Provided by: librinci-perl_1.1.78-1_all 
NAME
Rinci::function - Metadata for your functions/methods
VERSION
This document describes version 1.1.78 of Rinci::function (from Perl distribution Rinci),
released on 2015-09-03.
SPECIFICATION VERSION
1.1
INTRODUCTION
This document describes metadata for functions/methods. Since the metadata properties
describe features and the way a function works, this document also describes how a
function should support those properties.
This specification is part of Rinci. Please do a read up on it first, if you have not
already done so.
SPECIFICATION
Result envelope. Function should return an enveloped result to express error code/message
as well as actual result. The envelope can be produced by the function itself, or added by
a wrapper tool. Result envelope is modeled after HTTP or PSGI response; it is an array in
the following format:
[STATUS*, MESSAGE, RESULT, META]
STATUS is a 3-digit integer and is the only required element, much like HTTP response
status code and is explained further in "Envelope status codes". MESSAGE is a string
containing error message. RESULT (or PAYLOAD) is the actual content to be returned and can
be omitted or set to undef if the function does not need to return anything. META is
called result metadata, a defhash containing extra data, analogous to HTTP response
headers. Result metadata is specified further in Rinci::resmeta.
Some example of an enveloped results:
[200]
[200, "OK", 42]
[404, "Not found"]
[200, "Account created", {id=>9323}, {}]
[500, "Can't delete foo: permission denied", undef,
{"cmdline.exit_code"=>300, perm_err=>1}]
As mentioned, an enveloped result can contain error code/message as well as the actual
result. It can also be easily converted to HTTP response message. And it can also contain
extra data, useful for things like the transaction protocol (explained in
Rinci::Transaction).
Special arguments. Special arguments are some known arguments that start with dash ("-")
and serve special purposes. You need not specify them in the "args" metadata property.
Examples of special arguments include "-dry_run", "-tx_action", "-action", "-confirm/*",
"-arg_part_start", "-arg_part_len", "-res_part_start", "-res_part_len". They will be
explained in other related sections/documents.
Functions vs methods. Since in many programming languages (like Perl 5, Python, Ruby, PHP)
static functions are not that differentiated from methods, functions and methods share the
same Rinci spec. But there are certain properties that can be used to declare if a
function is (also) a method or not. See "is_func", "is_meth", "is_class_meth" properties
below for details.
Multiple dispatch. This specification also does not (yet) have any recommendation on how
to best handle functions in languages that support multiple dispatch, like Perl 6: whether
we should create multiple metadata or just one. It is more up to the tool and what you
want to do with the metadata.
Envelope status codes
In general, status codes map directly to HTTP response status codes. Below are the
suggestion on which codes to use (or avoid). An asterisk ("*") marks which codes are not
defined in HTTP specification and introduced by this specification.
• 1xx code
Currently not used. Some tools like Perinci::CmdLine assumes that status code is
always ">= 200", so you should perhaps never used status less than 200.
• 2xx code - success
200 should be used to mean success.
201 (created) can be used to signal success when creating something.
204 (no content) can also be used when there is no content to show. In HTTP, browsers
won't clear current page if response is 206 (instead of showing a blank page if
response is 200). Currently in Rinci there is no difference between 200 and 204.
206 (partial content) can be used to signal partial content. See "partial" property in
the "result" function property.
207 (multistatus) can be used to signal partial success, for example a function which
processed 5 items wanted to report that it successfully processed 2 items but failed
to process the rest 3 items. For each item's statuses, you can use result metadata
property "results". Note: 207 is used by WebDAV. Note: When all functions instead of
only some/partial items fail, you might want to return 4xx or 5xx instead of 207.
• 3xx code - further actions needs to be taken by user agent (caller)
301 (moved) can be used to redirect callers to alternate location, although this is
very rare.
304 (not modified, nothing done). Used for example by setup functions to indicate that
nothing is being modified or no modifying action has been performed (see Setup::*
modules in CPAN).
331* (confirmation required). Function requires confirmation, for example if action to
be taken is dangerous or requires user's attention. Confirmation message/prompt from
function can be returned in the message, or in the "confirm_prompt" property (e.g. to
provide translations). Confirmation from caller is in the form of special argument
"-confirm" with boolean value of true (TODO: A more detailed confirmation for
different actions can be specified later in the form of "-confirm_XXX" special
arguments.) For an example of application of this, see Perinci::Tx::Manager.
• 4xx code - client (caller) side error
400 (bad request, bad arguments) should be returned when the function encounters
invalid input. A function wrapper can return this code when the function arguments
fail the argument schema validation (specified in the "args" property).
401 (authentication required).
403 (forbidden, access denied, authorization failed).
404 (not found). Can be used for example by an object-retrieval functions (like
"get_user()") and the object is not found.
For object-listing functions (like "list_users()"), when there are no users found
matching the requested criteria, 200 code should still be returned with an empty
result (like an empty array or hash).
