Rinci::resmeta - Function/method result metadata




This document describes version 1.1.88 of Rinci::resmeta (from Perl distribution Rinci), released on 2019-04-15.


This document describes metadata for function/method result. This specification is part of Rinci. Please do a read up on it first, if you have not already done so.


There are currently several properties being used:

Property: undo_data => ANY

(DEPRECATED) Explained in undo feature section in Rinci::function.

Property: perm_err => bool

Indicate that error is permanent (instead of temporary/transient). This is to provide a feature like that found in SMTP/POP protocol, where 4xx codes indicate transient errors and 5xx permanent ones.

Properties: func.* => ANY

These properties allow function to return extra stuffs. Usually done to avoid breaking format of existing result (to maintain API compatibility). The attributes after func. is up to the respective function. An example is the get_args_from_argv() function in the Perinci::Sub::GetArgs::Argv Perl module. The function returns $args but from v0.26 it also wants to give hints about whether or not there are missing arguments. It can do this via func.missing_arg result metadata.

Properties: cmdline.*

Interpreted by Perinci::CmdLine. See its documentation for more detail.

Property: logs => ARRAY OF HASH

Store log of events happening to this result, stored chronologically (older first). Each log should be a hash which should have at least the following keys: time (Unix timestamp), type (string).

Normally, the first element of the log will contain information about who produced the result and where/when. It has the type key with the value of create. It should be a hash with the following keys:

  • package => STR

    Package (namespace) where this result is produced.

  • file => STR

    File name where the result is created. Might be a relative or absolute path.

  • line => INT

    Line number where the result is created.

  • func => STR

    Function name where this result is produced.

  • stack_trace => ARRAY

    Optional, a stack trace. In Perl this can be produced by using << [caller(1), caller(2), ...] >>.

Property: prev => ARRAY

Store "previous result". Result MUST be enveloped. Usually useful when tracing errors, especially in conjunction with logs: when reporting error that results from a call to another function, the original result can be set here, to preserve information. See Perinci::Sub::Util's err() for a convenience function for this, and Perinci::CmdLine's way of displaying it.


 sub f1 {
     if (error) { return [500, "Can't f1: blah"] }

 sub f2 {
     my $res = f1(...);
     if ($res is error) { return [500, "Can't f2", undef, {prev=>$res}] }

 sub f3 {
     my $res = f1(...);
     if ($res is error) { return [500, "Can't f3", undef, {prev=>$res}] }

Property: results => array

When a function returns an error response (in particular status 207, but other statuses can also use this), it can put detailed errors here. For example, a function which processed 5 items wanted to report that 2 items were successfully processed but the rest 3 failed:

 [207, "Multistatus", undef, {
      results => [
          {status=>200, message=>"OK", item_id=>1},
          {status=>403, message=>"Forbidden", item_id=>2},
          {status=>404, message=>"Not found", item_id=>3},
          {status=>500, message=>"Failed", item_id=>4},
          {status=>200, message=>"OK", item_id=>5},

Each result is a hash to be able to store status, message, as well as additional data like item_id or whatever the function wants.

Another example, a function wants to give information on what arguments fail validation:

 [400, "Some arguments fail validation", undef, {
      results => [
          {status=>400, arg=>"name", message=>"Missing"},
          {status=>400, arg=>"location/street", message=>"Missing"},
          {status=>400, arg=>"age", message=>"Must be numbers only"},
          {status=>400, arg=>"password", is_warning=>1,
           message=>"Should be longer than 4 characters"}, # warning only

Property: part_start => int

Property: len => int

Property: part_len => int

The len, part_start and part_len properties specifies the range of data when function sends partial result. Suppose your function is returning a partial content of a large file where total file size is 24500000 bytes and the returned content is from bytes 10000000 to 15000000, then len is 24500000, part_len is 5000000, and part_start is 10000000. When returning partial content, status will be 206.

Property: stream => bool

If set to true, signify that result is an output stream. Usually in implementations the result will be a filehandle or an object with getline or getitem methods, where caller can then fetch data from it.



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