# correspond.registry Which channels exist: the built-in channel table, the registry built from it, and what each channel needs. The table (`CHANNELS`) is the one place a channel is described: its adapter’s factory, the optional modules and extra it needs, the binaries and platforms, and every setting with its environment variable and where to get it. Adapters read settings through [`value()`](#correspond.registry.value) and [`require()`](#correspond.registry.require), so a variable name is written once. The process registry ([`channels()`](#correspond.registry.channels)) is an `xdol.Registry` built from the table on first use: a channel registers only when its optional modules import, and its adapter is constructed only when first asked for. [`check_requirements()`](#correspond.registry.check_requirements) explains what a channel is missing, without printing a secret. ```pycon >>> info("telegram").setting("token").env 'TELEGRAM_BOT_TOKEN' >>> info("signal").setting("number").env 'CORRESPOND_SIGNAL_NUMBER' ``` ### Functions | [`build_registry`](#correspond.registry.build_registry)([infos, name]) | A fresh `xdol.Registry` with a lazy entry for every built channel whose optional modules import. | |----------------------------------------------------------------------------------------------------|--------------------------------------------------------------------------------------------------------------------------------------------------------------| | [`channels`](#correspond.registry.channels)() | The process registry: built on first use, then shared. | | [`check_requirements`](#correspond.registry.check_requirements)(channel, \*[, registry, ...]) | What a channel needs and what is missing: the install command, binaries, platform, and every setting's source. | | [`info`](#correspond.registry.info)(channel) | The table entry for a built-in channel. | | [`load_factory`](#correspond.registry.load_factory)(ref) | The object a `module:attribute` reference names. | | [`register_channel`](#correspond.registry.register_channel)(adapter, \*[, name, ...]) | Add an adapter (tests, or a channel defined outside correspond). | | [`require`](#correspond.registry.require)(channel, key, \*[, config, run]) | A channel setting's value, or [`MissingRequirement`](correspond.errors.html.md#correspond.errors.MissingRequirement) saying how to set it. | | [`resolve`](#correspond.registry.resolve)(channel, setting, \*[, config, run, ...]) | `(value, source)`; source is `env`, `keychain`, `config`, `default` or `missing`. | | [`unregister_channel`](#correspond.registry.unregister_channel)(name, \*[, registry]) | Remove a channel from the registry. | | [`value`](#correspond.registry.value)(channel, key, \*[, config, run, keychain]) | A channel setting's value, or `None` when it is not set and has no default (`keychain=False`: skip the Keychain). | ### Classes | [`ChannelInfo`](#correspond.registry.ChannelInfo)(\*, name, summary[, factory, ...]) | Everything correspond knows about a channel before constructing its adapter. | |----------------------------------------------------------------------------------------------------|----------------------------------------------------------------------------------------------------| | [`Setting`](#correspond.registry.Setting)(\*, key, env, what[, where, secret, ...]) | One value a channel reads: its config key, its environment variable, what it is and how to get it. | ### *class* correspond.registry.ChannelInfo(, name, summary, factory='', modules=(), extra=None, binaries=(), platforms=(), settings=(), notes=(), check='', planned=None) Bases: [`object`](https://docs.python.org/3/builtins/functions.html#object) Everything correspond knows about a channel before constructing its adapter. #### setting(key) The setting named `key`. * **Return type:** [`Setting`](#correspond.registry.Setting) ### *class* correspond.registry.Setting(, key, env, what, where='', secret=False, required=False, default=None) Bases: [`object`](https://docs.python.org/3/builtins/functions.html#object) One