Also in general, an object-deletion function (like "delete_user()") should also return
200 (or perhaps 304, but 200 is preferred) instead of 404 when the object specified to
be deleted is not found, since the goal of the delete function is reached anyway.
408 (request timeout).
409 (conflict). Can be used for example by a "create_user()" function when receiving
an already existing username.
412 (precondition failed). Similar to 409, but can be used to indicate lack of
resources, like disk space or bandwidth. For lacking authentication and authorization,
use 401 and 403 respectively.
413 (request range not satisfiable). When client requests partial result outside the
range of available. See the "partial" property in "result" property for examples.
429 (too many requests).
(EXPERIMENTAL) 44x* codes are reserved for function-specific codes. Each function is
free to define what each number means. However, this is not really encouraged and
should only be used if necessary. Function should perhaps stick to predefined codes
here. To return more detailed status, result metadata can be used.
480* is general transaction error, e.g. transaction status is aborted so further
requests for this transaction is ignored until transaction is aborted.
484* (no such transaction).
• 5xx code - server (callee) side error
500 is the general code to use when a failure occurs during the execution of a
function. for example when a "delete_file()" function fails to delete specified file
(though in this case it can also choose to return 403 instead, which is more
specific).
501 (not implemented)
503 (service unavailable). You can use this when service is temporarily unavailable,
e.g. when system load is too high, a required service is down, etc. Users should try
again at a later time.
507 (insufficient storage)
521 (maximum retries reached)
531* (bad metadata) is used when there is something wrong with the metadata.
532* (failure in recording transaction) when there is a failure in updating
transaction status or in preparing/committing/rolling back the transaction.
(EXPERIMENTAL) 54x* codes are reserved for function-specific codes. Each function is
free to define what each number means. However, this is not really encouraged and
should only be used if necessary. Function should perhaps stick to predefined codes
here. To return more detailed status, result metadata can be used.
Try not to use code greater than 555, as some tools use (CODE-300) for error codes
that must fit in one unsigned byte (like Perinci::CmdLine).
Property: is_func => BOOL
Specify that the function can be called as a static function (i.e. procedural, not as a
method). Default is true if unspecified, but becomes false if is_meth or is_class_meth is
set to true.
Example:
# specify that function can be called a method *as well as* a static function
is_meth => 1
is_func => 1 # if not specified, will default to false after is_meth set to 1
Property: is_meth => BOOL
Specify that the function can be called as an instance (object) method. Default is false.
Example:
# specify that function is a method
is_meth => 1
Property: is_class_meth => BOOL
Specify that the function can be called as a class method. Examples of class methods
include the constructor, but there are others. Default is false.
Example:
# specify that function is a class method
is_class_meth => 1
Property: args => HASH
Specify arguments. Property value is defhash of argument names and argument specification.
Argument name must only contain letters, numbers, and underscores (and do not start with a
number).
Argument specification is a hash containing these keys:
• schema => SCHEMA
Data::Sah schema for argument value.
• default => ANY
Give default value for argument. This takes precedence over schema, which can also
specify default value. This is useful if you want to share a common schema over
several arguments but want to have different default for each argument. For example,
you have a "ticket_status" schema. In "create_ticket" function you want the default
"status" argument to be "new", while in "reply_ticket" you want the default "status"
to be "answered".
• summary => STR
From DefHash. A one-line plaintext summary, much like the "summary" property in
variable metadata.
• req => BOOL
Specify that argument is required (although its value can be undef/null). Default is
false.
• description => STR
From DefHash. A longer description of marked up text, much like the "description"
property. It is suggested to format the text to 74 columns.
• tags => ARRAY OF (STR|HASH)
From DefHash. An array of tags, can be used by tools to categorize arguments. Not
unlike the "tags" property.
• pos => INT
Argument position when specified in an ordered fashion, e.g. in an array. Starts from
zero.
• greedy => BOOL
Only relevant if pos is specified, specify whether argument should gobble up all
remaining values in an ordered argument list into an array.
• partial => BOOL
Whether or not argument value can be sent partially. Only argument types that have a
length notion can be set as partial (e.g. "str" where the unit is character, "buf"
where the unit is byte, and "array" where the unit is element).
There should at most be one argument with this property set to true.
To send partial argument, you can use the special arguments "-arg_len" (total argument
length), "-arg_part_start" (start position of the part that is being sent),
"-arg_part_len" (length of part that is being sent). Example (in Perl):
# function metadata
{
v => 1.1,
summary => "Upload a file",
args => {
name => {schema=>"str*", req=>1},
data => {schema=>"buf*", req=>1, partial=>1},
},
}
# function usage example: send the first 10MiB of data
upload_file(name=>"myvideo.mp4", data=>substr($data, 0, 10_000_000),
-arg_len => 24_500_000,
-arg_part_start => 0,
-arg_part_len => 10_000_000);
# send the next 10MiB
upload_file(name=>"myvideo.mp4", data=>substr($data, 10_000_000, 10_000_000),
-arg_len => 24_500_000,
-arg_part_start => 10_000_000,
-arg_part_len => 10_000_000);
# send the last 4.5 MiB
upload_file(name=>"myvideo.mp4", data=>substr($data, 20_000_000),
-arg_len => 24_500_000,
-arg_part_start => 20_000_000,
-arg_part_len => 4_500_000);
• stream => bool
By setting this property to true, function can specify that it accepts streaming data
for this argument. It is useful when argument value is large or of
undetermined/infinite length. To send value as a stream, caller must send a subroutine
reference (callback) instead which the function will call repeatedly until it gets
undef to signify exhaustion of data.
