> > # Parent 62939e0148f170b67ca8c7374f36c413b67fd387
> > configoptions: introduce registrar for config options
>
> I like the direction. I missed the discussion at the sprint. Was the
> consensus that this is the way to go?
>
>
> There were some side discussions. Not anything formal IIRC.
>
>
> What's the next step? Will you send a non-RFC series adding a few
> users as well? I'm also curious to see the "Actually hooking it up to
> config loading" step.
>
>
> I have no plans to work on this.
>
> I put the RFC out there because there were a number of conversations
> around overhauling configs and I wanted a tangible prototype for a
> formal config declaration mechanism to be in people's minds so they
> could consider benefits that a more formal config mechanism would
> have. (I think it can solve a lot of problems around things like
> environment variable mappings, config aliases, stronger type checking,
> mapping configs to command arguments, etc.)
>
>
> >
> > Various talks at the sprint have revolved around establishing more
> > formalization around config options. Specific problems we'd like
> > to solve or are thinking about solving include:
> >
> > * Experimental config options not documented and are not
> discoverable
> > to end-users.
> > * Config options aren't strongly typed (it depends how they are
> > accessed).
> > * Config options for extensions don't appear in `hg help config`.
> > * There is no formal mechanism to map a config option to command
> > argument behavior. e.g. have a config option imply a command
> > argument. Instead, logic is done in the command implementation,
> > which results in inconsistent behavior, error messages, weird
> > `hg help <command>` output.
> > * Config option validation is done at the call site and not as part
> > of config loading or command dispatching.
> > * Config options are declared by side-effect all over the repo. It
> > might be nicer to have a single "registry" so the full context of
> > all options is easily referenced.
> > * No mechanism to "alias" an old config option to a new one. e.g.
> > carrying over "experimental.feature" to its final value.
> >
> > This patch introduces a very eary proof of concept for improving
> > the situation. It adds config options to the "registrar" mechanism,
> > which allows their declaration to be formalized and recorded in
> > a central location. This is conceptually similar to populating a
> > central dict with the data. I chose to use decorators and (for now)
> > empty functions for declaring config options. This allows docstrings
> > to be used for writing the config help.
> >
> > In the future, one could imagine actually calling the function
> > declaring the config option. It could receive a ui instance and
> > an object defining the command being invoked. The function could
> > then look for conflicting options, adjust command arguments, etc.
> > It could do so in a way that is consistent across commands. e.g.
> > a ConfigOptionConflict exception could be raised and the ui or
> > dispatcher could consistently format that error condition rather
> > than leaving it to individual command functions to raise on their
> > own.
> >
> > It's worth noting that we need all the *core* options defined in
> > a central file because of lazy module loading. If a module isn't
> > loaded, the config option declarations wouldn't be called!
> >
> > There are several things missing from this patch and open issues to
> > resolve:
> >
> > * i18n of help text
> > * Actually using docstrings in `hg help`
> > * Hooking up strong typing or hinted typing
> > * Figuring out how to declare config options with sub-options
> > * Better solution for declaring config options that have both global
> > options and per-item sub-options (like hostsecurity.ciphers)
> > * Actually hooking it up to config loading
> > * Mechanism for declaring config options in extensions
> >
> > diff --git a/mercurial/configoptions.py b/mercurial/configoptions.py
> > new file mode 100644
> > --- /dev/null
> > +++ b/mercurial/configoptions.py
> > @@ -0,0 +1,102 @@
> > +# configoptions.py -- Declaration of configuration options
> > +#
> > +# Copyright 2017 Gregory Szorc <gregory.szorc at gmail.com
> <mailto:gregory.szorc at gmail.com>>
> > +#
> > +# This software may be used and distributed according to the
> terms of the
> > +# GNU General Public License version 2 or any later version.
> > +
> > +from . import (
> > + registrar,
> > +)
> > +
> > +configoption = registrar.configoption()
> > +
> > + at configoption('hostsecurity.ciphers')
> > +def optionciphers():
> > + """Defines the cryptographic ciphers to use for connections.
> > +
> > + Value must be a valid OpenSSL Cipher List Format as
> documented at
> > +
> https://www.openssl.org/docs/manmaster/apps/ciphers.html#CIPHER-LIST-FORMAT
> <https://urldefense.proofpoint.com/v2/url?u=https-3A__www.openssl.org_docs_manmaster_apps_ciphers.html-23CIPHER-2DLIST-2DFORMAT&d=DwMFaQ&c=5VD0RTtNlTh3ycd41b3MUw&r=Jw8rundaE7TbmqBYd1txIQ&m=6FYVT5Po5N2vyslmzAdZmMlUq8oQi1a-uYeozyLWArw&s=JbBgutXmiKYWcHYWQaz5_9SUBel8KfUtwNVbTj_RPRA&e=>.
> > +
> > + This setting is for advanced users only. Setting to
> incorrect values
> > + can significantly lower connection security or decrease
> performance.
> > + You have been warned.
> > +
> > + This option requires Python 2.7.