value a channel reads: its config key, its environment variable, what it is and how to get it. A `secret` is never read from the config file: it comes from `env`, else (on macOS) the Keychain. ### correspond.registry.build_registry(infos=(ChannelInfo(name='github', summary="GitHub issues, pull request conversations and discussions, through the gh CLI (the machine's gh login; correspond holds no token)", factory='correspond.channels.github:GitHub', modules=(), extra=None, binaries=(('gh',),), platforms=(), settings=(Setting(key='webhook_secret', env='GITHUB_WEBHOOK_SECRET', what='the webhook secret, used only to verify deliveries', where='the secret set on the repository or organization webhook (Settings, Webhooks)', secret=True, required=False, default=None), Setting(key='delivery', env='CORRESPOND_GITHUB_DELIVERY', what='where listen takes discussion activity from: poll (the activity walk alone) or webhook (the walk plus every discussion the discussion_comment webhook receiver saw)', where='', secret=False, required=False, default='poll'), Setting(key='webhook_store', env='CORRESPOND_GITHUB_WEBHOOK_STORE', what='where the webhook receiver keeps deliveries, as "module:attr" naming a MutableMapping of JSON-ready dicts, or a callable returning one (default: files under the data root)', where='', secret=False, required=False, default=None), Setting(key='webhook_allow_remote', env='CORRESPOND_GITHUB_WEBHOOK_ALLOW_REMOTE', what='true to let serve_webhook bind the webhook receiver to an address other machines reach (it binds 127.0.0.1 otherwise; put your HTTPS reverse proxy in front)', where='', secret=False, required=False, default='false')), notes=('log in once with \`gh auth login\` (https://cli.github.com/); check with \`gh auth status\`', 'webhook delivery of discussion comments on a server: install correspond[server], run correspond-github-webhook (127.0.0.1:8082, one worker) behind your HTTPS reverse proxy, add a repository or organization webhook (application/json, the webhook_secret, the Discussion comments event) pointing at it, and set delivery = webhook'), check='', planned=None), ChannelInfo(name='email', summary='Email: IMAP to read and listen, SMTP to send, with the standard library', factory='correspond.channels.mail:Email', modules=(), extra=None, binaries=(), platforms=(), settings=(Setting(key='imap_host', env='CORRESPOND_EMAIL_IMAP_HOST', what='the IMAP server', where="your mail provider's IMAP settings", secret=False, required=True, default=None), Setting(key='imap_port', env='CORRESPOND_EMAIL_IMAP_PORT', what='the IMAP port (TLS)', where='', secret=False, required=False, default='993'), Setting(key='smtp_host', env='CORRESPOND_EMAIL_SMTP_HOST', what='the SMTP server', where="your mail provider's SMTP settings", secret=False, required=True, default=None), Setting(key='smtp_port', env='CORRESPOND_EMAIL_SMTP_PORT', what='the SMTP port: 465 for TLS, 587 for STARTTLS', where='', secret=False, required=False, default='465'), Setting(key='user', env='CORRESPOND_EMAIL_USER', what='the mailbox login, usually its address', where='', secret=False, required=True, default=None), Setting(key='password', env='CORRESPOND_EMAIL_PASSWORD', what='the mailbox password, preferably an app password', where="your mail provider's app-password page (for Gmail: https://myaccount.google.com/apppasswords)", secret=True, required=True, default=None), Setting(key='from_address', env='CORRESPOND_EMAIL_FROM', what='the From address of sends (default: the login)', where='', secret=False, required=False, default=None), Setting(key='folder', env='CORRESPOND_EMAIL_FOLDER', what='the folder read and listened to when a reference names none (?folder=)', where='', secret=False, required=False, default='INBOX'), Setting(key='trusted_authserv_ids', env='CORRESPOND_EMAIL_TRUSTED_AUTHSERV_IDS', what='comma-separated authserv-ids of your own receiving server; only their Authentication-Results can make a sender \`domain\`', where='the topmost Authentication-Results header of a message