• cmdline_aliases => HASH
Specify aliases for use in command-line options (or other possibly suitable situation
where arguments are parsed from command-line-like options). Keys are alias names,
values are itself hashes (alias specification). Valid alias specification keys:
"summary" (a string, optional), "schema" (optional, defaults to argument's schema),
"is_flag" (bool, optional, if set to 1 then it is a shortcut for specifying "schema"
to "["bool", {"is":1}]"), "code" (a code to set argument value, optional, will be
given "(\%args, $val)"); if not set, the default behavior is simply to set the
argument value).
• cmdline_on_getopt => CODE
A hook that will be called when argument is specified as a command-line option. In
Perl, hook will be called with a hash argument containing this key: "arg" (str,
argument name), "value" (str, option value), "args" (hash, the argument hash defined
so far).
This can be useful if you want to process a command-line option directly on a per-
option basis instead of getting the final resulting argument value. For example (in
Perl):
args => {
library => {
schema => ['array*' => of => 'str*'],
cmdline_aliases => { I => {} },
cmdline_on_getopt => sub {
my %args = @_;
require lib;
lib->import($args{value});
},
},
module => {
schema => ['array*' => of => 'str*'],
cmdline_aliases => { M => {} },
cmdline_on_getopt => sub {
my %args = @_;
require Module::Load;
Module::Load::load($args{value});
},
},
}
With command-line argument like this:
-I dir1 -M mod1 -I dir2 -M mod2
Without any "cmdline_on_getopt" hooks, the function will receive this argument hash:
{ library => ['dir1', 'dir2'], module => ['mod1', 'mod2'] }
but there is no way to know the order of options being specified in the command-line.
With the hooks, the function can load modules correctly (e.g. loading "mod1" won't
search in "dir2" as that directory has not been added by -I).
• completion => CODE
A code to supply argument value completion. Will be explained in the examples.
• element_completion => CODE
A code to supply argument element value completion. Only applicable if argument type
is "array". Will be explained in the examples.
• is_password => STR
Experimental. Describe that argument holds password. Programs can react to this in
several ways, for example they can turn off echoing to terminal when asking value from
standard input. Or they can redact values to "****" when logging.
• cmdline_src => STR
Specify how to get the value for this argument, when function is run as a command-line
program. Valid values include: "file" (command-line argument value will be treated as
filename and function argument will be set to content of the file), "stdin" (means
that program should get function argument from the whole standard input until EOF), or
"stdin_or_file" (means that program should get value from content of file [from a
single command-line argument], or if none is specified, from standard input), or
"stdin_or_files" (means that program should get value from content of files [from all
command-line arguments], or if none is specified, from standard input), or
"stdin_line" (means that program should get value from a line of standard input;
newline ending will be removed from the argument value). Other sources might be
defined in the future.
When source is stdin/files, the whole standard input and files will be slurped into
memory and fed as argument value. It is possible to stream the value instead: see the
"stream" argument specification property.
There should only be one argument with "src" set to "stdin" or "stdin_or_file" or
"stdin_or_files".
Arguments with "cmdline_src" of "stdin_line" will be processed before "stdin".
TODO: Define "web_src" property?
TODO: A way to define record separator?
• cmdline_prompt => str
String to display when asking for argument value from stdin (if "cmdline_src" property
value is "stdin_line".
TODO: cmdline_prompt_template?
• meta => hash (EXPERIMENTAL)
This allows specifying argument submetadata, used e.g. when dealing with forms (a form
field/widget can be a subform). Value is Rinci function metadata.
• element_meta => hash (EXPERIMENTAL)
This allows specifying argument element submetadata, used e.g. when dealing with forms
(a form field/widget can contain an array of records/subforms). Value is Rinci
function metadata.
• deps => hash
This property specifies argument's dependencies to other arguments (but possibly to
other things too, in the future). This is similar to function's "deps" property. It is
a hash or dep types and values. The most important dep type is "arg" (dependency to
another argument). Some dep types are special: "all", "any", "none". Example:
args => {
delete => {
schema=>'bool',
},
force => {
summary => 'Force deletion',
schema => 'bool',
deps => {arg=>'delete'},
},
The above example states that argument "force" "depends on" "delete". What it means
(usually) is that specifying "force" only makes sense when "delete" is also specified.
