Provided by: librinci-perl_1.1.102-1_all 
NAME
Rinci::function - Metadata for your functions/methods
SPECIFICATION VERSION
1.1
VERSION
This document describes version 1.1.102 of Rinci::function (from Perl distribution Rinci),
released on 2022-04-22.
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
Enveloped result
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". Many of them will be explained in
other related sections/documents, but some will be described here:
• -content_type_ARGNAME
This special argument can be used to describe the MIME content type of an argument,
where "ARGNAME" is the argument name. For example, if you are creating a function that
accepts data upload (in Perl):
upload(data => '...', -content_type_data => 'image/jpeg');
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).
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
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
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
args (function property)
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 (argument property)
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 (argument property)
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 (argument property)
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 (argument property)
Array of (str|hash). From DefHash. An array of tags, can be used by tools to categorize
arguments. Not unlike the "tags" property.
pos
Non-negative integer. Argument position when specified in an ordered fashion, e.g. in an
array. Starts from zero.
slurpy
Bool. Only relevant if pos is specified, specify whether argument should gobble up all
remaining values in an ordered argument list into an array.
Old alias: "greedy"
greedy
Old alias for "slurpy". Will be removed in Rinci 1.2.
partial (argument property)
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 (argument property)
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 (argument property)
Code. A code to supply argument value completion. Will be explained in the examples.
index_completion
Code. A code to supply argument element index completion. Applicable to the following
argument types:
hash: for completing hash pair keys. (See also "element_completion" for completing hash
pair values).
See examples for how to use this property.
element_completion
Code. A code to supply argument element value completion. Applicable to the following
argument types:
array: for completing array element values.
hash: for completing hash pair values. (See also "index_completion" for completing hash
keys).
See examples for how to use this property.
is_password
Experimental. Bool. 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. Normally in a command-line program, command-line options and arguments will map to
function arguments, e.g. "--arg 2" will set the "foo" argument to 2 and positional
arguments (argument which specifies the "pos" property and optionally also a "slurpy"
property with true value) will get or slurp command-line arguments.
In some cases, this is not convenient. When supplying larger amount of data, a complex
structures, or a stream, we might want to use other sources. The "cmdline_src" property
can be set to one of the following value for this purpose:
• file
Command-line option/argument value will be treated as filename and function argument
will be set to content of the file (or in the case of streaming argument, to a
callback which can be used to get the file's content).
• stdin
This means that program should get function argument from the whole standard input
until EOF.
Note that only one argument can have its source set to "stdin" or "stdin_or_file" or
"stdin_or_files" or "stdin_or_args".
• stdin_or_file
This means that program should get argument value from content of file (the name of
which is given from the first remaining command-line argument after all other
arguments/options have been processed), or, if none is provided, from standard input.
• stdin_or_files
This means that program should get argument value from content of files (the names of
which are taken from the remaining command-line arguments after all other
arguments/options have been processed), or, or if no command-line argument remains,
from standard input. This behavior is similar to the "<>" (diamond operator) in Perl.
• stdin_or_args
This means that program should get argument value from remaining command-line
argument(s), or if no command-line argument remains, from standard input.
• stdin_line
This means that program should get argument value from a line of standard input;
newline ending will be removed from the argument value.
Arguments with "cmdline_src" of "stdin_line" will be processed before
"stdin"/"stdin_or_file"/"stdin_or_files"/"stdin_or_args".
Other sources might be defined in the future.
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
Experimental. Hash. 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
Experimental. Hash. 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 (argument property)
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 (function property)"
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:
# function metadata property
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.
To depend on any one of several arguments, use the dep type "any", e.g.:
# function metadata property
args => {
delete => {
schema=>'bool',
},
replace => {
schema=>'bool',
},
force => {
summary => 'Force deletion',
schema => 'bool',
deps => {any => [
{arg=>'delete'},
{arg=>'replace'},
]},
},
...
},
In CLI context, this means "--force" can be specified when "--delete" or "--replace" is
specified.
