notmuch/devel/schemata
Austin Clements 1c6195b9e3 cli: Framework for structured output versioning
Currently there is a period of pain whenever we make
backward-incompatible changes to the structured output format, which
discourages not only backward-incompatible improvements to the format,
but also backwards-compatible additions that may not be "perfect".  In
the end, these problems limit experimentation and innovation.

This series of patches introduces a way for CLI callers to request a
specific format version on the command line and to determine if the
CLI does not supported the requested version (and perhaps present a
useful diagnostic to the user).  Since the caller requests a format
version, it's also possible for the CLI to support multiple
incompatible versions simultaneously, unlike the alternate approach of
including version information in the output.

This patch lays the groundwork by introducing a versioning convention,
standard exit codes, and a utility function to check the requested
version and produce standardized diagnostic messages and exit
statuses.
2012-12-16 17:20:33 -04:00

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This file describes the schemata used for notmuch's structured output
format (currently JSON and S-Expressions).
[]'s indicate lists. List items can be marked with a '?', meaning
they are optional; or a '*', meaning there can be zero or more of that
item. {}'s indicate an object that maps from field identifiers to
values. An object field marked '?' is optional. |'s indicate
alternates (e.g., int|string means something can be an int or a
string).
For S-Expression output, lists are printed delimited by () instead of
[]. Objects are printed as p-lists, i.e. lists where the keys and values
are interleaved. Keys are printed as keywords (symbols preceded by a
colon), e.g. (:id "123" :time 54321 :from "foobar"). Null is printed as
nil, true as t and false as nil.
This is version 1 of the structured output format.
Common non-terminals
--------------------
# Number of seconds since the Epoch
unix_time = int
# Thread ID, sans "thread:"
threadid = string
# Message ID, sans "id:"
messageid = string
notmuch show schema
-------------------
# A top-level set of threads (do_show)
# Returned by notmuch show without a --part argument
thread_set = [thread*]
# Top-level messages in a thread (show_messages)
thread = [thread_node*]
# A message and its replies (show_messages)
thread_node = [
message|null, # null if not matched and not --entire-thread
[thread_node*] # children of message
]
# A message (format_part_sprinter)
message = {
# (format_message_sprinter)
id: messageid,
match: bool,
filename: string,
timestamp: unix_time, # date header as unix time
date_relative: string, # user-friendly timestamp
tags: [string*],
headers: headers,
body?: [part] # omitted if --body=false
}
# A MIME part (format_part_sprinter)
part = {
id: int|string, # part id (currently DFS part number)
encstatus?: encstatus,
sigstatus?: sigstatus,
content-type: string,
content-id?: string,
# if content-type starts with "multipart/":
content: [part*],
# if content-type is "message/rfc822":
content: [{headers: headers, body: [part]}],
# otherwise (leaf parts):
filename?: string,
content-charset?: string,
# A leaf part's body content is optional, but may be included if
# it can be correctly encoded as a string. Consumers should use
# this in preference to fetching the part content separately.
content?: string
}
# The headers of a message or part (format_headers_sprinter with reply = FALSE)
headers = {
Subject: string,
From: string,
To?: string,
Cc?: string,
Bcc?: string,
Reply-To?: string,
Date: string
}
# Encryption status (format_part_sprinter)
encstatus = [{status: "good"|"bad"}]
# Signature status (format_part_sigstatus_sprinter)
sigstatus = [signature*]
signature = {
# (signature_status_to_string)
status: "none"|"good"|"bad"|"error"|"unknown",
# if status is "good":
fingerprint?: string,
created?: unix_time,
expires?: unix_time,
userid?: string
# if status is not "good":
keyid?: string
# if the signature has errors:
errors?: int
}
notmuch search schema
---------------------
# --output=summary
summary = [thread*]
# --output=threads
threads = [threadid*]
# --output=messages
messages = [messageid*]
# --output=files
files = [string*]
# --output=tags
tags = [string*]
thread = {
thread: threadid,
timestamp: unix_time,
date_relative: string, # user-friendly timestamp
matched: int, # number of matched messages
total: int, # total messages in thread
authors: string, # comma-separated names with | between
# matched and unmatched
subject: string,
tags: [string*]
}
notmuch reply schema
--------------------
reply = {
# The headers of the constructed reply
reply-headers: reply_headers,
# As in the show format (format_part_sprinter)
original: message
}
# Reply headers (format_headers_sprinter with reply = TRUE)
reply_headers = {
Subject: string,
From: string,
To?: string,
Cc?: string,
Bcc?: string,
In-reply-to: string,
References: string
}