In a CLI context:
% prog --delete --force
Specifying "--force" without "--delete" doesn't make sense.
• filters => [array of str|code]
Experimental. Filters to apply before argument is converted from text and validated.
Example function metadata and its implementation in Perl:
$SPEC{multiply2} = {
v => 1.1,
summary => 'Multiple two numbers',
args => {
a => {
summary => 'The first operand',
description => '... a longer description ...',
schema=>'float*',
pos => 0,
tags => ['category:operand'],
},
b => {
summary => 'The second operand',
description => '... a longer description ...',
schema => 'float*',
pos => 1,
tags => ['category:operand'],
},
round => {
summary => 'Whether to round result',
description => '... a longer description ...',
schema => [bool => {default=>0}],
pos => 2,
tags => ['category:options'],
cmdline_aliases => {
r=>{},
R=>{summary=>'Equivalent to --round=0',
code=>sub {$_[0]{round}=0}},
},
},
}
};
sub multiply2 {
my %args = @_;
my $res = $args{a} * $args{b};
$res = int($res) if $round;
[200, "OK", $res];
}
By default, without any wrapper, the function is called with a named hash style:
multiply2(a=>4, b=>3); # 12
But with the information from the metadata, a wrapper tool like Perinci::Sub::Wrapper is
able to change the calling style to positional:
multiply2(4, 3.1, 1); # 12
A command-line tool will also enable the function to be called named options as well as
positional arguments:
% multiply2 --a 2 --b 3
% multiply2 2 --b 3
% multiply2 2 3
As mentioned earlier, "cmdline_alises" is parsed by command-line option parser:
% multiply2 2 3.5 -r ; # equivalent to multiply2 2 3 --round
% multiply2 2 3.5 -R ; # equivalent to multiply2 2 3 --noround (--round=0)
Aliases in "cmdline_aliases" are not recognized as real arguments:
multiply2(a=>4, b=>3, r=>0); # unknown argument r
Another example (demonstrates "cmdline_aliases"):
$SPEC{smtpd} = {
v => 1.1,
summary => 'Control SMTP daemon',
args => {
action => {
schema => ['str*' => {in=>[qw/status start stop restart/]}],
pos => 0,
req => 1,
cmdline_aliases => {
status => {
schema => [bool=>{is=>1}],
summary => 'Alias for setting action=status',
code => sub { $_[0]{action} = 'status' },
},
start => {
schema => [bool=>{is=>1}],
summary => 'Alias for setting action=start',
code => sub { $_[0]{action} = 'start' },
},
stop => {
schema => [bool=>{is=>1}],
summary => 'Alias for setting action=stop',
code => sub { $_[0]{action} = 'stop' },
},
restart => {
schema => [bool=>{is=>1}],
summary => 'Alias for setting action=restart',
code => sub { $_[0]{action} = 'restart' },
},
},
},
force => {
schema => 'bool',
},
},
};
Another example (demonstrates greedy):
$SPEC{multiply_many} = {
v => 1.1,
summary => 'Multiple numbers',
args => {
nums => {
schema => ['array*' => {of=>'num*', min_len=>1}],
pos => 0,
greedy => 1
},
},
};
sub multiply_many {
my %args = @_;
my $nums = $args{nums};
my $ans = 1;
$ans *= $_ for @$nums;
[200, "OK", $ans];
}
After wrapping, in positional mode it can then be called:
multiply_many(2, 3, 4); # 24
which is the same as (in normal named-argument style):
multiply_many(nums => [2, 3, 4]); # 24
In command-line:
% multiply-many 2 3 4
in addition to the normal:
% multiply-many --nums '[2, 3, 4]'
completion. This argument specification key specifies how to complete argument value (e.g.
in shell or Riap::HTTP) and is supplied an anonymous function as value. The function will
be called with arguments: word=>... (which is the formed word so far, ci=>0|1 (whether
completion should be done case-insensitively). The function should return an array
containing a list of possible candidates, or a hash containing these keys: "completion"
(array, list of possible candidates) and extra keys for formatting hints e.g. "is_path"
(bool, whether the list of completion is path-like, meaning it can be traversed/dug to
multiple levels) "path_sep" (string, path separator character), "type" (string, either
"filename", "env", or other types). For an example of implementation for this, see
Perinci::Sub::Complete in Perl which provides tab completion for argument values. Example:
$SPEC{delete_user} = {
v => 1.1,
args => {
username => {
schema => 'str*',
pos => 0,
completion => sub {
my %args = @_;
my $word = $args{word} // "";
# find users beginning with $word
local $CWD = "/home";
return [grep {-d && $_ ~~ /^\Q$word/} <*>];
},
},
force => {schema=>[bool => {default=>0}]},
},
};
When "delete_user" is executed over the command line and the Tab key is pressed:
$ delete-user --force --username fo<tab>
$ delete-user fo<tab>
then bash will try to complete with usernames starting with "fo".