your provider delivered (for Gmail: mx.google.com)', secret=False, required=False, default=None), Setting(key='own_domains', env='CORRESPOND_EMAIL_OWN_DOMAINS', what="comma-separated mail domains that are your own (and their subdomains); a recipient anywhere else makes an email's audience external", where='', secret=False, required=False, default=None), Setting(key='lists', env='CORRESPOND_EMAIL_LISTS', what='comma-separated mailing-list addresses, or @domain for a whole list server; local parts such as list, all, team, dev, announce and info count as lists anyway', where='', secret=False, required=False, default=None)), notes=(), check='', planned=None), ChannelInfo(name='ntfy', summary='Push notifications through an ntfy server (send only)', factory='correspond.channels.ntfy:Ntfy', modules=(), extra=None, binaries=(), platforms=(), settings=(Setting(key='url', env='NTFY_URL', what='the ntfy server', where='', secret=False, required=False, default='https://ntfy.sh'), Setting(key='topic', env='NTFY_TOPIC', what='the default topic, used by \`ntfy:\` with no topic', where='any long, hard-to-guess string; subscribe to it in the ntfy app (https://ntfy.sh)', secret=True, required=False, default=None), Setting(key='token', env='NTFY_TOKEN', what='an access token, for a server that requires one', where="your ntfy server's account page", secret=True, required=False, default=None), Setting(key='topic_remote', env='CORRESPOND_NTFY_TOPIC_REMOTE', what='an ssh host asked for the default topic when neither the environment nor the Keychain has it', where='', secret=False, required=False, default=None), Setting(key='topic_remote_file', env='CORRESPOND_NTFY_TOPIC_REMOTE_FILE', what='the file on that host holding a NTFY_TOPIC=... line', where='', secret=False, required=False, default=None), Setting(key='denies_anonymous_read', env='CORRESPOND_NTFY_DENIES_ANONYMOUS_READ', what='true when the server denies anonymous reads (its auth-default-access), so only the accounts it grants can read a topic; unset, anyone who knows a topic can', where='', secret=False, required=False, default=None), Setting(key='cache_duration', env='CORRESPOND_NTFY_CACHE_DURATION', what='how long the server keeps a message for subscribers who connect later (its cache-duration)', where='', secret=False, required=False, default='12h')), notes=('anyone who knows an unauthenticated topic can publish to it and read it: treat it as a secret',), check='', planned=None), ChannelInfo(name='macos', summary='Notification Centre banners on this Mac (send only)', factory='correspond.channels.macos:MacOS', modules=(), extra=None, binaries=(('terminal-notifier', 'osascript'),), platforms=('darwin',), settings=(), notes=('terminal-notifier (\`brew install terminal-notifier\`) keeps bodies intact; osascript is the fallback',), check='', planned=None), ChannelInfo(name='telegram', summary='A Telegram bot over the Bot API: listen with getUpdates or a webhook, read what was logged, send, edit, react', factory='correspond.channels.telegram:Telegram', modules=(), extra=None, binaries=(), platforms=(), settings=(Setting(key='token', env='TELEGRAM_BOT_TOKEN', what='the bot token', where='create a bot with BotFather in Telegram (https://core.telegram.org/bots/tutorial)', secret=True, required=True, default=None), Setting(key='api_url', env='CORRESPOND_TELEGRAM_API_URL', what='the Bot API server', where='', secret=False, required=False, default='https://api.telegram.org'), Setting(key='delivery', env='CORRESPOND_TELEGRAM_DELIVERY', what='where listen takes updates from: poll (getUpdates) or webhook (what the webhook receiver stored); Telegram serves one or the other', where='', secret=False, required=False, default='poll'), Setting(key='webhook_secret', env='CORRESPOND_TELEGRAM_WEBHOOK_SECRET', what='the secret token Telegram sends with every webhook delivery (1-256 of A-Z, a-z, 0-9, \_ and -)', where='generate one with: python -c "import secrets; print(secrets.token_urlsafe(32))"', secret=True, required=False, default=None), Setting(key='webhook_store', env='CORRESPOND_TELEGRAM_WEBHOOK_STORE', what='where