To depend on several arguments, use the dep type "all", e.g.:
# function metadata property
args => {
red => {
schema=>'uint',
pos => 0,
},
green => {
schema=>'uint',
pos => 1,
},
blue => {
schema=>'uint',
pos => 2,
},
rgb16 => {
schema => 'Use 3x16bits = 48bits to represent RGB value instead of the default 3x8 = 24bits',
deps => {all => [
{arg=>'red'},
{arg=>'green'},
{arg=>'blue'},
]},
},
...
},
In CLI context, this means specifying "--rgb16" only makes sense when all of "--ed",
"--green", "--blue" are specified.
filters
Experimental. Array of string, or code. Filters to apply before argument is converted from
text and validated.
examples (argument property)
Array. Each element is sample argument values. But if it is a hash, will be assumed as a
DefHash with the actual value put in the "value" property (so if your sample argument is a
hash like "{}" (in JSON), you have to specify it as "{"value":{}, "summary":"Optional
summary..."}" (in JSON).
Note that a Sah schema can also have an examples clause which you can use to put examples
in. And Rinci function metadata also has examples property too.
Example function metadata and its implementation in Perl:
$SPEC{multiply2} = {
v => 1.1,
summary => 'Multiple two numbers',
args => {
a => {
summary => 'The first operand',
description => '... a longer description ...',
schema=>['float*', {
examples => [1, -10, 0, 3.333],
}],
pos => 0,
tags => ['category:operand'],
},
b => {
summary => 'The second operand',
description => '... a longer description ...',
schema => 'float*',
pos => 1,
tags => ['category:operand'],
examples => [
1, -10, 0, 3.333,
{value => 1e-10, summary => 'Blah blah'},
],
},
round => {
summary => 'Whether to round result',
description => '... a longer description ...',
schema => [bool => {default=>0}],
pos => 2,
tags => ['category:options'],
cmdline_aliases => {
r=>{},
R=>{summary=>'Equivalent to --round=0',
code=>sub { my ($args, $val) = @_; $args->{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 slurpy):
$SPEC{multiply_many} = {
v => 1.1,
summary => 'Multiple numbers',
args => {
nums => {
schema => ['array*' => {of=>'num*', min_len=>1}],
pos => 0,
slurpy => 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 or hash elements. Argument type
must be "array" or "hash". Example for array:
$SPEC{delete_users} = {
v => 1.1,
args => {
usernames => {
schema => ['array*' => of => 'str*'],
req => 1,
pos => 0,
slurpy => 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
Example for hash (as well as index_completion property to complete hash keys):
$SPEC{create_file} = {
v => 1.1,
args => {
filename => {
schema => 'str*',
req => 1,
pos => 0,
},
content => {
schema => 'buf*',
req => 1,
pos => 1,
},
mode => {
summary => 'Permission mode',
schema => 'posint*',
},
extra_attrs => {
'x.name.is_plural' => 1,
'x.name.singular' => 'extra_attr',
schema => ['hash*' => of => 'str*'],
index_completion => sub {
# complete with list of known attributes
my %args = @_;
require Complete::Util;
Complete::Util::complete_array_elem(
word => $args{word},
array => [qw/mtime ctime owner group/],
);
},
element_completion => sub {
my %args = @_;
my $word = $args{word} // "";
my $index = $args{index};
if ($index eq 'owner') {
require Complete::Unix;
return Complete::Unix::complete_user(word=>$word);
} elsif ($index eq 'group') {
require Complete::Unix;
return Complete::Unix::complete_group(word=>$word);
} else {
return undef;
}
},
},
},
};
When "create_file" is executed over the command line:
$ create-file file1 "hello filesystem" --extra-attr <tab>; # will complete with list of known attributes
$ create-file file1 "hello filesystem" --extra-attr owner=<tab>; # will complete with list of Unix users
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
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.
result
DefHash. Specify function return value. It is a defhash containing keys:
• summary (result property)
From DefHash. Like the "summary" property in variable metadata.