element_completion. This is like completion, but for array elements. Argument type must
be "array". Example:
$SPEC{delete_users} = {
v => 1.1,
args => {
usernames => {
schema => ['array*' => of => 'str*'],
req => 1,
pos => 0,
greedy => 1,
element_completion => sub {
my %args = @_;
my $word = $args{word} // "";
# find users beginning with $word
local $CWD = "/home";
my $res = [grep {-d && $_ ~~ /^\Q$word/} <*>];
# exclude users already mentioned by user
my $ary = $args{args}{usernames};
$res = [grep {!($_ ~~ @$ary)}] @$res;
return $res;
},
},
},
};
When "delete_users" is executed over the command line:
$ delete-users c<tab> ; # will complete with all users beginning with c
$ delete-users charlie c<tab> ; # will complete with users but exclude charlie
$ delete-users charlie chucky <tab> ; # and so on
Property: args_rels => hash
This property is used to expression relationships between arguments. The value is actually
Sah schema hash clause set (see hash type in Sah::Type). The arguments are represented as
a hash, and you can use the various Sah clauses to express relationships between the
arguments (hash keys) because the Sah hash type supports such clauses, e.g. "choose_one",
"choose_all", "req_one", "req_all", "dep_any", "dep_all", "req_dep_any", "req_dep_all".
Examples:
args_rels => {
choose_one => ['delete', 'add', 'edit'],
choose_all => ['red', 'green', 'blue'],
}
The above example says that only one of "delete", "add", "edit" can be specified. And if
any of "red", "green", "blue" is specified then all must be specified. In CLI context this
translates to:
% prog --delete item
% prog --delete --add item ; # error, both --delete and --add specified
% prog --red 255 --green 255 --blue 0
% prog --red 255 --blue 0 ; # error, --green is missing
Another example:
XXX
Property: args_as => STR
Specify in what form the function expects the arguments. The value is actually
implementation-specific since it describes the function implementation. For example in
Perinci for Perl, these values are recognized: "array", "hash", "arrayref", "hashref".
This property is useful for wrapper to be able to convert one form to another.
The default value is also left to the implementation.
For interimplementation communication (e.g. via Riap::HTTP or Riap::TCP), named arguments
are always used so this property is irrelevant.
Property: result => HASH
Specify function return value. It is a defhash containing keys:
• summary
From DefHash. Like the "summary" property in variable metadata.
• description
From DefHash. Like the "description" property. Suggested to be formatted to 78
columns.
• schema => SCHEMA
A Sah schema to validate the result (the third element in the envelope result). This
schema should only be tested if status is 200. See also: "statuses".
• statuses => HASH
Can be used to specify different result schema for different statuses. For example:
statuses => {
206 => {
schema => 'str*',
},
}
• stream => bool
Specify that function returns streaming output. Note that function can also signify
streaming output by setting result metadata property "stream" to true.
Function must then return a subroutine reference (callback) as its actual result which
the caller can call repeatedly until it gets undef to signify exhaustion.
• partial => bool
If set to true, specify that it is possible to request partial result. An example is
in a function that reads contents from (potentially large) files:
# function metadata
{
v => 1.1,
summary => 'Read file contents',
args => {
name => {
summary => 'File name',
schema => 'str*',
req => 1,
},
},
result => {schema=>'buf*', partial=>1},
}
# example function usage: request to read first 10MiB of file content,
# -result_part_start defaults to 0.
my $res = read_file(name=>'myvideo.mp4', -res_part_len=>10000000);
# => [206, "Partial content", "data...", {len=>24500000, part_start=>0, part_len=>10000000}]
# request the next 10MiB
my $res = read_file(name=>'myvideo.mp4', -res_part_start=>10000000, -res_part_len=>10000000);
# => [206, "Partial content", "data...", {len=>24500000, part_start=>10000000, part_len=>10000000}]
# request the next 10MiB, since this actual file size is only 24500000,
# function should return 416 status
my $res = read_file(name=>'myvideo.mp4', -res_part_start=>20000000, -res_part_len=>10000000);
# => [416, "Request range not satisfiable, file size is only 24500000"]
# request the next 4.5MiB, this time succeeds
my $res = read_file(name=>'myvideo.mp4', -res_part_start=>20000000, -res_part_len=>4500000);
# => [206, "Partial content", "data...", {len=>24500000, part_start=>20000000, part_len=>4500000}]
Partial result request to a function which does not support partial result might have
the effect of the whole content being returned (status 200) or status 416.
Note that since functions normally return enveloped result, instead of returning:
RESULT
your functions normally have to return an enveloped result:
[STATUS, MESSAGE, RESULT, METADATA]
Examples:
# result is an integer
result => {schema => 'int*'}
# result is an integer starting from zero
result => {schema => ['int*' => {ge=>0}]}
# result is an array of records
result => {
summary => 'Matching addressbook entries',
schema => ['array*' => {
summary => 'blah blah blah ...',
of => ['hash*' => {allowed_keys=>[qw/name age address/]} ]
}]
}
Property: result_naked => BOOL
If set to true, specify that function does not envelope its results. The default is false,
to encourage functions to create envelopes. However, wrapper should be able to create or
strip envelope if needed. For example, if you have "traditional" functions which does not
do envelopes, you can set this property to true, and the wrapper can generate the envelope
for the functions.