the webhook receiver keeps updates, as "module:attr" naming a MutableMapping of JSON-ready dicts, or a callable returning one (a bytes store needs a JSON codec; default: files under the data root)', where='', secret=False, required=False, default=None), Setting(key='webhook_allow_remote', env='CORRESPOND_TELEGRAM_WEBHOOK_ALLOW_REMOTE', what='true to let serve_webhook bind the webhook receiver to an address other machines reach (it binds 127.0.0.1 otherwise; put your HTTPS reverse proxy in front)', where='', secret=False, required=False, default='false')), notes=('a bot can write only to chats that wrote to it first, or groups it was added to', 'privacy mode (on by default) hides group messages that do not address the bot', "webhook delivery on a server: install correspond[server], run serve_webhook() from correspond.channels.telegram (127.0.0.1:8081, one worker) behind your HTTPS reverse proxy, call Telegram().set_webhook('https://...'), and set delivery = webhook"), check='', planned=None), ChannelInfo(name='webinbox', summary="Reports posted from web pages to correspond's ASGI collector, and a reader over what it stored", factory='correspond.channels.webinbox:WebInbox', modules=(), extra=None, binaries=(), platforms=(), settings=(Setting(key='sites', env='CORRESPOND_WEBINBOX_SITES', what='comma-separated site names the collector accepts', where='', secret=False, required=False, default=None), Setting(key='origins', env='CORRESPOND_WEBINBOX_ORIGINS', what='comma-separated page origins allowed to post, e.g. https://app.example.org', where='', secret=False, required=False, default=None), Setting(key='secret', env='CORRESPOND_WEBINBOX_SECRET', what="the HMAC key shared with the host application's server, which signs its logged-in user (a single site; several sites need CORRESPOND_WEBINBOX_SECRET_ each)", where='generate one with: python -c "import secrets; print(secrets.token_hex(32))"', secret=True, required=False, default=None), Setting(key='max_age_s', env='CORRESPOND_WEBINBOX_MAX_AGE_S', what='how long a signed identity stays valid, in seconds', where='', secret=False, required=False, default='86400'), Setting(key='rate_per_minute', env='CORRESPOND_WEBINBOX_RATE_PER_MINUTE', what='reports accepted per client per minute, per site', where='', secret=False, required=False, default='10'), Setting(key='burst', env='CORRESPOND_WEBINBOX_BURST', what='reports a client may send in a burst', where='', secret=False, required=False, default='5'), Setting(key='max_body_bytes', env='CORRESPOND_WEBINBOX_MAX_BODY_BYTES', what='the largest request accepted, attachments included', where='', secret=False, required=False, default='5000000'), Setting(key='trusted_proxies', env='CORRESPOND_WEBINBOX_TRUSTED_PROXIES', what='how many reverse proxies of yours stand in front of the collector; the address rate-limited is read that many hops from the right of X-Forwarded-For (0: the connecting address)', where='', secret=False, required=False, default='0')), notes=('serve the collector on localhost behind your own server, e.g. \`uvicorn --factory correspond.channels.webinbox:app_from_env --host 127.0.0.1\`', 'for a reverse proxy on another host set CORRESPOND_WEBINBOX_TRUSTED_PROXIES (1 for one proxy), or every visitor shares one rate limit; uvicorn already resolves a proxy on 127.0.0.1', "several sites on one collector need a secret each, CORRESPOND_WEBINBOX_SECRET_ (upper case, - as \_) or the Keychain item correspond-webinbox-secret-, so no site's server can sign for another"), check='correspond.channels.webinbox:requirements_problems', planned=None), ChannelInfo(name='discord', summary='Discord: a bot reading, polling and posting in channels over REST, through discorddol', factory='correspond.channels.discord:Discord', modules=('discorddol',), extra='discord', binaries=(), platforms=(), settings=(Setting(key='token', env='DISCORD_BOT_TOKEN', what='the bot token', where='Discord Developer Portal (https://discord.com/developers/applications): your