> > + """
> > +
> > + at configoption('hostsecurity.minimumprotocol')
> > +def optionminimumprotocol():
> > + """Defines the minimum channel encryption protocol to use.
> > +
> > + By default, the highest version of TLS supported by both
> client and
> > + server is used.
> > +
> > + Allowed values are: ``tls1.0``, ``tls1.1``, ``tls1.2``.
> > +
> > + When running on an old Python version, only ``tls1.0`` is
> allowed since
> > + old versions of Python only support up to TLS 1.0.
> > +
> > + When running a Python that supports modern TLS versions,
> the default is
> > + ``tls1.1``. ``tls1.0`` can still be used to allow TLS 1.0.
> However, this
> > + weakens security and should only be used as a feature of
> last resort if
> > + a server does not support TLS 1.1+.
> > + """
> > +
> > + at configoption('hostsecurity.*:ciphers')
> > +def perhostciphers():
> > + """Per host version of ``hostsecurity.ciphers``."""
> > +
> > + at configoption('hostsecurity.*:fingerprints')
> > +def perhostfingerprints():
> > + """A list of hashes of the DER encoded peer/remote
> certificate. Values
> > + have the form ``algorithm``:``fingerprint``. e.g.
> > +
> ``sha256:c3ab8ff13720e8ad9047dd39466b3c8974e592c2fa383d4a3960714caef0c4f2``.
> > +
> > + The following algorithms/prefixes are supported: ``sha1``,
> ``sha256``,
> > + ``sha512``.
> > +
> > + Use of ``sha256`` or ``sha512`` is preferred.
> > +
> > + If a fingerprint is specified, the CA chain is not
> validated for this
> > + host and Mercurial will require the remote certificate to
> match one
> > + of the fingerprints specified. This means if the server
> updates its
> > + certificate, Mercurial will abort until a new fingerprint
> is defined.
> > + This can provide stronger security than traditional
> CA-based validation
> > + at the expense of convenience.
> > +
> > + This option takes precedence over ``verifycertsfile``.
> > + """
> > +
> > + at configoption('hostsecurity.*:minimumprotocol')
> > +def perhostminimumprotocol():
> > + """This behaves like ``minimumprotocol`` as described above
> except it
> > + only applies to the host on which it is defined.
> > + """
> > +
> > + at configoption('hostsecurity.*:verifycertsfile')
> > +def perhostverifycertsfile():
> > + """Path to file a containing a list of PEM encoded
> certificates used to
> > + verify the server certificate. Environment variables and
> ``~user``
> > + constructs are expanded in the filename.
> > +
> > + The server certificate or the certificate's certificate
> authority (CA)
> > + must match a certificate from this file or certificate
> verification
> > + will fail and connections to the server will be refused.
> > +
> > + If defined, only certificates provided by this file will be
> used:
> > + ``web.cacerts`` and any system/default certificates will not be
> > + used.
> > +
> > + This option has no effect if the per-host ``fingerprints``
> option
> > + is set.
> > +
> > + The format of the file is as follows::
> > +
> > + -----BEGIN CERTIFICATE-----
> > + ... (certificate in base64 PEM encoding) ...
> > + -----END CERTIFICATE-----
> > + -----BEGIN CERTIFICATE-----
> > + ... (certificate in base64 PEM encoding) ...
> > + -----END CERTIFICATE-----
> > + """
> > diff --git a/mercurial/registrar.py b/mercurial/registrar.py
> > --- a/mercurial/registrar.py
> > +++ b/mercurial/registrar.py
> > @@ -251,4 +251,20 @@ class templatefunc(_templateregistrarbas
> >
> > Otherwise, explicit 'templater.loadfunction()' is needed.
> > """
> > _getname = _funcregistrarbase._parsefuncdecl
> > +
> > +class configoption(_funcregistrarbase):
> > + """Decorator to register a config option."""
> > + def _getname(self, decl):
> > + return decl
> > +
> > + def _formatdoc(self, decl, doc):
> > + return pycompat.sysstr('.'.join(decl))
> > +
> > + def _extrasetup(self, name, func, *args, **kwargs):
> > + section, option = name.split('.', 1)
> > +
> > + self._section = section
> > + self._name = name
> > +
> > + self._extra = kwargs
> > diff --git a/mercurial/ui.py b/mercurial/ui.py
> > --- a/mercurial/ui.py
> > +++ b/mercurial/ui.py
> > @@ -27,8 +27,9 @@ from .node import hex
> >
> > from . import (
> > color,
> > config,
> > + configoptions,
> > encoding,
> > error,
> > formatter,
> > progress,
> > @@ -135,8 +136,11 @@ class ui(object):
> > Use uimod.ui.load() to create a ui which knows global
> and user configs.
> > In most cases, you should use ui.copy() to create a
> copy of an existing
> > ui object.
> > """
> > + # Ensure config options are imported as a side-effect.
> > + options = configoptions.configoption
> > +
> > # _buffers: used for temporary capture of output
> > self._buffers = []
> > # 3-tuple describing how each buffer in the stack behaves.
> > # Values are (capture stderr, capture subprocesses,
> apply labels).
>
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