Property: examples => ARRAY
This property allows you to put examples in a detailed and structured way, as an
alternative to putting everything in "description".
Each example is a defhash, it specifies what arguments are used, what the results are, and
some description. It can be used when generating API/usage documentation, as well as for
testing data. It can also be used for testing (function will be run with specified
arguments and the result will be matched against expected result). Known properties:
• args => HASH
Arguments used to produce result. Can be converted to "argv" by tool, e.g. when
displaying command-line eamples
• argv => ARRAY
An alternative to "args", for example when function is run from the command-line. Can
be converted to "args" most of the time when wanting to display examples in Perl
instead of command-line.
• src => STR
An alternative to "args" or "argv", to provide raw source code. See also: "src_plang".
This can be used to show more general examples. For example, you can show how a
function is used in an expression or code block, or how a command-line program is used
in a shell script.
Exactly one of "args", "argv", or "src" must be specified.
• src_plang => STR
The programming language the examples source code "src" is written in. Valid values
include: "perl", "bash".
Command-line interface tools will typically only show examples written in "bash" or
other shells, while Perl module tools will typically only show "perl" examples.
Required if "src" is specified.
• status => INT (default: 200)
Status from envelope. If unspecified, assumed to be 200.
• result => DATA
Expected result.
• summary => STR
From DefHash. A one-line summary of the example You should describe, in one phrase or
sentence, what the example tries to demonstrate. You can skip the summary if the
example is pretty basic or things are already clear from the "args" alone.
• description => STR
From DefHash. Longer marked up text about the example (e.g. discussion or things to
note), suggested to be formatted to 72 columns.
• tags => ARRAY
From DefHash.
• test => BOOL (default: 1)
Whether to actually test example or not. Examples are by default run as tests by a
test module (e.g. Perl module Test::Rinci. Setting this to 0 disables this example
from being included in a test.
TODO: more detailed testing instruction (e.g. only test in release candidate, or under
certain environment flag, etc).
Example:
# part of metadata for Math::is_prime function
examples => [
{
args => {num=>10},
result => 0,
# summary no needed here, already clear.
},
{
args => {},
result => 400,
summary => 'Num argument is required',
},
{
argv => [-5],
result => 1,
summary => 'Also works for negative integers',
},
],
Another example demonstrating "src" for a function called "list_countries":
examples => [
{
src => 'for c in `list-countries`; do wget http://flags.org/country/$c; done',
src_plang => 'bash',
},
{
src => <<'EOT',
my $res = list_countries(detail => 1, sort=>['-popsize']);
die "Can't list countries: $res->[0] - $res->[1]" unless $res->[0] == 200;
my $i = 0;
for my $c (@{ $res->[2] }) { $i++; say "$i. $_->{name}'s population: $_->{popsize}";
EOT
src_plang => 'perl',
},
],
Property: features => HASH
The "features" property is a deffhash. It allows functions to express their features. Each
hash key contains feature name, which must only contain letters/numbers/underscores.
Below is the list of defined features. New feature names may be defined by extension.
• feature: reverse => BOOL (default: 0)
If set to true, specifies that function supports reverse operation. To reverse, caller
can add special argument "-reverse". For example:
$SPEC{triple} = {
v => 1.1,
args => {num=>{schema=>'num*'}},
features => {reverse=>1}
};
sub triple {
my %args = @_;
my $num = $args{num};
[200, "OK", $args{-reverse} ? $num/3 : $num*3];
}
triple(num=>12); # => 36
triple(num=>12, -reverse=>1); # => 4
• feature: tx => HASH
Default is none. Specify transactional support, as specified in Rinci::Transaction.
Value is a hash containing these keys: "v" (int, protocol version, default if not
specified is 1).
Please see Rinci::Transaction for more details on transaction.
• feature: dry_run => BOOL (default: 0)
Default is false. If set to true, specifies that function supports dry-run
(simulation) mode. Example:
use Log::Any '$log';
$SPEC{rmre} = {
summary => 'Delete files in curdir matching a regex',
args => {re=>{schema=>'str*'}},
features => {dry_run=>1}
};
sub rmre {
my %args = @_;
my $re = qr/$args{re}/;
my $dry_run = $args{-dry_run};
opendir my($dir), ".";
while (my $f = readdir($dir)) {
next unless $f =~ $re;
$log->info("Deleting $f ...");
next if $dry_run;
unlink $f;
}
[200, "OK"];
}
The above Perl function delete files, but if passed argument "-dry_run" => 1
(simulation mode), will not actually delete files, only display what files match the
criteria and would have be deleted.