application, Bot, Reset Token; invite the bot to the server with the View Channels, Read Message History and Send Messages permissions', secret=True, required=True, default=None), Setting(key='public_key', env='DISCORD_PUBLIC_KEY', what="the application's public key (64 hex characters), which checks the Ed25519 signature on an HTTP interaction; needed by verify only", where='Discord Developer Portal (https://discord.com/developers/applications): your application, General Information, Public Key', secret=False, required=False, default=None), Setting(key='listen_via', env='DISCORD_LISTEN_VIA', what="how listen reaches Discord: rest (poll a channel's history: new messages only) or gateway (a short gateway window that resumes its session: new, edited and deleted messages)", where='', secret=False, required=False, default='rest'), Setting(key='listen_wait_s', env='DISCORD_LISTEN_WAIT_S', what='with listen_via = gateway, how many quiet seconds a listen waits on the gateway before it returns', where='', secret=False, required=False, default='5')), notes=('enable the Message Content intent (Developer Portal, Bot, Privileged Gateway Intents) or the bot reads empty text for messages that do not mention it',), check='', planned=None), ChannelInfo(name='slack', summary="Slack: drafts in Slack's own formatting (mrkdwn); reading, polling and posting with a token over the Web API, or posting through an incoming webhook", factory='correspond.channels.slack:Slack', modules=(), extra=None, binaries=(), platforms=(), settings=(Setting(key='token', env='CORRESPOND_SLACK_TOKEN', what='a Slack token: a bot token (xoxb-) acts as the app, a user token (xoxp-) as the person', where='api.slack.com/apps: create an app for your workspace (internal, not distributed), add the bot scopes channels:history, channels:read, chat:write and files:read (groups:history and groups:read for private channels), install it, copy the Bot User OAuth Token, and invite the app to each channel', secret=True, required=False, default=None), Setting(key='api_base', env='CORRESPOND_SLACK_API_BASE', what='the Web API your workspace lives behind: https://slack.com/api, or https://slack-gov.com/api for GovSlack (Socket Mode and file fetches then go to slack-gov.com hosts only)', where='', secret=False, required=False, default='https://slack.com/api'), Setting(key='signing_secret', env='CORRESPOND_SLACK_SIGNING_SECRET', what="the app's signing secret, used only to verify requests Slack sends (Events API, interactivity)", where='api.slack.com/apps: your app, Basic Information, App Credentials', secret=True, required=False, default=None), Setting(key='delivery', env='CORRESPOND_SLACK_DELIVERY', what='where listen takes messages from: poll (conversations.history), events (what the Events API receiver stored: new, edited and deleted messages) or socket (a short Socket Mode window, no public URL: the same events; needs app_token and the slack extra)', where='', secret=False, required=False, default='poll'), Setting(key='app_token', env='CORRESPOND_SLACK_APP_TOKEN', what="an app-level token (xapp-) with connections:write, used only by delivery = socket to open Slack's Socket Mode", where='api.slack.com/apps: your app, Socket Mode (turn it on), then Basic Information, App-Level Tokens, Generate Token and Scopes with connections:write; subscribe to the bot events message.channels (and message.groups) under Event Subscriptions', secret=True, required=False, default=None), Setting(key='listen_wait_s', env='CORRESPOND_SLACK_LISTEN_WAIT_S', what='with delivery = socket, how many quiet seconds a listen keeps Socket Mode open before it returns (at most 60; a window closes after 60 s in all)', where='', secret=False, required=False, default='5'), Setting(key='keep_channels', env='CORRESPOND_SLACK_KEEP_CHANNELS', what="with delivery = events or socket, the channel ids (comma-separated) whose message events are stored; the others are acknowledged and dropped (default: every channel's, kept a week); a running receiver reads it when it