• description (result property)
From DefHash. Like the "description" property. Suggested to be formatted to 78
columns.
• schema (result property)
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 (result property)
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 (result property)
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/]} ]
}]
}
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.
examples (function property)
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 (function example property)
Hash. Arguments used to produce result. Can be converted to "argv" by tool, e.g. when
displaying command-line examples.
• 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. Status from envelope. If unspecified, assumed to be 200.
• result
Any. Expected result.
• env_result
Array. Expected enveloped result.
• naked_result
Any. Expected naked result (payload).
• summary (function example property)
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 (function example property)
From DefHash. Longer marked up text about the example (e.g. discussion or things to
note), suggested to be formatted to 72 columns.
• tags (function example property)
From DefHash.
• test
Bool. Defaults to true. 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',
},
],
features
DefHash. 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.
• reverse
Bool. Default: false. 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
• 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.
• dry_run
Bool, or hash. If set to a true value, specifies that function supports dry-run
(simulation) mode. Can also be set to a hash like this: "<{default="1}>> to mean that
function supports dry-run and the default is dry-run mode. Example:
use Log::ger;
$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.
• pure
Bool. Default: false. 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;
• 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.
• 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.
• 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.
deps (function property)
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.
• 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'
• prog
Str of defhash. Require that a program exists and is executable. 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
As an alternative to just a string, the dep value can also be a defhash. Currently
known properties for the defhash: "name" (program name or path, str, required), "path"
(program path, str, optional), "min_version" (minimum version, dotted number version
str, optional).
• 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/'
• 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'
• 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 {$>} # i am not being run as root
Example in Ruby:
"code" => Proc.new { Process.euid > 0 } # i am not being run as root
• tmp_dir
Bool. If set to 1, specify that function requires temporary directory. Caller should
provide path to this using special argument "-tmp_dir".
• trash_dir
Bool. If set to 1, specify that function requires trash directory. Trash is not unlike
a temporary directory. Caller should provide path to trash directory using special
argument "-trash_dir".
Trash directory can be provided, e.g. by transaction manager (see Rinci::Transaction).
• all
Array of deps. A "meta" type that allows several dependencies to be joined together in
a logical-AND fashion. All dependency hashes must be satisfied. For example, to
declare a dependency to several programs and an environment variable:
all => [
{prog => 'rsync'},
{prog => 'tar'},
{env => 'FORCE'},
],
• any
Array of deps. Like "all", but specify a logical-OR relationship. Any one of the
dependencies will suffice. For example, to specify requirement to alternative Perl
modules:
or => [
{perl_module => 'HTTP::Daemon'},
{perl_module => 'HTTP::Daemon::SSL'},
],
• none
Array of deps. Specify that none of the dependencies must be satisfied for this type
to be satisfied. Example, to specify that the function not run under SUDO or by root:
none => [
{env => 'SUDO_USER' },
{code => sub {$> != 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).
HOMEPAGE
Please visit the project's homepage at <https://metacpan.org/release/Rinci>.
SOURCE
Source repository is at <https://github.com/perlancar/perl-Rinci>.
SEE ALSO
Related specifications: Sah, HTTP/1.1 (RFC 2068)
Rinci
AUTHOR
perlancar <perlancar@cpan.org>
CONTRIBUTING
To contribute, you can send patches by email/via RT, or send pull requests on GitHub.
Most of the time, you don't need to build the distribution yourself. You can simply modify
the code, then test via:
% prove -l
If you want to build the distribution (e.g. to try to install it locally on your system),
you can install Dist::Zilla, Dist::Zilla::PluginBundle::Author::PERLANCAR, and sometimes
one or two other Dist::Zilla plugin and/or Pod::Weaver::Plugin. Any additional steps
required beyond that are considered a bug and can be reported to me.
COPYRIGHT AND LICENSE
This software is copyright (c) 2022, 2021, 2020, 2019, 2018, 2017, 2016, 2015, 2014, 2013,
2012 by perlancar <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.
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.