Specifying a function as supporting dry_run means, among others:
• If dry_run is requested, function will have no side effects
It will behave like a pure function, and thus have the properties of a pure
function.
• feature: pure => BOOL (default: 0)
If set to true, specifies that function is "pure" and has no "side effects" (these are
terms from functional programming / computer science). Having a side effect means
changing something, somewhere (e.g. setting the value of a global variable, modifies
its arguments, writing some data to disk, changing system date/time, etc.) Specifying
a function as pure means, among others:
• it can safely be inculded in transaction without recording in journal;
• it can safely be included during dry run;
• feature: immutable => BOOL
Default is false. If set to true, specifies that function always returns the same
result when given the same argument values. This enables optimization like
memoization. An example of an immutable function is "sub { $_[0]+$_[1] }" where its
results only depend on the arguments. Example of a mutable function would be "rand()"
or "read()" that reads contents from a file.
• feature: idempotent => BOOL
Default is false. If set to true, specifies that function is idempotent. Idempotency
means that repeated invocation of a function (each with the same arguments) will have
the same effect as a single invocation. In other words, extra invocation will not have
any effect.
Some operations, like reading a database row or a file's content, is inherently
idempotent (or to be exact nullipotent). Another example is setting or updating an
entity to some specific value, or deleting some entity. Repeated invocation of the
operation will still sets the entity to the same value, or still deletes the entity.
Some other operations are inherently non-idempotent, for example sending an email.
Repeated invocation will cause multiple emails to be sent.
Yet some other operations are non-idempotent, but can be made idempotent simply by
checking whether the target object(s) has (have) reached the final desired state,
(optionally additionally also checking whether they are in the correct original state
to begin with). For example, a function that renames a file can record the original
file that was renamed (its MD5 checksum, size, or what not) or perhaps record the
action in a history database or flag file, and refuse to rename again if the file to
be renamed is not the original file.
• feature: check_arg => bool
Default is false. If set to true, specifies that function supports the action of
checking only a single argument. Usually useful when doing form processing, where we
want to check only a single form field (function argument). To check a single
argument, one passes "-action" special argument with the value of "check_arg" and also
passes the argument she wants to check. Function should check that argument and
immediately return 200 status upon success, or 400 upon validation failure.
Property: deps => HASH
This property specifies function's dependencies to various things. It is a hash of dep
types and values. Some dep types are special: "all", "any", and "none".
deps => {
DEPTYPE => DEPVALUE,
...,
all => [
{DEPTYPE=>DEPVALUE, ...},
...,
},
any => [
{DEPTYPE => DEPVALUE, ...},
...,
],
none => [
{DEPTYPE => DEPVALUE, ...},
....,
],
}
A dependency can be of any type: another function, environment variables, programs, OS
software packages, etc. It is up to the dependency checker library to make use of this
information.
For the dependencies to be declared as satisfied, all of the clauses must be satisfied.
Below is the list of defined dependency types. New dependency type may be defined by an
extension.
• dep: env => STR
Require that an environment variable exists and is true, where true is in the Perl
sense (not an empty string or "0"; " " and "0.0" are both true). Example:
env => 'HTTPS'
• dep: prog => STR
Require that a program exists. If STR doesn't contain path separator character '/' it
will be searched in PATH. Windows filesystem should also use Unix-style path, e.g.
"C:/Program Files/Foo/Bar.exe".
prog => 'rsync' # any rsync found on PATH
prog => '/bin/su' # won't accept any other su
• dep: pkg => STR
Specify dependency on a Riap package. STR must be a valid Riap package URI string.
Checker can check that requesting "info" on this URI succeeds and the type is indeed
"package". Example:
pkg => '/Foo/'
• dep: func => STR
Specify dependency on a Riap function. STR must be a valid Riap function URI string.
Checker can check that requesting "info" on this URI succeeds and the type is indeed
"package". Example:
pkg => '/Foo/somefunc'
pkg => 'http://gudangapi.com/ga/list_ubuntu_releases'
• dep: code => CODE
Require that anonymous function returns a true value after called, where the notion of
true depends on the host language. Example in Perl:
code => sub {$>} # i am not being run as root
Example in Ruby:
"code" => Proc.new { Process.euid > 0 } # i am not being run as root
• dep: tmp_dir => BOOL
If set to 1, specify that function requires temporary directory. Caller should provide
path to this using special argument "-tmp_dir".
• dep: trash_dir => BOOL
If set to 1, specify that function requires trash directory. Trash is not unlike a
temporary directory. Caller should provide path to trash directory using special
argument "-trash_dir".
Trash directory can be provided, e.g. by transaction manager (see Rinci::Transaction).
• dep: all => [DEPHASH, ...]
A "meta" type that allows several dependencies to be joined together in a logical-AND
fashion. All dependency hashes must be satisfied. For example, to declare a dependency
to several programs and an environment variable:
all => [
{prog => 'rsync'},
{prog => 'tar'},
{env => 'FORCE'},
],
• dep: any => [DEPHASH, ...]