starts", where='', secret=False, required=False, default=None), Setting(key='webhook_store', env='CORRESPOND_SLACK_WEBHOOK_STORE', what='where the Events API receiver keeps events, as "module:attr" naming a MutableMapping of JSON-ready dicts, or a callable returning one (a bytes store needs a JSON codec; default: files under the data root)', where='', secret=False, required=False, default=None), Setting(key='webhook_allow_remote', env='CORRESPOND_SLACK_WEBHOOK_ALLOW_REMOTE', what='true to let serve_events bind the Events API receiver to an address other machines reach (it binds 127.0.0.1 otherwise; put your HTTPS reverse proxy in front)', where='', secret=False, required=False, default='false')), notes=("slack: needs nothing for a dry run, which renders the draft as mrkdwn to paste; a real send needs the name's incoming webhook in CORRESPOND_SLACK_WEBHOOK_ (upper case, - and . as \_) or the Keychain item correspond-slack-webhook-", "create the webhook in your Slack app's settings (Incoming Webhooks), one per channel: https://api.slack.com/messaging/webhooks", 'with CORRESPOND_SLACK_TOKEN, read, listen and send use the Web API (and send replies in threads); without one, send uses the webhook', "push delivery on a server: install correspond[server], run correspond-slack-events (127.0.0.1:8083, one worker) behind your HTTPS reverse proxy, give its URL as the app's Event Subscriptions Request URL with the bot events message.channels (and message.groups), and set delivery = events", "push delivery without a public URL (local use; not for apps in Slack's Marketplace): install correspond[slack], turn Socket Mode on, put an app-level token (connections:write) in CORRESPOND_SLACK_APP_TOKEN, subscribe to message.channels (and message.groups), and set delivery = socket; a listen then opens the socket for listen_wait_s quiet seconds, so run listen often or messages sent between windows may be missed"), check='', planned=None), ChannelInfo(name='signal', summary='Signal through signal-cli-rest-api in JSON-RPC mode: listen over its WebSocket, read what was logged, send', factory='correspond.channels.signal:Signal', modules=(), extra='signal', binaries=(), platforms=(), settings=(Setting(key='number', env='CORRESPOND_SIGNAL_NUMBER', what='the number of the Signal account signal-cli is registered or linked to', where='link signal-cli to your account (signal-cli link) or register a number, then run the signal-cli-rest-api server (see its README)', secret=False, required=True, default=None), Setting(key='url', env='CORRESPOND_SIGNAL_URL', what='the signal-cli-rest-api server', where='', secret=False, required=False, default='http://127.0.0.1:8080'), Setting(key='listen_wait_s', env='CORRESPOND_SIGNAL_LISTEN_WAIT_S', what='how many quiet seconds a listen waits on the WebSocket before it returns', where='', secret=False, required=False, default='3')), notes=("signal-cli needs a registered or linked number; a signal-cli release older than about three months stops working against Signal's servers, so update it when listening goes quiet", "run signal-cli-rest-api with MODE=json-rpc: listen receives over its WebSocket (pip install 'correspond[signal]' adds the client)", 'there is no history before linking: read returns only what correspond logged', "the server's trust-new-identities setting is an authenticity policy; a changed safety number arrives as an identity.changed event"), check='correspond.channels.signal:requirements_problems', planned=None), ChannelInfo(name='gdrive', summary='A Google Drive folder, read only: the files a conversation announces, each as a message with the file attached', factory='correspond.channels.gdrive:GoogleDrive', modules=('pydrivedol',), extra='gdrive', binaries=(), platforms=(), settings=(Setting(key='service_account_file', env='CORRESPOND_GDRIVE_SERVICE_ACCOUNT_FILE', what='the path of a Google service-account key (JSON), used with the read-only Drive scope', where='Google Cloud console: create a service account with the Drive API enabled, add a JSON key, then share each