Like "all", but specify a logical-OR relationship. Any one of the dependencies will
suffice. For example, to specify requirement to alternative Perl modules:
or => [
{perl_module => 'HTTP::Daemon'},
{perl_module => 'HTTP::Daemon::SSL'},
],
• dep: none => [DEPHASH, ...]
Specify that none of the dependencies must be satisfied for this type to be satisfied.
Example, to specify that the function not run under SUDO or by root:
none => [
{env => 'SUDO_USER' },
{code => sub {$> != 0} },
],
Note that the above is not equivalent to below:
none => [
{env => 'SUDO_USER', code => sub {$> != 0} },
],
which means that if none or only one of 'env'/'code' is satisfied, the whole
dependency becomes a success (since it is negated by 'none'). Probably not what you
want.
If you add a new language-specific dependency type, please prefix it with the language
code, e.g. "perl_module", "perl_func", "ruby_gem", "python_egg". These dependency types
have also been defined by some existing tools: "deb" (dependency to a Debian package),
"rpm" (dependency to an RPM package), "js_url" (loading a remote JavaScript script URL),
"file" (existence of a), "perl_run_func" (running a Perl subroutine and getting a
successful enveloped result). Some of these might be declared as part of the core
dependency types in the future.
FAQ
What is the difference between "summary" or "description" in the Sah schema and arg
specification?
Example:
{
args => {
src => {
summary => "Source path",
description => "...",
schema => ["str*", {
summary => "...",
description => "...",
...
}],
...
},
dest => {
summary => "Target path",
description => "...",
schema => ["str*", {
summary => "...",
description => "...",
...
}],
...
},
...
},
}
As you can see, each argument has a "summary" and "description", but the schema for each
argument also has a "summary" and "description" schema clauses. What is the difference and
which should be put into which?
The argument specification's "summary" (and "description") describe the argument itself,
in this example it says that "src" means "The source path" and "dest" means "The target
path". The argument schema's "summary" (and "description") describe the data type and
valid values. In this example it could say, e.g., "a Unix-path string with a maximum
length of 255 characters". In fact, "src" and "dest" are probably of the same type ("Unix
path") and can share schema.
{
...
args => {
src => {
...
schema => "unix_path",
},
dest => {
...
schema => "unix_path",
},
...
},
}
What is the difference between setting req=>1 in the argument specification and req=>1 in
schema?
Example:
# Note: remember that in Sah, str* is equivalent to [str => {req=>1}]
args => {
a => { schema=>"str" },
b => { schema=>"str*" },
c => { req=>1, schema=>"str" },
d => { req=>1, schema=>"str*" },
}
In particular look at "b" and "c". "b" is not a required argument (no req=>1 in the
argument spec) but if it is specified, than it cannot be undef/null (since the schema says
[str=>{req=>1}], a.k.a "str*"). On the other hand, "c" is a required argument (req=>1 in
the argument spec) but you can specify undef/null as the value. The following are valid:
func(c=>undef, d=>1);
But the following are not:
func(b=>1, d=>1); # c is not specified
func(b=>undef, c=>1, d=>1); # b has undef value
func(b=>1, c=>1, d=>undef); # d has undef value
Should I add a new metadata property, or add a new feature name to the "features" property, or
add a new dependency type to the "deps" property?
If your property describes a dependency to something, it should definitely be a new
dependency type. If your property only describes what the function can do and does not
include any wrapper code, then it probably goes into "features". Otherwise, it should
probably become a new metadata property.
For example, if you want to declare that your function can only be run under a certain
moon phase (e.g. full moon), it should definitely go as a new dependency type, so it
becomes: deps => { moon_phase => 'full' }.
Another example, "reverse" is a feature name, because it just states that if we pass
"-reverse" => 1 special argument to a reversible function, it can do a reverse operation.
It doesn't include any wrapper code, all functionality is realized by the function itself.
On the other hand, "timeout" is a metadata property because it involves adding adding some
wrapping code (a timeout mechanism, e.g. an eval() block and alarm() in Perl).
SEE ALSO
Related specifications: Sah, HTTP/1.1 (RFC 2068)
Rinci
HOMEPAGE
Please visit the project's homepage at <https://metacpan.org/release/Rinci>.
SOURCE
Source repository is at <https://github.com/perlancar/perl-Rinci>.
BUGS
Please report any bugs or feature requests on the bugtracker website
<https://rt.cpan.org/Public/Dist/Display.html?Name=Rinci>
When submitting a bug or request, please include a test-file or a patch to an existing
test-file that illustrates the bug or desired feature.
AUTHOR
perlancar <perlancar@cpan.org>
COPYRIGHT AND LICENSE
This software is copyright (c) 2015 by perlancar@cpan.org.
This is free software; you can redistribute it and/or modify it under the same terms as
the Perl 5 programming language system itself.