folder with its client_email as Viewer', secret=False, required=True, default=None),), notes=('gdrive: lists the folder and its subfolders; it never listens or writes', "the folder must be shared with the service account's client_email"), check='', planned=None), ChannelInfo(name='apprise', summary='Apprise: send-only notifications to about 155 services, each named by an alias (send only)', factory='correspond.channels.apprise:Apprise', modules=('apprise',), extra='apprise', binaries=(), platforms=(), settings=(Setting(key='config', env='CORRESPOND_APPRISE_CONFIG', what='an Apprise config file (YAML or TEXT); an alias with no URL of its own is used as a tag in it', where='https://pypi.org/project/apprise/ (its configuration-file documentation)', secret=False, required=False, default=None),), notes=('apprise: sends to the URL in CORRESPOND_APPRISE_URL_ (or the Keychain item correspond-apprise-url-), else to the URLs tagged in the config file', "a reference never holds an Apprise URL: the URL carries the service's credentials"), check='', planned=None)), , name='correspond channels') A fresh `xdol.Registry` with a lazy entry for every built channel whose optional modules import. * **Return type:** [`MutableMapping`](https://docs.python.org/3/library/collections.abc.html#collections.abc.MutableMapping)[[`str`](https://docs.python.org/3/builtins/stdtypes.html#str), [`Any`](https://docs.python.org/3/library/typing.html#typing.Any)] ### correspond.registry.channels() The process registry: built on first use, then shared. * **Return type:** [`MutableMapping`](https://docs.python.org/3/library/collections.abc.html#collections.abc.MutableMapping)[[`str`](https://docs.python.org/3/builtins/stdtypes.html#str), [`Any`](https://docs.python.org/3/library/typing.html#typing.Any)] ### correspond.registry.check_requirements(channel, \*, registry=None, config=None, run=) What a channel needs and what is missing: the install command, binaries, platform, and every setting’s source. Never a secret’s value. * **Return type:** [`dict`](https://docs.python.org/3/builtins/stdtypes.html#dict) ### correspond.registry.info(channel) The table entry for a built-in channel. * **Return type:** [`ChannelInfo`](#correspond.registry.ChannelInfo) ### correspond.registry.load_factory(ref) The object a `module:attribute` reference names. * **Return type:** [`Any`](https://docs.python.org/3/library/typing.html#typing.Any) ### correspond.registry.register_channel(adapter, , name=None, replace=False, registry=None) Add an adapter (tests, or a channel defined outside correspond). `replace` swaps out an existing one. * **Return type:** [`Any`](https://docs.python.org/3/library/typing.html#typing.Any) ### correspond.registry.require(channel, key, \*, config=None, run=) A channel setting’s value, or [`MissingRequirement`](correspond.errors.html.md#correspond.errors.MissingRequirement) saying how to set it. * **Return type:** [`str`](https://docs.python.org/3/builtins/stdtypes.html#str) ### correspond.registry.resolve(channel, setting, \*, config=None, run=, keychain=True) `(value, source)`; source is `env`, `keychain`, `config`, `default` or `missing`. `keychain=False` skips the Keychain, so nothing runs: what a dry run does. * **Return type:** [`tuple`](https://docs.python.org/3/builtins/stdtypes.html#tuple)[[`str`](https://docs.python.org/3/builtins/stdtypes.html#str) | [`None`](https://docs.python.org/3/builtins/constants.html#None), [`str`](https://docs.python.org/3/builtins/stdtypes.html#str)] ### correspond.registry.unregister_channel(name, , registry=None) Remove a channel from the registry. * **Return type:** [`None`](https://docs.python.org/3/builtins/constants.html#None) ### correspond.registry.value(channel, key, \*, config=None, run=, keychain=True) A channel setting’s value, or `None` when it is not set and has no default (`keychain=False`: skip the Keychain). * **Return type:** [`str`](https://docs.python.org/3/builtins/stdtypes.html#str) | [`None`](https://docs.python.org/3/builtins/constants.html#None)